James HarperRobert Mifflin

June 7th, 2007Jacobs School of Engineering

University of California – San Diego

Advisors:Prof. Prab BandaruProf. SungHo JinProf. Frank Talke

Introduction◦ Selecting the Area of Nanotechnology to Enhance

Why is this area important? Does it pass the Moral / Ethics Test?

◦ Background Growth and Chirality Separation Techniques

Analyses of Separation Techniques◦ Dielectrophoresis◦ Flow Fractionalization Analysis and Improvement◦ Pulsed dielectrophoresis

Creating Pure Lines of Carbon Nanotubes◦ Selection and Release◦ The Perfect Carbon Nanotube Forest

Conclusion

Generating Pure Sets of CNTs on Demand

◦Why is this area important?

[1]

Carbon nanotubes can be used to enhance materials and create new sensors that impact everyday life

Electrical arena Wires, Batteries and Capacitors, Flex displays

[2] [3][4]

Carbon nanotubes can be used to enhance materials and create new sensors that impact everyday life

Electrical arena ◦ Conductive plastics, adhesives

Structural Arena ◦ Adhesives, Flexible circuits, Composites

[5] [6] [7]

Carbon nanotubes can be used to enhance materials and create new sensors that impact everyday life

Electrical arena ◦ Conductive plastics, adhesives

Structural Arena ◦ Adhesives, textiles, composites

Bio-molecule sensing

[8]

[9][10]

◦Does it pass the Moral / Ethics Test?

[11]

Growth and Chirality of Carbon Nanotubes◦ Formed from several processes, resulting in a sheet of

graphene in the form of a hollow continuous tube.

◦ Differences between SWCNT, MWCNT,M-SWCNT, S-SWCNT

SWCNT – Single Wall CNT

MWCNT – Multi-Wall CNT

M-SWCNT – Metallic SWCNT

S-SWCNT – Semiconductor SWCNT

[12]

Unbundling Carbon Nanotubes◦ Use sonication and ultra-centrifugation to separate

hydrophobic clumps of CNTs◦ Buffer with a surfactant sodium dodecyl sulphate

(SDS)

[13]

Unbundling Carbon Nanotubes◦ Use sonication and ultra-centrifugation to separate

hydrophobic clumps of CNTs◦ Buffer with a surfactant sodium dodecyl sulphate

(SDS) Purification / Sorting Techniques

◦ Ultra-centrifugation◦ Optical sorting◦ Fluid flow fractionalization ◦ Dielectrophoresis

Purification / Sorting Techniques◦ Ultra-centrifugation

[14][15]

Purification / Sorting Techniques◦ Optical sorting

[16]

Purification / Sorting Techniques◦ Optical sorting

[28]

Purification / Sorting Techniques◦ Fluid flow fractionalization

[29]

Purification / Sorting Techniques◦ Dielectrophoresis

[30]

Unbundling Carbon Nanotubes◦ Use sonication to separate clumps and ultra-centrifugation

Purification / Sorting Techniques◦ Ultra-centrifugation◦ Optical sorting◦ Fluid flow fractionalization ◦ Dielectrophoresis

Problem?◦ Each technique allows for partial separation of the desired

carbon nanotubes from the bulk solution – However ……

There is an overlap of sorting parameters!◦ Use of one technique independently will not discriminate

nanotubes with overlapping parameters

[17]

There is an overlap of sorting parameters!◦ And the number of parameters that can vary is large!

[18]

[19]

[20]

Partial Solution?◦ Multiple techniques must be used for to obtain a rough

sort of the material.

Ultra-centrifugation Optical sorting Fluid flow fractionalization Dielectrophoresis

And the resulting subset will still have a mixture of different nanotubes - albeit a set with many overlapping attributes.

Realize that absolute purity of nanotubes through top down or bottom up fabrication may not be achievable.

Recast the problem – what other system/industry has high variability – yet desires near exact to exact duplicates be used?

Look to the Bio Labs –◦ Generating a clone murine line for laboratory study.

Maps to --- CNT – rough sort desired CNTs--- CNT – individual capture--- Check the Chirality – using Raman scattering and conduction properties--- Release the individual CNT

--- Clone the CNT

Bio ProcessSelect an species Isolate the individualSequence the DNA

Release the individual(into a controlled environment)

Clone the individual

[21]

◦Can all of these steps be done?

◦ If so, perfect sorting may not be required.

