abstracts summaries - spiespie.org/documents/conferencesexhibitions/moems-mems-2008...

spie.org/pw · TEL: +1 360 676 3290 · +1 888 504 8171 · [email protected] 405

Abstracts Summaries

ContentsConference 6882: Micromachining

and Microfabrication Process Technology XII . . . . 406

Conference 6883: Advanced Fabrication Technologies for Micro/Nano Optics and Photonics . . . . . . . . . . . . . . . . . . . . . . . . . . . . 411

Conference 6884: Reliability, Packaging, Testing, and Characterization of MEMS/MOEMS VII . . . . . 420

Conference 6885: MEMS/MOEMS Components and Their Applications V Special Focus Topics: Transducers at the Micro-Nano Interface . . . . . . . 426

Conference 6886: Microfl uidics, BioMEMS, and Medical Microsystems VI . . . . . . . . . . . . . . . . 430

Conference 6887: MOEMS and Miniaturized Systems VII . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 438

Conference 6888: MEMS Adaptive Optics II . . . . . . 442


Conference 6882: Micromachining and Microfabrication Process Technology XIITuesday-Wednesday 22-23 January 2008 • Part of Proceedings of SPIE Vol. 6882 Micromachining and Microfabrication Process Technology XII

6882-18, Poster SessionThe effect of size on the etch rates of structures fabricated from photostructurable glass-ceramicJ. A. Stillman, The Aerospace Corp. and Univ. of California/ Los Angeles; J. W. Judy, Univ. of California/Los Angeles; H. Helvajian, The Aerospace Corp.

Photostructurable glass-ceramics (PSGCs), although not yet widely used, are well suited to many micro-optical and micromechanical applications. They can be patterned by laser-direct-writing with a high degree of three-dimensional control. A focused laser beam can selectively increase the etch rates of the irradiated regions of these transparent, photosensitive materials. In this experiment, we examined the dependence of the chemical etch rate on the sizes of structures made from Foturan, a commercially available PSGC. We fabricated three types of test structures in 1-mm-thick Foturan samples. First, we fabricated sets of square pits that ranged in width from 10 μm to more than 1 mm. These were etched briefl y to compare the vertical etch rates of structures of different sizes. Second, buried 4-mm-long channels that also ranged in width from 10 μm to more than 2 mm were etched to compare the lateral etch rates of various widths of channels. Third, sets of 4-mm-wide squares were outlined with through-exposed channels of various widths. The squares were examined after etching for 30 minutes, 45 minutes and 60 minutes to determine which channel widths etched completely through the wafer. The exposure system employed a pulsed Nd:Yag laser that was frequency-tripled to 355 nm and operated at a pulse rate of 10 kHz. Samples were etched at room temperature in 5% HF under ultrasonic agitation. We report the measured etch rates, the times at which the through-structures were released for various channel widths, and the variations in measurements for each class of sample.

6882-19, Poster SessionEffect of formulation variables on the formation of cholesterol nanoparticles of clozapine prepared by solvent evaporation methodN. V. Patel, Anand Pharmacy College/Gujarat (India); R. C. Patel, KB Raval College Of Pharmacy/Ahmedabad (India); M. P. Patel, Alembic Ltd. (India)

Effect of surfactant, organic solvent, external phase volume, osmogenic agent, solvent evaporation, and drying method on the morphology, encapsulation effi ciency and drug release behaviour of cholesterol nanoparticles of clozapine, an atypical antipsychotic drug, were studied. The nanoparticles were prepared by single emulsion and double emulsion solvent evaporation methods. Six different surfactant, viz., poly vinyl alcohol (PVA), polyvinyl pyroliidione, cremophore EL, poloxamer 188, poloxamer 407, tyloxapol, vit E TPGS, dextran sulfate were chosen for the study. It was found that the surfactant concentration affects the characteristics of nanoparticles. On increasing the concentration of surfactant the particle size of the nanoparticle and encapsulation effi ciency is reduced. Partially hydrolyzed PVA showed best result among all the surfactants. With 1.2% PVA concentration 19 % drug loading was obtained. The volume of external phase altered the drug release from nanoparticle. It was found that on increasing the external aqueous phase volume burst drug release increase. The addition of osmogenic agent and reduction of external aqueous phase led to marked reduction in the burst release of the drug. Dichloromethane and ethyl acetate were selected as solvent medium for dissolving clozapine and cholesterol. It was observed that with ethyl acetate sticky nanoparticles are produced. The dichloromethane, on the other hand, produced discrete nanoparticles. Hence, dichloromethane was selected as the solvent for the fabrication of nanoparticles.

The method of solvent evaporation and time allowed for solvent evaporation on the properties of nanoparticles studied and it was found that the time required for evaporation of organic solvent could be markedly reduced if evaporation is done under the atmosphere of carbon dioxide. The drying of fabricated nanoparticles was tried by lyophilization, vacuum drying, and simple drying methods it was found

that reconstitution was best in the case of lyophilization.

6882-20, Poster SessionDry fi lm process development for electroplating and lift-off of metal layersP. R. Kanikella, M. J. O’Keefe, C. Kim, Univ. of Missouri/Rolla

A dry fi lm photoresist (MX 5020 from DuPont Electronic Technologies) was selected to fabricate microstructures with high sidewall verticality. Sidewall verticality of dry fi lm is very important for better pattern transfer and sharp features. A fractional factorial design (FFD) method was used to identify the signifi cant process variables for sidewall optimization. The most signifi cant factor was determined to be exposure energy, as other factors were not signifi cant in improving sidewall verticality. It was found that the sidewall slope increased with a decrease in exposure energy. The fabricated dry fi lm molds with nearly vertical sidewalls (86°) were used for copper electroplating and sputter deposited Ti lift-off applications. The electroplating process was also optimized using a fractional factorial design. A lower plating current density resulted in a smoother, fi ne grained deposit compared to the higher current density, and the dry fi lm resist was able to withstand a very acidic (pH ~1) copper sulfate plating solution. Sputtered titanium fi lms with a thickness of 200 nm were also successfully lifted-off using dry fi lm patterning.

6882-21, Poster SessionElectrical properties of thin epoxy-based polymer layers fi lled with n-carbon black particlesM. Macek, Univ. v Ljubljani (Slovenia); M. Klanjsek Gunde, N. Haupt-man, National Institute of Chemistry Slovenia (Slovenia)

Photo sensible epoxy based polymer, known under a commercial name SU8 is widely used negative photo resist used for MOEMS, MEMS and LIGA fabrication due to its excellent properties. They can be changed in a considerable extent if such a polymer is used for the host material of a nano-composite structure, while the photolithographic properties of the host polymer are possible to retain.

The conductive carbon black (CB) with small average primary particle size and high specifi c surface area was applied in the epoxy-based SU8 matrix material. Different weight concentrations of solid particles, as calculated for the solid nanocomposite were used to prepare dispersions. Much attention was paid to control the state of dispersion of solid particles. The layers underwent the standard recommended procedure for SU8 photo resist. The prepared nano-composites were analyzed in terms of specifi c resistance of thin fi lms deposited onto glassy substrates. It was found out, that a proper dispersion of n-particles plays a crucial role. Samples with the same composition (wt% of n-CB) differ in specifi c resistance by few orders of the magnitude. Scanning electron microscopy confi rms that the agglomeration of nano-particles decreases the conductance of the samples.

6882-01, Session 1BioMEMS-enabling technologies for POC testingN. Zhang, General MEMS Corp.

Recent development of innovative disposable lab-on-a-chip system will be reviewed. They typical Lab-on-chip system includes passive or active microfl uidics and varying detection metrologies. The technology advance in Bio-MEMS has opened a new era for the point-of-care testing in clinical diagnostics. Several challenging issues in the development of the disposable lab-on-a-chip have been explored and addressed in this review. A new disposable “dynamic” lab-on-a-chip developed for immunoassay is presented in this paper as an example of Bio-MEMS application.

407 spie.org/pw · TEL: +1 360 676 3290 · +1 888 504 8171 · [email protected]

6882-02, Session 1Advances in CLIPP for the fabrication of surface modifi ed micro-fl uidicM. P. C. Watts, Optical Associates, Inc.; R. Sebra, Univ. of Colarado at Boulder; H. Simms, Univ. of Colorado at Boulder; K. Ansteh, Univ of Colarado at Boulder

The challenge in manufacturing disposable bio micro-fl uidic devices centers on making complex structures with controlled wetting and adhesion characteristics that can be used with fluorescence detection at a very low cost of < $1 a part. We will report on a new low fl uorescence UV curable material that can be patterned in the Contact Liquid Photolithographic Polymerization (CLiPP) process developed at U Colorado [1]. We will show results on reduced protein adhesion in these materials.

A generic micro fl uidic device can be thought of as a liquid delivery, reaction, and detection package. The mechanics of fluid delivery require a series of delivery ports, chambers, and valves that form a complex internal structure. The CLiPP process was invented to make these complex structures by using a contact mask to image a UV curable liquid. The material is crosslinked in the exposed region, and the uncrosslinked liquid washed away. Multiple layers with embedded structures can be made by repeat exposures. Closed cells are formed by lamination, or by temporarily fi lling the structure with wax and them capping with UV material.

The unique feature of CLiPP is that different materials can be used at each layer, so that the inside surface of the device can be engineered. Most microfl uidic devices are made in hydrophobic polymers that have the advantage that the device does not swell in water. Unfortunately the hydrophobic surface also make the cell diffi cult to fi ll without bubbles, and proteins adhere to the surface (non specifi c binding). Devices are often washed with a surface treatment to reduce protein adhesion.

In CLiPP, the surface is modifi ed by including an initiator in the crosslinked layer. This initiator is then activated in the presence of a second monomer which is then grafted on the surface. This second monomer can be hydrophilic or contain bio sensor molecules such as antigens. The grafting of multiple antigens greatly increases detection sensitivity.

Finally, the majority of bio tests use fl uorescence tags to detect specifi c protein binding. This requires low background fl uorescence and low non specifi c binding. Most UV cured materials tend to fl uorescence due to the presence of initiators and UV absorbing monomers. We will show fl uorescence data from a new class of UV cured materials that can be used to provide very high sensitivity detection.

[1] T. Haraldsson et al; 3D polymeric microfl uidic device fabrication via contact liquid photolithographic polymerization (CLiPP); Sensors and Actuators B 113 (2006) 454-460

6882-03, Session 1Fabrication of silicon nanowall chips for DNA binding yield enhancementR. M. Badam, Institute of Microelectronics (Singapore); R. Uppili, SiMEMS Pte Ltd. (Singapore); B. Narayanan, Institute of Microelec-tronics (Singapore)

Silicon micro-fabrication techniques are becoming handy to realize a variety of devices particularly for biological applications. In this work we demonstrate fabrication of silicon based chips for the enhancement of DNA binding yield. A fully CMOS compatible process fl ow was designed with 200mm dia silicon substrate. Highly dense three dimensional nano-structure wall arrays were formed using deep UV lithography and reactive-ion etch technique. We optimized the resist patterning process to create fi ne dense patterns of 200nm width and gap (CD) using KrF lithography scanner eliminating the need of using E-beam lithography which has low throughput. During subsequent silicon etching silicon-di-oxide layer was used as hard mask to over come the etch selectivity issues and control the etch CD bias. Such nano structured dense arrays enhanced the surface-area by more than fourteen times for a given chip base area. These chips were further functionalised for DNA binding and the yield was quantifi ed. We achieved more than four times of DNA binding yield compared to the fl at silicon surface. Further,

it is possible to increase the DNA binding yield by suitable design and process modifi cations of the nano wall arrays. The CMOS compatible process provides greater integrate-ability of devices to realize Lab-on-Chip concepts. Such devices have potential biological applications such as PCR amplifi cation. As the processes designed were production adapt-able cost effectiveness can also be achieved.

6882-04, Session 1Microfabricated needles for transdermal delivery of macromolecules and nanoparticles: fabrication methods and transport studiesR. C. Patel, KB Raval College Of Pharmacy/Gujarat (India); N. V. Patel, Anand Pharmacy College/Gujarat (India)

Arrays of micrometer-scale needles could be used to deliver drugs, proteins, and particles across skin in a minimally invasive manner. We therefore developed microfabrication techniques for silicon, metal and biodegradable polymer microneedle arrays having solid and hollow bores with tapered and beveled tips and feature sizes from 1 to 1,000 μm. When solid microneedles were used, skin permeability was increased in vitro by orders of magnitude for macromolecules and particles up to 50 nm in radius. Intracellular delivery of molecules into viable cells was also achieved with high effi ciency. Hollow microneedles permitted fl ow of microliter quantities into skin in vivo, including microinjection of insulin to reduce blood glucose levels in diabetic rats.

6882-05, Session 2Micromachining of a fi ber-to-waveguide coupler using grayscale lithography and through-wafer etchT. E. Dillon, S. Shi, J. Murakowki, D. W. Prather, Univ. of Delaware

For some time, the micro-optics and photonics fields have relied on fabrication processes and technology borrowed from the well-established silicon integrated circuit industry. However, new fabrication methodologies must be developed for greater fl exibility in the machining of micro-optic devices. To this end, we have explored grayscale lithography as an enabler for the realization of such devices. This process delivers the ability to sculpt materials arbitrarily in three dimensions, thus providing the fl exibility to realize optical surfaces to shape, transform, and redirect the propagation of light effi ciently. This has opened the door for new classes of optical devices.

As such, we present a fi ber-to-waveguide coupling structure utilizing a smoothly contoured lensing surface in the device layer of an SOI wafer created using grayscale lithography. The structure collects light incident normally to the wafer from a single mode optical fi ber plugged through the back surface, and turns the light into the plane of the device layer, focusing it into a single mode waveguide. The basis of operation is total internal refl ection, and the device therefore has the potential advantages of providing a very wide bandwidth operation, polarization insensitivity, high effi ciency, and small footprint. The structure was optimized with a simulated annealing algorithm in conjunction with FDTD simulation, and achieves theoretical effi ciency of approximately eighty percent, including a loss due to Fresnel refl ection from the oxide/silicon interface. The fabricated device has validated the principle of operation.

We will discuss the complete fabrication fl ow in detail, as these processes advance the capabilities of micro-machining and are therefore of general interest. Attention will be directed to the required models and process control that enable precise sculpting of the optical surfaces, needed to achieve a high effi ciency device. We will also discuss the through-wafer etch for mechanical stabilization and alignment of the optical fi ber to coupling structure. Refi nement of the process for high etch rate and appropriate sidewall taper, in addition to the mechanism for alignment of the through-wafer etch to the coupling structure, will be discussed.

6882-06, Session 2Laser beam shaping for micromaterial processing using a liquid crystal displayF. Friederich, U. Klug, M. Boyle, Laser Zentrum Hannover e.V. (Ger-

Conference 6882: Micromachining and Microfabrication Process Technology XII


many)

In the last decades the technology behind liquid crystal displays expanded by an exponential rate. The high demand of this technology by the entertainment industry leads to higher resolutions, smaller pixel pitch and reduced costs. Today, high quality, nematic liquid crystal on Silicon (LCoS) microdisplays with resolutions of 1920 x 1080 pixels and 8 μm pixel pitch are available.

Laser material processing demands high beam quality with different beam profi les, usually achieved by custom-built masks. A computer controlled microdisplay provides the opportunity to actively control and alter the spatial distribution of the incident electromagnetic fi eld. Phase changes by a fraction of a wavelength up to 2π in the IR-Region enhance this element as an adaptive diffractive beam shaping device.

For operation of the display as a diffractive device, several effects have to be taken into account. The LCoS displays are typically controlled by a digital addressing scheme that causes phase fl icker. In addition, the thermotropic behavior of the liquid crystal molecules results in a power dependence of the incident electromagnetic fi eld.

In reference to these characteristics, the application of an LCoS microdisplay (Holoeye HEO1080P) as a beam shaping device for material processing will be discussed. This includes the presentation of a simple method for characterization and calibration of the liquid crystal display.

6882-07, Session 2A novel fabrication technology for anti-refl ex wafer-level vacuum packaged microscanning mirrorsM. Oldsen, U. Hofmann, H. Quenzer, K. Gruber, B. Wagner, Fraunhofer Institut für Siliziumtechnologie (Germany)

Resonantly operating microfabricated scanning mirrors are supposed to be a key component for a variety of mass applications in the fi eld of laser projection and imaging. To ensure the feasibility of mass production the devices must be hermetically encapsulated on wafer level. A vacuum encapsulation reduces the required driving voltages and enhances the achievable mirror defl ection angles. Different to inertial MEMS a wafer level package for MOEMS must also provide perfect optical quality.

This work presents a complete process technology allowing the fabrication of wafer-level vacuum packaged electrostatically actuated scanning micromirrors for laser projection. The MOEMS wafer containing the active mirror devices is sealed at the frontside by a structured and anti refl ective coated glass wafer containing up to 500 μm deep cavities with perfect optical quality. A eutectic bonded silicon wafer hermetically seals the assembly from the backside. While even an anti refl ective coating on the structured glasswafer does not fully eliminate the parasitic refl ection of the laser beam on the glass interfaces, this work also presents an effective full anti-refl ective package solution on wafer level.

To enable the standard wafer bonding processes, such as eutectic, anodic and glass frit bonding, the MOEMS wafer process features two 30 μm thick epitactically grown and CMP polished polysilicon layers. A buried thin polysilicon layer enables the integration of lateral electrical feedthroughs.

First measurements of the vacuum level showed a package pressure of approx. 1 mbar. An optional getter layer can be integrated into the package for further improvement of the vacuum level.

6882-08, Session 2Parallel kinematic mechanism-based monolithic XY micro-positioning stageD. Mukhopadhyay, J. Dong, P. M. Ferreira, Univ. of Illinois at Urbana-Champaign

Micro-positioning stages fabricated using Micro Electro Mechanical Systems (MEMS) based processes have been critical in enabling micro/nano manipulation and probing. These stages have been extensively used in micro-force sensors, scanning probe microscopy and micro optical lens scanners. This paper presents the design, kinematic and dynamic analysis, fabrication and characterization of a novel monolithic micro-positioning XY stage. The design of the proposed micro-positioning stage

is based on a Parallel Kinematic Mechanism (PKM). The PKM based design decouples the motion in the XY direction. Additionally, it restricts the parasitic rotation of the end-effector (table) of the micro-positioning stage while providing an increased motion range. The motion of the stage is linear in the operating range thus simplifying its kinematics. The truss like design of the stage structure reduces its mass while keeping the stage stiffness high. This leads to a high natural frequency of the micro-positioning stage while the PKM based design leads to a high Q-factor. The stage mechanism is fabricated on a Silicon-On-Insulator (SOI) substrate and is actuated by integrated electrostatic rotary comb drives. The fabrication process uses multi-layer patterning along with an Inductively Coupled Plasma Deep Reactive Ion Etching (ICP-DRIE). The use of ICP-DRIE enables the high aspect ratio etching that is required for the stage fabrication and its optimal actuation using the integrated electrostatic rotary comb drives. The fabricated stages have a motion range of more than 30 microns of decoupled displacements along the X and Y directions at a driving voltage of 200V.

6882-09, Session 2Microinductors integrated on silicon for dc-dc convertersT. El Mastouli, J. Laur, Lab. d’Analyse et d’Architecture des Systèmes (France) and Paul Sabatier Univ. (France); J. Sanchez, Lab. d’Analyse et d’Architecture des Systèmes (France)

For applications such as computers, cellular telephones and Microsystems, it is essential to reduce the size and the weight of electronic devices. More particularly, this evolution implies the miniaturization of high effi ciency on-chip dc-dc converters providing low voltage to the various ICs. Therefore, fabrication of magnetic components dedicated to power conversion becomes necessary. To miniaturize inductors, the micromachining techniques provide solutions based on low-temperature process compatible with active part of the converter.

The proposed inductor topology is based on a spiral-type structure which consists in a copper conductor sandwiched between two CoNiFe (60%-15%-25%) layers shielding the magnetic fl ux of the inductor winding. Considering a 1-5 MHz operating switching frequency, a laminated core has been investigated in order to reduce eddy-current induced in the core. We have made several investigations on the electroplating bath’s parameters by changing temperature, pH and current density values in order to obtain optimum magnetic properties (Bsat=2.3T, low Hc, μr=250, resistivity>30 μOhm.cm). These proprieties are measured by SQUID and the composition is analyzed using quantitative energy dispersive X-ray analysis.

Research reported in this paper is an example relative to the microinductors fabrication for micropower applications. It shows the feasibility of a spiral inductor structure with a laminated core adequate for a high frequency switching operation. The fi nal paper will describe with more details the characterizations of a ten turns prototype exhibiting a 1μH inductance value.

6882-10, Session 2Electrodeposition of Au for self-assembling 3D microstructuresM. E. Kiziroglou, A. G. Mukherjee, Imperial College London (United Kingdom); R. W. Moseley, Microsaic Systems Ltd. (United Kingdom); P. Taylor, Semefab (Scotland) Ltd. (United Kingdom); S. Pranonsatit, A. S. Holmes, E. M. Yeatman, Imperial College London (United Kingdom)

Rotation of structures fabricated by planar processing into out-of-plane orientations can be used to greatly increase the 3-dimensionality of microstructures. Previously this has been achieved by a self-assembly process based on surface tension in meltable hinges. An important application is in fabricating vertical inductors on silicon, to reduce the substrate coupling and thus increase quality factor and self-resonance frequency. Previous processes have used copper tracks, and Pb-Sn hinges. However, the use of Cu limits potential applications because of oxidation, since the fi nal structure is not embedded. Moreover, a substitute hinge material is also required, as a result of legislative restrictions on Pb use. In this paper, Au is used as an alternative to Cu



for the fabrication of self-assembled 3D inductors. A process has been developed to overcome photoresist decomposition problems due to the alkaline nature of Au electro-deposition solutions. Furthermore, pure Sn is used instead of Pb-Sn as the hinge material. A Ni metal layer is introduced between the Au coils and the Sn hinge to prevent inter-diffusion and formation of eutectic Au-Sn compounds. Finally a gold capping technique is proposed to protect the Sn hinge from oxidation during hinge refl ow. The fabrication techniques developed here are compatible with post-processing on active CMOS circuits, and can be adopted for other MEMS applications.

6882-11, Session 3Microcantilever force sensor fabricated by femtosecond laser micromachiningP. S. Shiakolas, N. Uppal, M. Mayyas, The Univ. of Texas at Arlington

Femtosecond lasers have been used to process various materials for different applications in the micro/nano domain. In this work, a femtosecond Ti: Sapphire laser (800 nm wavelength and 120 fs pulse width) is used to fabricate a micro cantilever for contact force sensing applications. The microcantilever with micro/nanoforce resolution is designed and its performance optimized reference to the resistance change as function of applied force. The microcantilever force sensor is composed of a PMMA fi lm sputtered with copper. The femtosecond laser is utilized to obtain the desired copper geometry using a bulk-micromachining process over the entire length of the elastic PMMA layer. Optimization criterions for the resistance change vs. force/defl ection have been mathematically derived for the laminated layers. The micron and submicron machining capabilities along with the optimization criterions have allowed introducing a range of MEMS FS which are suitable for force and displacement measurement of MEMS actuators.

6882-12, Session 3Fabrication of buried channel waveguides in polydimethylsiloxane (PDMS) using proton beam writing (PBW): Applications for fl uorescence detection in microfl uidic channelsC. N. B. Udalagama, S. F. Chan, S. Homhuan, A. A. Bettiol, F. Watt, National Univ. of Singapore (Singapore)

Proton beam writing (PBW) is a lithographic technique that utilizes MeV protons in a direct write mode to fabricate micro/nano features in suitable resist material (E.g PMMA, SU-8, silicon, Foturan...). These micro/nano structures may be used in an electroplating step to yield robust metallic stamps/molds for the replication of the original and lends itself to the fabrication of micro/nano fl uidic channels that are important components in devices such as biophotonics chips. Another feature of proton bombardment is its ability to induce an increase in refractive index along the ion’s path, in particular at the end of its range where there is substantial nuclear scattering. This allows PBW to directly write buried waveguides that can be accurately aligned with fl uidic channels.

Polydimethylsiloxane (PDMS) is an optically clear, biocompatible polymer that can be readily used with a mold (such as that created with PBW) to produce micro/nano fl uidic channels necessary for biophotonics chips. It is usual to embed optical fi bres within such a device to allow for the coupling of light necessary for analysis. This requires additional considerations for the proper alignment of these fi bres.

In this paper we present results of the fabrication and characterization of proton beam written buried waveguides in PDMS as means of directly coupling light into microchannels in biophotonics chips without resorting to embedding optical fi bres.

6882-13, Session 3MEMS post-processing of MPW dies using BSOI carrier wafersA. G. Mukherjee, M. E. Kiziroglou, A. S. Holmes, E. M. Yeatman, Impe-rial College London (United Kingdom)

Multi-project-wafer (MPW) services provide an economical route for

prototyping of new electronic circuit designs. However, addition of MEMS functionality to MPW circuits by post-processing (also known as MEMS-last processing) is diffi cult and ineffi cient because MPW typically yields individual dies. One solution to this problem is to embed the MPW dies in a carrier wafer prior to MEMS processing. We have developed a process which allows 300 micrometer thick CMOS dies to be embedded in a BSOI (bonded silicon-on-insulator) carrier prior to low-temperature processing for integration of metal MEMS. Deep reactive ion etching (DRIE) with an STS Multiplex ICP etcher is used to form cavities in the device layer of a BSOI wafer. By adjusting the passivation and etching cycles, the DRIE process has been optimized to produce near-vertical sidewalls when stopping on the buried oxide layer. The cavity sizes are closely matched to the die dimensions to ensure placement of the dies to within +/-15 micrometer. Dies are placed in all the cavities, and then a photoresist layer is deposited by spin-coating and patterned to provide access to the required IC contact pads. The photoresist has the dual role of securing the dies and also planarizing the top surface of the carrier. After an appropriate baking cycle this layer provides a suitable base for multi-level electroplating or other low-temperature MEMS processing. Details of the process optimisation will be reported, along with examples of RF MEMS devices that have been successfully fabricated over CMOS circuits by this route.

6882-14, Session 3Microstructures with rounded concave and sharp-edged convex corners in a single step wet anisotropic etchingP. Pal, K. Sato, Nagoya Univ. (Japan); M. Gosalvez, Helsinki Univ. of Technology (Finland); M. Shikida, Nagoya Univ. (Japan)

The conventional design of silicon micromachining based microstructures has sharp edge convex and concave corners. This design exhibits stress concentration at the concave corners when load is applied which may initiate micro cracks. By providing rounded concave corners instead of sharp one, the stress can be smoothening, and that will improve the mechanical effi ciency. However, the fabrication of this type of geometry is diffi cult as severe undercutting start at convex and rounded concave corners during wet anisotropic etching.

In this work, we have developed the microstructures with rounded concave and sharp-edged convex corners in (100)-silicon wafer in a single step wet anisotropic etching process. It was realized by analyzing the etching characteristics of TMAH solution when non-ionic surfactant NC-200 is added. The NC-200 contains 100% polyoxethylene-alkyl-phenyl-ether.

To demonstrate the technique, various kinds of microstructures with rounded concave and sharp edged convex corners are fabricated on p-type (100)-silicon wafers. The etch rates, average surface roughness and convex undercutting ratio in pure and surfactant added TMAH solution at different concentrations are compared. In average, the undercutting ratio in 25 wt% TMAH reduces by 92% which is less than the values reported for IPA and other surfactant added TMAH solution. Various kinds of MEMS structures based on silicon (such as the cantilever beams) require thickness of about 2~10 μm. It should be stressed that, in this work, we have achieved rounded concave and sharp edge convex corners with negligible undercutting for thicknesses up to 20 μm without the addition of any compensating structure.

6882-15, Session 3TACD tool for innovative MEMS and MOEMS: a all-in-one solutionU. Triltsch, S. Büttgenbach, Technische Univ. Braunschweig (Ger-many)

No abstract available



6882-16, Session 3Sensitivity and stress of composite Si-micro/macro porous siliconS. L. Narayanan, E. Bhattacharya, Indian Institute of Technology Madras (India)

Since porous silicon (PS) has a lower Young’s Modulus as compared to silicon, Silicon/Porous Silicon (Si/PS) composite membranes are expected to show higher sensitivity as compared to membranes of silicon alone. We have earlier reported improvement in the sensitivity of pressure sensors with Si/microPS composite membranes [1]. Electrochemical etching in an organic electrolyte composed of HF and DMF (Dimethyl Formamide) is known to yield macroPS [2]. In this paper we discuss the fabrication and testing of Si/PS composite membranes where a part of the silicon membrane depth is converted into macroPS. The composite membrane with macroPS also shows an increase in the sensitivity though the improvement is less than that with microPS. Formation of microporous and macroporous silicon produces stress on the membrane varying with the porosity. The variation in compressive stress on the membrane with porosity for both micro and macro PS has been studied by measuring the deformation of the composite membrane with a surface profi ler and the stress is found to be larger for macroPS. The compressive stress results in an increase in the offset voltage by more than an order of magnitude for composite membranes with macroPS with porosity above 50% as compared to one with a single crystalline silicon one. Though the composite membranes exhibit saturation and hysteresis at higher pressures, the response is linear and repeatable at pressures below 1 bar making this a viable option for sensing low pressures.

References

1. L.Sujatha and E. Bhattacharya, Proceedings of SPIE Volume: 6464 MEMS / MOEMS Components and Their Applications IV, Photonics West 2006, p 64640O01-08.

2. E.A. Ponamarev et.al., Journal of Porous Materials (7), 2000, p 51-56.

6882-17, Session 3Three dimensional waveguide fabrication in PMMA using femtosecond laser micromachining systemP. S. Shiakolas, N. Uppal, M. Rizwan, The Univ. of Texas at Arlington

Femtosecond lasers have been widely used for the micro structuring of transparent materials for a wide range of applications. When the ultrashort laser pulse is focused in the bulk of transparent material, the material undergoes local refractive index modifi cation because of the nonlinear absorption of laser energy. This local change in refractive index by the irradiation of laser pulse has been exploited for various applications ranging from optical data storage to the fabrication of waveguides and couplers. In this work, a Ti: Sapphire femtosecond laser (800nm, ~100 fs and 1 KHz) is used for the fabrication of three dimensional waveguides in thick PMMA substrates. The femtosecond laser system (FLM) also consists of there translational (X, Y and Z) stages and one rotational stage. The combined motion of these four stages can be used to achieve desired three dimensional pattern inside the transparent material due to refractive index modifi cation. This work will present the designing of 3D waveguide using commercially available solid modeler and generation of machining codes using customized post processor. Also, control of the laser process parameters to obtain desired feature quality by minimizing self focusing and fi lament formation in PMMA is discussed. This FLM system along with the 4 axis machining capability can be effectively used for the fabrication of complex 3D waveguide circuits rapidly in a single step process.



Conference 6883: Advanced Fabrication Technologies for Micro/Nano Optics and PhotonicsMonday-Wednesday 21-23 January 2008 • Part of Proceedings of SPIE Vol. 6883 Advanced Fabrication Technologies for Micro/Nano Optics and Photonics

6883-01, Session 1Fabrication of nanophotonic structures for information processingS. M. Spillane, Q. Xu, D. A. Fattal, W. Wu, Hewlett-Packard Labs.; P. Kornilovich, Hewlett-Packard Co.; R. G. Beausoleil, Hewlett-Packard Labs.

Nanophotonic structures are useful for both classical and quantum information processing applications. Here we discuss the fabrication of nanophotonic structures using nanoimprint lithography, and compare their performance with other fabrication techniques such as electron beam lithography.

6883-02, Session 1Formation of anti-refl ective structure on the surface of optical glass by moldingK. Yamada, M. Umetani, T. Tamura, Y. Tanaka, Matsushita Electric Industrial Co., Ltd. (Japan); J. Nishii, National Institute of Advanced Industrial Science and Technology (Japan)

The formation of a surface having a periodic subwavelength structure (SWS) is a well-known technique for reducing the Fresnel refl ection of transmissive optical elements. We successfully fabricated an anti-refl ective surface with a two-dimensional periodic structure of 300 nm in pitch on an optical glass by a precision molding process using a silica glass mold coated with a thin carbon fi lm. The surface structure on the mold was formed by a reacting ion etching (RIE) method using fl uorocarbon plasma. A thin chromium fi lm, which was used as the etching mask, was patterned with an electron beam lithography and a wet etching process. The anti-refl ective surface was formed on a phosphate glass with a deformation point of 412°C and refractive index of 1.60 at a wavelength of 462 nm. The phosphate glass was molded at 420°C for 510 sec. under a pressure of 5 MPa. The height of periodic structure on the mold was 550nm and the height of that on the formed glass was 480 nm. Therefore the fi lling rate of the phosphate glass to the mold was 87%. The surface refl ectance of the glass was estimated to be 0.56% at a wavelength of 462 nm, which was approximately 1/10 compared with that of the optically polished surface.

