MEMS — MICROELECTROMECHANICAL SYSTEMS— are now basic to products ranging from inkjetprinters to automobile air bags, and work contin-ues to develop this technology for many new uses.Scientists and engineers at NJIT and AmericanSensor Technologies (AST) have pooled their talentsfor one such effort — commercializing a superiorMEMS-based sensor for monitoring the flow ofgases and liquids. Their work is a matter of microns;a critical component of the new sensor is just a singlemicron in thickness. At one millionth of a meter,it would take some 1000 microns to stack up to thethickness of a dime.

Essentially, this joint effort involved creating amicron-thick layer of silicon semiconductor mate-rial on a flexible substrate by means of a processknown as plasma enhanced chemical vapor depo-sition. The substrate, some 50 microns thick in theprototype sensor, flexes when pressure is appliedfrom below, which in turn causes the electricalresistance of the semiconductor layer to vary. Thevariations in resistance can be correlated with evenminute changes in the pressure exerted by a streamof liquid or gas.

The design originated by NJIT and licensed toAST offers several advantages for many applications,most notably the sensitivity to detect and measurepressures from 0 to 2 pounds per square inch gauge(psig). It is difficult to monitor pressure below 2psig with other types of comparably sized sensors

now on the market. In addition, the combinationof semiconductor material on an inert polymersubstrate makes the new sensor suitable for opera-tion in corrosive and electromagnetically activeenvironments.

Technology, talent and timingThe development of this unique sensor is muchmore than the story of a technological break-through. It’s a saga of entrepreneurial foresightand good timing as well. It also demonstrates howcreative research can point the way to other appli-cations as a new technology evolves.

The key players at NJIT include Hee Lim, assis-tant research professor, and Roumiana Petrova,assistant director of the undergraduate programand special lecturer in the Department of Physics.Petrova and Lim, who earned his PhD at the uni-versity, are co-inventors of the new thin-filmpressure sensor. A patent covering their innovationis now pending.

But no matter how brilliant a technological con-cept may be, it won’t move far from experimenta-tion in the lab without adequate funding. This iswhere Gordon Thomas and John Federici, profes-sors of physics, were of assistance. Thomas wasinterested in thin-film technology for biomedicalapplications prior to joining the NJIT faculty.Earlier, while he was at Massachusetts Institute ofTechnology, he had also looked into the fabrication

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AUTHOR: DEAN L. MASKEVICHis editor of NJITMagazine.

PHOTOS: BILL WITTKOP

SENSINGINNOVATION

MEMS TECHNOLOGY BRINGSNJIT AND INDUSTRY TOGETHER

ON A SMALL SCALE

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The 16 experimental sensor elements depositedon the flexible substrate shown are only a micronin thickness.

capabilities that Princeton University could pro-vide with respect to chemical vapor deposition.

When Thomas came to NJIT several years ago,he brought his interest in thin-film applicationsand teamed up with Federici to establish a rela-tionship with the fabrication facility at Princeton.They also secured additional funding from theNew Jersey Commission on Science and Technology

for the research already under way in Newark.That funding amounted to nearly a million dollarsfor NJIT. However, one piece was still needed tocomplete the thin-film sensor picture.

Some very significant classworkThe New Jersey Commission on Science andTechnology is charged with promoting economicdevelopment in the state along with encouragingtechnological innovation. To achieve this commer-cial objective, NJIT needed to find an appropriatepartner for the thin-film sensor project. Fortuitously,

as the thin-film work advanced toward the pointwhere a patent application was warranted, Petrovawas also teaching two graduate courses — Funda-mentals of Engineering Materials and MechanicalBehavior of Materials. One of her students, a PhDcandidate, was Karmjit Sidhu. He also happened tobe AST’s vice president of business development.

Petrova says that her classes require completionof a project, which can be related to work a studentis currently doing for an employer. As she andSidhu discussed the possibilities, they realized thata project based on NJIT’s thin-film research couldbe of considerable benefit to everyone involved,including AST.