6883-03, Session 1Fabrication of plasmonic waveguides by nanoimprint and UV-lithographyR. B. Nielsen, A. Kristensen, A. E. Boltasseva, Danmarks Tekniske Univ. (Denmark); S. I. Bozhevolnyi, V. S. Volkov, Aalborg Univ. (Den-mark)

We present a novel approach for the fabrication of plasmonic waveguides. The process developed allows manufacturing of profi led metal surfaces including wedges and V-groove channels. It is based on a combination of nanoimprint lithography (NIL) and UV-Lithography to allow high volume production.

Plasmonic waveguides have attracted a lot of attention lately due to their combination of relatively low propagation loss and subwavelength guiding. However applications have been limited because focused ion beam (FIB) milling, a slow serial process, was the only fabrication method demonstrated [1].

In the NIL based process presented here the features are formed on a silicon stamp by various anisotropic etches, and then imprinted in PMMA polymer. After gold deposition the polymer structures are fi lled with a UV curable hybrid polymer (Ormocomp(r), micro resist technology), which is selectively exposed through a mask to create macro features used to allow access with fi ber optics. Finally the PMMA is dissolved to release the gold on polymer structures, which are exact replicas of the original silicon stamp, allowing for very low surface roughness.

This approach has the advantage of allowing cutback measurements, a feature not previously shown for this type of plasmonic devices.

Measurements on the fabricated devices have shown the presence of both channel plasmon polariton (CPP) and wedge plasmon polariton (WPP) modes. CPP modes are found to propagate along the bottom of fabricated V-grooves with a propagation loss as low as 5 dB/mm, while WPP modes are found at the upper edges of the channel.

[1] S. I. Bozhevolnyi, V. S. Volkov, E. Devaux, T. W. Ebbesen, Phys. Rev. Lett. 95, 046802 (2005).

6883-04, Session 1Advances in roll to roll manufacturing of opticsM. P. C. Watts, Impattern Solutions

Optical elements are being fabricated on the scale of meter sheets using roll to roll processing. They are used as light enhancement layers for liquid crystal display backlights, and also as light management fi lm in all sorts of passive displays such as eye catching marketing and for enhanced traffi c information. The fi lms are manufactured by either thermal or UV embossing techniques. There are major captive and merchant suppliers for these fi lms. In this paper, the different applications, optical structures, and manufacturing techniques will be compared.

Thermal embossing has been commercial since the mid 80’s to manufacture security holograms. This can be done at very high speed compared to imprint because there is a large reservoir of material in the fi lm to fl ow into the pattern. UV embossing is starting to become more and more popular because of the quality of the pattern transfer from the mold. Merchant suppliers have developed the ability to superimpose multiple embossing operations creating complex optical components.

Embossed fi lms are available today in meter wide sheets that meet all the uniformity requirements for display backlights. 3M in particular have built up a billion dollar business in backlight fi lms, that is being viewed enviously by many competitors.

Examples of products and target specifi cations for fi lms will be compared based on public disclosures and interviews with the major suppliers.

6883-05, Session 2Silicon photonic wire circuits for on-chip optical interconnectsW. M. J. Green, F. Xia, S. Assefa, M. J. Rooks, L. Sekaric, Y. G. A. Vlasov, IBM Thomas J. Watson Research Ctr.

The continued scaling of power performance in electronic hardware for high-performance computing is rapidly being limited due to the large power consumption and restricted throughput of traditional electrical interconnects. One possible solution is to replace conventional global interconnects with a CMOS compatible intra-chip optical network, based on Silicon-On-Insulator (SOI) photonic integrated circuits. While the bandwidth and power consumption advantages of SOI optical interconnects are potentially immense, ensuring the performance of chip-scale networks places stringent requirements upon the control of the manufacturing process, and its infl uence upon the operation of individual optical components. I will present recent work on the design, fabrication, and demonstration of various passive and electrooptic devices required for high speed optical interconnect applications, including high-order optical fi lters and modulators. Various aspects of the CMOS compatible fabrication process used at IBM Research for manufacturing SOI photonic wire circuits will be discussed, including waveguide loss, surface roughness, device dimensions, and microresonator frequency uniformity.

6883-06, Session 2Metamaterials for “free space on a chip” applicationsU. Levy, Univ. of California/San Diego; M. Abashin, Del Mar Photonics, Inc.; K. Ikeda, Y. Fainman, Univ. of California/San Diego

We present our recent progress on the design, fabrication and characterization of metamaterials that can be used as basic building


blocks for “free space on a chip” nanophotonic system integration. These devices are realized by fabricating nanostructures with space variant duty cycle on Silicon on insulator (SOI) material platform. The devices are characterized with Heterodyne Near-fi eld Scanning Optical Microscope that allows a direct measurement of both amplitude and phase of the near fi eld. Using the described concept, we show specifi c examples of light bending, focusing and splitting. A design for mode matching between two different waveguides is also shown.

6883-07, Session 2Fabrication techniques for creating a thermally isolated TM-FPA (thermal microphotonic focal plane array)M. J. Shaw, M. Watts, G. N. Nielson, Sandia National Labs.

A novel fabrication strategy has produced uniform optical resonating ring structures that are thermally isolated from a silicon wafer substrate. The microphotonic ring designs are based on the massive thermo-optic effect and these thermally isolated micro-resonators could potentially produce higher sensitivity than standard bolometric techniques. Several fabrication strategies were investigated using waveguide materials such as LPCVD Silicon Nitride on Oxide and SOI (Silicon on Insulator). Fabrication challenges and loss reduction strategies will be presented along with some initial thermal testing results.

6883-08, Session 2Sub-10 nm zone plates using the overlay nanofabrication processesW. Chao, Univ. of California/Berkeley; E. H. Anderson, Lawrence Berkeley National Lab.; D. T. Attwood, Univ. of California/Berkeley and University of California Berkeley

Soft x-ray zone plate microscopy has proven to be a valuable imaging technique for nanoscale studies. The workhorse of the microscopy is high quality Fresnel zone plates, which enable a few tens nanometer resolution to be obtained on a daily basis. The highest spatial resolution demonstrated with the soft x-ray microscopy is sub-15 nm, achieved by imaging zone plates of 15 nm outermost zone width. The zone plates, which to our knowledge have the narrowest zones fabricated to date, were realized with e-beam lithography using an internally developed zone plate nanofabrication process based on overlay. In the overlay process, a zone plate pattern is sub-divided into two (or more) semi-isolated, complementary patterns, which are fabricated sequentially and are overlaid with high accuracy on the same substrate to form the desired pattern. This process, similar in concept to the double exposure technique used in semiconductor industry, takes advantage of the fact that isolated lines of width narrower the smallest half-pitch of a dense grating can be routinely fabricated. The 15 nm zone plates, which cannot be achieved using a single exposure process, were realized using the process, with 1.7 nm alignment accuracy at the Center for X-ray Optics Nanofabrication Laboratory. The overlay process, combined with sub-pixel overlay accuracy achieved with our electron beam writer (Nanowriter), provides a pathway to sub-10 nm resolution zone plates. In the talk, I will report the latest development of this process towards realization such zone plates. In addition, I will discuss a scheme that can permit fabrication of high resolution, high effi ciency zone plates with tilted zones using the overlay process.

6883-09, Session 3Nanoimprint lithography for nanomechancal optical structuresL. Montelius, G. Luo, D. Hessman, S. G. Nilsson, I. Maximov, M. Graczyk, D. Adolph, Lunds Univ. (Sweden); T. Zhu, Z. Liu, Peking Univ. (China); H. Xu, Lunds Tekniska Högskola (Sweden)

Nanoimprint lithography (NIL) is a low cost, high throughput patterning technique with high resolution allowing pattern defi nition over large areas. Here we introduce the NIL based fabrication and performance characterization of a novel optical device which is laterally defl ectable cantilever array structures. In this talk I will fi rst highlight the major characteristics of the NIL-technology. Then I will discuss prospects

and challenges and its use for fabrication of cantilever based grating structures allowing a dynamic control of sub-wavelength grating perfromance. I will show applications of this kind of structures not only for optics (diffraction/refl ection), but also for electronics (tunable RF-fi lter)l as well as for biosensors (mass detection). The structure of the NEMS device is a laterally deformable double-fi nger interdigitated cantilevers array, which are made on SiO2/Si surface and evaporated with a metal layer. When a bias is applied, the cantilevers of the device will bend to each other due to electrostatic force. By applying DC voltage and AC voltage with different frequency, the defl ection and oscillating behavior of the cantilevers is studied under microscope. Those behaviors were related to the intensity of diffraction pattern by using a digital camera or a photodiode. The results show that the device could be used as an optical switching element that in turn can be applied as an accelerometer. The resonance frequency of the cantilever array could also be determined. Then, fi nally, I will give an outlook and discuss about it´s role as a very versatile alternative for future nanoscience based production.

6883-10, Session 3High-volume applications of wafer-scale opticsM. Rossi, Heptagon Oy (Switzerland)

Major design advances and manufacturing technology improvements for micro-optic systems have facilitated the trend towards miniaturization in optics. Up to the mid 1990’s, micro-optics development was primarily for defense applications requiring components with small size and low weight. With the introduction of high-quality micro-optical components produced by UV-embossing and micro-injection molding technologies, these replicated components can now comfortably withstand the harsh environmental requirements of the consumer electronics industry, including IR refl ow and thermal shock.

The attraction of micro-optics for an optical system, particularly for consumer products, depends upon a successful optimization of the design, mastering, tooling and production steps; this typically requires a close interaction between the micro-optics producer and the product developer. Consumer products, which can be characterized as products produced in large quantities for non-technical users, represent an ideal industrial segment for micro-optical components and systems.

Double-sided and aligned wafer-scale UV-embossing has been developed at Heptagon. This process, is an extension of the standard UV-replication process to large area glass or opto-electronic wafers. Heptagon’s production line has been optimized and automized. It now yields high quality and low-cost micro-optical elements and modules with a capacity of several million components per month.

The combination of customized functionality, small size and cost-effective production make micro-optics particularly attractive for beam-shaping applications and for imaging optics for CMOS sensor modules for mobile phones and PDA’s. The recent and ongoing developments in design and production technology are resulting in replicated micro-optics becoming an important factor in a wide variety of markets.

6883-11, Session 3Microtransfer molding of SU-8 micro-opticsA. Cannistra, The Univ. of North Carolina at Charlotte; P. Srinivasan, College of Optics & Photonics/Univ. of Central Florida; E. G. Johnson, T. J. Suleski, The Univ. of North Carolina at Charlotte

SU-8 is a very promising polymer for micro-optics. It is mechanically robust with high thermal and chemical resistance, has high transmission at visible and near-infrared wavelengths, and has relatively high refractive index after curing. While lithographic patterning of SU-8 is relatively common, molding of SU-8 is more diffi cult due to challenges with solvent removal and cross linking.

In this paper, we discuss techniques for microtransfer molding of micro- and nano-optics in SU-8. Elastomeric mold templates are fi rst cast from master structures fabricated using lithographic and micromachining methods. The elastomeric templates are then used in a low pressure molding process to produce high-fi delity refractive and diffractive micro-optics in SU-8. The use of the elastomeric replica mold also enables realization of a wider variety of optical surfaces than can be

Conference 6883: Advanced Fabrication Technologies for Micro/Nano Optics and Photonics


achieved with conventional lithographic patterning techniques in SU-8, and further enables conformal fabrication of SU-8 micro-optics on non-planar surfaces, which is very diffi cult to achieve with lithographic fabrication methods. Molding processes and experimental results for both thin (diffractive) and thick (refractive) elements are presented, and sample micro-molding applications leveraging the optical and material properties of SU-8 are discussed.

6883-12, Session 3Step and fl ash imprint process integration techniques for photonic crystal patterning: template replication through wafer patterning irrespective of toneM. L. Miller, C. Brooks, D. Lentz, G. F. Doyle, D. J. Resnick, D. L. LaBrake, Molecular Imprints, Inc.

Photonic crystal structures in for example light emitting diodes (LED) have been demonstrated to improve performance by preferential mode coupling near the surface of the diode.1 Such demonstrations were limited by using direct write e-beam lithography due to long write times, a single tone and only small areas patterned for study. S-FIL technology provides a means to pattern entire wafers in a single imprint step using templates replicated by step and repeat (S&R) imprint (2). Large area template replication by S-FIL/R has been described using S&R templates (3). Photonic crystal based LED manufacturers prefer holes in substrates requiring pillar tone templates for S-FIL patterning. Pillar tone templates are not the preferred e-beam tone for sub-200 nm template fabrication. Therefore step and repeat and/or whole wafer template replication by the combination of S-FIL and/or S-FIL/R can be used to produce the desired working template tone. These processes further enable the desired tone and wafer die layout for fully patterning wafers to their edge. The advantages of using S-FIL processes for template and wafer patterning are clear in that there is no tone preference required by the original e-beam generated pattern. The present work will describe template replication processes for the fabrication of either pillar or hole tone templates and subsequent wafer pattern processes, through oxide hard mask, producing both pillar and hole tone patterns. In summary process fl ows exist so that any e-beam written template tone can be used to produce either tone in replicated templates and/or patterned wafers.

1. III-nitride LEDs with photonic crystal structures, Proc. SPIE, Vol: 5739, pp. 102-107, 2005, J. Wierer, et. al.

2. Whole Wafer Imprint Patterning Using Step and Flash Imprint Lothography: A Manufacturing Solution for Sub 100 nm Patterning, David Lentz, Gary Doyle, Mike Miller, Gerard Schmidt, Maha Ganapathisuramanian, Xiaomong Lu, Doug Resnick and Dwayne LaBrake, Proc. SPIE Advanced Lithography 6517, 2007

3. M. Miller, et. al., NNT 2006

6883-13, Session 4Nonplanar surface structures of inorganic optical materials fabricated by femtosecond laser lithographyH. Nishiyama, M. Mizoshiri, Osaka Univ. (Japan); J. Nishii, National Institute of Advanced Industrial Science and Technology (Japan); Y. Hirata, Osaka Univ. (Japan)

Diffractive optical elements (DOEs) of inorganic materials such as SiO2 and Si are expected to be useful for optical interconnection and information appliances. Most DOEs have been fabricated by the semiconductor fabrication processes. Although this process is effective for the formation of fi ne patterns, there are two serious problems. (1) This process can be applicable only to the planar substrates. (2) The cross-sections of the patterns are always fl at-top structures. In this study, the nonplanar surface microstructures of inorganic optical materials were created by the combined process of femtosecond laser lithography and plasma etching for the highly integrated DOEs.

Blazed grating patterns were written directly inside a negative-tone resists coated on SiO2 substrates. Here, we can write the arbitrary 3-D patterns by femtosecond lasesr-induced nonlinear optical absorption, unlike the standard photolithography. Then, the resist patterns were

transferred to SiO2 by CHF3/O2 plasma. As a result, SiO2-based blazed gratings with smooth surfaces were obtained. There was no thermal damage nor cracks.

Next, we fabricated line patterns on a groove structure as deep as 50 um. The positive-tone resists were coated on the Si grooves. The resist thickness was not uniform because of the surface tension of resist. However, we can irradiate the region inside the resists directly. Therefore, after plasma etching, we could obtain Si-based line structures with uniform widths across the groove in spite of the non-uniformity of resist coating. Our proposed process is expected to be useful for highly integrated DOEs such as diffractive/refractive hybrid microlens.

6883-14, Session 4Spin-on-glass smoothing of diamond turned optics for use in the extreme ultraviolet regimeF. H. Salmassi, P. P. Naulleau, E. M. Gullikson, Lawrence Berkeley National Lab.

Mirror substrates intended for use in the extreme ultraviolet (EUV) regime have exceedingly stringent requirements on surface fi nish. Rendering a substrate refl ective at EUV wavelength and near normal angles of incidence requires these mirrors to be coated with high-quality multilayer coatings forming a Bragg refl ector. These coatings typical have period requirements on the order of 7 nm. It is evident that any appreciable roughness on this scale would destroy the resonant behavior the Bragg structures signifi cantly degrading the refl ectivity of the mirror. A rule of thumb is that approximately 2% refl ectivity is lost per Å of surface roughness on the substrate. These requirements signifi cantly increase the cost and fabrication time for EUV optics. This is especially true when dealing with non-conventional shapes such as toroids and fl y-eye mirrors. Here we present a spin-on-glass process capable of generating super-polished parts from inexpensive substrates. The method is used to render complex diamond-turned optics compatible for use in the EUV regime. The method is described in detail and experimental results are presented demonstrating the effectiveness of the process. Issues of fi gure control are also discussed.

6883-15, Session 4Free-form machining for micro-imaging systemsM. L. Barkman, B. Dutterer, M. A. Davies, T. J. Suleski, The Univ. of North Carolina at Charlotte

While mechanical ruling and single point two-axis diamond turning has been a mainstay of optical fabrication for many years, many types of micro-optical devices and structures are not conducive to simple diamond turning, ruling, or even two-axis turning with fast tool servo. Examples include many microlens arrays and optical surfaces with non-radial symmetry. More recent developments in machining technology have enabled signifi cant expansion of fabrication capabilities. Modern machine tools can generate complex three-dimensional structures with optical quality surface fi nish, and fabricate structures across a dynamic range of dimensions not achievable with lithographic techniques. In particular, fi ve-axis free-form micromachining offers a great deal of promise for realization of essentially arbitrary surface structures, including surfaces not realizable through binary or analog lithographic techniques.

In this paper, we discuss techniques and applications of free-form surface machining of micro-optical elements, including turning, high-speed micromilling, and surface microgrinding. Aspects of diamond machine tool design to realize desired surface geometries in specifi c materials are discussed, along with results of experiments showing precision placement and alignment of fabricated structures relative to lithographically placed features. Several examples are presented, including fabrication of aspheric lens arrays in germanium for compact infrared imaging systems, and fabrication of mold templates for replication of micro-optical structures.



6883-17, Session 4Hollow waveguide optimization for fl uorescence based detectionE. J. Lunt, B. S. Phillips, C. J. Jones, A. R. Hawkins, Brigham Young Univ.; P. Measor, S. Kuehn, H. Schmidt, Univ. of California/Santa Cruz

Previously, we created antiresonant reflecting optical waveguides (ARROWs) with hollow cores that guide light through gas and liquid media. We have demonstrated that these ARROWs can be used in sensing applications with single particle sensitivity using fl uorescence correlation spectroscopy. To increase sensitivity for single molecule sensing, we have improved our initial designs and fabrication methods to decrease ARROW background fl uorescence, improve transitions between solid and hollow waveguides, and decrease loss of solid waveguides. Photoluminescence of ARROW layers creates background fl uorescence that masks the desired fl uorescence signals. To improve sensitivity, we have decreased the total background by optimizing the PECVD ARROW layers to minimize the photoluminescence of each layer. Sensing applications require that hollow waveguides interface with solid waveguides on the substrate to direct light into and out of test media. Our previous ARROW designs required light at these interfaces to pass through the anti-resonant layers. Although in theory, high transmission through ARROW layers can be achieved, in practice, passing through these layers has limited transmission effi ciencies. A new design coats the top and sides of the hollow core with only silicon dioxide, allowing light at interfaces to pass directly from silicon dioxide into the hollow core. Initially, our solid core waveguides were formed by etching into the top ARROW layer. These waveguides are limited by the loss inherent in PECVD oxide and surface roughness produced during fabrication. We have investigated new fabrication methods and waveguide materials to reduce the solid core loss and improve the sensitivity of our ARROW sensors.

6883-18, Session 5Three-dimensional recording inside dielectrics for photonic applicationsS. Juodkazis, H. Misawa, Hokkaido Univ. (Japan)

Three-dimensional (3D) structuring of glasses, ceramics, crystals, and polymers by tightly focused femtosecond laser pulses is a promising technique for microfluidic, micro-optical and micro-mechanical applications. Tightly focused laser pulses can reach dielectric breakdown intensity (irradiance) without self-focusing when sub-1 ps pulses are used inside dielectric. Hence, a photo-structuring by 3D tightly focused laser pulses realizes the direct laser writing approch in a well controlled manner. By using objective lens of a high numerical aperture NA > 1 the focal spot size and, consequently, the photo-modifi ed region can be contained within a volume of sub-micrometer cross-sections. The photomodifi cations can range from induced defects, color centers, polymerized voxels, and ultimately voids depending on material, focusing, and pulse energy. Photo-polymerization of 3D photonic crystal templates with photonic stop bands in IR-spectral region will be demonstrated by direct laser writing and holographic recording techniques.

Photo-structuring of glasses and crystals by wet etching of the dielectric breakdown regions will be demonstrated. This opens new material processing routes for inert dielectrics. Altered chemical properties of shock-affected regions inside silica glass, quartz, and sapphire were revealed by wet etching of “shocked” regions in aqueous solution of hydrofl uoric acid. The achievable resolution limits and potential of the fabricated 3D patterns in photonics, microfl uidics, and sensor applications are discussed.

6883-19, Session 5Fabrication of variable effective refractive index artifi cial mediaP. Srinivasan, College of Optics & Photonics/Univ. of Central Florida; E. G. Johnson, The Univ. of North Carolina at Charlotte

Optical properties of periodic structures formed at the sub-wavelength scale differ signifi cantly from those of the bulk materials in which these

structures are formed. Prior research has shown that periodic structures at the sub-wavelength scale possess a polarization sensitive artifi cial effective refractive index. This effective index has been shown to be dependent upon both the duty cycle for a constant period and the period to wavelength ratio. Anti-refl ective structures, beam splitters and polarization converting elements have be conceived and realized by using this optical phenomenon. Recently, broadband blazing using structured media has been demonstrated by using the duty cycle dependent refractive index variation. Fabrications of such devices has largely relied on patterning using electron beam lithography (EBL) - an inherently serial process unsuitable for mass production - and subsequently transfer etching the structures into the desired medium.

In this paper we describe a novel technique for the patterning and fabrication of sub-wavelength structures with the effective refractive index changing across the optic using a combination of additive lithography and analog optics technology that our group has previously developed.3 Exposure characteristic for Shipley 1813 used in this work. By overlaying two binary gratings rotated from each other by 90° in subsequent exposures at the bias value, a two dimensional array of holes is created. The resist in any hole of the array is now exposed about three quarters of the way to full exposure. By using an analog intensity profi le generated from a phase mask, the resist exposure is saturated. The exposure is tailored such that the point of least intensity will still completely expose the photoresist in any of the holes in the array. The local size of the opening created upon development is dependent upon the amount of over-exposure. The patterns thus formed are then transfer etched into GaAs using a SiCl4/He plasma process that has a selectivity of 10:1 to Shipley resist. The fabricated structures are 8 μm deep.

As the duty cycle of the holes increases the structure transitions from a hole array to a pillar array since the structure between the holes are all that remain. In order to obtain the effective refractive index dependence upon the fi ll factor, the refl ection from the sub-wavelength grating structure was fi rst calculated by rigorous coupled wave analysis. The index of a homogenous slab that would provide same refl ectivity was then determined theoretically.

6883-20, Session 5Layer-by-layer three-dimensional chiral photonic crystalsG. von Freymann, Forschungszentrum Karlsruhe (Germany); M. Thiel, M. Wegener, Univ. Karlsruhe (Germany)

Periodic chiral dielectric or metallic nanostructures have recently attracted considerable attention because of the possibility of obtaining giant circular dichroism or giant gyrotropy in the optical regime. To date, chiral dielectric structures outperform chiral metallic structures by a large margin regarding losses.

Interesting dielectric candidates are the recently introduced circular-spiral designs - three-dimensional nanostructures of considerable complexity. While it is conceivable that high-quality circular-spiral structures might be fabricated on large areas at low cost via holographic lithography, it would be highly desirable to have blueprints at hand that are accessible by a variety of different approaches suitable for large-area low-cost mass fabrication. Regarding a distinct class of periodic structures, namely photonic-band-gap materials, layer-by-layer approaches such as the famous woodpile structure have proven to be accessible by a large variety of different techniques. Thus, chiral layer-by-layer structures appear to be attractive as well.

We fabricate and characterize polymeric three-dimensional layer-by-layer chiral photonic crystals via direct laser writing in the commercially available photoresist SU-8. The obtained circular dichroism from polarization stop bands is comparable to that of recently demonstrated circular-spiral photonic crystals. For the here presented layer-by-layer chiral photonic crystals, the transmittance in the polarization stop band centered around 1.55 μm wavelength is about 91% for right-handed circular incident polarization (RCP) impinging on a left-handed structure and about 2% for left-handed circular incident polarization (LCP) and the same structure. As expected for ideal structures without unintentional linear birefringence, LCP and RCP interchange for a right-handed structure.



6883-21, Session 5Metallo-dielectric nanophotonic materials via direct laser writing and electroless metallizationS. M. Kuebler, Y. Chen, A. Tal, College of Optics & Photonics/Univ. of Central Florida

Interest in three-dimensional (3D) metallo-dielectric photonic crystals (MDPCs) has grown considerably given their potential applications in optics and photonics. MDPCs can exhibit intriguing and potentially useful optical properties, including ultra-wide photonic bandgaps, engineered thermal emission, and negative refractive index. Yet experimental studies of such materials remain few because of the difficulties associated with fabricating 3D micron- and sub-micron-scale metallic structures. We report a route to MDPCs based on metallization of a 3D polymeric photonic crystal (PC) fabricated by multi-photon direct laser writing. Polymeric PCs having face-centered tetragonal symmetry and micrometer-scale periodicity were created using a cross-linkable acrylate or epoxide pre-polymer. The resulting PCs were metallized by electroless deposition of silver or copper. Analysis of the metallized structures in cross-section by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy shows that silver deposited conformally onto the entire micro-porous lattice. The dielectric and metallized PCs were characterized by Fourier transform infrared (FTIR) spectroscopy. The polymer photonic crystals exhibit a stop band with strong refl ectance near 4 to 6 microns, depending upon the lattice period. In contrast, FTIR spectra of the metallized PCs show widened stop bands of nearly 6 microns and greater and maximum refl ectance exceeding 90%. The appreciable broadening of the stop band due to the presence of the deposited metal is a result consistent with previously reported theoretical and experimental data for all-metallic 3D PCs. Thus, the approach reported here appears suitable for fabricating 3D MDPCs of many symmetries and basis sets and provides a path for integrating such structures with other micron-scale optical elements.

6883-22, Session 6Low-refractive index materials: A new class of materials for photonic applicationsE. F. Schubert, J. K. Kim, Rensselaer Polytechnic Institute

The refractive index, a most fundamental quantity in optics and optoelectronics, determines many fi gures of merit of optical components such as refl ectors, fi lters, and resonators. Here we present a new class of optical thin-fi lm materials with a very low refractive index. Low-refractive-index thin fi lms (low-n fi lms) are suitable to revolutionize the fi eld of photonics as we know it today. High-quality specular fi lms of optical quality with refractive indices as low as 1.05 are demonstrated. A series of new optical components and devices will be presented, illustrating the usefulness of the low-index materials. For example, we will present a graded-index omni-directional anti-refl ection coating based on low-n materials that virtually eliminates Fresnel refl ection over a broad wavelength range. Whereas conventional anti-refl ection coatings are non-refl ective at only a single wavelength, the graded-index anti-refl ection coatings are non-refl ective over an arbitrarily broad wavelength range. Furthermore, we will present a conductive distributed Bragg refl ector made of only a single material, indium tin oxide. The application of the new material in light-emitting diodes and solar cells will be discussed as well.

6883-23, Session 6Fabrication technology for highly anistropic dielectric structures with special regard to pulse compression applicationsM. K. Bender, C. Schild, H. Heeren, D. Mademann, JENOPTIK Laser, Optik, Systeme GmbH (Germany); T. Lindsey, G. T. Borek, MEMS Op-tical, Inc.; P. W. Weissbrodt, JENOPTIK Laser, Optik, Systeme GmbH (Germany)

The availability of highly effi cient pulse compression techniques is a prerequisite for a large range of applications, including material processing, health care, etc.. Going down to the fs-pulse regime,

compression strategies using gratings, either in transmission or refl ection operation mode, is becoming more attractive.

We report on the fabrication technology of pulse compression gratings in different dielectric materials. Both, transmission as well as refl ection gratings, have been investigated in detail. Specifi cally, highly effi cient dielectric refl ection grating fabrication is challenging since they consist of multilayer dielectric materials featuring novel materials.

In this work both, the lithographic defi nition of the structures as well as the transfer etching techniques have been developed. The defi nition of nanostructures has been carried out via electron beam lithography featuring a high fl exibility with dimensional accuracy. The structure transfer becomes challenging by the introduction of new materials like HfO2 and Ta2O5 and requires process adapted etching strategies.

The results of this fabrication technology development for highly anisotropic nanostructures in different dielectric materials, including their effects on the optical performance in pulse compression grating applications will be presented and discussed.

6883-24, Session 6A new approach for antirefl ective fused-silica surfaces by statistical nanostructuresM. Schulze, H. Fuchs, E. Kley, Friedrich-Schiller-Univ. Jena (Germany); A. Tünnermann, Fraunhofer-Institut für Angewandte Optik und Fein-mechanik (Germany) and Friedrich-Schiller-Univ. Jena (Germany)

The deposition of multilayer-coatings is a commonly used technology for the fabrication of antirefl ective surfaces. However, antirefl ective coatings are limited in terms of angle acceptance of the incident light and application to pre-structured surfaces such as gratings or holograms. For those special requirements new methods are in demand. Nanostructured surfaces, so-called motheye structures, act as a broadband antirefl ective surface as well. But the creation of such sub-wavelength structures is still a challenging issue. In this work we present a new technique in order to create antirefl ective surfaces with the help of statistical nanostructures on fused silica. A specifi c plasma etching process was found to serve this purpose, as thereby nanostructures are created through self-masking. Therefore, aluminum has to be present in the etching chamber. During the etching process aluminum is a source for microcontaminations. The reaction of aluminum and fl uorine provided by the etching chemistry, ion sputtering and polymer generation lead to those contaminations. Under specifi c etching conditions the contaminations create nanostructures on the surface. In this way lateral structures with dimensions down to 20 nm, which act as an antirefl ective nanostructure, can be achieved. Structures created in this way raise the transmission of fused silica in the wavelength range from 370 nm to 500 nm to more than 99.5%. Within the close UV range (from 200 nm up to 400 nm) the transmission can be raised by 4.8% to 97.1% on average. Hydrocarbons adsorbed during the process of deterioration of a sample as well as mechanical infl uence reduce the transmission degree. However, the adsorption of hydrocarbons can be diminished by means of a temperature treatment.

6883-25, Session 6Grayscale homogenizers in calcium fl uorideJ. S. Lawrence, L. R. Simmons, J. G. Smith, A. Stockham, G. T. Borek, MEMS Optical, Inc.; M. Cumme, R. Kleindienst, JENOPTIK Laser, Optik, Systeme GmbH (Germany)

Standard UV materials, such as ArF-grade fused silica, have impurities that lead to low transmittance, high absorption, and fl uorescence when exposed to high irradiance. Due to its low defect density and high transmission in the deep UV regime, calcium fl uoride (CaF2) is a promising material for use as an optical diffuser for applications at 157nm, 193nm, and 248nm. In this paper, we discuss our method for fabricating Gaussian homogenizers in calcium fl uoride using a grayscale photolithography process. Refractive microlens array homogenizers and Gaussian generators have been fabricated in CaF2 and tested at 193nm for effi ciency and uniformity. Using an excimer laser, uniformity results were obtained for cylindrical lens arrays in tandem and crossed to observe the homogeneity in an imaging confi guration and for producing




a square output. Effi ciency, uniformity, and zero order measurements are provided for the Gaussian generators.

6883-26, Session 6Spectroscopic ellipsometry characterization of silicon/silicon-dioxide superlattices for photoluminescence and electroluminescenceT. Creazzo, L. M. Prather, B. Redding, S. Shi, D. W. Prather, Univ. of Delaware

Silicon based light emitting materials are of particular interest for integrating electric and photonic devices into an all-silicon platform. The progress of nano-scale fabrication has led to the ability to realize silicon emitters based on quantum confi nement mechanisms. Quantum confi nement in nano-structured silicon overcomes the indirect bandgap present in bulk silicon allowing for radiative emissions. Silicon/silicon dioxide superlattices employ two-dimensional confi nement leading to light emission. Strong photoluminescence (PL) has been demonstrated in Si/SiO2 superlattices, confi rming the presence of quantum confi nement effects. Our super lattice structures are grown using plasma enhanced chemical vapor deposition (PECVD) with alternating layers of silicon and silicon dioxide. Sub-10 nanometer periods are confi rmed via transmission electron microscopy (TEM) and x-ray reflectivity (XRR) studies. However, consistent and predictable PL and electroluminescence (EL) relies on precise measurement and control of the deposition process. Spectroscopic ellipsometry (SE) offers a non-destructive extremely sensitive method of optical characterization which provides us with the required control. We present characterization of our superlattice structures using spectroscopic ellipsometry. The ellipsometer allows us to measure optical properties of the individual layers of ultra-thin silicon and silicon dioxide. Using the obtained material properties, we generate deposition rate curves for very specifi c PECVD recipes and apply this information to further SE characterization and modeling of multi-period superlattice structures. The fi nal characterization allows us to confi rm measurements taken previously via TEM and XRR.

6883-36, Poster SessionA fabrication technique for microlens array with high fi ll-factor and small radius of curvatureH. Hsieh, G. J. Su, National Taiwan Univ. (Taiwan)

In this paper, we propose a technique for microlens array (MLA) fabrication based on lithography and thermal refl ow process. There are only one photo mask and two opposite tone PR to complete full process. The boundary of MLA is fi rstly defi ned by a thin negative photoresist (PR) layer. Then, the second thick PR cylinders are patterned inside the microholes defi ned by the fi rst PR layer. MLA is formed after heating. In the past process, the gaps between the thick PR cylinders are large due to the diffraction effect. So, the fi ll-factor is low. To increase the fi ll factor, some residual PR between the cylinders makes the PR fl ow outward. But the PR cylinders merge together easily at inaccurate refl ow time and temperature distribution. It results in small radius of curvature and poor uniformity. These are critical for large area application such as LCD backlighting. In our experiment, the fi rst thin PR becomes a limiting wall, no cylinders merge together even over refl owing. Therefore, both the uniformity and the radius of curvature can be well controlled. Besides, the gap is small and the fi ll-factor is very high due to the diffraction effect is not signifi cant at fi rst thin PR layer. The results showed that the 50 μm pitch MLA with only 2 μm gap in hexagonal arrangement. The focal length is 50 μm and the radius of curvature is 28 μm calculated by a replicate transparent polymer MLA thin fi lm under microscope and bottom emitting light.

6883-37, Poster SessionDesign of axially superresolving phase pupil fi lter for high-numerical aperture applicationsT. Jabbour, S. M. Kuebler, College of Optics & Photonics/Univ. of Central Florida

The method of generalized projection was used to design a phase pupil

fi lter that produces in the non-paraxial regime an axially superresolved point-spread-function (PSF) with controlled side-lobe intensities. The resulting phase pupil fi lter has a binary 0/pi eleven-zone rotationally symmetric profi le. The fi lter can axially narrow the PSF central lobe by 29% while maintaining the side-lobe intensity at or below 52% of the peak intensity. Although the fi lter’s performance is satisfactory in theory, it can be greatly compromised by imperfections introduced during experimental implementation. Such imperfections include fabrication errors, surface quality variation, and optical misalignment. A model based on Wolf’s electromagnetic diffraction integrals was used to simulate and quantitatively analyze the effect of these imperfections on the axially superresolved PSF.

6883-38, Poster SessionExperiments and characterization of two photon polymerization using 1 KHz femtosecond laser systemP. S. Shiakolas, N. Uppal, The Univ. of Texas at Arlington

Two Photon Polymerization (2PP) is a powerful technique to fabricate 2-D and 3-D microstructures by focusing ultrashort pulses inside the polymer resin containing photo initiator. By scanning the focused laser beam in bulk resin, an arbitrary complex three dimensional pattern can be fabricated with micrometer resolution. This work presents an attempt to fabricate microstructures using 2PP with a Ti:sapphire femtoseond laser working at 800 nm with a pulse width of about 100 fs. The maximum pulse repetition rate of the laser system is 1 KHz, which is much smaller as MHz systems are normally used for polymerization process. Also, dry lenses have been used instead of oil immersion lenses and this makes characterization of the fabrication process different then previously published research in this area. Characterization experiments are performed on commercially available acrylate monomer and photoinitiator. The polymerization threshold and damage threshold of the monomer is evaluated. Voxel size is also measured experimentally and its relationship with varying input power and photoinititor concentration is identifi ed. Also the effect of self focusing and fi lament formation on the fabricated microfeatures is presented.

6883-39, Poster SessionEnhancing direct-write laser control techniques for bimetallic grayscale photomasksG. H. Chapman, J. M. Dykes, C. Plesa, Simon Fraser Univ. (Canada)

Novel grayscale photomasks are being developed consisting of bimetallic thin-fi lms of Tin on Indium (Sn/In) with optical densities (OD) ranging from ~3.0OD to <0.22OD. To create precise 3D microstructures such as microlenses, the mask’s transparency must be fi nely controlled for accurate gray level steps. To improve the quality of our direct-write masks, the design of a feedback system is presented where the mask’s transparency is measured and used to adjust the writing process while making the mask. The feedback would account for local variations in the fi lm and enhance the control over the mask’s transparency such that >64 gray level masks become possible. An application of the feedback system is towards the production of beam-shaping masks. When placed in the unfocussed path for the writing system, they improve the consistency of the grayscale patterns by altering the laser to have a more uniform “top-hat” distribution. To quantitatively analyze the consistency improvement offered by beam-shaping masks, an iterative approach is used where one beam-shaping mask is used to manipulate the laser while patterning the next. On each iteration, test patterns of the same transparency are written and measured. The feedback system aids the production of beam-shaping masks since the processes of writing, verifying, and using the mask are all performed with the same wavelength. In developing the feedback system, two methods were examined for verifying grayscale patterns. The fi rst utilizes the writing system’s focused beam along with two photodiode sensors; the second utilizes image analysis techniques on lower resolution microscope images.



6883-40, Poster SessionFabrication of 3D polymer photonic crystals for near-IR applicationsP. Yao, L. Qiu, S. Shi, G. J. Schneider, D. W. Prather, Univ. of Dela-ware; A. S. Sharkawy, E. J. Kelmelis, EM Photonics, Inc.

Photonic crystals have stirred enormous research interest and became a growing enterprise in the last 15 years. Generally, PhCs consist of periodic structures that possess periodicity comparable with the wavelength that the PhCs are designed to modulate. If material and periodic pattern are properly selected, PhCs can be applied to many applications based on their unique properties, including photonic band gaps (PBG), self-collimation, super prism, etc. Strictly speaking, PhCs need to possess periodicity in three dimensions to maximize their advantageous capabilities. However, many current research is based on scaled two-dimensional PhCs, mainly due to the diffi culty of fabrication such three-dimensional PhCs.

Many approaches have been explored for the fabrication of 3D photonic crystals, including layer-by-layer surface micromachining, glancing angle deposition, 3D micro-sculpture method, self-assembly and lithographical methods. Among them, lithographic methods became increasingly accepted due to low costs and precise control over the photonic crystal structure. There are three mostly developed lithographical methods, namely X-ray lithography, holographic lithography and two-photon polymerization. Although signifi cant progress has been made in developing these lithography-based technologies, these approaches still suffer from signifi cant disadvantages. X-ray lithography relies on an expensive radiation source. Interferometric lithography lacks the fl exibility to create engineered defects, and multi-photon polymerization is not suitable for parallel fabrication.

In our previous work, we developed a multi-layer photolithography processes that is based on multiple resist application and enhanced absorption upon exposure. Using a negative lift-off resist (LOR) and 254nm DUV source, we have demonstrated fabrication of 3D arbitrary structures with feature size of several microns. However, severe intermixing problem occurred as we reduced the lattice constant for near-IR applications. In this work, we address this problem by employing SU8. The exposure is vertically confi ned by using a mismatched 220nm DUV source. Intermixing problem is eliminated due to more densely crosslinked resist molecules. Using this method, we have demonstrated 3D “woodpile” structure with 1.55μm lattice constant and a 2mm-by-2mm pattern area.

6883-27, Session 7Stretchable polymer photonic crystalsJ. J. Baumberg, Univ. of Cambridge (United Kingdom); O. Pursiainen, Univ. of Southampton (United Kingdom); B. Viel, P. Spahn, T. E. Ruhl, Technische Univ. Darmstadt (Germany)

Structural color in nature arises mostly from optical interference of multiple light paths refl ected inside periodically-textured materials. Natural opals consisting of stacked silica spheres acquire their characteristic iridescence due to Bragg interference from the lattice planes. Here we present here an alternative but industrially-scalable approach that produces low contrast fl exible opals from polymers for structural color applications.[1-4] In contrast to previous methods for producing fl exible opals, large-scale structural assembly is directed by the shear-fl ow alignment of core-shell nano-spheres in a polymer melt. This process additionally allows the localized doping of these opals by incorporation of nanoparticles, which is diffi cult to achieve in other fabrication procedures. Such nanoparticle doping allows the color hue and directionality to be tailored, despite the low relative refractive index contrast between the polymeric components. These crystals exhibit color features not explained by any conventional Bragg diffraction scheme, which is the normal mechanism invoked for the structural colors of butterfl y wings, iridescent beetles or natural opals. Instead, they rely on a new color generation phenomenon arising from resonant scattering events that take place inside the structured environment of the photonic crystal. Our ability to compression mould these fl exible fi lms, and to create emissive quantum-dot-doped polymer opals, anticipates their use in a range of decorative, sensing, security and photonic applications.

Our results also suggest a re-examination of structural color in nature which we believe may exploit the same phenomena.

[1] T Ruhl et al., Polymer 44, 7625 (2003)

[2] OLJ Pursiainen et al., Appl. Phys. Lett. 87, 101902 (2005)

[3] OLJ Pursiainen et al., submitted to Adv Mat. (2007)

[4] OLJ Pursiainen et al., accepted for Opt. Exp. (2007)

6883-28, Session 7Fabrication and testing of plasmonic optimized transmission coatingsA. A. Cruz-Cabrera, L. I. Basilio, D. W. Peters, J. R. Wendt, S. A. Kemme, Sandia National Labs.; S. Samora, L&M Technologies, Inc.

We present fabrication and test results from surface-plasmon-based transmissive coating coatings in the MWIR (mid wave infrared) and LWIR (long wave infrared). These coatings are designed to investigate the science of the coupling interaction between photons and plasmons at the metal/air interface. This method offers certain advantages to current coatings technologies such as thin-fi lm stacks and two-dimensional surface structuring (e.g. motheyes) while exploring an entirely different physical mechanism for achieving transmission. Thin fi lms rely on interference between layers of the stack. Many layers are often required for a high-performance coatings. Two-dimensional surface structuring can optimized transmission over a broad spectral and angular domain. Here the physical mechanism is an effective index matching approach from air to the material’s surface consisting of tall pyramids. These pyramids must have a high-aspect ratio, resulting in a surface of many tall thin fi ngers of materials. We created a transmissive surface out of a metal skin perforated with an array of subwavelength holes. The surface resembles that of a frequency selective surface (FSS) common in the microwave regime. Such perforated metal surfaces were predicted to have nearly 100% transmission over a selected wavelength range. This range is tailored by array period, hole size, and hole shape, allowing the designer considerable freedom. Array geometry and aperture shape were investigated for tailoring spectral features.

6883-29, Session 7Fabrication approaches for metallo-dielectric plasmonic waveguidesM. P. Nezhad, Univ. of California/San Diego; S. Zamek, Ben-Gurion Univ. of the Negev (Israel); L. Pang, Y. Fainman, Univ. of California/San Diego

Different techniques for fabricating long-range plasmonic metallo-dielectric waveguides are presented. Techniques such as casting for elastomeric claddings and wafer bonding for semiconductor claddings are discussed.

6883-30, Session 7Bottom-up tailoring of photonic nanofi bersF. Balzer, M. Madsen, H. Rubahn, Syddansk Univ. (Denmark)

The bottom up design of ensembles of organic nanowires on dielectric substrates has to led to a number of promising nanophotonic devices within the last few years. Within that are organic nanolasers [1], waveguides [2], and nanoscopic frequency doublers [3] from phenylenes, thiophenes, and phenylene-thiophene cooligomers. The self-assembly process of these conjugated organic molecules, especially in combination with stamping techniques [4], is an attractive way of producing huge amounts of organic nanofi bers. Depending on the combination substrate/organic molecules either one, two, or three simultaneous growth directions are accessible. Isolated nanofi bers are also accessible by, e.g., a liquid assisted transfer process. However, for basic research as well as for morphologically tailored devices a more direct control of the fi bers growth is desirable. For instance easily adjustable mutual distances between the wires or even the growth of upright needles instead of lying ones are demanding features. For these purposes, nanowire assembly from phenylenes on micro- and nanostructured substrates is explored. Mesoporous alumina substrates


as well as microfabricated grating structures on silicon are used to steer the needle formation into the demanded directions. Possible applications will be discussed.

[1] F. Quochi, F. Cordella, A. Mura, G. Bongiovanni, F. Balzer, and H.-G. Rubahn, Appl. Phys. Lett. 88 (2006) 041106.

[2] F. Balzer, V.G. Bordo, A.C. Simonsen, and H.-G. Rubahn, Phys. Rev. B 67 (2003) 115408.

[3] J. Brewer, M. Schiek, A. Lützen, K. Al-Shamery, and H.-G. Rubahn, Nano Lett. 6 (2006) 2656.

[4] J. Brewer, H. Henrichsen, F. Balzer, L. Bagatolli, A.C. Simonsen, H.-G. Rubahn, Proc. SPIE 5931 (2005) 250.

6883-31, Session 8Highly dispersive dielectric transmission gratings with 100% diffraction effi ciencyT. Clausnitzer, T. Kämpfe, F. Brückner, R. Heinze, E. Kley, Friedrich-Schiller-Univ. Jena (Germany); A. Tünnermann, Fraunhofer-Institut für Angewandte Optik und Feinmechanik (Germany) and Friedrich-Schil-ler-Univ. Jena (Germany)

Due to the rapid progress in high-power laser systems, there is an increasing demand for highly effi cient damage resistant components. One decisive role in the power limitation of such systems, e.g. chirped pulse amplifi cation setups, is played by the grating pair, which is used to recompress the amplifi ed optical pulses. In order to achieve pulse peak powers in the megawatts range, these gratings have to be dielectric. Up to now, one of the main drawbacks of transmission gratings was the problem of signifi cant refl ection losses in the case of high dispersion and grazing incidence. These losses are typically in the range above 10% for grating periods near half of the wavelength. However, we have developed a simple grating layout, which can be optimized to avoid any refl ection losses, thus achieving theoretically 100% diffraction effi ciency in the highly-dispersive -1st diffraction order, when the grating is illuminated in Littrow-mounting. In this layout a rectangular surface relief grating is etched into a fused silica substrate and afterwards covered by a second silica substrate. By optimizing the geometrical parameters of this embedded grating, the refl ection can be suppressed completely, while simultaneously all the transmitted light is defl ected to the -1st order. Samples were fabricated utilizing electron-beam lithography, dry etching and fused silica anodic bonding, which resulted in mechanically stable and highly effi cient gratings. By covering a surface relief grating an improvement of the diffraction effi ciency up to 98% was measured, in contrast to 82% compared to its conventional surface relief counterpart. These gratings are, thus, ideal devices for high laser-power setups, where highest effi ciency and resistance against laser-induced damage are required. They are, furthermore, protected against dust and mechanical damages like scratches.

6883-32, Session 8Spiral zone plate imaging for soft x-ray microscopyA. E. Sakdinawat, Y. Liu, Univ. of California/Berkeley

Phase sensitive x-ray microscopy techniques are important in the study of samples that exhibit phase contrast. One way to detect these phase effects is to optically implement the radial Hilbert transform by using spiral zone plates (SZPs), which results in the isotropic measurement of the amplitude and phase gradient in a sample. This is similar to differential interference contrast imaging in light microscopy. Soft x-ray microscopy using a SZP as a single element objective lens was demonstrated through the imaging of a 1 μm circular aperture at a wavelength of 2.73 nm (454 eV). A regular zone plate, a charge 1 SZP, and a charge 2 SZP were fabricated on a silicon nitride membrane using electron beam lithography. The negative e-beam resist hydrogen silsesquioxane (HSQ) was used for patterning, and the zone plates were electroplated with nickel. These zone plates were then used as the imaging optic in a soft x-ray microscopy setup. The charge 1 and charge 2 SZP images exhibited isotropic edge enhancement as a result of radial Hilbert fi ltering.


6883-33, Session 8Tailored surfaces for managing thermal emission: plasmon/photon coupling using subwavelength diffractive optics technologyS. A. Kemme, A. A. Cruz-Cabrera, R. A. Ellis, D. W. Peters, T. Carter, S. Samora, Sandia National Labs.

We will present simulations, fabrication techniques, and measurements of a technology that can manipulate thermal angular and wavelength emission. This work is representative of Sandia National Laboratories’ efforts to investigate advanced technologies that are not currently accessible for reasons such as risk, cost, or limited availability. The goal of this project is to demonstrate a passive thermal emission management surface that can tailor the direction of emission as well as the wavelength bands of emission.

This new proposed technology enables thermal emission pattern management by structuring of the surface on a subwavelength scale. This structuring may be in either the lateral or depth dimension. A lateral structuring consists of a shallow grating on a metal surface. This air/metal interface allows photon/plasmon coupling, which has been shown to coherently and preferentially emit at certain wavelengths.

Any material radiates energy, which is a function of its temperature, and so can be called a thermal source. A thermal source is typically viewed as noise to be eliminated; but this emission is diffi cult to manage as it is incoherent and quasi-isotropic with radiation exiting the surface at every angle. The radiation pattern emitted by the surface is broadband, Lambertian, and not easily directed. If the thermal radiation was instead coherent, then the angular emission could be directed into desirable lobes, as in antenna patterns, allowing control of the largely infrared emission.

6883-34, Session 8100% refl ectivity from a monolithic dielectric microstructured surfaceF. Brückner, H. Hartung, T. Clausnitzer, E. Kley, Friedrich-Schiller-Univ. Jena (Germany); A. Tünnermann, Fraunhofer Institut für Angewandte Optik und Feinmechanik (Germany) and Friedrich-Schiller-Univ. Jena (Germany)

Commercially available highly-refl ective dielectric devices are commonly built of multilayer stacks containing at least two different layer materials. For special applications these dielectric stacks can appear as a drawback due to the complex alternating coating technique, the laser induced damage threshold or the substrate deformation caused by the layer thickness. Alternative mirror/fi lter setups are known as so-called corrugated waveguides usually exhibiting narrowband phenomena. Utilizing the resonant behavior of light coupling of a micro-structured high index layer attached to a low index substrate (e.g. resonant waveguide grating) high refl ectivity can be achieved. However, besides the micro-structuring process at least one residual coating step is involved for the fabrication of such elements. In this work we propose a new mirror architecture based on a monolithic dielectric micro-structured surface. Hence, no prior coating process is needed, which promises a signifi cant increase of the laser induced damage threshold of the mirror device and simultaneously a decrease of the substrate tension. By specifi cally structuring the monolithic surface resulting in T-shaped ridges of a sub wavelength grating a resonant behavior of light coupling can be realized leading to theoretically 100% refl ectivity. Moreover, our approach enables us to properly control the surface refl ectivity in terms of polarization dependency by means of parameter tuning. Concerning this matter, we will give a short intelligible explanation of the light propagation processes within the grating region, which is closely associated to the effective media theory and the functionality of corrugated waveguides. Systematic design considerations as well as potential manufacturing techniques will be presented including proof-of-principle samples in silicon and lithium niobate.



6883-35, Session 8Coherent thermal-source formed by periodic microcavitiesN. Dahan, A. Niv, G. Biener, Y. Gorodetski, V. Kleiner, E. Hasman, Technion-Israel Institute of Technology (Israel)

An extraordinary coherent thermal emission from an anisotropic microstructure is experimentally and theoretically presented. The enhanced coherency is due to coherent coupling between resonant cavities obtained by surface standing waves, where each cavity supports a localized fi eld that is attributed to coupled surface phonon-polaritons. We show that it is possible to obtain a polarized quasi-monochromatic thermal source from a SiC microstructure with a high quality factor Q ~ 600 at the resonant frequency of the cavity, and a spatial coherence length lc ~ 760λ which corresponds to angular divergence of 1.3mrad.


Conference 6884: Reliability, Packaging, Testing, and Characterization of MEMS/MOEMS VIIMonday-Tuesday 21-22 January 2008 • Part of Proceedings of SPIE Vol. 6884 Reliability, Packaging, Testing, and Characterization of MEMS/MOEMS VII

6884-01, Session 1Understanding and Improving Longevity in RF MEMS Capacitive SwitchesC. Goldsmith, D. Forehand, D. Scarbrough, MEMtronics Corp.; Z. Peng, C. Palego, J. C. M. Hwang, Lehigh Univ.; J. O. Clevenger, Exponent Inc.

Capacitive switching technology possesses many benefi ts over both conventional electronic switching devices and ohmic-contact MEMS switches at microwave and millimeter-wave frequencies. These benefi ts include a very high fi gure of merit, low effective on-resistance, reliable hot-switched operation, miniscule power consumption, and ultra-high linearity. To date, the lifetime limiting mechanism within capacitive switching has been dielectric charging of the switch insulator. This has limited the cycle lifetimes and continuous “on” operation of these switches.

Recent advancements in our understanding of dielectric charging are paving the way to improved device operation. Developments in electronic characterization have demonstrated that transient current spectroscopy can be effectively used to characterize the charging phenomenon within MEMS capacitive switches. Using the appropriate charge models, relevant characteristics of the charged carriers can be extracted, including such important characteristics as carrier lifetimes and densities as a function of voltage and temperature.

This improved understanding of the charging phenomena enables improved switch designs which reduce the amount of dielectric charging and ensure suffi cient restoring force to overcome stiction due to charging. Strategies for improving capacitive switch lifetime include 1) reducing operating bias voltages, 2) incorporating electrical designs which trade capacitance ratio for lifetime (typically achieved through a change in the dielectric to air ratio), and 3) innovative materials development.

This presentation overviews the challenges, successes, and failures associated with the quest to improve capacitive RF MEMS switch lifetime. Data featuring lifetime demonstrations over 100 billion cycles will be included.

6884-02, Session 1Experimental study of electrical breakdown in MEMS devices with micrometer scale gapsP. Carazzetti, Ecole Polytechnique Fédérale de Lausanne; P. Renaud, H. R. Shea, Ecole Polytechnique Fédérale de Lausanne (Switzerland)

This paper presents a study of DC breakdown between electrodes fabricated with MEMS technology in several different gases as a function of gas pressure P. Unlike most published work where the objective is to avoid breakdown, the emphasis of this research is to identify geometries that favor the creation of low-voltage discharges. Interdigitated aluminum electrodes with gaps d ranging from 6 to 500 micron are fabricated on insulating substrates. A variety of geometries were studied, including smooth fi ngers, suspended fi ngers, as well as fi ngers with serrated edges to increase the fi eld strength and hence lower the voltage needed for breakdown.

Aluminum fi lms up to 8 micron-thick are sputter deposited on glass wafers and patterned with an anisotropic ICP dry-etch. Partially suspended structures to decouple the device from the substrate are fabricated using a highly selective process based on the release of a sacrifi cial 6 micron-thick SiO2 layer by HF vapor phase etch.

The breakdown voltage U_bd is recorded as a function of gas type (Ar, He, N2 and air) and pressure (1 to 600 mbar) for different geometries, and is plotted as a function of the P*d product. The experimental curves follow a Paschen-like behavior over a P*d range from 10 to 10^5 mbar*micron. The lowest U_bd values in Argon are obtained for electrodes with serrated patterns and range from 208 V to 227 V. Electrodes with smooth edges exhibit signifi cantly higher U_bd values, over 245 V. Results for different gases will be presented.

6884-03, Session 1Degradation evaluation of microelectromechanical thermal actuatorsJ. K. Luo, Univ. of Bolton (United Kingdom); Y. Fu, J. A. Williams, Univ. of Cambridge (United Kingdom); S. M. Spearing, Univ. of South-ampton (United Kingdom); W. I. Milne, Univ. of Cambridge (United Kingdom)

Metal-based thermal-actuators have many advantages over Si-based ones owing to their operation temperature. However, they suffer from degradation at a much lower temperature and have a much shorter lifetime.

The planar thermal actuators were made of electroplated Ni on a Si substrate, were then released by SF6 plasma etch. The hot and cold arm lengths were 400 and 60μm, respectively and the width 6μm. The microactuators deliver a maximum displacement of ~20μm at an average temperature of ~450‚°C, much lower than that of Si-based actuators for the similar displacement. However Ni-actuators showed a severe back bending, which increases with the applied current. The displacement increases with temperature, and then decreases as the temperature increases further. The average temperature to initiate the back bending was found to be as low as ~150‚°C, and the back bending reaches the maximum at ~450‚°C.

SEM investigation reveals an evaluation of degradation along the hot arm of the actuators. The surfaces of the top part near the cold areas remain almost unchanged from the as-made ones. As approaching the middle of the hot arm, the surface becomes rough, and bulky structures are visible, whereas the middle part of the arm becomes round, a direct evidence of melting and re-growth of Ni. EDX analysis confi rmed severe oxidation with the O/Ni ratio near ~50% at the middle of the hot arm, indicating the occurrence of oxidation deep inside the Ni beam, rather than at the surface. These results have clearly shown that degradation of the thermal actuators is mainly caused by oxidation and material-refl ow.

6884-04, Session 1An integrated AFM/Raman tool for local stress measurements of MEMS devicesA. Lewis, R. Dekhter, Nanonics Imaging Ltd. (Israel); N. Axelrod, The Hebrew Univ. of Jerusalem (Israel); A. Khatchatouriants, Nanonics Imaging Ltd. (Israel)

Microelectromechanical (MEMs) devices are composed of silicon structures of various geometries and forms. These forms could extend from fl oating structures to bridges and membranes. Raman microspectral analysis has been recognized for many years as a tool that could monitor local stress in silicon. The local silicon stress that has been monitored in the past by Raman spectroscopy has in general been a result of thermal oxidation, wafer thinning, and chip bonding. Atomic force microscopy (AFM) has also been used for many years for characterizing MEMs structures. Although numerous papers have been published with each of these tools on these devices the world of AFM and Raman have been separate and apart. In this presentation we will describe the fi rst tool that combines the uniqueness of AFM for mechanical characterization with the capability of Raman to measure the chemical characteristics associated with local and highly defi ned silicon stress.

For this application of the integration of the worlds of defi ned and local AFM stress with Raman analysis of such stress we have developed a singular atomic force microscope (Nanonics Imaging Ltd. MultiView 1000 SPM System). This is the fi rst such microscope that can be combined with any upright optical microscope for the analysis of opaque structures with AFM and Raman simultaneously.

An essential aspect of this combined system is the AFM probe that is used in these measurements. AFM cantilevers have a signifi cant silicon background Raman signal that would prevent the measurements described in this presentation. Nanonics has developed glass AFM cantilevers that not only are the fi rst AFM cantilevers to permit a clear view of the tip of the probe by the on-line optical microscope but also


do not have any Raman background.

With such a combination of an AFM platform fully integrated into a conventional upright microscope complexed to a state of the art Renishaw PLC InVia Raman spectrometer defi ned measurements of local strain in silicon MEMs devices can be monitored. This presentation will demonstrate such AFM defi ned Raman spectral analysis. The results indicate a variety of interesting phenomena such as hysteresis, wear etc.

6884-05, Session 2FIB sectioning and imaging on the micron to nanometer scale and it’s application to MEMSM. W. Phaneuf, Fibics Inc. (Canada)

Abstract not available

6884-06, Session 2Development of nondestructive testing/evaluation methodology for MEMSJ. L. Zunino III, D. R. Skelton, U.S. Army Armament Research, Devel-opment and Engineering Ctr.; R. T. Marinis, A. R. Klempner, P. Hefti, R. J. Pryputniewicz, Worcester Polytechnic Institute

Development of MEMS constitutes one of the most challenging tasks in today’s micromechanics. In addition to design, analysis, and fabrication capabilities, this task also requires advanced test methodologies for determination of functional characteristics of MEMS to enable refi nement and optimization of their designs as well as for demonstration of their reliability. Until recently, this characterization was hindered by lack of a readily available methodology. However, using recent advances in photonics, electronics, and computer technology, it is possible to develop a NonDestructive Testing (NDT) methodology suitable for evaluation of MEMS.

In this paper, an optoelectronic methodology for NDT of MEMS is described and its application is illustrated with representative examples. This methodology provides quantitative full-fi eld-of-view measurements in near real-time with high spatial resolution and nanometer accuracy. By quantitatively characterizing performance of MEMS, under different vibration, thermal, and other operating conditions, specifi c suggestions for their improvements can be made. Then, using the methodology, we can verify the effects of these improvements. In this way, we can develop better understanding of functional characteristics of MEMS, which will ensure that they are operated at optimum performance, are durable, and are reliable.

6884-07, Session 2Measurement of thin fi lms and interfacial surface roughness using SWLIM. Conroy, Taylor Hobson Ltd. (United Kingdom)

Introduction

The use of scanning white light interferometry (SWLI) to analyse thin fi lms is becoming more and more widespread as understanding of the measurement increases. Techniques for measurement of thick fi lms of 1.5 micrometres or greater using interferometry have been available for a few years now but measurement of thinner fi lms using interferometry is a much newer possibility. Other measurement possibilities such as interfacial surface roughness are now becoming a possibility.

Thick and Thin Film Analysis

When we have a transparent or semi transparent fi lm coating on a surface it is possible to measure the thickness of the fi lm using SWLI if the fringe envelopes arising from the two surfaces can be resolved. This limits the thinnest fi lms that can be measured with any confi dence to between 1-2 microns depending on the refractive index of the fi lm. When the fi lm is too thin for the individual fringe envelopes to be resolved a different approach has to be used. One solution is the application of a helical conjugate fi eld (HCF) function to the raw data in order to extract information about the thin fi lm coatings. This technique, in combination

with knowledge of some of the optical properties of the materials is able to analyse thin fi lms down to at least about 20 - 30 nm.

Interfacial Surface Roughness

Application of the HCF function to SWLI can also be used to extract interfacial surface roughness. This includes analysis of the top surface and other types of interface between thin fi lms and substrates.

6884-08, Session 2Reliability of MEMS devices in shock and vibration overload situationsS. Kurth, Fraunhofer-Institut für Zuverlässigkeit und Mikrointegration (Germany); A. V. Shaporin, K. Hiller, C. Kaufmann, Technische Univ. Chemnitz (Germany); T. Gessner, Fraunhofer-Institut für Zuverlässig-keit und Mikrointegration (Germany)

Since MEMS penetrate the world of consumer and automotive products more and more, a lot of effort is made to protect the devices from mechanical overload of sensitive parts like elastic suspensions or hinges by mechanical stoppers, adequate dimensions, shape and gas damping. Even though numerical analysis is utilized for overload capability prediction, comprehensive tests are necessary in every case. Various standards for shock and random vibration capability defi ne the margins for conventional devices and instruments. However, MEMS devices show higher resonant frequencies and lower damping of its inner parts in contrast to conventional ones which results in different overload behaviour. Hinge damages as result of simple handling mistakes are to be observe in spite of the fact that this devices passed half sine 1000g 1ms shock tests for instance. This contribution describes the investigation of the reasons for failure based on linear vibration theory by superposition of resonant mode reaction to the overload and on observation of the reaction in time domain in case that linearity can not be assumed. The behaviour due to vibration load is analysed by scanning laser Doppler interferometer and stroboscopic video microscopy at loads leading to failure of the structure on the example of laser scanners and Fabry-Perot-Interferometer based tuneable infrared fi lters. It gives information about week parts of the structure and fi nite element analysis is applied for an approach to optimise the stress distribution in order to enhance the overload capability. The optimisation is verifi ed on the example of a micro scanner.