Sidhu’s class project was the starting point foradding an important new product to AST’s offer-ings. Located in Landing, New Jersey, the companyis a leading manufacturer of MEMS-based pressuresensors and related process-control components.Incorporated in 1997, AST specializes in supplyingproducts customized for a growing number ofclients, including firms that need such technologyfor hydraulics, water treatment, energy management,and oil and gas processing. In 2004, AST receivedone of the Finest Private Companies awards giveneach year by NJBIZ magazine to honor the state’s25 fastest-growing privately held companies.

From Sidhu’s perspective, the collaborationbetween AST and NJIT will enable his company totake a serious look at new market segments. He

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Teaming up with a successful company is amuch faster track to the commercialization of intellectual property than attempting toacquire the requisite business savvy withoutan experienced partner.

Mounted in a prototype test unit such as the one on the left, the innovative sensing element on the substrate in the center candetect the slightest variation in the pressure of a gas or liquid.

says, “Working with NJIT significantly extends ourreach in terms of research and development. Itgives us access to the intellectual and developmen-tal resources of a major research university.” Theseresources, Sidhu adds, could help AST enter espe-cially challenging commercial areas, such as thebiomedical market.

Michael Eldredge, AST’s executive vice president,cites the benefits that linkage with the private sec-tor can hold for NJIT. He says that teaming upwith a successful company is a much faster track tothe commercialization of intellectual property thanattempting to acquire the requisite business savvywithout an experienced partner. “We’ve alreadyopened doors to the real world of the marketplace,and we know what to expect when you go throughthem. It’s definitely to the advantage of both NJITand our company that we work together to explorewhat lies beyond those doors.”

Smart next stepsThe genesis of the technology that NJIT has licensedto AST is to be found in the multidisciplinary “smartcoatings” research initiated under the leadership of Daniel Watts, Panasonic Chair in Sustainabilityand executive director of the Otto H. York Centerfor Environmental Engineering and Science. Thiswork was funded initially by the U.S. Departmentof Defense, which was interested in coatings foruse on vehicles and weapons systems that couldsense deterioration and make repairs in surfacebreaks without human intervention. The depart-ment also wanted to investigate the possibility thatsuch coatings could change color and pattern in achameleon-like manner for camouflage purposes.

Federici, who has contributed to the work withAST, explains that the thin-film concepts basic tocreating smart coatings for large pieces of militaryhardware can also be adapted for use on a muchsmaller scale and for very different applications —such as the pressure sensor invented by Lim andPetrova. As an example of another application,Federici says that it’s possible to develop a “smartdecal” just a few square inches in size that might beused to monitor corrosion and metal fatigue in keyautomotive components. Installed throughout afleet of trucks, for example, such a device couldwarn of deterioration by turning on an indicatorlight or other visible display.

Thomas, along with colleagues at NJIT, theUniversity of Medicine and Dentistry of NewJersey and Harvard Medical School, is continuingto develop thin-film sensor technology on a verysmall scale in the biomedical field. One projectinvolves incorporating a minute sensor in animplantable shunt that can be used to relieve theabnormal accumulation of cerebrospinal fluid(CSF) within the brain that afflicts individualswith hydrocephalus.

Current shunt designs do not allow for monitor-ing CSF pressure and flow. Enhancing a shunt witha highly sensitive thin-film sensor would providethis capability. Further, as in the larger AST-licensed version, the shunt sensor’s semiconductorlayer is deposited on a non-metallic substrate,which minimizes problems that could be caused byambient magnetic fields.

“This is certainly a versatile technology,” Thomassays. “On one scale, you can use it to monitorindustrial processes or environmental conditionsmore effectively, and on another to help peoplesuffering from a condition like hydrocephalus.That’s an impressive range of possibilities.” ■

Department of Physics: http://physics.njit.eduDepartment of Biomedical Engineering:www.njit.edu/bme

For more on smart coatings, see the homelandsecurity section in the 2003 Annual Report, onlinein the Publications Library at www.njit.edu.

NJIT faculty members Roumiana Petrova and Hee Lim, co-inventors of the MEMS-basedpressure sensor licensed to American Sensor Technologies for commercial development

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