6884-29, Session 2Mechanics of post initiation stiction repair of microcantilevers using structural vibrationsA. A. Savkar, K. D. Murphy, Univ. of Connecticut

Recently it has been shown that structural vibrations are an effi cient means to repair stiction failed microcantilever beams. Experiments and analysis have identifi ed excitation parameters (amplitude and frequency) that successfully initiated the debonding process between the microcantilever and the substrate. That analysis could not describe what happened after the debonding process was initiated. For example it could not predict if the beam would transition from a s-shaped to an arc-shaped confi guration or even be repaired to a free-standing beam. The current research examines the post-initiation behavior of stiction failed microcantilever beams. A new-coupled fracture/vibration model is formulated and used to track the evolution of the repair in order to determine the extent of repair under various conditions. This model successfully explains phenomenological observations made during the experiments regarding the repair process being dependent on direction of frequency sweeps, complete and partial repair, and effect of frequency tracking. The study monitors the degree of repair - no repair, partial repair or complete repair along with releases time associated with such repairs.

6884-09, Session 3A perspective on the reliability of MEMS-based components for telecommunications (Keynote)J. C. McNulty, DfR Solutions LLC

Conference 6884: Reliability, Packaging, Testing, and Characterization of MEMS/MOEMS VII



Despite the initial skepticism of OEM companies regarding reliability, MEMS-based devices are increasingly common in optical networking. This presentation will discuss the use of MEMS devices in a variety of network applications, from tunable transponders, fi lters, and receivers to variable optical attenuators, wavelength selective switches, and optical switches. The failure mechanisms of these devices will be addressed in terms of reliability physics, packaging methodologies, and process controls, with differentiation between the occurrence and mode of failures observed during production and in extended fi eld use. Typical OEM concerns and requirements will also be presented, including testing beyond of the scope of conventional Telcordia qualifi cation. The key conclusion is that, with suffi ciently robust design and manufacturing controls, MEMS-based devices are substantially more reliable than many mature and extensively-deployed optical components.

6884-10, Session 3Reliability testing and analysis of MEMS-based safety and arming devices for munition fuzesJ. L. Zunino III, D. R. Skelton, U.S. Army Armament Research, Devel-opment and Engineering Ctr.; C. H. Robinson, U.S. Army Armament Research, Development and Engineering Ctr

To address the lack of MEMS device and packaging reliability data as well as a standardized methodology for assessing reliability, the Army Corrosion Offi ce (ACO) at Picatinny Arsenal has initiated a MEMS Reliability Assessment Program. This lack of data has been identifi ed as a barrier to the utilization the MEMS in DOD systems. Of particular concern are the impacts of long-term storage and environmental exposure on the reliability of devices.

Specifi c objectives of the ACO program include:

• Identifi cation of MEMS devices to be utilized in weapon systems.

• Assessment of the operational environments in which the military MEMS device may be utilized.

• Analyze the compatibility of selected MEMS device materials with energetic and other hazardous materials.

• Identify physics of failure, failure mechanisms, failure rates and develop accelerated test protocols for assessing the reliability of MEMS.

• Develop of reliability models for these devices.

• Conduct testing and modeling on representative devices of interest to Army and DOD.

• Develop a methodology and capability for conducting independent assessments of reliability that cannot be obtained from private industry.

In support of this effort, the components and packaging of the MEMS-based safety and arming (S&A) device for the XM25 Integrated Air Burst Weapon System (IAWS) are being tested. The objectives are to test the S&A as a representative device for the identifi cation of potential failure modes and other effects for devices of the same class. Information derived from this testing will be used to develop standardized test protocols and establish design criteria as well as support the S&A development effort. To date, Environmental Stress Screening (ESS) tests have been performed on the device. Along with the ESS testing, a failure-modes-and-effects (FMEA) analysis has been developed and reliability modeling is under way.

6884-11, Session 3Interferometric characterization of MOEMS devices in cryogenic environment for astronomical instrumentationF. Zamkotsian, E. Grassi, Lab. d’Astrophysique de Marseille (France); S. Waldis, Univ. de Neuchâtel (Switzerland); R. Barette, P. Lanzoni, C. Fabron, Lab. d’Astrophysique de Marseille (France); W. Noell, N. F. de Rooij, Univ. de Neuchâtel (Switzerland)

Next generation of infra-red astronomical instrumentation for space telescopes as well as ground-based extremely large telescopes requires MOEMS devices with remote control capability and cryogenic operation,

including programmable multi-slit masks for multi-object spectroscopy (MOS).

For the complete testing of these devices, we have developed in parallel and coupled a high-resolution Twyman-Green interferometer and a cryo-chamber for full surface and operation characterization. The interferometer exhibits a nanometer accuracy by using phase-shifting technique and low-coherence source. The cryo-chamber has a pressure as low as 10e-6 mbar and is able to cool down to 60K. Specifi c interfaces minimizing stresses for vacuum and cryo have been set.

Within the framework of the European program on Smart Focal Planes, micro-mirrors have been selected for generating MOEMS-based slit masks. A fi rst 5x5 micro-mirror array (MMA) with 100x200μm2 mirrors was successfully fabricated using a combination of bulk and surface silicon micromachining. They show a mechanical tilting angle of 20° at a driving voltage below 100V, with excellent surface quality and uniform tilt-angle. The mirrors could be successfully actuated before, during and after cryogenic cooling. The surface quality of the gold coated micro-mirrors at room temperature and below 100K, when they are actuated, shows a slight increase of the deformation from 35nm peak-to-valley to 50nm peak-to-valley, due to CTE mismatch between silicon and gold layer. This small deformation is still well below the requirement for MOS application.

This coupled interferometric and cryo set-up will be used for full characterization of larger 100x200 MMA, which are currently being fabricated.

6884-12, Session 3Qualifi cation testing of engineering camera and platinum resistance thermometer sensors for MSL project under extreme temperatures to assess reliability and to enhance mission assuranceR. Ramesham, J. N. Maki, G. C. Cucullu, Jet Propulsion Lab.

Package Qualifi cation Verifi cation (PQV) of advanced electronic packaging and interconnect technologies and various other types of qualifi cation hardware for Mars Exploration Rover/Mars Science Laboratory fl ight project has been performed to enhance the mission assurance. The qualifi cation of hardware under extreme cold temperatures has been performed with reference to various project requirements. The fl ight-like packages and subassemblies have been selected for the study to survive three times (3x) the total number of expected temperature cycles resulting from all environmental and operational exposures occurring over the life of the fl ight hardware including all relevant manufacturing, ground operations and mission phases. Qualifi cation has been performed by subjecting above fl ight-like qual hardware to the environmental temperature extremes and assessing any structural failures or degradation in electrical performance due to either overstress or thermal cycle fatigue. Experimental fl ight qualifi cation test results will be described in this presentation.

6884-13, Session 4Measuring MEMS through silicon capsM. Hazel, M. S. Karpman, Analog Devices, Inc.

MEMS used in inertial sensors rely on the movement of mechanical elements, generally systems of masses and springs. Shielding these structures from foreign contamination requires that the MEMS elements be inside a cavity. This cavity is typically produced by placing a silicon cap over the MEMS at the wafer level. However, once the device is capped, it is no longer accessible for visual inspection. This creates a unique challenge for product analysis. A challenge which was overcome due to the transmissive properties of infrared light through lightly doped silicon. IR microscopy has allowed for the examination of MEMS through silicon caps, and recently, IR confocal microscopy as been adapted for this use as well. This paper reviews the use of conventional IR microscopy in imaging through silicon caps, the limitations of conventional IR microscopy in this application, and the new capabilities afforded by the use of IR confocal microscopy for through cap imaging.


6884-14, Session 4Characterization of microresistance welding with electro-thermal actuator for micro assemblyC. Chang, W. Hsu, National Chiao Tung Univ. (Taiwan)

The principle of resistance welding is based on generating high temperature at contact point due to its high contact resistance while current passing through, which is a common assembly technique in macro scale. However, only very few investigations have been reported in assembling micro structures. Here micro resistance welding with electro-thermal actuator is proposed and experimentally investigated to assembly micro structures.

The proposed micro resistance welding with electro-thermal micro actuator can be described in three steps: 1) Press: Actuator unit pushes two welding units to contact with each other. 2) Hold and Weld: The electrical current passes through the contact joint to perform resistance welding. 3) Release: The actuator unit is released from the welding units. To characterize the infl uence of operation parameters on micro resistance welding, important parameters including contact pressure, contact resistance and applied electrical energy are calibrated. Moreover, the mechanical strength of welded joint is also measured by pulling the welded joint with a probe tip after the successful welding to evaluate the performance of micro resistance welding.

Experimental results indicate that larger pushing force can lead to smaller contact resistance and stronger welding strength. It is also found that the input welding energy is very critical to the success of micro resistance welding. When welding energy is below the threshold limit of 0.05 J, the welding trials all failed. For the welding energy above 1 J, the successful rate can reach 100 %. More detailed design issues and experimental results will be presented in the conference.

6884-15, Session 4Characterization of low-temperature wafer bonding based on Ag-In systemR. I. Made, Institute of Microelectronics (Singapore) and Nanyang Technological Univ. (Singapore); C. L. Gan, Nanyang Technological Univ. (Singapore); C. Lee, National Univ. of Singapore (Singapore) and Institute of Microelectronics (Singapore); L. L. Yan, A. Yu, S. U. Yoon, J. H. Lau, Institute of Microelectronics (Singapore)

Indium-silver multilayer as a solder material for low temperature bonding had been reported by Prof. C. C. Lee at UC Irvin. In theory the fi nal bonding interface composition is determined by the overall materials composition. Multilayer bonding method facilitates precise control of the alloy composition and the joint thickness. Thus the bonding temperature and post bonding re-melting temperature could be designed by controlling the multilayer solder materials. Low temperature bonding and high re-melting temperature feature is necessary in MEMS application. However there had not been much attempt to look into the detail of bonding process in term of bonding time, bonding pressure, and bonding temperature to the fi nal characteristic in term of mechanical strength, re-melting temperature, and hermetic quality. In this paper, a more fundamental study of Ag-In solder materials is carried out. Samples of multiple In and Ag layers bonded at 180°C and temperatures less than 180°C are studied. Bonding interface’s microstructure and composition cross-sections are studied using scanning electron microscopy and energy dispersive X-rays. Cross-section characterization had shown the formation of high temperature melting phase up to 600°C. On contrary to the earlier concept, the result also shows the preference of the solder materials to form a √-phase across different bonding condition. This √-phase forms mostly although the initial design allows for formation of higher melting temperature phase. In practical, this result implied that we can have a wider processing window. From manufacturing points of view, it would allow more tolerances to certain variation of the solder materials composition.

6884-16, Session 4Microfabricated implantable fl owmeterS. Liu, H. C. Lim, New Jersey Institute of Technology; J. L. Zunino III, U.S. Army Armament Research, Development and Engineering Ctr.; R. C. Farrow, G. A. Thomas, J. F. Federici, New Jersey Institute of Technology

An implantable wireless fl ow meter is proposed that would enable measurement of the micro fl ow fl uid through the implantable shunt, currently used to treat hydrocephalus patients. Using MEMS microfabrication methods, the fl ow meter is manufactured at a size small enough to be integrable with implanted shunts. The key elements in the fl ow meter are capacitive structures that change properties with change in fl ow. Radiative coupling between the internal passive circuitry and an external detection circuit allows implantation of the fl ow meter without the need for implanted batteries or transcutaneous wires.

6884-17, Session 4Photosensitive etch protection coating for silicon wet-etch applicationsJ. Dalvi-Malhotra, X. Zhong, C. E. Planje, Brewer Science, Inc.

A spin-on polymeric material has been developed to replace the silicon nitride mask used in the MEMS industry for silicon wet-etch processing. Built-in photosensitivity eliminates need for additional photoresists in the system. The process consists of coating an organosilane primer layer onto a silicon wafer and then applying a layer of photosensitive (ProTEK(r) PS) coating. After a soft bake, the coating is imaged by exposing it to ultraviolet light. After a post-exposure bake, the coating is developed by a solvent. After a fi nal bake, the prepared wafer is then etched in a hot concentrated base solution to complete the pattern transfer. The polymer-coated area remains protected with insignifi cant and controllable undercutting during extended hours of wet etching. The effects of various parameters such as, use of different etchants, effect of etchant concentration and delayed processing on undercutting are investigated.

6884-18, Session 5MEMS as low-cost high-volume semiconductor solutions it’s all in the packaging and assembly (Keynote)J. Brown, M. Lutz, A. Partridge, P. O. Gupta, E. Radza, SiTime Corp.


6884-19, Session 5Measuring mass fl ows in hermetically sealed MEMS & MOEMS to ensure device reliabilityR. C. Kullberg, D. J. Rossiter, Oneida Research Services, Inc.

Many MEMs and MOEMs devices require controlled ambient environments for successful operation. These controlled environments must fi rst be obtained and then maintained to prevent their degradation over the device lifetime. Controlled ambients decay in quality over time due to various mechanisms including poor processing and outgassing of species like hydrogen and water vapor from the interior surfaces of the package surrounding the device. The key to controlling the process of degradation is to understand in a quantitative manner which species are present and their mass fl ow rates into the controlled ambient.

The current work describes a new technique for determining these species and mass fl ow rates. This new technology provides tremendous sensitivity to package volumes < 0.01cc compared to standard quadrupole techniques, which are applicable to samples larger than 0.01 cc. The technology is based on a high speed, high mass resolution, and highly sensitive Time-Of-Flight (TOF) spectrometer to test the tiniest of devices with signifi cant advancement in signal-to-noise ratios. Key operational parameters demonstrated include:

- Spectra Acquisition speed: 1 full spectra every 20 μs.



- Mass Range: mass 2 to 150 standard (2-500 capable)

- Mass resolution: 0.1 AMU

- Calibration Fixtures: 0.0001, 0.0005, 0.001, 0.005 and 0.01 cc

- Sample temperature: 100°C standard (room temperature to 150°C capable)

6884-20, Session 5A new model for vacuum quality and lifetime prediction in hermetic vacuum bonded MEMSA. Bonucci, S. Guadagnuolo, A. Conte, M. Marco, SAES Getters S.p.A. (Italy)

In many MEMs applications the level of vacuum is a key issue as it directly affects the quality of the device, in terms of response reliability. Due to the unavoidable desorption phenomena of gaseous species from the internal surfaces, the vacuum inside a MEM, after bonding encapsulation, tends to be degraded, unless a proper getter solution is applied. The in situ getter fi lm (PaGeWafer(r)) is recognised to be the most reliable way to get rid of degassed species, assuring uniform, high quality, performances of the device throughout the life.

Moreover, post process vacuum quality control and reliability for hermetic bonding is extremely important for overall device reliability and process yield. Process optimization is all the more time consuming and extremely costly for vacuum requirements as it involves extremely accurate and reliable residual gas analyses (RGA) obtained by high level mass spectrometry and vacuum technology competences and insight.

In this paper we will discuss the main factors that are critical in the attainment of vacuum and will present a novel calculation model that enables the prediction of vacuum level after bonding, making also possible the estimate of the lifetime.

The vacuum conditions, as calculated by means of the model, are correlated to experimental data to show the suitability of the tool in optimizing the bonding process and improving the device reliability.

6884-21, Session 5Quantitative characterization of true leak rate of micro to nanoliter packagesB. Han, Univ. of Maryland/College Park

The helium mass spectrometer has been used extensively for qualitative analysis of fi ne leaks. However, qualitative analysis for the small volumes (typically < 10-3 cc) of MEMS packages can lead to completely opposite results during selection process of leaky packages. In addition, the qualitative use of the helium fi ne leak test does not allow comparison of two different packages. Nor can the results be correlated with data from accelerated tests such as 85deg C/85%RH test. These limitations warrant the development of a method to assess hermeticity quantitatively.

This paper proposes a procedure to quantitatively measure the true leak rate of micro to nanoliter packages using the helium mass spectrometer. The proposed method is based on the fact that the profi le of the measured leak rate signal depends only on the true leak rate and the volume of the package. Prior knowledge of the volume of the package enables determination of the true leak rate by performing a weighted non-linear regression analysis of the data.

The method was implemented to measure the true leak rate of a MEMS RF fi lter package. The package was tested under three different test conditions yielding three different signal profi les. The method yielded a consistent value for the true leak rate, which verifi ed the robustness of the method.

The proposed method provides a true leak rate as a quantitative measure of hermeticity. The accurate true leak rates will help evaluate new bonding materials/processes and package designs fast and effectively.

6884-22, Session 5The challenges of designing and processing extreme low-G MEMS accelerometersT. P. Swiler, U. Krishnamoorthy, P. J. Clews, M. S. Baker, D. M. Tanner, Sandia National Labs.

There is an increasing demand to build highly sensitive, low-G, microscale acceleration sensors with the ability to sense accelerations in the nano-G (10-8 m/s2) regime. The high sensitivities and the diffi culty in integrating robust mechanical stops into these designs makes these parts inherently weak and lacking the robustness to survive low level accelerations encountered in standard handling through release processing until the time they are packaged. We fi nd that successful implementation of such sensors requires starting with a clean and robust MEMS design, performing careful and controlled release processing, and designing and executing a robust packaging solution.

6884-23, Session 5Low-temperature vacuum hermetic wafer-level package for uncooled microbolometer FPA’sS. Garcia Blanco, Y. Desroches, H. Jerominek, P. A. Topart, Institut National d’Optique (Canada)

Micro-Electro-Mechanical Systems (MEMS) packaging constitutes most of the cost of such devices. For the integration of MEMS with microelectronics systems to be widespread, a drastic reduction of the overall price is required. Wafer-level-packaging allows a fundamental reduction of the packaging cost by combining wafer-level microfabrication techniques with wafer-to-wafer bonding. To achieve the vacuum atmosphere required for the operation of many MEMS devices, bonding techniques such as anodic bonding, eutectic bonding, fusion bonding and gold to gold thermo-compression bonding have been utilized, which require relatively high temperatures (>300° C) being in some cases incompatible with MEMS and microelectronics devices. Furthermore, to maintain vacuum integrity over long periods of time, getters requiring high activation temperatures are usually employed.

INO has developed a hybrid wafer-level micropackaging technology based on low temperature fluxless solder joints (<185° C). The micropackages have been designed for 160x120 microbolometer FPAs. Ceramic spacers are patterned by standard microfabrication techniques followed by laser micromachining. AR-coated floatzone silicon IR windows are patterned with a solderable layer. Both, microbolometer dies and windows are soldered to the ceramic tray by a combination of solder paste stencil printing, refl ow and fl uxless fl ip-chip bonding. A low temperature getter is also introduced to control outgassing of moisture and CO2 during the lifetime of the package. Vacuum sealing is carried out by locally heating the vacuum port after bake out of the micropackages. In this paper, the vacuum integrity of micropackaged FPA dies will be reported. Base pressures as low as 5 mTorr and equivalent fl ow rates at room temperature of 4x10-14 Torr.l/s without getter incorporation have been demonstrated using integrated micro-pressure gauges. A study of the infl uence of different packaging parameters, such as low-temperature getter incorporation, on the lifetime and reliability of micropackaged 160x120 microbolometer FPA dies will be presented.

6884-24, Session 5DesiPaste(r) for hermetically sealed device packagingM. Erdmann, Sud-Chemie AG (Germany); A. Kirtikar, Sud-Chemie; R. Ramesham, Jet Propulsion Lab.


6884-25, Session 6An electrical approach to measure undercut and fi nal beam thickness in a micromachined cantilever beamS. Bhat, E. Bhattacharya, Indian Institute of Technology Madras (India)

Test structures are necessary to extract device and material properties of micromachined structures since there can be structural changes during



processing. In a surface micromachined cantilever, the gap between beam and the substrate, beam thickness and beam shape can get modifi ed during fabrication. Due to undercut, the beam cross-section gets transformed from rectangular to trapezoidal. Since performance of sensors and actuators strongly depend on the fi nal geometry, it becomes essential that these parameters are measured. We have earlier reported on the determination of the fi nal gap from electrical measurements [1]. This paper discusses an electrical approach to measure the undercut and the beam thickness. Resonance frequency measurement is used to get the undercut and polysilicon resistors are used to get the beam thickness. Measurements are done on oxide anchored cantilever beams of different lengths and widths made of in-situ phosphorous doped polysilicon. Resonance frequency is measured using an electrical technique based on pull-in [2]. For a given length, by fi nding the ratio between measured resonance frequencies for two beam widths, the value of undercut can be determined. We measure an undercut of 2.65 micrometers for polysilicon beams patterned with HNA, an isotropic etchant. The expected undercut from etch rates of HNA is 2.68 micrometer. For the fi nal beam thickness, we measure the resistance of a polysilicon beam before and after release. Ratio of the measured resistance values yields the thickness of the beam after release.

[1] Somashekara Bhat and Enakshi Bhattacharya, Parameter extraction from simple electrical measurements on surface micromachined cantilevers, JMMM, accepted for publication.

[2] Somashekara Bhat and Enakshi Bhattacharya, Simple measurement technique for resonance frequency of micromachined cantilevers, Proceedings of Symposium on Reliability, Packaging, Testing and Characterization of MEMS/MOEMS VI, SPIE Photonics West, January 20 - 25, San Jose, California, USA, 2007, P64630N1-8.

6884-27, Session 6Support for microsystems simulation: Are we watching the clock?C. K. Drummond, ASM International

Modelling of Microsystems devices potentially improves problem understanding, debate over design process pathways and, ultimately, refinement in building blocks to be used in simulations. Despite tremendous advances in computational power, current simulation practice seems to stop short of providing insight on packaging reliability and early life failure. A limiting factor to practical applications tends to be with materials characterization and materials life models. ASM International has completed the fi rst of three phases of a unique database product development effort. Phase 1 modelling was recently completed and focused on Microsystems packaging processes and materials. Phase 2 is now under development and will address the more general case of Microsystems materials and their compatibilities; Phase 3 will extend the materials characterization effort into the nanotechnology domain. Taking a cue from successful genomics research, Kohane, Kho, and Butte (Massachusetts Institute of Technology, 2003) describe the watch metaphor in which microarray expression would transform the discovery of how a watch works from observational studies that are hypothesis validating to interventions tending to be hypothesis generating. In Microsystems simulation research, are we still watching the clock? A materials database can benefi t systems design and simulation efforts, but a phased approach to this undertaking is essential. Case-studies originally intended to validate the database became a surprising component of development strategy. ASM is seeking and welcomes opportunities for collaboration with other research groups as this interdisciplinary project moves forward.

6884-28, Session 6Confocal optical system design with stray light fi lter and scan by DMDY. Fang, National Kaohsiung First Univ. of Science and Technology (Taiwan)

This research proposes a new method to exam the surface quality and microstructure without surface contact. This method indicate that optical system designed in this research collect response of high frequencies from object surface form the image pattern with fast scanning under advanced programming, after being read the image by CCD camera; fi nally calculate then defi ne the curves of the image surface fl uctuation. DMD (digital micro-mirror device) was employed in this research to replace the conventional pinhole array in order to improve the resolution of optical system. System with DMD takes advantage of fast scan, higher contrast and better S/N (ratio of signal to noise) without miscellaneous interference such as astigmatism Due to employment of non-coherent light source in this research, elimination of stray light play the signifi cant role; A newly developed stray light fi lter is introduced in this paper to eliminate its effect, which will effi ciency remove the background noise then enhance image contrast. From the mirror under advanced programming control developed in this research, image’s S/N could be further improvement. Finally, the experimental results shows image contrast ratio of system in this research has been improved up to 60%, which reach great success conclusively.

6884-26, Poster SessionUncertainty analysis on optical testing with a Shack-Hartmann sensor and a point sourceD. W. Kang, J. W. Hahn, J. S. Lee, Yonsei Univ. (South Korea); H. Yang, Korea Research Institute of Standards and Science (South Korea)

Optical testing of high NA optical components to be used in high-density data storage device is important to achieve high resolution and small spot size. We build an optical testing system using a Shack-Hartmann sensor and a pinhole source. A 200-nm-diameter pinhole illuminated by a focused laser beam generates a spherical wave with a large diffraction angle. This spherical wave turns into a plane wave which has some wavefront distortion as it transmits through a testing optic. The wavefront distortion is measured with a Shack-Hartmann sensor to evaluate aberrations of the optical components. In the present work, we analyze the uncertainty in the optical testing system using a Shack-Hartmann sensor for a wavefront measurement device. The main uncertainty sources of the optical testing system are the Shack-Hartmann sensor, the image relay optics, and the pin-hole source. Using a home-made high-precision plane-wave source as a reference, we develop a simple method to calibrate the optics of the system and the Shack-Hartmann sensor itself. It is found the wavefront error of a pinhole source is negligible and that of relay optics installed between the lens under test and the Shack-Hartmann sensor is 0.030 λ (rms). By warming up the Shack-Hartmann sensor about 1 hour, the measurement values are stabilized within 0.001 λ (rms). After calibrating the optical testing system with the reference source, overall uncertainty of the optical testing system is reduced to 0.009 λ (rms). Performance of the optical testing system is evaluated by measuring the wavefront errors of various optical components, such as, a NA 0.23 aspheric lens, a digital video disc pick up lens, a 0.9 NA microscope objective lens.



Conference 6885: MEMS/MOEMS Components and Their Applications V Special Focus Topics: Transducers at the Micro-Nano InterfaceMonday-Tuesday 21-22 January 2008 • Part of Proceedings of SPIE Vol. 6885 MEMS/MOEMS Components and Their Applications V. Special Focus Topics: Transducers at the Micro-Nano Interface

6885-02, Session 2Controlling quantum dynamics phenomenaH. Rabitz, Princeton Univ.

Since the development of the laser some 40 years ago, a long standing dream has been to utilize this special source of radiation to manipulate dynamical events at the atomic and molecular scales. Hints that this goal may become a reality began to emerge in the 1990’s, due to a confl uence of concepts and technologies involving (a) control theory, (b) ultrafast laser sources, (c) laser pulse shaping techniques, and (d) fast pattern recognition algorithms. These concepts and tools have resulted in a high speed instrument confi guration capable of adaptively changing the driving laser pulse shapes, approaching the performance of thousands of independent experiments in a matter of minutes. Each particular shaped laser pulse acts as a “Photonic Reagent” much as an ordinary reagent would at the molecular scale. Although a Photonic Reagent has a fl eeting existence, it can leave a permanent impact. Current demonstrations have ranged from manipulating simple systems (atoms) out to the highly complex (biomolecules), and applications to quantum information sciences are being pursued. In all cases, the fundamental concept is one of adaptively manipulating quantum systems. The principles involved will be discussed, along with the presentation of the state of the fi eld.

6885-03, Session 2Frontiers in device engineering: Synthesis for non-intuitive designA. F. J. Levi, Univ. of Southern California

Today, nano-science provides an overwhelmingly large number of experimentally accessible ways to confi gure the spatial position of atoms, molecules, and other nanoscale components to form devices. The challenge is to fi nd the best, most practical, confi guration that yields a useful device function. In the presence of what will typically be an enormous non-convex search space, it is reasonable to assume that traditional ad-hoc design methods will miss many possible solutions. One approach to solving this diffi cult problem is to employ machine-based searches of confi guration space that discover user-defi ned objective functions. Such an optimal design methodology aims to identify the best broken-symmetry spatial confi guration of metal, semiconductor, and dielectric that produce a desired response. Hence, by harnessing a combination of modern compute power, adaptive algorithms, and realistic multi-physics models, it should be possible to seek robust, manufacturable designs that meet previously unobtainable system specifi cations.

In this talk I will discuss some of our experience creating electronic and photonic components using optimal design methods we have developed and provide a vision of what this frontier in device engineering might lead to.

6885-04, Session 2The quantum limit for electrical amplifi ers: can we reach it?A. Rimberg, Dartmouth College

Any scientifi c instrument, including an electrical amplifi er, necessarily adds noise in the process of performing a measurement. As might be expected from knowledge of Heisenberg’s uncertainty principle, quantum mechanics sets strict limits on how little noise a measurement can add. There is a great deal of current interest in performing measurements at the quantum limit on such systems as qubits and nanomechanical resonators. This talk will introduce the notion of quantum limited electrical measurement, and discuss recent progress toward this goal at Dartmouth.

6885-05, Session 3Controlled assembly of gold nanoparticles using De Novo designed polypeptide scaffoldsB. Liedberg, D. Aili, K. Enander, Linköpings Univ. (Sweden); L. Baltzer, Uppsala Univ. (Sweden)

De novo synthesized polypeptides that are known to homo- and/or hetero dimerise and fold into rigid four helix bundles in solution have been used as building blocks and as a glue to generate “switchable” hybrid nanoparticle materials. The folding/aggregation properties of the generated architectures can be controlled by tuning the pH, ionic strength and by addition on metal ions, e.g. Zn2+, to the supporting solution. We describe in this contribution a series of experiments to reveal the aggregation behaviour of such peptide-decorated nanoparticles.1 The same concept also can be used to generate complex supramolecular assemblies like strings, rings and branched architectures. The potential applications of these building blocks as a nanoscale Lego for the development of new functional materials and bioanalytical devices are discussed, including colorimetric assays based on optical extinction and plasmonic assays for metal-enhanced fl uorescence detection. The latter two application areas are of prime interest since the de novo designed polypeptides can be chemically modifi ed in a sequential and site-selective manner with specifi c ligands and reporter groups, e.g., fl uorophores.2,3 A model system based on the specifi c interaction between human Carbonic Anhydrase and a polypeptide modifi ed with a ligand - benzenesulphoneamide - is utilized to demonstrate the potential of the system.

D. Aili: K. Enander; J. Rydberg; I. Lundström; L. Baltzer; B. Liedberg; J. Am. Chem. Soc., 128, 2194-2195, 2006.

K. Enander; G.T. Dolphin; L.K. Andersson; B. Liedberg; I. Lundström; L. Baltzer;J. Org.Chem. 67,3120-23, 2002.

K. Enander; G. T. Dolphin; L.K. Andersson; B. Liedberg; I. Lundström; L. Baltzer; Chem. Eur. J. 10, 1-11, 2004.

6885-06, Session 3A microfl uidic chemical/biological sensor based on dissolvable membrane incorporating gold nanoparticles and optical absorptionC. Lo, H. Jiang, Univ. of Wisconsin/Madison

Here we introduce a method of fabricating a detection membrane which is incorporated with Au nanoparticles. The membrane is fi rst fabricated by the method reported in our previous work and then soaks the membrane with 5 mM of Au3+ solution for 24 hours. Au3+ ions have the tendency to be chemically stabilized around the disulfi de bonds in the membrane which is then reduced by NaBH4 aqueous solution to obtain Au nanoparticles inside the membrane. The membrane with high concentration of Au nanoparticles exhibits red-brown color while the membrane without Au nanoparticles is transparent. The device is aligned between the LED and detector throughout the experiment by using micropositioners. After the sample fl ows through the membrane, the detection membrane begins to disintegrate and becomes blurry as time goes by. The dissolution of the membrane results in change of optical intensity and causes the output signal to change. The variation in the intensity of transmitted light is plotted with respect to time for 1M DTT and water. The optical absorption changes as much as 7%. We observe that the PAAm membrane takes ~1000 sec to be completely dissolved while the membrane does not change in optical absorption when DI water fl ows in.


6885-07, Session 3A dual-refl ective electrothermal MEMS micromirror for full circumferential scanning endoscopic imagingL. Wu, H. Xie, Univ. of Florida

Full circumferential scan (FCS) is crucial for intravascular imaging. Several FCS-EOCT imaging probes have been developed, such as by spinning the entire fi ber, employing MEMS micromotors to spin a mirror or prism, or by an MEMS scratch drive array. In this paper, we propose a new FCS-EOCT probe by employing a dual-refl ective MEMS micromirror. Two optical fi bers are used to deliver light beams to either surface of the micromirror, which can rotate ±45 degree (or 90 degree) and thus a 180 degree optical scanning is obtained from each mirror surface, resulting in full circumferential scans. A novel surface- and bulk-combined micromachining process based on SOI wafers is developed for fabricating the dual refl ective micromirror. Single-crystal-silicon device layer of SOI is used for mirror fl atness, and Al is coated on both sides for high refl ectivity. The mirror plate is connected to the substrate by a series of Al/SiO2 bimorph beams. Platinum heaters located between the bimorph beams and the substrate are used for electrothermal actuation. A 1mm-by-1mm dual-refl ective mirror was successfully fabricated. A 98.6-degree scan angle (mechanical) has been obtained at only 3.9Vdc. Dynamic scanning experiments with two laser beams incident on both surfaces of the mirror plate were performed and full circumferential scanning patterns have been observed. Other measured data include resonant frequency: 328Hz, radius of curvatures: -124 mm (front surface) and 127 mm (back surface), and the refl ectances: 81.3% (front surface) and 79.0% (back surface).

6885-08, Session 3Self-assembled single-digit micro-display on plasticE. Saeedi, S. S. Kim, B. A. Parviz, Univ. of Washington

We present the design and construction of micro-displays consisting of independently microfabricated light emitting diodes (LEDs) on unconventional substrates such as fl exible plastics. Inorganic LEDs are fabricated and released to form a powder like collection of elements stored in DI water. A plastic template containing binding sites was built through conventional fabrication methods using low temperature steps. Each binding site on the template consisted of a well with a shape complementary to that of the released LEDs. At the bottom of the well, electrical interconnects and low melting point alloys were positioned. Self assembly was used to incorporate the LEDs on the template. The plastic template was submerged into heated solution, and the LED elements where introduced over the template. Shaking and fl uid fl ow helped the elements to reach the proper receptor sites on template, gravity and shape recognition helped the elements to fall into wells with complimentary shapes, and capillary forces between the molten alloy on template and the metal pads on LEDs helped to secure the LEDs in place mechanically, and formed electrical connection. Self assembly method used in this research is a fast and parallel fabrication method which enables us to incorporate single crystalline semiconductors on fl exible, cheap and transparent substrates. Low cost, totally roll-able displays taking advantage of durable and effi cient inorganic LEDs have lots of applications in entertainment, communication and other industries.

6885-09, Session 3Metal-semiconductor-metal (MSM) photodetectors based on single-walled carbon nanotube fi lm-silicon Schottky contactsA. Behnam, Univ. of Florida and Stanford Univ.; J. L. Johnson, Y. Choi, Univ. of Florida; M. G. Ertosun, Stanford Univ.; Z. Wu, A. G. Rinzler, Univ. of Florida; P. Kapur, K. C. Saraswat, Stanford Univ.; A. Ural, Univ. of Florida

Single-walled carbon nanotube (CNT) fi lms have attracted signifi cant attention recently due to their conductive, transparent, and fl exible nature. In addition, they have the advantage of having uniform physical and electronic properties due to ensemble averaging.

In this talk, we fabricate and experimentally characterize metal-

semiconductor-metal (MSM) photodetectors with CNT fi lm Schottky electrodes on silicon substrates. As a result, we demonstrate a photodetector at the micro-nano interface, where a nanoscale CNT film is integrated with a conventional micro-scale semiconductor optoelectronic device.

We extract a Schottky barrier height of ~0.46 eV for CNT fi lms on Si, demonstrate a reduced dark current compared to standard Ti/Au metal based photodetectors, characterize the impact of geometry on dark current, and characterize the photoresponse of the CNT fi lm-Si MSM photodetector by illuminating the samples with a 633 nm HeNe laser. The extracted barrier height corresponds to a CNT fi lm workfunction of ~4.5 eV, which is within the range of the previously reported workfunction values for individual CNTs. We observe that while the photocurrent of the CNT fi lm MSM devices is similar to that of the Ti/Au control samples, their signifi cantly lower dark current results in a much higher photo-to-dark current ratio relative to the control devices. We explain these observations by comparing the two interfaces.

In conclusion, we demonstrate CNT fi lm-Si MSM photodetectors with very low dark current and good responsivity. This work opens up the possibility of integrating CNT fi lms as transparent and conductive Schottky electrodes in conventional semiconductor electronic and optoelectronic devices.

6885-10, Session 3Reduced order thermal modeling of a one-dimensional electrothermally actuated micromirror deviceS. Pal, K. Jia, H. Xie, Univ. of Florida

This paper reports a reduced order thermal model of a one-dimensional (1D) electrothermally actuated micromirror device. The mirror plate is 1mm x 1.2mm. It consists of a 40μm thick single-crystal silicon (SCS) layer with a 1μm thick aluminum layer on top. The micromirror is attached to the substrate by an array of 72 thermal bimorph actuators. Each thermal bimorph actuator is 8.5μm wide and 135μm long and consists of a 1μm thick PECVD SiO2 layer and a 1μm thick aluminum layer with a Pt heater layer embedded between them. A current passing through the embedded platinum heater results in Joule heating. The difference in the thermal expansion coeffi cients of the SiO2 and aluminum layers causes the bimorphs to bend, thereby causing the mirror to tilt. Voltage in the range 0-15V is used for actuation, resulting in rotation angles in the range of 0-35 degrees. Neglecting the temperature variation perpendicular to the length of the bimorphs, a 2D fi nite element thermal model is built. The accuracy of the model is verifi ed by comparing the simulation results with thermal imaging data. The fi nite element consists of 1831 nodes. Using a Krylov subspace based algorithm, a reduced order model is extracted from the fi nite element model. It is found that static and dynamic results obtained from a reduced model with order ≥ 5 agree well with fi nite element results. Hence, a reduced order thermal model that saves computation time and resources without compromising the computation accuracy has been demonstrated.

6885-11, Session 3Manufacturing fi ber optic guide using PDMS and measuring optical characteristics of fl ow cellJ. Yang, S. Kim, S. Park, Kyungpook National Univ. (South Korea)

This paper is intended to manufacture the existing fl ow cell analysis system consisting of plenty of complicated lens and optical systems as a low priced and simple structure using optical fi ber. In addition, in designing the system, pigtailed laser diode connector was adopted in order that the unstable connection of laser diode and optical fi ber and the optical signal of laser diode would be stable against external environments while PDMS of which optical transmission is excellent was used to measure optical characteristics as well as observe cell fl ow. Flow cell analysis system can quickly measure each particle or cell when such particles or cells pass through a certain detective section, seize a variety of characteristics such as the size, shape, antigen or element of a cell simultaneously and separate a specifi c part according to circumstances. By aligning sample cells in the middle of channel by means of controlling 2-D sample, the cells could be aligned in a line regardless of the size

Conference 6885: MEMS/MOEMS Components and Their Applications V

Special Focus Topics: Transducers at the Micro-Nano Interface


of channel while the optical characteristics of cells, which passed over the core of inserted optical fi ber, could be observed. The measuring part, the core part of the existing fl ow cell analysis system, which can examine the types and coeffi cients by measuring the characteristics of fl ow cells, was manufactured in micro size and it could be confi rmed that the system would be replaced with a low cost one. The system can be utilized for biochemical fi elds such as size of various cells, classifi cation of nucleated or non-nucleated red blood cells and virus detection as well as measuring cell’s characteristics and the coeffi cients.

6885-12, Session 4Compact modeling of inertial and rarefaction effects on quality factor of MEMS torsional structures in continuum to molecular fl owsR. Pratap, A. K. Pandey, Indian Institute of Science (India)

The operating pressure, the characteristic flow length and the characteristic time scale of the vibrating MEMS and NEMS devices play very important roles on the dynamic characteristics of such devices. Generally the fl uid fl ow around the vibrating structures is governed by the rarifi ed gas dynamics equations. For isothermal and incompressible fl ow, the rarifi ed fl ow through micro and nano channels may be characterized by two important characteristic numbers --- the Knudsen number, Kn, and the modifi ed Reynolds number, Re. For most analysis, the Knudsen number, which is a ratio of the mean free path of the gas molecules to the characteristic fl ow length of the device, alone, may be suffi cient to model the rarefaction effect. Such conditions exist when (1) the characteristic length is suffi ciently small compared to the length of the vibrating plate and (2) the characteristic time, which is inversely proportional to the frequency of vibration, is larger than the mean free time of the rarifi ed fl ow. In this paper, we take a case of large characteristic fl ow length compared to the length of the vibrating plate in which the rarifi ed fl ow is also infl uenced by inertial effect ( i.e., Re>1).

To study the effect of inertia due to a large air-gap thickness and the rarefaction effect due to low operating pressures on the quality factor of the MEMS torsional structure (a double gimballed mirror), a compact analytical model is developed which is a function of the modifi ed Reynolds number, Re, and the Knudsen number, Kn. The proposed analytical model and another model available in the literature are compared with the experimental results. It is found that the proposed model captures both the inertial as well as the rarefaction effect quite accurately. It also gives a very good match with the experimental results over the entire fl ow regimes, namely, the continuum, slip, transition, and molecular regimes. But the other model, which is just based on the Knudsen number, starts deviating from the experimental results at the onset of the transition regime and fi nally gives an error of more than 200% in the molecular regime. Hence, the formula presented in this paper can be used to model the rarefaction as well as the inertial effect with a very good precision over the large range of Knudsen number. However, the range of applicability of the present model over the Knudsen number is limited by the upper frequency limit such that the compressibility effect is neglected.

6885-13, Session 4A mechanistic model for adsorption-induced change in resonance response of submicron cantileversH. Sadeghian, Technische Univ. Delft (Netherlands) and Microelectron-ics Dept, Defl t Univ. of Technology (Netherlands); H. F. Goosen, A. Bossche, F. van Keulen, Technische Univ. Delft (Netherlands)

Submicron cantilever structures have been demonstrated to be extremely versatile sensors and have potential applications in physics, chemistry, and biology. The basic principle in submicron cantilever sensors is the measurement of the resonance frequency shift due to the added mass of the molecules bound to the cantilever surface.

This paper presents a theoretical model to predict the resonance frequency shift due to molecular adsorption on submicron cantilevers. The infl uence of mechanical properties of the adsorbed molecules bound to the upper and lower surface on the resonance frequency has been studied. For various materials, the ratio between the thicknesses of the

adsorbed layer and the cantilever where either stiffness or added mass is dominant will be determined. The critical ratio between the thickness of the adsorbed layer and the cantilever and ratio between stiffness and density of adsorbed layer and cantilever have been determined. The calculations show how the opposite contributions of the added mass and stiffness can be decoupled. This model gives insight into the decoupling of both opposite effects and is expected to be useful for the optimal design of resonators with high sensitivity to molecular adsorption based on either stiffness or mass effects.

6885-15, Session 5Template-based massively parallel assembly for microchip solid state cooling applicationR. Baskaran, Intel Corp.

In a microprocessor package design, two thermal power metrics are signifi cant - the total thermal design power and the cooling of ‘hot spots’ or high heat fl ux regions of the ‘core’[1]. Many active cooling solutions have been proposed including microchannel liquid cooling [2] and solid state refrigeration [3]. In the case of thermoelectric cooling (TEC), simulations using methods in [4] show that the hot spot temperature reduction is enhanced by upto 3x when TEC element density is changed from 25% to 90% at use conditions. To this end, in this talk we present a massively parallel assembly method to obtain densely packed array of parts from 200-800um size.

Self-assembly is the spontaneous organization of components into ordered structures, driven by energy minimization [[5-8]]; it is employed here to arrange the two types of TEC cooling elements into regular arrays without the use of robotic pick-and-place. The approach taken here is distinct from prior work by the combination of (a) dry assembly using vibratory agitation and shape matching, (b) re-usable assembly templates and a novel parts transfer approach after self-assembly. We also present a theoretical framework inspired by similarities to chemical/biochemical reaction kinetics, developed to quantitatively understand design and materials parameters that infl uence rates and yields of assembly.

6885-16, Session 5Thermopower measurement of freestanding nanowires using a MEMS workbenchN. B. Duarte, H. Romero, P. C. Eklund, S. A. Tadigadapa, The Pennsyl-vania State Univ.

In the past fi fteen years the search for better thermoelectric power generation and refrigeration has been revitalized by theoretical predictions of increased thermoelectric fi gure of merit (ZT) in nanowires. While research has been done to show the predicted increase, there is still the question as to how size specifi cally affects this property. The fi rst step towards a study of thermoelectric power to size dependence is the development of a platform on which variously sized nanowires can be easily studied. Current techniques, which require AFM and other nanowire manipulation methods to place the nanowires, prove to be diffi cult and extremely time consuming. Our approach has been to eliminate the problem of nanomanipulation by creating a workbench with a high density of testing locations.

Out measurement workbench consists of a 40μm long microfabricated freestanding bridge with a nanowire across it. During operation the suspended bridge is electrically heated and the thermoelectric voltage is measured between the bridge and one of three fi ngers on the other side of the gap using a lock-in amplifi er. Nanowire deposition is performed by dropping a liquid that holds nanowires in suspension. For the sake of increased yield, 12 of these units are placed in series with two sets placed parallel.

This work presents the detailed fabrication and experimental temperature calibration of the thermoelectric workbench fabricated for the accurate measurement of the Seebeck coeffi cient of nanowires. We present detailed measurements on gold nanowires as a function of the size of the nanomaterials at room temperature.




6885-17, Session 5Circuit requirement for MEMS-based mechanical-to-electrical power conversionH. Kim, H. Kim, S. Khang, Chung-Ang Univ. (South Korea); Y. Lee, Korea Institute of Science and Technology (South Korea)

Energy scavenging is a technology that derives microwatt level power to drive electronics from ambient heat, light, radio, or vibration, that is otherwise wasted. Piezoelectric vibration-to-electricity converters or piezoelectric micropower generators (PMPG) have been of particular interest, since they have high electromechanical coupling, require no external voltage source, and are compatible with MEMS fabrication process. However, all of research works to optimize the mechanical to electrical energy conversion effi ciency have been done under the assumption of ideal rectifying diodes for ac-to-dc conversion. PSPICE simulation with real diodes show that, particularly in case of PVDF micropower generator, the low reverse-leakage current characteristic rather than the low forward-voltage drop of the rectifying diodes is much more benefi cial to improve conversion effi ciency and that the storage capacitor should be as small as possible to reduce the time to store required amount of energy. Experimental and PSPICE results show that, when ultra-low leakage current diodes are adopted for a bridge rectifi er, the mechanical-to-electrical energy conversion effi ciency is doubled or more in some cases, and the charging speed is increased by 20%, compared to the circuit that adopts Schottky diodes. It is also found that, compared to the circuit with larger storage capacitor, the circuit with smaller storage capacitor requires shorter time to store the same amount of energy and can drive voltage regulator more frequently. This study suggests that low reverse leakage diode and small storage capacitor should be used to build effi cient, high-performance piezoelectric energy scavenging systems for ubiquitous sensor networks.

6885-18, Session 5A active giant magneto-resistive-sensor with current interface for anti-rock break system on vehicleS. H. Kim, S. Park, Kyungpook National Univ. (South Korea)

In this paper wheel speed sensor integrated circuit based on Giant Magneto Resistive effect is presented. Speed of magnetized Target wheels or ferromagnetic target wheels are detected.

In this sensor, Four resistance of the magnetic input signal are favorable for detecting the target speed.

A two-wire current output directly linked to the input signal frequency indicates speed. Speed information and detection of specifi c amplitudes of the magnetic input signal are encoded in its output pulse-width. basically, Giant Magneto resistive element is guarantee approximately from -40 up to 150 and also this sensor is guarantee high temperature and suitable for automotive applications. Finally, this sensor has been tested in the lab and on vehicle.

In the lab test we used HILS (Hardware In the Loop Simulator) equipment and after got on vehicle test in order to verify the operation of this sensor.

This sensor performance has been proven reliable wide operating ranges and challenging automotive requirements such as precision spaniel ability for reality vehicle Speed to applicate the ABS(Anti rock system) and others.

6885-19, Session 5Micro-opto electro mechical(MOEM) accelerometers: a performance analysisJ. Nayak, Research Ctr. Imarat (India)

Micro Electro Mechanical accelerometers (often called as MEMS Accelerometers) are commercialized, however, the low performance of these accelerometers limit their use to less demanding automotive applications[1,2]. High performance accelerometers are in demand for navigation of vehicles and micro space craft. Micro Opto Mehcanical (MOEM) based sensors are emerging from laboratories to provide better performance than the existing MEMS based sensors[3,4,5].

We analyzed two different types of MOEM accelerometer - one is based on optical intensity modulated schemes and other is based on interferometric acceleration induces phase difference between the two optical beams. Analytical model is developed relating the optical output to the acceleration induced defl ection and stress. It involves relating structural parameters of cantilever beam namely, dimensions, stiffness and mass, to optical properties of pickoff namely, waveguide cross section, and refractive index profi le. The analysis provides design of high sensitivity and dynamic range accelerometer with a resolution of 1 g/Hz, a dynamic range of 10 g and shock survivability of better than 3000 g is analyzed and simulation results are presented.

REFERENCE

1. Special Issue on Optical MEMS, IEEE Journal of Selected topic in Quantum Electronics, vol.8, no.1, January/Febuary 2003.

2. Jagannath Nayak, “Design and Analysis of High Performance MOEM Accelerometers”, Ph.D, Thesis, Dept. of Electrical Communication Engineering, Indian Institute of Science, Bangalore, August 2003.

3. Jagannath Nayak, T. Srinivas A. Selevarajan, and DVK Sastry, “Design and analysis of an intensity modulated micro-opto-electro-mechnical accelerometer based on nonuniform cantilever beam proof mass”, Journal of microlithography, microfabrication and microsystem, October 2006 - Vol.5, Issue 4, 043012.

4. Selevarajan A, Jagannath Nayak, T. Srinivas and DVK Sastry, “Analysis of a nonuniform cantilever mbeam MOEM accelerometer under closed loop operation”, SPIE, Vol. 5763, p.276-283, Smart Structures and Materials, 2005.

5. Jagannath Nayak and V.K Saraswat “Studies on micro opto electro mechanical (MOEM) inertial sensors for future inertial navigation systems”, Proceedings of ISSS 2005, International Conference on Smart Materials Structures and Systems, July 28-30, 2005, Bangalore, India.

6885-20, Session 5Temperature compensation of constant current mode microfl ow sensor using GIC circuitD. Han, S. Park, Kyungpook National Univ. (South Korea)

The micro fl ow sensor can operate in various modes. Both modes need the temperature compensation as heat transfer rate shows different values for certain fl ow temperature. Constant current mode has more fast response time than other modes. In various modes, in case of constant current mode, with using Wheatstone bridge circuit, other research used to compare to resistance between temperature compensation element and heater, and remove effect of fl uid temperature. However, in this study, we designed constant current mode micro fl ow sensor to reward circuit with using active fi lter circuit which is used GIC (generalized impedance converter) used to DC current-to-current converter. The Heater and the temperature sensor used PTC (positive temperature coeffi cient) thermistor. When fl ow velocity is zero, in case that we change fl uid temperature, resistance of heater is increased. So that, even if input current is constant, output voltage is increased. This study adjusted current as fl uid temperature with inserting temperature sensor in GIC circuit. Without relation about fl uid temperature, making circuit have constant voltage, and operate sensor, we can get only change of output voltage depend on fl ow velocity. Without relation about temperature of fl uid, we materialize temperature compensation of output voltage, which is increased by temperature, through adjusting input current. The case which it will apply to the automobile AFS (air fl ow sensor) it needs a fast response time, it has superior characterization.




Conference 6886: Microfl uidics, BioMEMS, and Medical Microsystems VITuesday 22 January 2008 • Part of Proceedings of SPIE Vol. 6886 Microfl uidics, BioMEMS, and Medical Microsystems VI

6886-01, Session 1Develops the “In-Check” platform for diagnostic applicationsM. Palmieri, STMicroelectronics (Italy)


6886-02, Session 1Cytometric biochips with optically active surfaces for spatial engineering of fl uorescence excitationH. D. Summers, R. J. Errington, P. Smith, Cardiff Univ. (United King-dom); D. R. Matthews, Kings College London (United Kingdom); J. F. Leary, Purdue Univ.

The integration of thin (< 100 nm) metal fi lms with micro-scale optical waveguides provides a route to controlled spatial excitation of cellular fl uorescence within a biochip platform. Surface bound electron-plasma oscillations (surface plasmon waves) interact with photons to produce an evanescent fi eld localized within 100nm of the chip surface. These plasmon fi elds can therefore be used as a near-fi eld probe of analytes situated at the surface e.g. surface plasmon resonance (SPR) sensing. If a grating with sub-wavelength periodicity is fabricated at the surface then coupling of the plasmons to free-space photons can be achieved and a highly directional beam of light is produced. We have been developing surface-active biochips using these processes to provide selective excitation of fl uorescently labeled, live cell populations. These chips effectively combine a number of commonly used techniques such as SPR, TIRF and epi-fl uorescence within a single device and have the potential to provide sub-cellular discrimination of excitation in 3-D. Thus within a single fi eld of view we can selectively excite membrane versus cytoplasm and localise the excitation within the lateral plane to an area of a few square microns. We demonstrate the potential of the biochip by monitoring the uptake and internalization of quantum dots via endocytosis.

6886-03, Session 1Non-instrumented nucleic-acid amplifi cation assayB. H. Weigl, G. Domingo, P. LaBarre, J. Gerlach, PATH

We have developed components of a diagnostic disposable platform that will both take molecular diagnostics to the Point-of-Care and stabilize specimens to feed into a central surveillance system. The proposed diagnostic is targeted for use in low-resource settings by minimally trained health workers. The disposable device does not require any additional instrumentation and will be almost as rapid and simple to use as a lateral fl ow strip test-yet offering the sensitivity and specifi city of PCR assays.

The low-cost integrated device is composed of three subunits: (1) a sample-processing and reverse-transcription subunit that will generate cDNA, (2) a NA amplifi cation subunit, and (3) a NA amplicon-detection subunit capable of detecting and differentiating up to three RNA virus targets. The device integrates chemical exothermic heating, temperature stabilization using phase change materials, and autocirculation-based PCR or isothermal amplifi cation. So far we have demonstrated the generation of cDNA using exothermic materials, temperature stabilization of exothermic materials using phase change materials, initial microfl uidic circuits for performing circulation-based PCR, and visual membrane-based detection of amplicons.

The aim of developing this system is to provide PCR-level sensitivity to the three target viruses, and additional viruses as needed, in settings that have no direct or ready access to higher-level facilities. If an outbreak occurs, patients would be tested with the disposable in the fi eld, and the spent disposable can be sent to a central laboratory facility and the cDNA analyzed further if needed.

6886-05, Session 1Latex immunoagglutination assay for bovine viral diarrhea utilizing forward light scattering in microfl uidic deviceB. Heinze, The Univ. of Arizona; J. Y. Song, National Veterinary Research Quarantine Service (South Korea); J. Yoon, The Univ. of Arizona

The bovine viral diarrhea virus (BVDV) causes a number of syndromes and diseases in both beef and dairy cattle, leading to productive and reproductive losses. Scheduled testing of herds for the presence of the virus and subsequent isolation of infected individuals, coupled with vaccination of healthy cattle remains as the most effective means for prevention of the disease. Current detection methods, however, are somewhat costly and time consuming, such that development of a more cost effective and rapid detection technique would prove benefi cial. This research is centered on development of a lab-on-a-chip latex immunoagglutination assay utilizing forward light scattering measurements via close proximity optical fi bers for rapid and sensitive detection of the BVD virus. Monoclonal antibodies are passively adsorbed onto 0.51 micron highly-carboxylated latex microspheres. This solution is incubated with an equal volume of solution containing modifi ed live BVDV in tissue culture media and fetal calf serum. Upon contact with target viral proteins, agglutination of the latex microspheres occurs, increasing effective particle diameter. This effective increase in particle size is observable and quantifi able via monitoring of forward light scattering intensity. Modifi ed live BVDV was successfully detected to a solution concentration as low as magnitude 10^1 TCID50/ml. This assay was conducted in a two well slide towards proof of concept and initial optimization of light source wavelength as well as particle surface coverage. This assay will be demonstrated in a microfl udic channel, and the light scattering method will be compared to PCR/gel electrophoresis in terms of sensitivity and specifi city.

6886-07, Session 2Microfabricated implantable fl owmeter for CSF shuntsS. Liu, H. C. Lim, New Jersey Institute of Technology; J. L. Zunino III, U.S. Army Armament Research, Development and Engineering Ctr.; J. F. Federici, G. A. Thomas, R. C. Farrow, New Jersey Institute of Technology

An implantable wireless fl ow meter is proposed that would enable measurement of the fl ow of cerebrospinal fl uid (CSF) through the ventriculoperitoneal (VP) shunt, currently used to treat hydrocephalus patients. CSF fl ow is a key indicator of shunt function, and there is currently no way to measure it in situ, resulting in the absence of clinical methods to directly assess shunt function or to predict its failure. Using MEMS microfabrication methods, the proposed fl ow meter is manufactured at a size small enough to be integrable with implanted VP shunts. The key elements in the fl ow meter are capacitive structures that change properties with change in CSF fl ow. Radiative coupling between the internal passive circuitry and an external detection circuit allows implantation of the fl ow meter without the need for implanted batteries or transcutaneous wires.

6886-08, Session 2Highly integrated microfl uidic sensorsD. E. Angelescu, H. Chen, J. Jundt, H. Berthet, Schlumberger Ltd.; B. Mercier, F. Marty, Groupe ESIEE (France)

We have developed fabrication techniques allowing easy integration of suspended, electrically addressable, micro-structures in fl uidic chips, as well as monolithic integration of sensors within microfl uidic channels. We employ a combination of wet and dry etching of SOI silicon and glass in conjunction with multiple-layer anodic bonding and wafer back grinding. Such techniques are often used in the MEMS fi eld for fabricating isolated transducers, yet their application in creating highly


integrated microfl uidic systems has largely been overlooked. Creative use of state-of-the-art MEMS fabrication techniques allows the microfl uidic integration of a number of sensors, for simultaneous measurement of, for example, fl ow velocity, thermal conductivity and normal stress. The resulting systems allow determination of multiple fl uid parameters (thermal conductivity, fl ow velocity, etc) simultaneously and with high accuracy, utilizing minute amounts of fl uid. Such integrated sensors should fi nd applications in fi elds such as fl uid analysis, process control, medicine and pharmaceuticals, to name a few. We will demonstrate the versatility of the fabrication techniques we have developed with several examples: anemometric fl ow detection, high-accuracy extended-range thermal time-of-fl ight fl ow metering, monolithic integration of stress transducers. As an example, we will present our recent work related to the development and optimization of a microfl uidic fl ow meter with sub-microliter swept volume, allowing simultaneous determination of thermal conductivity and fl ow rate in a range from a fraction of microliter to milliliters per minute.

6886-10, Session 2Novel 3D micromirror for miniature optical bio-probe SiOB assemblyJ. Singh, Y. Xu, T. H. S. Jason, C. S. Premachandran, Institute of Microelectronics (Singapore); N. Chen, National Univ. of Singapore (Singapore)

This article presents a novel design and development of 3D micromirror for large defl ection scanning application in in-vivo OCT bio-imaging probe. Miniaturization of probe is critical to reduce patient trauma and access narrow cavities in affected limbs. A compact mirror design requires smaller mirror plate size and minimization of dead space on the chip. A mirror plate less than 500 micrometer in diameter will be detrimental to imaging quality as the same plate is used to collect scattered or refl ection light from the sample under study. In this study, mirror chip sizes of 1 x 1 mm2 and 1.5 x 1.5 mm2 were developed with respectively 400 and 500 micrometer diameter mirror plates. The design includes electro thermal excitation mechanism in the same plane as mirror plate, to achieve 3D free space scanning. Larger defl ection requires large actuators, which usually increase the overall size of the chip. New actuators having linear and curved beam parts were integrated in the mirror chip, which helped to reduce a lot of dead space and produce compact size mirror chip. Actuators of total length of 850 micrometer provided large defl ections up to 16 degrees. DRIE process module was used to etch through hole windows in the silicon substrate, which also helped to reduce the overall size and also provided much needed free space for micromirror movements.

6886-37, Session 2A nanofl uidic system for massively parallel implementation of the polymerase chain reaction (PCR)C. Brenan, BioTrove, Inc.

Massively parallel nanofl uidic systems are lab-on-a-chip devices where solution phase biochemical and biological analyses are implemented in high density arrays of nanoliter holes micro-machined in a thin platen. Hydrophilic polyethylene glycol linked to the interior surfaces of the holes and a covalently coupled fl urosilane makes the exterior surface of the platen hydrophobic. This allows precise and accurate self-metered loading of liquids into each hole without cross-contamination. We have created a “nanoplate” based on this concept, equivalent in performance to standard microtiter plates, having 3072 thirty-three nanoliter holes in a stainless steel platen the size of a microscope slide. Critical to nanoplate functionality has been development of tools for facile fl uidic transfer of reagents and samples from microplates into individual or groups of holes in a nanoplate. We report on the performance of this device for PCR-based single nucleotide polymorphism (SNP) genotyping or quantitative measurement of gene expression in applications ranging from plant and animal diagnostics, agricultural genetics and human disease research.

6886-11, Session 3A MEMS-based Coulter counter for cell sizingM. Korampally, J. D. Benson, J. K. Critser, M. F. Almasri, Univ. of Mis-souri/Columbia

This paper describes the design, fabrication and testing of a MEMS Coulter counter, based on gold electroplated electrodes, SU-8 microchannels. The aim is to monitor cellular volumetric changes of mouse and rat spermatozoa cells which are available in relatively small numbers, after an exposure to various media. The device consists of three regions; mixing, focusing, and measurement regions. The mixing region is designed with a serpentine shape channel, enabling complete mixing of a sample and a reactant before entering the focusing region. The focusing region consists of two electrodes used to generate negative dielectrophoresis for focusing the cells in line and hence prevent the channel-clogging. The measuring region consists of a narrower channel with width ranging from 20-25 um, and depth of 25 um with multiple electrode pairs. The electrodes are used to measure the change in impedance at multiple points along the channel as a cell passes through. A thick positive photoresist was used to form a mold. Gold was electroplated in the mold to create vertical electrodes with thickness of 20 um. PDMS sheet with input and output fl uidic ports was used to cover the SU-8 channel, and allow the passage of both the cells and the reactant media. This device allows extremely small sample sizes (101 compared to 105 cells per experiment), an extremely short time frame from the exposure to reactant media to the initial measurement, serial time series measurements of a single cell, and light microscopic monitoring of the experiment.

6886-12, Session 3Detection of bacterial cells based on microchannel gatingM. Javanmard, A. H. Talasaz, M. Nemat-Gorgani, R. F. W. Pease, M. Ronaghi, R. W. Davis, Stanford Univ.

Current microbiological techniques used for pathogen detection involve expensive and time consuming methods such as culture enrichment, which can take several days. Described below is a rapid and inexpensive technique which can be used to detect single bacterial cells electrically (label-free format) in real-time. We have successfully demonstrated real-time detection of target cells by measuring instantaneous changes in ionic impedance.

The biosensor used in this study contains two electrodes integrated into a microfl uidic channel. The region in between the two electrodes is the active region of the detector, where antibodies are immobilized. A sample suspicious of bacterial cell contamination is injected into the micro-channel. If the sample contains the targeted bacteria, the cells will attach to the channel wall in between the electrodes, partially clogging the channel thus resulting in ionic resistance increase. By monitoring the impedance across the micro-electrodes, it is possible to detect the channel gating caused by bacterial cell attachment inside the channel. By choosing channel and electrode geometries close to the cell size, the sensitivity of the device can be increased down to single cell detection.

The micro-fl uidic biochip used consists of a set of microelectrodes on a glass substrate and a channel right above, formed in PDMS. In order to verify our electrical measurements, the channels were monitored using optical microscopy simultaneously as electrical impedance was measured. Results show an instantaneous increase in electrical impedance as a small number of cells bind to the surface of the electrodes, demonstrating real time detection of cell capture.

6886-39, Session 3Portable CE-system with contactless conductivity detection in an injection molded polymer chip for on-site food analysisH. Becker, Microfl uidic ChipShop GmbH (Germany); H. Mühlberger, W. Hoffmann, Forschungszentrum Karlsruhe (Germany); T. Clemens, CLEMENS GmbH (Germany); R. Klemm, C. Gärtner, Microfl uidic Chip-

Conference 6886: Microfl uidics, BioMEMS, and Medical Microsystems VI


Shop GmbH (Germany)

While chip-based capillary electrophoresis has established itself as one of the fastest and potentially convenient methods for the analysis of larger molecules in many biotechnological and clinical applications, the large and economically attractive fi eld of analysis of foodstuff has not been addressed with the same intensity. We have addressed this issue with a fully integrated chip-based capillary electrophoresis unit (called “MinCE”), where all the electronics including high-voltage power supplies and the chip itself fi t into a metal box with dimensions 20 cm x 10 cm x 5 cm (length, width, height). Readout and control is realized using a conventional laptop computer.

In order to allow for a low-cost disposable chip, the chips are injection molded from polymethyl-methacrylate (PMMA) from a precision machined stainless steel master. The fl uidic reservoirs have already been integrated into the chip to avoid additional assembly steps. The detection of analytes is realized by contactless conductivity detection. The electrodes necessary are made by screen-printing. The separation channel has the dimensions 50 μm width, 50 μm in height, the electrodes have a design width of 100 μm with an electrode gap for measuring of 150 μm.

First experimental data of a wine standard, with the peaks indicating the organic acids contained in the wine and an analysis of mineral water will be presented.

6886-13, Session 4Microchips fabricated by femtosecond laser micromachining in glass for observation of aquatic microorganismY. Hanada, K. Sugioka, H. Kawano, I. Ishikawa, A. Miyawaki, K. Midorikawa, The Institute of Physical and Chemical Research (RIKEN) (Japan)

An optical microscope is a very common tool for inspection of microorganims for biologists. Combination of the optical microscope and the high-speed camera enables the biologists to study microorganims. However, in the novel microscopic system, normal glass substrates such as a cover glass or a slide glass, are generally used to place microorganisms even though the fi eld of the image is only several hundred μm in diameter. For this reason, the biologists often fi nd it diffi cult to capture images of a moving cell. Additionally, high N.A. objective lens is often used in the conventional microscopic system, so that the low depth of focus makes it diffi cult to get the clear images of microorganims. To solve these problems, scale-down the glass substrate i.e., to three-dimensionally capture a microorganims in a limited area is highly demanded.

In the meanwhile, we developed 3-D microfabrication technique of glass by a femtosecond laser direct writing with post wet etching to create microdevices like a microchamber and a microreactor. In this paper, we apply this technique to fabricate microstructure to capture microorganisms in a limited area.

The procedure for fabricating the 3D hollow microstructures consists of (1) 3D direct writing by fs laser, (2) baking to form the modifi ed regions at the laser exposed regions, (3) wet etching in dilute HF solution to selectively remove the modifi ed regions, and (4) post annealing to smooth the etched surfaces. After microchip fabrication, dynamic observation of aquatic microorganisms were carried out by encapsulating microorganims in the microchip.

6886-14, Session 4Femtosecond laser microfabrication of optical waveguides in commercial microfl uidic lab-on-a-chipR. Osellame, R. Martinez Vazquez, R. Ramponi, G. Cerullo, Politec-nico di Milano (Italy); C. Dongre, R. Dekker, H. J. W. M. Hoekstra, M. Pollnau, Univ. Twente (Netherlands)

One of the main challenges of lab-on-a-chip technology is the on-chip integration of photonic functionalities by manufacturing optical waveguides for sensing biomolecules fl owing in the microchannels. Such integrated approach has many advantages over traditional free-

space optical sensing, such as compactness and portability, enhanced sensitivity and the possibility of parallel excitation at multiple points in the channel. Femtosecond laser pulses allow the microfabrication of optical waveguides into glass substrates, by exploiting nonlinear absorption in the focal volume, to induce a local refractive index modifi cation. It is a direct, maskless, three-dimensional fabrication technique, which is particularly suited for waveguide inscription in already formed LOCs. In this work we report on the use of femtosecond laser pulses to inscribe optical waveguides in commercial fused silica LOCs in different geometries with respect to the microfl uidic channels. We use the astigmatic beam shaping technique, previously developed by our group, to obtain waveguides with circular cross-section employing a 1 kHz repetition rate amplifi ed Ti:sapphire laser. We demonstrate single mode waveguides in the visible with propagation losses lower than 1 dB/cm. Such waveguides provide highly selective excitation of small volumes of fl uorescent solutions fi lling the channels and integrated collection of the fl uorescent signal. Application to capillary electrophoresis will be discussed.

6886-15, Session 4Fluorocarbon fi lms using pulsed PECVD for microfl uidic lab-on-a-chipE. T. Peterson, T. D. Mantei, I. Papautsky, Univ. of Cincinnati

Microfl uidic devices for analysis of environmental samples require non-fouling surfaces to function properly, both to inhibit bacterial adhesion and to reduce nonspecifi c binding of contaminants. Fluorocarbon fi lms are desirable for this purpose because they are chemically inert, have excellent dielectric properties, and can form low energy, non-fouling, biocompatible surfaces. Tefl on has therefore been the gold-standard for many years, however, Tefl on is diffi cult to process due to high molding temperatures (>300C) and poor adhesion to substrates. In this work, pulsed-plasma enhanced chemical vapor deposition (PECVD) is used to deposit fl uorocarbon fi lms at low temperatures for microfl uidic applications.

Fluorocarbon fi lms were deposited in an electron cyclotron resonance (ECR) PECVD reactor with a pulsed 2.45 GHz microwave source, using hexafl uoropropylene oxide (HFPO) as the deposition precursor. HFPO (C3F6O) has been investigated in various pulsed systems and has been shown to provide high densities of CF2 radicals, which can undergo recombination to polymerize into fi lms. We have investigated a range of pulse parameters, using short on-times and long off-times (duty cycles of 3-13%) and microwave powers of 800-1000W. For deposition times of 30min, substrate temperatures remain below 85C with no substrate cooling, making this technique suitable for deposition on a variety of materials, including polymers. Etched silicon shadow masks were used to selectively deposit 100μm square patterns on glass and silicon substrates. X-ray photoelectron spectroscopy (XPS) characterization was used to determine fi lm composition, and analysis of the C(1s) spectra showed that fi lms with fairly high CF2 percentages could be obtained. Sessile drop measurements on the fi lms yielded contact angles of 110°±2°, which is consistent with the properties of commercially available Tefl on.

Fluorocarbon fi lms deposited from HFPO using pulsed PECVD offer several critical advantages, including low temperature deposition, easy patterning through shadow masks, permanently hydrophobic surfaces, and ability to deposit on a wide variety of materials. These advantages make the approach ideally suited for polymer microfl uidic lab-on-a-chip devices.

6886-16, Session 5Application concepts for complementary micro-pneumatic devices and circuitsA. K. Henning, Aquarian Microsystems

Previously, we proposed novel microvalve structures, amenable to bulk micromachining, which demonstrated fully complementary behavior. Two distinct microvalves were devised, one analogous to the p-MOSFET, and the other analogous to the n-MOSFET found in complementary MOSFET devices and circuits. Ring oscillator behavior based on NOR logic gates



was described, for both micro-pneumatics (based on compressible gas fl ow) and micro-hydraulics (based on incompressible liquid fl ow). In this work, micro-pneumatic circuits are described. In particular, a micro-pneumatic operational amplifi er is described and simulated in detail. Also, prospects for energy harvesting or scavenging based on micro-pneumatic circuits are discussed.

6886-17, Session 5Hybrid polymer fabrication process for electro-enzymatic glucose sensorJ. N. Patel, B. Kaminska, B. L. Gray, B. D. Gates, Simon Fraser Univ. (Canada)

In this article, we present a novel self-aligned and hybrid polymer fabrication process for an electro-enzymatic glucose sensor. The self-aligned fabrication process is carried out using polydimethylsiloxane (PDMS) as a process substrate material, SU-8 as a sensor structural material and gold as an electrode material. The advantages of PDMS as a process substrate become apparent during the fabrication process. During the fabrication process, SU-8 has enough adhesion to the PDMS substrate when treated with controlled temperature. However, after completion of all fabrication steps, the SU-8 based sensors can be easily peeled-off from the PDMS substrate. The PDMS substrate prepared on a glass wafer is reusable for more process cycles. Such an SU-8 release technique from a PDMS substrate has never been proposed before. The active and reference gold electrodes are sandwiched between two SU-8 layers with contact pad openings and the active area opening to the top SU-8 layer. The enzyme (glucose oxidase) is immobilized within the confi ned active area opening.

After successful fabrication using the hybrid process, the overall thickness of the sensors is measured between 117.15 μm and 140.15 μm. The sensor area and the electrode area is 2 mm x 3 mm and 2 mm x 2 mm respectively. The resulting glucose sensors are fl exible and can withstand a defl ection of ~33° prior to breaking. The current generated for 600 mg/dl and 50 mg/dl glucose concentration gave a real-time response of 241±49 nA and 74±24 nA over 165 minutes respectively.

6886-18, Session 5Microfabrication of an integrated optical cell counter for Cytometry applicationG. Shao, W. Wang, Louisiana State Univ.


6886-19, Session 6Chaotic passive micromixers with microstructures placed on the top and bottom fl oors of channelJ. Chen, National Pingtung Univ. of Science and Technology (Taiwan); Y. Lai, J. Lin, National Chiao Tung Univ. (Taiwan)

The objective of this study is to present chaotic micromixers in which a series of microstructures are placed on the top and bottom fl oors of channels. Passive micromixers fabricated by MEMS technologies with cross obstacles, X-type grooves, and X-type obstacles are considered. Numerical simulations using the commercial software CFD-ACE(U) are employed to predict the effects of various patterns of microstructures on mixing effi ciency with the range of Reynolds number from 0.05 to 50. The infl uences of non-dimensional parameters such as the Reynolds number and Peclet number as well as the geometrical parameters on the mixing performance are presented in terms of the mixing index. While Re is less than 1, molecular diffusion is the only way to achieve the mixing processes. As Re increases, Peclet number increases as well. The convective transport becomes more important than diffusive transport. The mixing index decreases for all micromixers. While Re is greater than 1, the mixing index of the micromixer with cross obstacles starts to increase as Re increases. This means that the fl ow fi eld in this micromixer results in effi cient chaotic mixing. Micromixers which are made of PDMS are used to investigate the mixing characteristics influenced by the different kinds of microstructures. A significant amount of stirring resulting from chaotic mixing can be seen due to the

fl uids fl owing through the cross obstacles embedded on the channel. Experimental results show that micromixer with cross obstacles has great mixing effi ciency and the mixing index increases 82% when the Reynolds number is about 50.

6886-20, Session 6A novel approach on fl uid dispensing for a DNA/RNA extraction chip packageL. Xie, C. S. Premachandran, M. Chew, Institute of Microelectronics (Singapore); D. Xu, Q. Yao, Institute of High Performance Computing (Singapore); P. Damaruganath, Institute of Microelectronics (Singa-pore)

Development of DNA/RNA LOC (Lab on a Chip) chip package is done using a polymer material, PDMS (Poly dimethyl siloxane). PDMS is a biocompatible, transparent material and has good resistance to chemicals. Rectangular channels with dimension 500um are made on the bottom PDMS substrate and are connected to the micro channels of a LOC . In the DNA LOC chip, DNA extraction process requires blood and other reagents, such as high salt, ethanol, water, air etc. Except blood other fl uids can be stored in the package and can be injected into the package during the DNA extraction process. Reservoirs are fabricated on the PDMS package and the fl uids are stored in the reservoir. The novelty in this package is the integration of reservoir inside the package for storing reagents for DNA LOC chip and eliminating the contamination issue from tubes and bottles used in the old system.

A membrane based pump integrated with a pin valve is developed to dispense the fl uid in a controlled manner. The developed membrane pump is integrated into the sample preparation cartridge for DNA/RNA extraction. A thin membrane of highly elastic, biocompatible material is bonded to cover reservoir space. An external actuator pushes the membrane down and the resulting displacement of the membrane pushes the fl uid into the channel through a pin valve. The fl uid displaced inside the reservoir is proportional to the external actuation. The displacement of the membrane is controlled by an external actuation and is proportional to the fl uid fl ow rate.

The pumping mechanism of the membrane pump is studied using CFD (Computational Fluid Dynamics) simulation. A transient CFD simulation resulted due to the interaction between the membrane and the fl uid. In the simulation of the membrane pump the maximum displacement and the principal strain is in the center of the reservoir. The velocity distributions of the fl uid fl ow in the membrane pump at the junction of the reservoir and outlet are also described. The simulated results are validated with the experimental results and the relative error was with in 2%.The selection of membrane material, ratio of mixing the parts is studied and is reported in this paper. The membrane material is selected based on the longest elongation of the membrane with smaller force. A correlation study of the membrane displacement volume with respect to the external actuation is done and a calibration curve is plotted to obtain the actuation speed for varying fl ow rate Fluid fl ow mechanism with simulation and detailed development of the fl uid dispensing with experimental results with fl ow rate control will be presented in the full paper

6886-21, Session 6Development and characterization of a microheater array device for real-time DNA mutation detectionL. D. Williams, The Univ. of Utah; M. Okandan, Sandia National Labs.; A. Chagovetz, S. Blair, The Univ. of Utah

DNA analysis, specifically single nucleotide polymorphism (SNP) detection, is becoming increasingly important in rapid diagnostics and disease detection. Temperature is often used in these detection events to help speed reaction rates and perform melting of hybridized oligonucleotides. Based on the differences in melting temperatures, Tm, between complementary oligonucleotides and SNPs, specifi city can be increased. We have characterized Tm’s in solution and on two different solid substrates of three oligos from known mutations associated with Cystic Fibrosis. Taking advantage of Tm differences, a microheater array device was designed to enable individual temperature control of up to 18 specifi c hybridization events. The device was fabricated at Sandia



National Laboratories using surface micromachining techniques. The microheaters have been characterized using an IR camera at Sandia and show individual temperature control with no thermal cross talk. Development of the device as a real-time DNA detection platform, including surface chemistry and associated microfluidics, will be described.

6886-22, Session 6Connecting interface for modularization of digital microfl uidicsH. Yang, S. Fan, W. Hsu, National Chiao Tung Univ. (Taiwan)

Modularization is an approach to reduce the complexity of microchip, and provide the fl exibility for functional extension, breakdown replacement or consumable parts disposability. For continuous fl ow-based microfl uidics, several fl uidic modules have been commercialized, such as Agilent (HPLC-Chip), and AgnitioST (BioIC). However, device or technique to connect droplet-based microfl uidic chips has not been reported yet. Here, a new connecting interface is proposed and investigated to achieve the modularization of digital microfl uidics.

The proposed connecting interface is designed to be compatible with the electrowetting-based device of two plates design. Two devices can be connected by this interface design. The gap size of interface is a key factor for droplet passing the interface. To determine the feasible range of the design, especially for droplet crossing the interface gap, an investigation on various gap sizes are performed. However, in preliminary tests without proper interface edges, droplet is not able to cross the gap even at high voltage of 140 Vac. By utilizing perpendicular cutting method, a smooth edge surface can be obtained to provide successful results.

DI water droplets of 1.5 ul, 2.5 ul, and 3.5 ul are tested with various gap sizes from 50 um to 350 um on the control electrodes of 1500 um wide and spacer of 500 um thick. It is shown that all droplets can smoothly pass the 200 um gaps. Finally, the droplet passing through the interface is successfully demonstrated. More detailed design issues and discussion will be presented in the conference.

6886-23, Session 6Spiral microfl uidic nanoparticle separatorsA. A. S. Bhagat, S. S. Kuntaegowdanahalli, I. Papautsky, Univ. of Cincinnati

Nanoparticles are becoming ubiquitous in the environment-from sunscreens to leaching out of dishwashing machines. Yet, their effects on human and animal health are not known or fully understood. Conventional micro and nano particle separation systems traditionally employ membrane-based fi ltering schemes that are limited by the membrane pore size, making them ineffi cient for separating a wide range of sizes. In this paper, we describe passive spiral microfl uidic geometries for momentum-based fl uidic separations. The proposed design is capable of separating particulate mixtures over a wide dynamic range and will prove useful in a wide range of applications that involve rapid separation of nanoparticles in real-world samples with a wide range of particle components.

Spirally shaped microchannels can be used to separate micro and nano particle mixtures by exploiting the hydrodynamic and inertial differences between particles of different sizes fl owing through the micro channel. The device works on the principle of centrifugal acceleration experienced by particles fl owing in a curved microchannel. Depending on their size, and hence their mass, centrifugal force causes particles to move towards the outer channel wall. As a result of these forces, particles form different streams according to their size and mass. In this work, the spiral microchannel designs were successfully modeled and simulated using CFD ACE+ software (ESI-CFD Inc., Huntsville, AL). During modeling, polystyrene particles of various sizes (<1 μm), dispersed in a fl uid were investigated. Spiral geometries having varying number of loops and diameters were modeled to achieve separation of particles as small as 60 nm in size. Modeling results were experimentally verifi ed by fabricating devices in polydimethylsiloxane (PDMS). PDMS (Sylgard 184) was cast on SU-8 molds and bonded to standard 3” x 1” microscope

slides using O2 plasma. Experimental characterization was performed using fl uorescently labeled polystyrene beads of varying sizes on an inverted fl uorescent microscope equipped with a 12 bit CCD camera for image capture.

As predicted in the model, all the 590nm particles present in the bottom half of the channel at the inlet move to the top half at the outlet.

In conclusion, these results suggest that nanoparticles can be rapidly separated using a spiral microchannel geometry. The experimental data are in excellent agreement with the numerical models. The designs are planar simplifying fabrication and integration with existing LOC technologies. We expect that spiral nanoparticles separators will enable numerous biological and environmental applications.

6886-04, Poster SessionUsing a T-junction microfl uidic chip for manipulating the UV-photopolymerized microparticles and their utilization as a potential microcapsuleC. Yeh, K. Huang, S. Lai, Y. Lin, National Cheng Kung Univ. (Taiwan)

The use of microfl uidic T-junction for uniform nanoparticles-loaded UV-photopolymerized microparticles generation is presented. Our strategy is based on shear force for the formation of a series of self-assembling emulsions, and employing a 365 nm UV light to solidify (polymerization) the emulsions. We could control the size of the emulsions from 410 to 700 μm in diameter by altering the fl ow rates of the dispersed phase and continuous phase. In addition, the encapsulation of gold nanoparticles (AuNPs) was also studied.

No attention has been paid to applying microfl uidic T-junction to control the performance of monodisperse polymer capsules, even though a T-junction design is one of the most frequently used microfl uidic geometries to produce immiscible fl uid segments. The mechanism of T-junction microfl uidic chip in emulsions-volume control was well represented in the recent literature [1-2]. Therefore, the goal of this study focuses on using microfl uidic T-junction for the manipulation and the generation of monodisperse polymer capsules.

The encapsulation of a model material was examined to verify the applicability of this microfl uidic technique. We fi nd that the AuNPs were absorbant with a peak of around 520 nm and polymer solution was non-absorbant in UV-Vis. Furthermore, the absorption spectra of AuNPs-loaded polymeric microparticles showed a broad peak around 566 nm which indicated 5 nm AuNPs were entrapped in the polymeric microparticles.

The uniformity of the size of the UV-photopolymerized microparticles could be controlled by altering the fl ow rates of sample and oil fl uid phase without a follow-up process to adjust the size. We successfully applied polymer microparticles to encapsulated AuNPs by using microfl uidic technique and the approach in manipulation of polymer microparticles would provide many potential usages for pharmaceutical applications.

REFERENCES

[1] “Using a Microfluidic Chip and Internal Gelation Reaction for Monodisperse Calcium Alginate Microparticles Generation”, K.S. Huang, T.H. Lai, Y.C. Lin, Frontiers in Bioscience, 12, 3061(2007).

[2] “Synthesis of Monodisperse Biodegradable Microgels in Microfl uidic Devices”, B.G. De Geest, J.P. Urbanski, T. Thorsen, J. Demeester, S.C. De Smedt, Langmuir, 21, 10275(2005).

6886-25, Poster SessionAnalysis of propulsion mechanisms for microswimming robotsM. Koz, F. A. Tabak, S. Yesilyurt, Sabanci Univ. (Turkey)

In fl ow regimes with a Reynolds number much smaller than 1, screw-like motion of a swimmer is an effective technique to use. This screw-like motion is already being used by the single-celled organisms, like sperms, in the nature. Therefore, microswimmers can be based on this appropriate propulsion system. Micropumps can also be based on the same propulsion system. The main focus of this study is showing how fl ow rate is affected by performance parameters. These parameters



are frequency, amplitude and wave length. For achieving the objective, parametric simulations were done by using software called, COMSOL. Because of having a Reynolds number close to 0.001, all of the models solved by COMSOL were based on Stokes equation. Moreover, in order to keep the continuity of the rotating mesh, “moving mesh” module of the COMSOL was also used.

The parametric simulations are based on non-dimensional parameters. For this fact, the value of each parameter itself does not have any importance in this study. However, the ratio of these values has a great importance. Hence, the simulations show that how much a change in one parameter affect the fl ow rate.

The results show that frequency has a linear effect on fl ow rate. The amplitude variable has a stronger effect with quadratic relation. On the contrary to two former parameters, wave length is inversely proportional to fl ow rate.

6886-26, Poster SessionDissolved oxygen sensing using organometallic dyes deposited within a microfl uidic environmentQ. Chen, H. Ho, L. Jin, B. W. Chu, M. Li, V. W. Yam, The Chinese Univ. of Hong Kong (Hong Kong China)

This work primarily aims to integrate dissolved oxygen sensing capability with the microfl uidic platform in which there might be arrays of micro bio-reactors or bio-activity indicators. The measurement of oxygen concentration is of signifi cance for a variety of bio-related applications such as cell culture and gene expression. Optical oxygen sensors based on luminescence quenching are gaining much interest in light of the fact their low power consumption, quick response and high analyte sensitivity in comparison to similar oxygen sensing devices. In our microfl uidic oxygen sensor device, a thin layer of oxygen-sensitive luminescent organometallic dye is covalently bonded to a glass slide. Micro fl ow channels are formed on the glass slide using patterned PDMS (Polydimethylsiloxane). Dissolved oxygen sensing is then performed by directing an optical excitation probe beam to the area of interest within the microfl uidic channel. The covalent bonding approach for sensor layer formation offers many distinct advantages over the physical entrapment method including minimizing dye leaching, ensuring good stability and fabrication simplicity.

6886-27, Poster SessionFlexible enclosure for fl uidic sealing of microcomponentsT. Ueda, B. L. Gray, Simon Fraser Univ. (Canada)

A fl exible enclosure for fl uidic sealing of SU-8 microcomponents was developed using polydimethylsiloxane (PDMS). The fl exible enclosure is fabricated separately and can be mechanically assembled to SU-8 microchannels even in the presence of liquid or living cells. Oxygen plasma surface activation is usually used to achieve a fl uid tight seal between PDMS and SU-8 surfaces. However, this process results in a permanent seal, and the channels cannot already contain immobilized enzymes or cells. If PDMS is attached to SU-8 without surface activation, the two can be separated easily but only maintain a fl uid tight seal at very low fl ow rates/pressures, which is unsuitable for experiments involving fl ow. We now present PDMS and SU-8 substrates containing interlocking structures to create a stronger fl uid tight seal that is completely reversible. Interlocking 500 μm peaks and valleys were fabricated on PDMS and SU-8 surfaces that hold the two pieces in place to prevent PDMS lid and SU-8 microchannels separation during handling and fl uid fl ow. Furthermore, the 100 μm peak on the PDMS surface, which has the same dimensions as the 800 μm deep SU-8 microchannel, acts as a plug to keep the fl uid within the microchannel and prevent leakage between the PDMS-SU-8 interface. The assembled microchannels and enclosures can withstand manually applied fl uidic pressure via a syringe which is noticeably much higher than channels with a simple lid and no interconnect structures. The device is currently being further quantifi ed for pressure versus fl ow rate using a syringe pumps and pressure sensor.

6886-28, Poster SessionMechanical assembly and magnetic actuation of polydimethylsiloxane-iron composite interconnects for microfl uidic systemsS. Jaffer, B. L. Gray, D. G. Sahota, M. H. Sjoerdsma, Simon Fraser Univ. (Canada)

We present magnetically-actuated micromechanical interconnects for microfl uidic applications fabricated in-house using PDMS-iron elastomer-ferromagnetic composites (EFCs). Interconnects are fl uid-tight, interlocking cylindrical posts and holes whose assembly can be made easier by magnetically actuating the EFC cylinders via axial extension and radial contraction. Towards this goal, we demonstrate magnetic actuation and quantify the mechanical disassembly of PDMS-iron interconnects. Previously, we showed the mechanical assembly and disassembly of hybrid combinations of non-magnetic SU-8, silicon, and polydimethylsiloxane (PDMS) microfl uidic interconnects, as well as their use for world-to-chip coupling when integrated with sample components (Gray et al., 2004-7). However, these interconnects were made in silicon or simple (non-magnetic) polymers, and were assembled through conventional mechanical peg-in-hole deformation, which requires tighter fabrication tolerances. Recently, magnetorheological materials have been used in applications including reducing shock and vibration in automobiles (Sjoerdsma, 2005), and active membranes in micropumps (Nagel et al., 2006). We fabricate EFCs for our interconnects by embedding iron microspheres (<63% by weight) in PDMS. We employed permanent magnets to create 0.045-0.065T constant fi elds, along with an optics test set-up that included an LED source and magnifi cation to quantify micron-sized defl ections. The interconnects exhibited radial contractions of 3-12% and axial elongation of 2-11%. Without the magnetic field, disassembly forces of 36-71mN were measured by a controlled force linear actuator for PDMS-iron cylinders from PDMS and PDMS-iron holes. This work shows promise for radial contraction of cylinders for assembly with lower forces while maintaining high disassembly forces once the interconnects are assembled and the magnetic fi eld is removed.

6886-29, Poster SessionDevelopment of an evaporation-based microfl uidic sample concentratorN. R. Sharma, A. Lukyanov, R. L. Bardell, L. Seifried, M. Shen, Micro-Plumbers Microsciences LLC

Over the last several years numerous micro-techniques and devices requiring less than 100 microliters of sample have been developed for bacterial, viral and protein-based pathogen detection. However, the sensitivity limit of these devices may not be suffi cient for detection without prior sample preparation and pre-concentration steps. Off-line sample preparation methods do exist, however the methods currently available are either labor or instrument-intensive and do not lend themselves to integration in a microfl uidic device or method.

MicroPlumbers Microsciences LLC, has developed an inexpensive concentrator device based on isothermal evaporation. The device allows for rapid concentration of dissolved or dispersed substances and microorganisms (e.g. bacteria, viruses, proteins, toxins, enzymes, antibodies, etc.) under conditions gentle enough to preserve their specifi c activity or viability. It is capable of removing close to 1 ml of water per minute at 37°C, and has dimensions compatible with typical microfl uidic devices. The concentrator can be used stand-alone or integrated into many different processes and analytical devices, substantially increasing their sensitivity and decreasing their processing time. The evaporative concentrator has applications in many areas such as biothreat detection, civil environmental monitoring, forensic medicine, pathogen analysis, and agricultural industrial monitoring.

In our presentation, we describe various versions of concentrator design. In addition, we present results of CFD modeling of evaporation performance under various conditions, as well as results of actual experiments involving concentration of protein and microparticulate samples.



6886-30, Poster SessionAnalysis of surface-tension-driven blood fl ow using spectral domain optical coherence tomographyY. Ahn, Univ. of California/Irvine; S. Cito, I. Katakis, J. Pallares, Univ. Rovira i Virgili (Spain); Z. Chen, Univ. of California/Irvine

Lab-on-a-chip is a device handling bio-fl uids that integrate (multiple) laboratory functions on a single micro chip. Small volumes reduce the time taken to synthesize and analyze a product. Compact devices allow samples to be analyzed at the point of need rather than a centralized laboratory. Small size of channel also impacts on the actuation means for liquid handling. A passive pumping using the surface tension only is the most effective method because the effect of surface tension on the fl ow is signifi cant in microscale. The leading edge of the surface-tension-driven fl ow is the triple point where a liquid, the chip wall, and a stationary gas meet. The movement of the triple point, i.e., the advancing front of the fl ow, is driven by surface tension, resisted by viscous shear stress, and balanced by the inertial force. In previous studies, the motion of meniscus has been predicted theoretically with one-dimensional model. However, three-dimensional fl ow fi eld around the meniscus and the effect of cross-sectional shapes on the fl ow have not assessed yet. Here, we visualized and analyzed the surface-tension-driven blood fl ow using spectral-domain Doppler optical coherence tomography (SDDOCT). SDDOCT is an emerging imaging modality that has high-speed, high-resolution, noninvasive, cross-sectional imaging capability. Since SDDOCT allows simulteneous real-time visualization of structure and fl ow, it is a good tool for imaging multi-phase fl ows with interfaces. We, here, quantifi ed fl ow recirculation near the meniscus in circular, square, and rectangular glass channels, and measured the speed of the meniscus and compared to the analytical result.

6886-31, Poster SessionOn-board pnuematic valves for multiplexed applications in microfl uidic devicesL. Levine, J. Goldstein, ALine, Inc.

Most immunoassays are multistep processes and involve washes with buffer and addition of capture antibodies and other reagents to detect the analyte. To develop and contain an assay on an enclosed, fl uidic cartridge, on board valves are required to permit various fl uid streams to reach the sample chamber. Pneumatically activated on board valves produced using a laminate fabrication process offers a low-dead volume and cost effective way to perform these various steps while dispensing from on-board reservoirs. This permits the entire assay to be contained in a single disposable device. While on-board pneumatic valves are not a new concept in microfl uidic devices, an important consideration for incorporation into a commerically viable device is the reproducible manufacture and robust perforamnce of such valves under application conditions. We have developed a method of incorporating robust, pneumatic valves that can be readily incorporated into multiplexed microfl uidic devices. In this paper we demonstrate the application of such valves to support washing and uniform delivery of eight different reagents to eight samples.

6886-32, Poster SessionProcess development for waveguide chemical sensors with integrated polymeric sensitive layersR. Amberkar, Z. Gao, D. Henthorn, Univ. of Missouri-Rolla; J. Park, C. Kim, Univ. of Missouri/Rolla

Due to the proper optical property and flexibility in the process development, an epoxy-based, high-aspect ratio photoresist SU-8 is now attracting attention in optical sensing applications. Manipulation of the surface properties of SU-8 waveguides is critical to attach functional fi lms such as chemically-sensitive layers. We describe a new integration process to immobilize fl uorescence molecules on SU-8 waveguide surface for application to intensity-based optical chemical sensors.

We use two polymers for this application. Spin-on, hydrophobic, photopatternable polydimethyl siloxane (PDMS) is a convenient material to contain fl uorophore molecules and to pattern a photolithographically

defi ned thin layer on the surface of SU-8. We use fumed silica powders as an additive to uniformly disperse the fl uorophores in the PDMS precursor. In general, additional processes are not critically required to promote the adhesion between the SU-8 and PDMS. The other material is poly(2-hydroxyethyl methacrylate), (p-HEMA). Recently we demonstrated a novel photografting method to modify the surface of SU-8 using a surface bound initiator to control its wettability. The activated surface is then coated with a monomer precursor solution. Polymerization follows when the sample is exposed to UV irradiation, resulting in a grafted p-HEMA hydrogel layer incorporating fl uorophores within the hydrogel matrix. Since this method is based the UV-based photografting reaction, it is possible to grow off photolithographically defi ned hydrogel patterns on the waveguide structures.

The resulting fi lms will be viable integrated components in optical bioanalytical sensors. This is a promising technique for integrated chemical sensors both for planar type waveguide and vertical type waveguide chemical sensors.

6886-33, Poster SessionFemtosecond laser writing for selective chemical etching and optical device integration in 3D optofl uidic systemsS. Ho, M. L. Ng, S. M. Eaton, H. Zhang, C. C. Qu, P. R. Herman, J. S. Aitchison, Univ. of Toronto (Canada)

Femtosecond lasers offer attractive means for creating three-dimensional (3D) optofl uidic systems in fused silica glasses that promise high density lab-on-a-chip integration for fl exible routing of fl ow channels and optical sensing circuits. Selective chemical etching of laser irradiated glass with diluted hydrofl uoric acid (HF) enables microfabrication of high aspect-ratio micro-channels inside glasses, alleviating the channel crossing and fl uid mixing problems in planar fl uidic systems. In this paper, single- and multi-parallel laser modifi cation tracks were written in fused silica glass (Corning 7980) with a fi ber-amplifi ed ultrafast laser (IMRA μJewel D-400-VR) operating at 1-MHz repetition rate and providing 220-fs pulses (Lorentzian profi le) at 522-nm wavelength. Laser pulse energy of 100 to 200 nJ was focused with a 40x aspherical lens (NA = 0.55) to modify the transparent glass and form buried optical waveguides or modifi cation tracks susceptible to the HF chemical etching. Laser polarization, multi-line scanning, sample scan speed (0.2 to 0.5 mm/s) and HF etching (1-5%) were optimized as control parameters to enhance or inhibit the formation of optical waveguides and microfl uidic channels and thereby facilitate the full 3-D integration of waveguide devices with the microfl uidic channels in a two-step fabrication method. We present laser processes for controlling waveguide properties-single or multi-mode-and micro-channel cross-sectional profi le and demonstrate several examples of integrated optofl uidic systems. In this way, femtosecond laser processing is shown as a promising rapid prototyping technique for creating novel 3-D optofl uidic systems in fused silica glasses.

6886-34, Poster SessionEvaluation of passive planar microfl uidic devices for mixing of particle fl owsK. T. Wurm, A. A. S. Bhagat, I. Papautsky, Univ. of Cincinnati

On the microscale, the behavior of liquids is much different than that observed at the macroscale. Liquids fl ow with excellent laminar profi les, with no turbulence and mix predominantly by diffusion. This presents a signifi cant challenge for mixing samples and reagents in miniaturized bioanalysys systems, as mixing length may be on the order of 10 cm at Re = 1 for fl ows in microchannels. Obviously, such mixing lengths are not practical for microfl uidic devices. Thus micromixing has been the subject of intense research in the recent years, and many conventional micromixers have been designed and tested for homogeneous mixing in disposable lab-on-a-chip (LOC) systems. Nevertheless, despite the great success of mixing pure liquids, in real-world applications micromixers need to mix particulate fl ows such as blood, cell or microorganism suspensions. In this work we report on the design and characterization of a passive micromixer intended for both fl uid and particle mixing.



The micromixer designs were successfully modeled and simulated using CFD ACE+ software. During modeling, particles 1μm in diameter were introduced into one of the inlet streams and their path as they traversed downstream was traced. To quantify the effi ciency of the micromixer for mixing particles, the dispersion of the microparticles across the channel width was measured. At the inlet, microparticles are confi ned to one half of the channel width (the other half is buffer solution devoid of any microparticles). Complete mixing was achieved when particle dispersion occurred across the entire microchannel width. Modeling results were experimentally verifi ed by fabricating devices in PDMS (cast on SU-8 molds, and bonded to standard 3” x 1” microscope slides using O2 plasma). The micromixers were fi rst tested with a 1 μM fl uorescein solution for Re 0.1 to 10 to quantify mixing and then tested using fl uorescently labeled 590 nm polystyrene beads dispersed in water.

Our results suggest that conventional passive micromixers, while effi cient in mixing liquids, are not necessarily effi cient for mixing particles. For real-world applications, mixing of particlulate fl ows is important. Thus, the nature of the sample to be mixed must be considered in order for the designed micromixers to be practical.

6886-35, Poster SessionInterdigitated array microelectrode capacitive sensor for detection of Paraffi nophilic MycobacteriaA. Sampson, E. T. Peterson, I. Papautsky, Univ. of Cincinnati

Mycobacterium Avium Complex (MAC) is an opportunistic pathogen that threatens public health and has high clinical relevance. While culture-based and molecular biology techniques for identifi cation are available, these methods are prone to error and require weeks to perform. There is a critical need for improved portable lab-on-a-chip sensor technology which will enable accurate and rapid point-of-care detection of these microorganisms. In this work, we describe a new capacitive sensing strategy exploiting the paraffi nophilic nature of MAC. Due to a unique hydrophobic cell envelope combined with an ability to process long chain aliphatic hydrocarbons, paraffi n baiting can be used to selectively extract these microorganisms from complex samples. In our approach, paraffi n wax fi lm is deposited over interdigitated array (IDA) microelectrodes; as bacteria consume the dielectric paraffi n layer, the fringing electric fi elds and charging currents of the IDA change to facilitate detection.

Several IDA geometries were designed and simulated using CFD-ACE+ modeling software package. Electrode characteristics were modeled using a 5V driving potential at 166 kHz and IDA capacitances as well as 3D electric fi eld maps were determined. These IDAs were fabricated by patterning 200nm thick gold electrodes on 1mm thick glass substrates and characterized using a charge-based capacitive measurement (CBCM) technique. Measured charging currents of 1.1 μA on a 10 μm feature IDA correlate to a device capacitance of 3.1 pF and verifi ed modeling results to within ~12% of actual device capacitance.

Using this approach, detection of femto Farad changes in capacitance is possible, making this a feasible technique for sensing small changes in the paraffi n as the bacteria consume the fi lm. This new sensing strategy will allow for rapid detection of Mycobacterium species and thus enable doctors to diagnose infections at point-of-care for faster and more effective treatments.

6886-36, Poster SessionGeneral 3D microporous structures fabricated with two-photon laser machiningY. Liu, L. J. Pyrak-Nolte, D. D. Nolte, Purdue Univ.

Microporous structures are a common theme in biomedical devices, microfl uidics, geology and other fi elds of study. However because of the complexity and lack of symmetry, it has been difficult to fabricate 3D arbitrary microporous structures with broad-illumination photolithography. We apply two-photon polymerization and femtosecond laser direct-writing techniques to fabricate 3D microporous structures in photopolymers. Three dimensions are built up from 2D patterned-microchannels with random geometry. The height and the width of the features are about 40μm and 5μm, respectively. We make 3D microchannels with random apertures and obstacles in two layers that allows liquid to fl ow through multiple random fl owpaths. We also fabricate three-layered lattice-like microstructures. In each layer, the height and the width of the walls are about 18μm and 2μm, respectively. Our current application of these microporous structures is for a fundamental study of internal fl uid interfaces in microfl uidic systems during imbibition and drainage, using interfacial areas per volume as a measure of internal energy density as a function of saturation and capillary pressure.

This material is based upon work supported by the National Science Foundation under Grant No. 0509759 and Sandia National Laboratories.

6886-38, Poster SessionPyrosequencing on a microfl uidic fi beroptic-faceplate integrated with CMOS image sensorS. Goel, H. Eltoukhy, A. Agah, P. Griffi n, M. Nemat-Gorgani, B. Gharizadeh, R. W. Davis, M. Ronaghi, Stanford Univ.

Pyrosequencing is emerging as a popular platform for DNA analysis. Steps towards the development of a low-cost instrument based on Pyrosequencing in high-density picotiterplates are underway. This will enable any lab to perform de novo genome sequencing. To reach this goal, signifi cant improvements have been made in the chemistry, picotiterplate fabrication, microfl uidics, base-calling, assembly, and detection parts. Here we describe a strategy to fabricate picolitre sized 50 micron wells by SU-8 photolithography on fi beroptic faceplates. The DNA fragments and enzymes are immobilized on 30 micron controlled porous glass (CPG) beads and 2 micron paramagnetic beads respectively. The beads are centrifuged into the SU-8 wells resulting only one DNA bead per well. The fi nal device is integrated by pitch-matching wells on picotiterplate to pixels of an inexpensive and custom designed CMOS image sensor. A microfl uidic fl ow-system consisting of a valve selector and peristaltic pump is designed to direct the reagent from one of the seven input reservoirs to the inlet of the device. The whole system is computer controlled and a graphical-user-interface has been designed to visualize the data during the sequencing run. Using the improved base-calling software we have achieved read-length upto 500 base-pairs. The 50mm X 2mm region of the device is capable to sequence more than one million bases.



Conference 6887: MOEMS and Miniaturized Systems VIITuesday-Wednesday 22-23 January 2008 • Part of Proceedings of SPIE Vol. 6887 MOEMS and Miniaturized Systems VII

6887-20, Poster SessionMobile fl at mirrors for micro-optical scannersG. Molar-Velazquez, F. J. Renero-Carrillo, W. Calleja-Arriaga, Instituto Nacional de Astrofísica, Óptica y Electrónica (Mexico)

Mobile fl at mirrors are used in different applications, particularly in optical scanning systems. These mirrors are manufactured in crystalline silicon through MEMS (Micro-Electro-Mechanical -Systems). We have simulated, by means of the CoventorWare software(tm), the humid etching process for 10 microns resolution. Thus, we present a simulation of a fl at mirror movement versus voltage, for a two-dimensional micro-optical scanner.

6887-21, Poster SessionNew approach for MEMS scanning mirror for laser projection systemsH. Grueger, J. Knobbe, M. Scholles, H. Schenk, H. K. Lakner, Fraun-hofer-Institut für Photonische Mikrosysteme (Germany)

Fraunhofer IPMS already demonstrated a technology for resonant 2D MEMS scanning mirrors, where the resonant driving principle has been established for mirror and frame. Using frequencies of 1250Hz for the frame and 28kHz for the mirror full color laser projection systems have been developed. Multiple Lissajous patterns are needed for the generation of one picture. Thus effi ciency and frame rate are limited.

Recently, a new approach has been invented: still a resonantly moving mirror is used for the fast movement but the frame is driven by a quasi static drive. Among the several driving mechanisms possible the piezoelectric drive is the most promising. By choosing appropriate piezoelectric materials MEMS process integration is feasible.

Besides a quasi static deviation to generate pictures further options arise. The picture generation algorithm can be simplifi ed if the movement along the rows is stepwise and the movement back is one fast step. This saw tooth like motion could be achieved through the high frequency response of piezoelectric materials.

The setup of the chip is similar to the existing 2d scanning mirrors: Inside the mirror with an area of 0.25 to 9 mm2 is mounted on two spring bearings to the frame and resonantly driven through comb structures. The frame baring to the chip is realized through fl at bending actuators. Either the position change has to be considered at the picture generation or a layout has to be designed in a way that ensures a Pivot point in the middle of the mirror.

6887-01, Session 1A novel diffractive micro-optical modulator for mobile projection display applicationsS. K. Yun, J. H. Song, S. An, I. Yeo, Y. Choi, Y. Lee, H. Park, K. Han, H. S. Yang, V. Yurlov, I. Shyshkin, A. Lapchuk, H. Kim, J. Jang, J. Kyo-ung, J. Yang, S. Yoon, C. Park, J. Cheong, Y. Hwang, K. Woo, S. Ryu, S. Lee, C. Koh, Y. Paek, D. Bae, H. Lee, J. Lee, Y. Ryu, H. Hwang, C. Yang, O. Lim, D. Park, S. An, J. Bae, S. Cho, B. Go, S. Hong, H. Jung, S. Kim, K. Lee, J. Park, J. Yang, G. Byun, S. Byun, Y. Cho, C. Kim, J. Kim, S. Kim, S. Lee, W. Lee, K. Oh, S. Oh, W. Shin, B. Song, SAM-SUNG Electro-Mechanics Co., Ltd. (South Korea)

A diffractive optical modulator has been fabricated based on a micromachining process. Novel properties of its fast response time and dynamics were fully understood and demonstrated for the strong potentials in embedded mobile laser display. A bridged thin fi lm piezo-actuators with so called open mirror diffraction structure has been designed. Optical level package was also achieved to successfully prove its display application qualities. Display circuits and driving logic were developed to fi nally confi rm the single-panel laser display at a 240Hz VGA (640*480). With its effi ciency of more than 75% the 13cc volume optical engine with the MEMS-based VGA resolution SOM showed 6Lm brightness at a 2W electrical-power-consumption. Described will be design principle, fabrication, packaging, performances, and product reliabilities of the invented SOM.

6887-02, Session 1Two dimensional microscanners with large horizontal-vertical scanning frequency ratio for high-resolution laser projectorsS. Hsu, Fraunhofer-Institut für Photonische Mikrosysteme (Germany)

Miniature laser projector is a promising application for MEMS microscanners. To produce high resolution two-dimensional images, the scanner needs: 1. a large scan angle-diameter product (theta-D), 2. a high horizontal scan frequency, and 3. a large horizontal-to-vertical scanning frequency ratio. The above requirements can be achieved by increasing the scan angle, diameter, and resonant frequency of a mirror. However, this also increases the dynamic deformation and reduces the mirror’s optical quality. In addition, a fast scanner needs to be coupled with a laser source, which can be modulated with even higher frequency. The availability of lasers becomes more diffi cult as the frequency requirement gets higher. In response to the constraint, we present two designs of two-dimensional gimbal microscanners with low vertical scan frequencies of ~70 Hz and ~330 Hz and a reasonably high horizontal scan frequency of 30 kHz. The scanner is fabricated in a 30 um silicon-on-insulator with backside structures for both mirror and gimbal-frame. The backside structure under the frame increases the frame weight and effectively reduces the stiffness of the rotation spring. The slow vertical scan can thus be achieved without reducing the spring width dramatically. A patterned backside structures also reinforces the mirror plate during actuation such that the root-mean-square dynamic deformation of the 1 mm diameter mirror is less than 40 nm (lamda/10 for violet) at ±10 degrees mechanical scan angle. The microscanners are installed into prototype laser projectors to demonstrate their capabilities of producing SVGA quality (800 pixels x 600 pixels) images.

6887-03, Session 1Slow scanning electromagnetic MEMS scanner for laser displayH. Jeong, Y. Park, H. Jeong, Y. Cho, S. Chang, J. Kim, S. Kang, J. Hwang, J. Lee, SAMSUNG Advanced Institute of Technology (South Korea)

A small size, low power consuming, shock proven scanner with capacitive comb type rotational sensors was designed, fabricated, and characterized. In order to minimize the power consumption as well as device size, the mirror surface was placed on the opposite side of the coil plate. To prevent thermal deformation of the mirror, the mirror was partially connected to the center point of the moving body. For shock proof, mechanical stoppers were designed as a component of the device. The scanner was fabricated from two silicon wafers and one glass wafer using a bulk micromachining technology. The packaged scanner consisted of the scanner chip, a pair of magnets, yoke rim, and base plate. The fabricated package size is 9.2x10x3 mm3 (0.28 cc) and the mirror size is 3x1.5 mm2. The scanner chip has no damage after the shock test with impact of 2000 G in 1 ms. In case of full optical scan angle of 30° at 120 Hz with 98% linearity, the driving current and power consumption are measured within 50 mA and 60 mW, respectively, which are suitable for mobile display applications.

6887-04, Session 1Flat electrowetting optics and displaysJ. C. Heikenfeld, Univ. of Cincinnati

A recent explosion of growth in electrowetting research can be partially attributed to the discovery of numerous applications in photonics. Innovations include, but are not limited to, liquid lenses, high-brightness displays, and area tunable refl ectors. The University of Cincinnati has launched a multi-faceted program in fl at electrowetting optics that involves AFSOR supported work in laser radar applications, fundamental work supported by NSF, and 4 commercial partners with interests ranging from conformal electro-camoufl age, to switchable retrorefl ectors, to high-brightness video displays.

In this paper we will present the fundamental principles behind


electrowetting optics. Also presented will be use of MEMs fabrication principles to create device arrays exceeding 1 million elements per 4x4” substrate. Two technologies will be highlighted:

****** Electrowetting micro-prisms and micro-mirrors utilize a square micro-channel constructed with four electrowetting sidewalls. Electrowetting at each sidewall produces a saline/oil contact angle change of 35°<8¸<170°. This large change in contact angle can be used achieve as much as +/-105° of laser beam defl ection in a single element device. In arrayed format, such devices produce +/-80° of beam defl ection. Switching speed for ~100 μm size elements is projected at ~100’s μs.

****** 12,800 pixel electrowetting displays have been fabricated with PEN-substrate/electrode/hydrophobic-dielectric/hydrophilic-grid. Pixel sizes have been constructed down to 50x150 μm using liquids that are dosed via self-assembly. 15 V pixels generate >70% refl ective mode operation for e-paper, >80% transmission effi ciency for back-lit displays, and even a fl uorescent emissive mode architecture with >10 lm/W effi ciency.

6887-05, Session 2Wafer-level vacuum packaged resonant micro-scanning-mirrors for compact laser projection displaysU. Hofmann, M. Oldsen, H. Quenzer, B. Wagner, Fraunhofer Institute for Silicon Technology (Germany)

Laser projection in combination with resonantly actuated MEMS scanning mirrors is expected to overcome the limitations of today’s commercially available displays in mobile devices, in particular the small screen size. On the other hand compact laser projection modules can also overcome the limitations of today’s automotive display solutions by offering higher format and resolution fl exibility than TFTs. For mobile applications stable scanning mirror operation is required over a broad temperature range. Therefore hermetic packaging of the electrostatically actuated MEMS scanning mirrors is essential to protect the sensitive actuator structures from particle contamination and to avoid breakdown due to condensation. This paper reports about design, fabrication and test of resonantly actuated two-dimensional micro scanning mirrors that are hermetically sealed at wafer level. A Pyrex glass cap with several hundred microns deep cavities and almost perfect quality of the optical window enables large mirror defl ections. Driving the scanning mirrors at pressure levels of around 10mTorr enables large scan angles of up to 100 degree even at a frequency of more than 23kHz with a 15Volt driving signal. Even at resonance frequencies of more than 100kHz considerable scan amplitude can be achieved. To enable stable operation of such a high Q resonator comb electrodes not only for driving but also separate comb electrodes for continuous capacitive position sensing are implemented in the micro mirror design.

6887-06, Session 2Development of wafer level packaged scanning micromirrorsA. Yu, Institute of Microelectronics (Singapore); J. Thillaigovindan, National Univ. of Singapore (Singapore); L. L. Yan, Institute of Micro-electronics (Singapore); R. I. Made, C. L. Gan, Nanyang Technologi-cal Univ. (Singapore); Q. X. Zhang, S. U. Yoon, J. H. Lau, Institute of Microelectronics (Singapore); C. Lee, National Univ. of Singapore (Singapore) and Institute of Microelectronics (Singapore)

This paper presents wafer level packaged MEMS scanning mirror design and simulation, and fabrication process development. The high speed scanning micromirror is one of the key components for a wide range of applications, such as laser scanning displays and handheld projectors. In view of market demands in these potential areas, we developed electrostatic comb actuated micromirrors with area sizes ranging from 1mmx1mm to 1.2mmx1.2mm. The dynamic vibration characteristics have been analyzed by using FEM tools. Torsion bars of various shapes have been characterized. By varying the design of the torsion bar of the micromirrors, different scanning frequencies ranging from 12 KHz to 20 KHz can be achieved. Besides, the hermetically sealed packaged is favored by commercial applications. We developed novel In-Ag solder based wafer level packaging technology, while we systematically studied

the packaging structures, interconnect designs, and bonding conditions, etc. The wafer level package is successfully carried out at process temperature less than 200°C. The material characterization of bonding interface shows the intermetallic compound of high melting temperature is formed. This new wafer level packaging approach allows us to have high temperature stability of packaged scanning mirror devices. It is a promising technology for commercializing MEMS scanning mirrors.

6887-07, Session 2A biocompatible miniaturized package housing for a 3D micro-mirror-based optical bioprobe for OCT (optical coherence tomogrpagy) applicationC. Premachandran, A. Khairyanto, K. Chen, J. Singh, Institute of Microelectronics (Singapore)

In this paper the development a optical bioprobe housing with a 3 D micro mirror is discussed. Silicon optical bench ( SiOB) is fabricated to attach the 3Dmicro mirror and the grin lens. The probe has a lower substrate and upper substrate. A trench is formed on the bottom substrate where the micro mirror is attached . A 0.5mm Grin lens with fi ber is attached on to the top substrate using UV curable epoxy ( ). The top substrate with grin lens is aligned to the micro mirror in a optical stage for better coupling effi ciency. The fabricated optical probe is tested with a fi xed high refl ective mirror (instead of sample) to verify the refl ected signal. The optically tested probe is tested in a OCT test up. A swept source OCT system is used to test the optical bio probe effi ciency. The tested probe is attached into a probe housing which is fabricated by a micro injection molding method. Optical probe housing is critical for the animal modeling purpose and the material used should be bio compatible. Poly carbonate material with transparency of wavelength 1300nm is used for this application. To minimize the optical loss, antirefl ection coating for 1300nm is used on the inner and outer side of the probe housing material. Custom made connectors are used in connecting the traces on the SiOB and taking out the optical fi ber from the module. The targeted dimension of the probe is less than 4mm diameter which can be used for Minimal Invasive Surgery application. Detailed development of biocomaptible probe housing and Bioimaging on the tissues by exvivo method will be explained in the full paper.

6887-08, Session 3Advanced artifi cial compound-eye imaging systemsA. Brückner, J. Duparré, A. H. Bräuer, Fraunhofer-Institut für Ange-wandte Optik und Feinmechanik (Germany)

We propose an advanced multi-channel imaging system which is realized by micro-optical fabrication techniques. The major advantage of such an artifi cial compound eye is the decoupling of the size of the fi eld-of-view (FOV) and the focal length. A large FOV can be achieved with a system that has a thickness of a fraction of a Millimeter. Compared to former developments, the presented device combines a large FOV of up to 100 degrees with an increased image resolution which is achieved by acquiring sub-images with a size of several pixels within each channel. Different design strategies show that either a physical or digital stitching of the sub-images is applicable to produce an overall image. However, the digital stitching of sub-images largely eases the fabrication tolerances what makes it the technology of choice here. Furthermore, the complexity of the optical system is decreased by using tailored microlens profi les to minimize optical aberrations and provide beam defl ection to achieve near-normal incidence of the chief ray on the image sensor plane. The so-formed ultra-compact camera system images a large FOV with constant resolution and sensitivity with respect to the fi eld angle in object space which is suitable for applications in machine vision, automotive industry or surveillance.

6887-09, Session 3MEMS-based optoelectronic system for distance measurement applicable for panorama camerasM. Schaulin, Technische Univ. Dresden (Germany); L. Kleinmann, J. Knobbe, H. K. Lakner, U. Schelinski, M. Scholles, K. Seidl, Fraunhofer-

Conference 6887: MOEMS and Miniaturized Systems VII


Institut für Photonische Mikrosysteme (Germany); H. Schönherr, KST GmbH Kamera & System Technik (Germany)

MEMS-based optoelectronic system for distance measurement applicable for Panorama Cameras Photogrammetric imaging and measurement techniques are widely used for capturing three-dimensional scenes in sciences and arts. Traditional approaches performing extensive calculations on multiple images are more and more replaced by higher integrated and faster operating measurement devices. This paper presents a MEMS-based system for distance measurement that can be integrated into a commercially available panorama camera and will add three-dimensional measuring capabilities.

This combination is very suitable to displace the current procedural manner using different instruments to acquire three-dimensional data on the one hand and texture on the other hand. The data acquisition is simplifi ed and extensive calibration and data transformations is no longer needed. Thereby the accurate allocation between texture and distance data is always secured by design.

This work outlines the optical concept to couple both measuring systems into one optical path. While texture is captured line wise, the distance is acquired sequentially. Integration of both functionalities into one housing and one optical system design requires miniaturized components for defl ection of the measurement beam. One solution is to use a resonant MEMS scanning mirror. The paper describes the resulting optical setup in detail.

The integrated construction principle induces special requirements for the LIDAR distance measuring method used here. In order to ensure eye safety, the measuring light beam is limited to low power signals. The contribution also will present an approach for processing low level signals and performing high measuring rates.

6887-10, Session 3Micromirrors for multi-object spectroscopy: optical and cryogenic characterizationS. Waldis, Univ. de Neuchâtel (Switzerland); F. Zamkotsian, P. Lanzoni, Lab. d’Astrophysique de Marseille (France); W. Noell, N. F. de Rooij, Univ. de Neuchâtel (Switzerland)

We are developing micromirror arrays (MMA) for future generation infrared multiobject spectroscopy (MOS) requiring cryogenic environment. So far we successfully realized small arrays of 5x5 single-crystalline silicon micromirrors. The 100μm x 200μm micromirrors show excellent surface quality and can be tilted by electrostatic actuation yielding 20° mechanical tilt-angle. An electromechanical locking mechanism has been demonstrated that provides uniform tilt-angle within one arc minute precision over the whole array.

Infrared MOS requires cryogenic environment and coated mirrors, silicon being transparent in the infrared. We report on the infl uence of the refl ective coating on the mirror quality and on the characterization of the MMA in cryogenic environment.

A Veeco/Wyko optical profi ler was used to measure the fl atness of uncoated and coated mirrors. The uncoated and unactuated micromirrors showed a peak-to-valley deformation (PTV) of below 10nm. An evaporated 10nm chrome/50nm gold coating on the mirror increased the PTV to 35nm; by depositing the same layers on both sides of the mirrors the PTV was reduced down to 17nm.

Cryogenic characterization was carried out on a custom built interferometric characterization bench onto which a cryogenic chamber was mounted. The chamber pressure was at 10e-6 mbar and the temperature measured right next to the micromirror device was 86K. The micromirrors could be actuated before, during and after cryogenic testing. The PTV of the chrome/gold coated mirrors increased from 35nm to 50nm, still remaining in the requirements of < lambda/20 for lambda=1μm. In conclusion the MMA is functional and remains within the specs at temperatures below 100K.

Further cryogenic characterization will be carried out on large arrays of 100x200 micromirrors, which are currently being fabricated.

6887-11, Session 4A porous silicon thermally tunable optical fi lterD. Song, N. Tokranova, A. Gracias, J. Castracane, SUNY/Univ. at Albany

Porous silicon (PSi) is a promising material for the creation of optical components for chip-to-chip interconnects because of its unique optical properties, fl exible fabrication methods and integration with conventional CMOS material sets. In this paper, we present a novel active optical fi lter made of PSi to select optical wavelengths in both the visible and infrared ranges. The tunable membrane type optical fi lter is based on a Fabry-Perot interferometer employing two Bragg refl ectors separated by an adjustable air gap, which can be thermally controlled. The Bragg refl ectors contain alternating layers of high and low porosities. These layers were created by electrochemical etching of p+ type silicon wafers by varying the applied current during etching process. Micro bimorph actuators are designed to control the movement of the top DBR mirror, which changes the cavity thickness. By varying the applied current, the proposed fi lter can tune the transmitted wavelength of the optical signal. Various geometrical shapes and sizes ranging from 100um to 1mm of the active fi ltering region have been realized for specifi c applications. The MOEMS technology-based device fabrication is fully compatible with the existing IC mass fabrication processes, and can be integrated with a variety of active and passive optical components to realize inter-chip or intra-chip communication at the system level at a relatively low cost.

6887-12, Session 4Dual-detector optical MEMS spectrum analyzer: advances, applications, and prospectsT. Otto, R. Saupe, T. Gessner, Fraunhofer-Institut für Zuverlässigkeit und Mikrointegration (Germany); V. Stock, A. Weiss, Technische Univ. Chemnitz (Germany)

The spectroscopy market is enduring and growing one, in which the near infrared spectroscopy by means of the advances plays an important and indispensable roll. Some nameable advances are the noninvasive character, the rapidity, which allows real-time measurements or the fl exible sampling and sample presentation. To establish near infrared spectroscopic methods and tests at a wide variety of applications new technological innovations are necessary. One of these technological innovations is a modern scanning micro mirror spectrometers. We have developed a small sized, light weight MOEMS-spectrometers for different spectral regions which are due to the optical parameters less expensive, more fl exible and offer better performance than traditional spectrometers even yet. The central component of the optical set-up is a large area scanning micro mirror, which oscillates in resonance with 250Hz. Thus, to record a single spectrum only 4 milliseconds are necessary.

One of the important factors of NIR spectroscopy, which affects qualitative and quantitative determination, is the sample presentation. For optimal signal processing different sample presentation techniques such as transmission and fl ow cells, integrating spheres and attenuated total refl ection (ATR) probes were realized. Consequently in combination with chemometric methods e.g. partial least square or principal component analysis several applications could be performed and investigated. This article describes the principles and the advances of the promising technology as well as some realized applications. Furthermore infl uences of the sample presentation and calibration procedures will be discussed closer.

6887-14, Session 53D MOEMS-based optical micro-bench platform for the miniaturization of sensing devicesS. Garcia Blanco, J. Caron, S. Leclair, H. Jerominek, P. A. Topart, Institut National d’Optique (Canada)

As we enter into the 21st century, the need for miniaturized portable diagnostics devices is increasing continuously. Portable devices fi nd important applications for point-of-care diagnostics, patient self-monitoring and in remote areas, such as unpopulated regions where the cost for large laboratory facilities is not justifi able, underdeveloped



countries and other remote locations such as space missions. The advantage of miniaturized sensing optical systems include not only the reduced weight and size but also reduced cost, decreased time to results and robustness (e.g. not need for frequent re-alignments).

Recent advances in micro-fabrication and assembly technologies have enabled important developments in the fi eld of miniaturized sensing systems. INO has developed a technology platform for the three dimensional integration of MOEMs in an optical microbench. Building blocks of the platform include microlenses, micromirrors, fi lters, dichroic beamsplitters, fi lters and optical fi bers, which can be positioned into a three dimensional microbench to build the desired miniaturised system without the limitations associated to planar confi gurations. The technologies involve standard microfabrication, thick resist UV-lithography, thick metal electroplating, soldering, replication in sol-gel materials and fl ip-chip bonding processes. The technology is compatible with wafer-to-wafer bonding. A placement accuracy of ± 5 microns has been demonstrated thanks to the integration of alignment marks co registered with the other optical elements on the different wafers.

In this paper, the building blocks of the technology will be detailed. The design and fabrication of a 5x5 channels light processing unit including optical fi bers, mirrors and collimating microlenses will be described. Application of the technology to various kinds of sensing devices will be discussed.

6887-15, Session 5Novel optical viscosity sensor using laser-induced capillary waveA. Ebisui, Y. Taguchi, Y. Nagasaka, Keio Univ. (Japan)

In recent years, viscosity has been one of the most important thermophysical properties, and its new sensing applications in a noninvasive method with small sample volume are required in a broad fi eld. For example, in the medical fi eld, the viscosity of body fl uid, such as blood, is an essential parameter for diagnosis. In the present study, we have developed a new miniaturized optical viscometer, namely MOVS (Micro Optical Viscosity Sensor), which is applicable to the noninvasive, high speed, small sample volume, in situ and in vivo measurement of a liquid sample based on laser-induced capillary wave (LiCW) technique in both medical and industrial fi elds. In our experimental setup, two excitation laser beams (pulsewidth of 6 ns, wavelength of 1064 nm) interfere on a liquid surface and generate the LiCW. By observing the behavior of the LiCW using a probing laser, which contains the surface information of the sample liquid, viscosity and surface tension can be obtained. MOVS chip has two wide U-grooves (width of 273 um) holding fi bers for excitation and two narrow U-grooves (width of 126 um) holding fi bers for probing, both fabricated on SOI substrate by DRIE dry etching and HF wet etching. In this paper, the fabrication of prototype MOVS chip using micro-electro mechanical systems (MEMS) technology for the fi rst time and the discussion of the validity of the viscosity measurement were reported. Preliminary measurement using distilled water with carbon black pigment was demonstrated, and nanosecond order high speed damping oscillation was successfully observed.

6887-16, Session 5Radiation-pressure effects upon a micromirror in a high-fi nesse optical cavityA. Heidmann, CNRS (France) and Ecole Normale Superieure (France) and Univ. Pierre et Marie Curie (France); O. Arcizet, C. Molinelli, T. Bri-ant, P. Cohadon, Univ. Pierre et Marie Curie (France)

We present an experiment where the motion of a silicon micro-mechanical resonator is optically monitored with a very high-fi nesse optical cavity, down to a quantum-limited sensitivity at the 10-19 m/âˆ_Hz level. We have observed the thermal noise of the resonator at room temperature over a wide frequency range, and fully characterized its optomechanical behaviour.

We have experimentally demonstrated for the fi rst time a direct effect of intracavity radiation-pressure upon the dynamics of the micro-resonator in a detuned high-fi nesse optical cavity: depending on the sign of the detuning, we have obtained both self-cooling and heating, with an


effective temperature ranging from 10 to 2000 K. We have also observed a related radiation-pressure induced instability of the resonator.

Current upgrade of the experimental setup includes the use of smaller resonators and cryogenic operation. Experimental conditions to observe quantum effects of radiation pressure and zero-point fl uctuations of the resonator will be discussed. We propose to reach the quantum regime of such a macroscopic mechanical resonator using a new experimental approach, taking advantage of the unequalled sensitivity of optical interferometry. The very low temperature required for the observation of the quantum fl uctuations, in the 100 Ã‚ÂμK range, will be obtained by a mixing of standard cryogenic cooling and optical cooling performed either by the intracavity radiation pressure or by an external cold damping mechanism, as already demonstrated with our experimental setup.

6887-17, Session 5One-axis metallic electrostatic micromirror arrayK. Tondapu, Q. Cheng, M. F. Almasri, Univ. of Missouri/Columbia

The design, fabrication and testing of a new micromachined micromirror array structure is presented. The micromirror utilizes primarily electroplated nickel, a mechanically durable material with a high glass transition temperature and with controllable residual stress as the main structural material. The goal of this research is to develop micromirror array for switches and optical cross-connects. The high glass transition temperature of nickel allows it to be used at high temperature. Micromirror arrays with 6x6 pixels were designed and fabricated with an area between 0.1x-0.1 mm2 and 0.5x-0.5 mm2 to provide high fi ll factor and uniform stress distribution. The micromirror fabrication process was performed by surface micromachining technologies with a thick photoresist sacrifi cial layer. The torsion beams were designed with a serpentine shape in order to optimize the voltage necessary to tilt the micromirror by ± 10°. The micromirrors were simulated using Coventor fi nite element tool in order to determine their geometries and performance. A voltage of 30 volts was required to rotate the mirror with a diameter of 0.5 mm by 10°. In addition, the mirror was operated at a resonant frequency of 2 kHz. The micromirror with the largest area was characterized. A full rotation was observed using an optical microscope.

6887-19, Session 5Design and implementation of wafer transporting system for photolithographerK. Wang, Tsinghua Univ. (China)

Wafer transporting system is a vital part of IC manufacturing system. This paper presents the design and implementation of the wafer transporting system. Approaches in pre-aligning process and re-locating process are important to the performance of the system. In pre-aligning, Least Square Circle Fitting is adopted to locate the center of the wafer and the notch of the wafer. In re-locating, special locations of sensors are applied to calculate the wafer eccentricity relative to the fi ducially position. The precision of the whole system is very high.


Conference 6888: MEMS Adaptive Optics IITuesday-Thursday 22-24 January 2008 • Part of Proceedings of SPIE Vol. 6888 MEMS Adaptive Optics II

6888-32, Poster SessionTurbulence compensation using micromirror arrays: the array designW. C. Sweatt, M. T. Valley, Sandia National Labs.

An array of micromirrors can be used to correct the wavefront aberrations due to atmospheric turbulence. A simple method is presented for estimating the number of piston-only micromirrors needed to correct the seeing. We also consider how many piston-tip-tilt micromirrors would be required . The three-actuator micromirrors are found to produce a more effi cient solution, requiring 4X fewer actuators for the same improvement in the Strehl ratio.

6888-01, Session 1Characterisation of MEMS mirrors for use in atmospheric and ocular wavefront correctionM. N. Devaney, D. J. Coburn, C. Coleman, C. J. Dainty, E. Dalimier, T. D. Farrell, D. Lara, D. Mackey, R. Mackey, National Univ. of Ireland/Galway (Ireland)

The Applied Optics group at the National University of Ireland, Galway, is engaged in research into various aspects of the application of adaptive optics to both ocular and atmospheric wavefront correction. A large number of commercially available deformable mirrors have been selected by the group for AO experiments, and these mirrors have been carefully characterised to determine their suitability for these tasks. In this paper we describe the approach we have used in characterising deformable mirrors and present results for several MEM mirrors, including membrane mirrors from Agileoptics and Flexible Optical BV, a segmented micromirror from IrisAO and a 140-actuator mirror from Boston micromachines. We also present initial results from studies into techniques to reduce the effect of actuator saturation and non-linearity.

6888-02, Session 1MEMS in adaptive optics scanning laser ophthalmoscopy: achievements and challengesA. Dubra, Imperial College London (United Kingdom); D. C. Gray, W. Merigan, J. I. Morgan, D. R. Williams, Univ. of Rochester


6888-03, Session 1Villages: an on-sky visible wavelength astronomy AO experiment using a MEMS deformable mirrorD. T. Gavel, S. A. Severson, Univ. of California Observatories; B. J. Bauman, Lawrence Livermore National Lab.; D. R. Dillon, M. R. Reinig, C. Lockwood, Univ. of California Observatories; D. W. Palmer, Law-rence Livermore National Lab.; K. M. Morzinski, S. M. Ammons, E. L. Gates, B. Grigsby, Univ. of California Observatories

The MEMS-AO/Villages project consists of a series of on-sky experiments that will demonstrate key new technologies for the next generation of adaptive optics systems for large telescopes. One of our fi rst goals is to demonstrate the use of a micro-electro-mechanical systems (MEMS) deformable mirror as the wavefront correcting element. Experiments will take place at the 1-meter Nickel Telescope at the UCO/Lick Observatory on Mount Hamilton and will use a 140 element (10 subapertures across) deformable mirror. The system will produce diffraction-limited images at mid visible wavelengths. The system is now assembled in the laboratory undergoing fi nal integration and test and is scheduled for fi rst light on the telescope in September 2007. We will report on the initial performance test results at the January meeting.

6888-04, Session 1Towards isotropic ultrahigh resolution OCT using pancorrectionW. Drexler, Cardiff Univ. (United Kingdom)


6888-05, Session 1The Naval Research Laboratory MEMS adaptive optics programS. R. Restaino, J. R. Andrews, T. Martinez, C. C. Wilcox, Naval Re-search Lab.

The Naval Prototype Optical Interferometer (NPOI) is the longest baseline at visible wavelengths interferometer in the world. The astronomical capabilities of such an instrument are being exploited and recent results will be presented. NPOI is also the largest optical telescope belonging to the US Department of Defense with a maximum baseline of 435 meter has a resolution that is approximately 181 times the resolution attainable by the Hubble Space Telescope (HST) and 118 times the resolution attainable by the Advanced Electro-Optical System (AEOS). It is also the only optical interferometer capable of recombining up to six apertures simultaneously. The NPOI is a sparse aperture and its sensitivity is limited by the size of the unit aperture, currently that size is 0.5 meters. In order to increase the overall sensitivity of the instrument a program was started to manufacture larger, 1.4 meter, ultra-light telescopes. The lightness of the telescopes requirement is due to the fact that telescopes have to be easily transportable in order to reconfi gure the array. For this reason a program was started three years ago to investigate the feasibility of manufacturing Carbon Fiber Reinforced Polymer telescopes, including the optics. Furthermore, since the unit apertures are now much larger than r0 there is a need to compensate the aperture with adaptive optics (AO). Since the need for mobility of the telescopes, compact AO systems, based on MEM devices, have been developed. This paper will present the status of our adaptive optics system and some of the results attained so far with it. We will discuss the integration program of the larger telescopes into the NPOI and the immediate and longer term plans for this facility.

6888-06, Session 1AO-OCT with dual wavefront correctorsJ. S. Werner, Univ. of California/Davis Medical Ctr.


6888-07, Session 2Use adaptive optics to increase non-linear imaging signal in mouse bone morrowY. Zhou, T. Bifano, Boston Univ.; C. P. Lin, Massachusetts General Hospital

In a recent effort, scientists from Wellman Center of Photomedicine use fl uorescence signal provided by single- or two-photon excitation, second harmonic generation and coherent anti-Stokes Raman spectroscopy (CARS) to illustrate the cell level detail of mouse bone marrow [1]. However the several non-linear imaging techniques suffered on a common base: signal degradation with deeper light penetration. The fl uorescence signal weakening from the mouse skull is caused by the decreased excitation light intensity. With deeper imaging depth, the excitation light suffers tissue scattering, absorption and optical aberration. The last one of the causes spreads the light intensity away from its diffraction limited focal spot. In consequence, less fl uorescence light is produced in the enlarged focal volume. In this paper, I will introduce Adaptive Optics (AO), a system for real time optical aberration compensation, to improve the non-linear fl uorescence signal in the mouse bone marrow imaging. A parallel stochastic gradient decent algorithm based on Zernike polynomial is employed to control the deformable mirror in real time aberration compensation.


[1] Sipkins et al., “In vivo imaging of specialized bone marrow endothelial microdomains for tumour engraftment”, Nature 435 (16): 969 - 973 (2005)

6888-08, Session 2Applying adaptive optics to wide-fi eld microscopyP. A. Kner, Univ. of California/San Francisco; Z. Kam, Weizmann Insti-tute of Science (Israel); D. A. Agard, J. W. Sedat, Univ. of California/San Francisco

Depth aberrations are the major source of image degradation in 3D wide-fi eld microscopy, causing a signifi cant loss of resolution and intensity deep into the sample. These aberrations occur because of an inevitable mismatch between the sample refractive index and the immersion medium index. We have built a wide-fi eld fl uorescence microscope that incorporates a large-throw deformable mirror to correct for depth aberrations in 3D imaging. We demonstrate the ability of this system to correct the microscope point spread function (PSF) for spherical aberration and to focus into the sample. We further discuss the performance of this system in correcting images of biological samples.

6888-09, Session 2Image-based adaptive optics for imaging and microscopyM. J. Booth, D. Debarre, T. Wilson, Univ. of Oxford (United Kingdom)

Adaptive optics schemes for microscopy aim at reducing wavefront aberrations using an adaptive element, thereby improving image quality and penetration depth. In most imaging systems, direct wavefront sensing is not straightforward and wavefront sensorless schemes are often employed: a metric related to image quality is measured for several trial corrections, and the adaptive element is reconfi gured accordingly until image quality is acceptable [1,2]. Previous work in this area has used various optimisation metrics appropriate for image-based adaptive optics. However, the derivation of a corresponding constructive model is complicated by the image formation process, which depends on both aberrations and object structure. Therefore, model-free algorithms have been used which require numerous measurements to achieve correction.

To overcome this limitation, we have demonstrated an effective model-based scheme using the low spatial frequency content of the image as an optimisation metric, which permits the separation of aberration and object infl uences on the measurements. By representing aberrations as an expansion in Lukosz modes, the optimisation of each mode can be performed independently using only three measurements per mode [3]. Finally, the sensitivity to aberration can be adjusted to provide optimal correction accuracy over a wide range of initial aberration amplitude.

This effi cient scheme has been demonstrated experimentally in an incoherent transmission microscope [4] and a structured illumination microscope.

References

[1] M.J. Booth et al., PNAS 99, 5788-5792 (2002)

[2] M.J. Booth, Optics Express 14, 1339-1352 (2006)

[3] M.J. Booth, Optics Letters 32, 5-7 (2007)

[4] D. Debarre et al., Optics Express 15, 8176-8190 (2007)

6888-10, Session 3High-resolution MEMS AO for stellar interferometryS. Rao, J. K. Wallace, M. Shao, Jet Propulsion Lab.; R. Samuele, Northrop Grumman Space Technology

We use a 1000-element MEMS deformable mirror to control the path length in an interferometer, a nulling coronagraph for imaging of extrasolar planets. A second interferometer (rather than the traditional Shack-Hartmann sensor) measures the wavefront error of the coronagraph, allowing path length control with rms error of 1nm across the pupil. I will explain the results of this demonstration and illustrate how a calibration

interferometer can be used in a closed-loop adaptive optics system.

6888-11, Session 3Performance of a MEMS refl ective wavefront sensorJ. R. Andrews, Naval Research Lab.; S. W. Teare, New Mexico Insti-tute of Mining and Technology; S. R. Restaino, Naval Research Lab.; T. Martinez, Air Force Research Lab.; C. C. Wilcox, Naval Research Lab.; D. V. Wick, W. D. Cowan, O. B. Spahn, B. E. Bagwell, Sandia National Labs.

An all refl ective Shack Hartmann style wavefront sensor has been developed using Sandia National Laboratory segmented Micro-Electro-Mechanical (MEM) deformable mirrors. This wavefront sensor is presently being explored for use with adaptive optics systems at the Naval Prototype Optical Interferometer and other experimental adaptive systems within the Naval Research Laboratory. The 61 MEM mirror segments are constructed in a hexagonal array and each segment can be constructed with either fl at or optically powered surfaces. The later allows each mirror segment to bring its subaperture of light to a focus on an imaging array, creating an array of spots similar to a Shack Hartmann. Each mirror segment has tip, tilt and piston functionality to control the position of the focused spot such that measurement of the applied voltage can be used to drive a deformable mirror. As the system is refl ective and each segment is controllable, this wavefront sensor avoids the light loss associated with refractive optics and has larger dynamic range than traditional Shack Hartmann wavefront sensors. This wavefront sensor can detect large magnitude aberrations up to and beyond where the focused spots overlap, due to the ability to dither each focused spot. Previous publications reported on this novel new technique and the electrical specifi cations, while this paper reports on experiments and analysis of the open-loop performance, including repeatability and linearity measurements. The suitability of using the MEM deformable mirror as a high dynamic range refl ective wavefront sensor will be discussed and compared to current wavefront sensors and future work will be discussed.

6888-12, Session 3A novel method of creating a surface micromachined 3D optical assembly for MEMS-based, miniaturized FT-IR spectrometersD. Reyes, E. R. Schildkraut, J. Kim, P. A. Kotidis, D. J. Cavicchio, Spectra Optics/Block Engineering

A miniaturized, MEMS-based Fourier Transform (FT) IR spectrometer for the detection and identifi cation of toxic or fl ammable gases is described. By measuring the absorption of specifi c IR wavelengths of the target material, unambiguous detection can be achieved. The device uses a surface micromachined, Michelson interferometer capable of modulating light in the 2 - 14 μm spectral region. An inherent advantage of FT-IR absorption spectroscopy-extremely low false alarm rate-is extended through the use of surface micromachining to achieve small size, low manufacturing cost, and unprecedented laboratory instrument-grade performance.

A key challenge of this new design is the need for an order of magnitude larger modulation stroke in the reference arm of the interferometer, which precludes electrostatic actuation scheme in a surface normal direction, and has motivated the innovative, out of plane, 3-D optical mirror assembly described in this paper. Each mirror assembly consists of a primary mirror segment having a 1 mm clear aperture, two assisting secondary components, and supplementary locking features. Assembly is achieved in a fl ip-book manner by applying an electric fi eld above the MEMS die. The primary rises and aligns to the electrostatic fi eld, followed by the secondaries which hold the primary in place. The motion of the secondaries displaces the locking features to engage and lock in place, achieving full irreversible assembly. Due to extremely small mechanical tolerances in the secondaries, the MEMS die is piezoelectrically vibrated to provide stick-slip lubrication. Moreover, a new thermal actuator developed specifi cally for this device provides a 250 μm moving mirror displacement in a discrete manner without skipping; and long term tests show zero skips in over 300 million cycles. The manufacturing process is robust and promises low cost mass production.

Conference 6888: MEMS Adaptive Optics II


6888-13, Session 3Fast calibration techniques for adaptive compensation for a wide-fi eld microscopeJ. Castillo, T. G. Bifano, Boston Univ.

The Adaptive Scanning Optical Microscope (ASOM) allows for a wide fi eld of view at high resolution. High resolution is obtained via a calibration process, whereby a micro-deformable mirror adaptively compensates for optical abberations using a defi ned optimization algorithm. Effi cient optimization can be characterized by speed, repeatability, and overall image improvement. This presentation applies several optimization algorithms to the calibration process and compares results.

6888-14, Session 3Compact MEMS-based adaptive optics optical coherence tomography for clinical useD. C. Chen, S. S. Olivier, S. M. Jones, Lawrence Livermore National Lab.; R. J. Zawadzki, Univ. of California/Davis Medical Ctr.; J. W. Ev-ans, Lawrence Livermore National Lab.; S. S. Choi, J. S. Werner, Univ. of California/Davis Medical Ctr.

We describe a compact MEMS-based adaptive optics (AO) optical coherence tomography system with improved AO performance and ease of clinical use. A typical AO system consists of a Shack-Hartmann wavefront sensor and a deformable mirror that measures and corrects the ocular and system aberrations. Because of the limitation on the current deformable mirror technologies, the amount of real-time ocular-aberration compensation is restricted and small in the previous AO-OCT instruments. In this instrument, we propose to add an optical apparatus to correct the spectacle aberrations of the patients such as myopia, hyperopia and astigmatism. This eliminates the tedious process of the trial lenses in clinical imaging. Different amount of spectacle aberration compensation is achieved by motorized stages and is automated with the AO computer for ease of clinical use. In addition, the compact AO-OCT is optimized to have minimum system aberrations to reduce AO registration errors and improve AO performance. The whole optical system is confi ned to a 2’x 3’ cart for mobility in clinical settings.

6888-15, Session 3Performance of a MEMS-based AO-OCT systemJ. W. Evans, Lawrence Livermore National Lab.; R. J. Zawadzki, Univ. of California/Davis Medical Ctr.; S. M. Jones, Lawrence Livermore National Lab.; S. O. Okpodu, Univ. of California/Davis Medical Ctr.; S. S. Olivier, Lawrence Livermore National Lab.; J. S. Werner, Univ. of California/Davis Medical Ctr.

Adaptive optics (AO) and Optical coherence tomography (OCT) are powerful imaging modalities that, when combined, can provide high-resolution, 3-D images of the retina. The AO-OCT system at UC Davis has been under development for 2 years and has demonstrated the utility of this technology for microscopic, volumetric, in vivo retinal imaging. The current system uses an AOptix bimorph deformable mirror (DM) for low-order, high-stroke correction and a 140-actuator Boston Micromachines DM for high-order correction. We present our on-going characterization of AO system performance with particular emphasis on MEMS DM performance. Residual WFEs are broken down into constituent errors in an error budget including sources like calibration and bandwidth. Careful characterization of the AO system will lead to improved performance and inform the design of future systems.

6888-16, Session 4MEMS adaptive optics for the Gemini Planet Imager: control methods and validationL. A. Poyneer, Lawrence Livermore National Lab.; D. R. Dillon, S. J. Thomas, Univ. of California Observatories

The Gemini Planet Imager AO system will use a high-order MEMS deformable mirror for phase compensation.

GPI’s strategy for controlling the MEMS device will be discussed in

detail, with a focus on its Fourier mode approach to wavefront control that allows compensation of the MEMS infl uence function. We will also discuss the impact on closed-loop control of non-linearities in the MEMS response.

Our most recent experimental results will be presented.

6888-17, Session 4High-contrast imaging testbedK. L. Baker, D. A. Silva, L. A. Poyneer, B. A. Macintosh, B. J. Bau-man, D. W. Palmer, T. P. Remington, M. Delgadillo-Lariz, Lawrence Livermore National Lab.

Future adaptive optics instruments on telescopes, such as the Gemini Planet Imager(GPI), will enable direct observation of extrasolar Jovian planets. These types of instruments will study such planet populations at relatively small working distances from the parent star. In order for these instruments to be successful, a number of algorithms and hardware confi gurations must be tested in a laboratory setting before the implementation of these instruments on telescopes takes place. As such, a spatially fi ltered Shack-Hartmann adaptive optics system has been constructed to evaluate new algorithms and hardware confi gurations. We present preliminary results from this adaptive optics system.

6888-18, Session 4Amplitude variations on an ExAO testbed using MEMS deviceS. J. Thomas, Univ. of California Observatories; J. W. Evans, D. W. Phillion, Lawrence Livermore National Lab.; D. T. Gavel, D. R. Dillon, Univ. of California Observatories; B. A. Macintosh, Lawrence Liver-more National Lab.

Micro-electrical-mechanical-systems (MEMS) deformable mirrors (DMs) are under study at the Laboratory for Adaptive Optics for inclusion in possible future adaptive optics systems, including open loop systems or extreme adaptive optics (ExAO). MEMS DMs have several advantages in these areas because of low (to zero) hysterisis and high actuator counts. In this paper, we present work in the area of high-contrast adaptive optics systems, such as those needed to image extrasolar planets. These are known to require excellent wavefront control and diffraction suppression. On the ExAO testebed we have already demonstrated wavefront control of better than 1 nm rms within controllable spatial frequencies, however, corresponding contrast measurements are limited by amplitude variations, including variations introduced by the MEMS. Results from experimental measurements and wave optic simulations on the ExAO testbed will be presented. In particular the effect of small scale MEMS structures on amplitude variations and ultimately high-contrast far fi eld measurements will be examined. Experimental results include interferometer measurements of phase and amplitude using the phase shifting diffraction interferometer, direct imaging of the pupil, and far fi eld imaging.

6888-19, Session 4Synthesis of approximate zonal controllers for MEMS DMA. R. Guesalaga, Pontifi cia Univ. Católica de Chile (Chile); D. Guz-man, Univ. of Durham (United Kingdom); M. Kowalczyk, Univ. de Chile (Chile); R. M. Myers, R. M. Sharples, T. J. Morris, A. G. Basden, C. D. Saunter, Univ. of Durham (United Kingdom)

We present a novel technique for the design of DM controllers for open-loop and high spatial resolution adaptive optics systems. It is based on a Shack-Hartmann (SH) fi gure sensor and multiple overlapping MIMO controllers based on the H-infi nity synthesis method. The controller synthesis is carried out periodically using a linearized representation of a continuously adjusted model that accounts for varying physical or ambient conditions and considers the spatial geometry of the SH. The fi gure sensor is based on a bright source and a fast CMOS detector to sample the DM surface sequentially, using an optical arrangement not to interfere with the main corrected beam. Taking the full advantage of such robust techniques the controller can successfully handle the



dynamics and non-linearity of the DM, allowing one to decouple, from the main AO control loop standpoint, the turbulence estimation errors from those originated in the DM servo-loop. It can also account for noise and vibration rejection without compromising the loop stability, pushing the control bandwidth to the physical limits imposed by hardware and software components. By splitting the control function into several overlapping controllers, implementation complexity is reduced and continuous updating of the controller can be easily achieved. Simulations show its ability to successfully control the DM shape, in spite of a partial and non-simultaneous sampling of the SH fi gure sensor due to detector speed limitations.

6888-20, Session 5MEMS active optics updateW. D. Cowan, Sandia National Labs.


6888-21, Session 5Towards a compact “plug and play” MEMS deformable mirror systemM. A. Helmbrecht, C. Kempf, N. Doble, Iris AO, Inc.

In recent years, the performance of MEMS deformable mirrors (DM) has improved considerably, making them more viable for use in commercial applications. However, the development of drive electronics and overall ease-of-use have lagged in comparison. Most drive electronics offered by DM manufacturers to actuate the DMs are quite large, with footprints commensurate with 19” rack-mounted equipment. At best, the DMs shipped today are delivered with a fl atten fi le and either nominal response curves or experimental response curves for only a few actuators.

If, instead, DMs were shipped with known surface-profi le infl uence functions, it would make building and aligning an AO system much easier. With good open-loop positioning enabled by known infl uence functions, the DM could be fl attened, allowing it to be built into an AO system immediately instead of building up and initially aligning the system with a reference fl at. Furthermore, various surface profi les could be placed on the DM in order to check alignment, plate scales, and so forth as the system is being built up.

This paper will demonstrate greater DM functionality by describing the latest advances incorporated into the Iris AO Smart Driver II(tm) drive electronics and S37-X DM. Calibration coeffi cients are built directly into the hardware, enabling a simple DM command interface that can be used with any Iris AO DM and drive electronics. The interface linearizes the device operation with high accuracy throughout the entire operating space, enabling surface profi les to be placed directly onto the DM.

6888-22, Session 5Wavefront fi tting characterization of a piston-tip-tilt segmented MEMS deformable mirrorM. A. Helmbrecht, C. Kempf, N. Doble, Iris AO, Inc.

Characterizing the surface profi le a deformable mirror (DM) can create is critical to evaluating whether a particular DM is suitable for an application. This paper will present theoretical and experimental wavefront fi tting results for the Iris AO 37-segment piston-tip-tilt deformable mirror for up to 5th order Zernike modes.

Theoretical evaluation will quantify the wavefront fi t of an Iris AO DM using a Zernike-to-piston/tip/tilt conversion function Iris AO includes with its DM controller. The theoretical evaluation will demonstrate how effective the hexagonal segments are at fi tting Zernike-basis wavefronts and will compare these, as best as possible, to other published results.

Experimental evaluation will quantify the wavefront fi t of an actual DM used in open- and closed-loop positioning, based on measurements using a Wyko white light interferometer. Thus surface fi gure errors and any other non-idealities will be included in the comparison.

6888-23, Session 5MEMS deformable membrane mirror with integrated control electronicsF. P. Shevlin, Dyoptyka Ltd. (Ireland)

We are developing a deformable membrane mirror with integrated low voltage, high voltage, and control system electronics. Its reliability, repeatability, robustness, speed, and cost characteristics are suited to consumer and industrial imaging applications. Potential uses include variation of focus or zoom without mechanical lens translation and correction of higher order aberration specifi c to each state of focus or zoom.

We have completed our evaluation of a printed circuit board (PCB) prototype version. A more compact multi-chip module (MCM) version will be available for purchase in Q1 2008. It is being designed so as to facilitate its transformation to an application-specifi c integrated circuit (ASIC) suited to high-volume, low-cost markets.

The Al-coated mirror aperture is 15mm in diameter. There are 37 control electrodes arranged in a hexagonal pattern below the mirror. Optical characteristics are similar to other similarly-confi gured membrane mirrors on the market, i.e. up to fi fth order correction of aberration, albeit with low magnitudes of correction at higher-order modes. Resonant frequency of the membrane is circa 1kHz. Power consumption is 4W. On-board processor and memory allow autonomous operation. USB 2.0 data and GPIO triggering interfaces allow synchronization with external systems.

We are collaborating on optical system design with several manufacturers in the consumer and industrial imaging markets with a view to the inclusion of our device in the next generation of their products.

6888-24, Session 6Precise open-loop control of MEMS deformable mirror shapeT. G. Bifano, J. B. Stewart, A. Diouf, Boston Univ.

A compact and accurate electromechanical model for electrostatically actuated silicon MEMS deformable mirrors is introduced. This model allows accurate prediction of required voltages to achieve close approximation to a prescribed shape. The model is empirically tested, and produces shapes accurate to <30nm RMS for shapes up to to 1.5μm in amplitude.

6888-25, Session 6Nonlinear plate equation analysis for the design of large stroke deformable mirrorO. A. Azucena, Jr., J. A. Kubby, Univ. of California/Santa Cruz

Adaptive optics (AO) improves the quality of astronomical imaging systems by using real time measurement of the turbulent medium in the optical path. The measurements are then taken and applied to a deformable mirror (DM) that is in the conjugate position of the aberrations in the optical path. The quality of the reconstructed wavefront directly affects the images obtained. One of the limiting factors in current DM technology is the amount of stroke available to correct the wavefront distortions which can be as high as 20 microns of optical path difference. We have developed a simulation analysis using Galerkin’s method to solve the nonlinear plate equation. The analysis uses a set of orthogonal equations that satisfi ed the boundary condition to solve for the linear deformation on the mirror surface. This deformation is used to iteratively converge to the fi nal solution by applying the nonlinear plate equation and the nonlinear actuator forces. This simulation was used to design a Microelectromechanical DM with 10 um of stroke.



6888-26, Session 6Simulation and interferometer results of MEMS deformable mirrorsB. R. Fernandez, J. A. Kubby, Univ. of California/Santa Cruz

Various types of large stroke actuators for Adaptive Optics (AO) were simulated individually and as part of a mirror systems consisting of actuators bonded to face plates with different boundary conditions. The actuators and face plate were fabricated using a high aspect ratio process that enables the creation of 3-dimensional Micro-Electro-Mechanical System (MEMS) devices. This paper will review simulation results along with actual testing measurements of the actuators and face plate utilizing a white-light interferometer. Both simulations and interferometer scans have shown the availability of the actuators to achieve displacement of 1/3 of the gap between the spring layer and the counter electrode.

6888-27, Session 6Characterizing MEMS deformable mirrors for open-loop operation: high-resolution measurements of thin-plate behaviorK. M. Morzinski, Univ. of California Observatories; A. P. Norton, Univ. of California/Santa Cruz; D. R. Dillon, D. T. Gavel, Univ. of California Observatories

New concepts for astronomical adaptive optics (AO) are enabled by the use of micro-electrical mechanical systems (MEMS) deformable mirrors (DMs). Unlike traditional DMs now used in astronomical AO systems, MEMS devices are smaller, less expensive, and exhibit extraordinarily repeatable actuation. Consequently, MEMS technology allows for novel confi gurations, such as multi-object AO, that require open-loop control of many DMs. Open-loop control in this sense refers to commanding the DM to correct wavefront error for science observations without the benefi t of feedback derived from correcting the guide-star light. At the UCO/Lick Observatory Laboratory for Adaptive Optics we are pursuing this concept in part by creating a phase-to-voltage model for the DM. Discrete electrostatic MEMS actuators are attached via posts to a thin continuous-surface refl ective top plate. We model the surface defl ection approximately by the thin-plate equation, which has a linear relationship between force and defl ection. MEMS actuators, although nonlinear in force response to applied voltage, are independent of each other except through forces transmitted by the top plate. Using this modeling technique, we have achieved open-loop control accuracy in the laboratory to ~15 nm rms in response to ~500 nm amplitude commands. Our most recent measurements are aimed at verifying that the top plate’s deformation indeed follows the thin-plate equation behavior. High-resolution measurements of the displacement between actuator posts are compared to the homogeneous solution of the thin-plate equation. In this paper we will report on the level of experimental agreement with the model and comment on the nature of the differences.

6888-28, Session 6Closed-loop AO demonstration of MEMS SLM with piston, tip and tilt controlH. Dyson, F. Pardo, R. Ryf, V. A. Aksyuk, R. E. Frahm, A. Gasparyan, R. Papazian, D. A. Ramsey, M. E. Simon, S. Arney, Lucent Technolo-gies/Bell Labs.

A MEMS SLM with an array of 64x64 pixels, each 120um x 120um in size, with 98 fi ll-factor, has been developed. Each pixel in the array is capable of 5um of stroke, and +/- 4 degrees tip and tilt, with resonance frequencies for piston and angular motion each being ~30kHz. From a prototype array, 14 contiguous pixels have been independently wired-out to off-chip drive electronics. An extensive characterisation and calibration procedure has been undertaken to construct a model to allow any desired piston, tip and tilt position to be translated into the 4 actuator control voltages required for each pixel.

These 14 pixels have been demonstrated to be effective for open-loop beam steering and in an off-the-shelf closed-loop AO system (with requisite modifi cations to suit the SLM). In the case of beam steering, it has been demonstrated that, for a mechanical tilt of 3 degrees, the

steered beam has a 40% greater intensity when the piston motion is used to eliminate the step discontinuity (modulo 2pi) between adjacent pixels. For a low-order static aberration, correction using piston, tip and tilt improved the measured Strehl ratio has been improved from 0.069 to 0.861, a factor of 12 improvement.

6888-29, Session 6Electrostatic actuator array fabricated using anodic wafer bonding for MEMS deformable mirror controlA. Diouf, J. B. Stewart, M. Gingras, T. G. Bifano, Boston Univ.

Future space-based stellar observatories planned by NASA for high-resolution, high-contrast optical imaging require signifi cantly improved deformable mirror (DM) designs for their adaptive optics systems. In contrast to Earth-based observatories, wavefront aberrations in these telescopes are slowly varying and are primarily created by imperfect optics, shifts in telescope alignment during launch, and thermal fl uctuations during observation. Wavefront errors of this nature do not necessarily require DM stroke beyond 1μm for correction (tip, tilt and focus terms can be corrected for with other optical elements). Instead, wavefront correction requires a DM that has high precision positioning resolution, nanometer level stability, and hysteresis-free motion, all of which are advantages of an electrostatically controlled MEMS DM. Furthermore, the DM must have a mirror surface with roughness below 5nm RMS, and thousands of actuators over a clear aperture diameter on the order of 100 mm. Current MEMS DM technology at Boston University (BU) is fabricated using a conventional surface micromachining process that limits the mirror aperture size and its optical quality (due to print through effects). In order to harness the electrostatic control benefi ts of MEMS-based DMs, a new fabrication process is under development that combines micromachining and wafer bonding steps to produce a large aperture DM with unprecedented optical quality and thermal stability. The successful fabrication of an electrostatic actuator array and membrane DM produced with this new technique is presented here, as well as plans for future fabrication of the DM.

6888-30, Session 6A 4096 element continuous facesheet MEMS deformable mirror for high-contrast imagingS. A. Cornelissen, Boston Micromachines Corp.; T. G. Bifano, Boston Univ.; P. A. Bierden, Boston Micromachines Corp.

A 4096 Element Continuous Facesheet MEMS Deformable Mirror for High-Contrast Imaging

6888-31, Session 6TBDS. Bucourt, Imagine Optic (France)



abstracts summaries - spiespie.org/documents/conferencesexhibitions/moems-mems-2008...

Documents