Introduction◦ Selecting the Area of Nanotechnology to Enhance

Why is this area important? Does it pass the Moral / Ethics Test?

◦ Background Growth and Chirality Separation Techniques

Analyses of Separation Techniques◦ Dielectrophoresis◦ Flow Fractionalization Analysis and Improvement◦ Pulsed dielectrophoresis

Creating Pure Lines of Carbon Nanotubes◦ Selection and Release◦ The Perfect Carbon Nanotube Forest

Conclusion

Uncharged particle + non-uniform electric field = force◦ Caused by uneven charge distribution◦ Depends strongly on…

Medium’s and particles' electrical properties Particles' morphology Frequency of the electric field

More polarizable particles move toward stronger electric field

For CNTs,

where , and

2)Re( EKF fm

*

**

m

mpfK

i*lr 2

6

-+ - -

+ + + -

++

++

+++

-

-----

---

[22]

[23]

CNTs with dissimilar conductivitiesand morphologies develop differentterminal velocities within a fluid flow,as described by

Separation is most efficient when vT

of different sizes of CNTs is most

dissimilar.◦ Adjust friction factor f by changing orientation

uf

Fv dep

T

[24]

Three possible orientations◦ Parallel

Because ,

vT α f -1 when u is constant.

)/2ln(

6

rl

lfrandom

1)/2ln(2

16

rl

lf perp

1)/2ln(2

8

rl

lf para

ufFv depT

◦ Perpendicular ◦ Random

[25]

)/2ln(

6

rl

lfrandom

1)/2ln(2

16

rl

lf perp

1)/2ln(2

8

rl

lf para

Orientation

Inverse of Friction Factor (s/kg) Differenc

e (s/kg)100 nm length

2 μm length

Perpendicular 4.5 × 105 51.3 × 105 46.8 × 105

Random 6.4 × 105 76.8 × 105 70.4 × 105

Parallel 8.9 × 105 103.0 × 105 94.1 × 105

Maximum difference attained with parallel orientation

34% larger difference than random orientation Significant?

May be difficult to implement in practice Possibly use dielectrophoretic force itself to orient

nanotubes parallel to flow

Difference between Dielectrophoresis (DEP) and Pulsed Dielectrophoresis (PDEP)◦ DEP is typically set up for an asymmetrical field

with constant frequency. We would like to look at varying the duty cycle to try to separate CNT that have very closely overlapping properties.

◦ Example - Lets look at some cells

Distributed populations of spherical shell models of mammalian

cells. (Top Left) 10% variation across all three DEP parameters, radius, permittivity, and conductivity. (Top Right) Constant conductivity with varying permittivity and radius. (Lower Left) Constant radius. (Lower Right) Constant permittivity.

Difference between Dielectrophoresis (DEP) and Pulsed Dielectrophoresis (PDEP)

103

105

107

109

1011

-1

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1

Frequency, Hz

Re

[f

TextEnd

CM

TextEnd

] TextEnd

Variable Parameters

103 105 107 109 1011-1

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1

Frequency, Hz

Re

[f

TextEnd

CM

TextEnd

] TextEnd

Constant Conductivity

103

105

107

109

1011

-1

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1

Frequency, Hz

Re

[f

TextEnd

CM

TextEnd

] TextEnd

Constant Radius

103 105 107 109 1011-1

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1

Frequency, Hz

Re

[f

TextEnd

CM

TextEnd

] TextEnd

Constant Permittivity

Distributed populations of spherical shell models of mammalian

cells. (Top Left) 10% variation across all three DEP parameters, radius, permittivity, and conductivity. (Top Right) Constant conductivity with varying permittivity and radius. (Lower Left) Constant radius. (Lower Right) Constant permittivity.

The equations

Complex Permittivity

Permittivity of CNT

Metallic = 2000 Media = 18.6

Modified Clausius Mossotti

E field between electrodes volts per meter

And the friction factor

2)Re( EKF fm

i

2

f 2 2 2

( ) ( )Re{k }= m p m m m p

m m

241 ( )a

g

e N

E m

0

62.5E

0

8

2ln(2 / ) 1

l

l r

Capture occurs due to Dielectrophoresis attracting the CNT dipoles. ◦ CNT lands on the probes and

causes the field to be modified◦ Thus self assembly/placement

Modify the probe surface with LBL deposited materialfor sticktion and later lift off

[26]

Use Raman scattering and conduction parameters to analyze the CNTs

Electronic and mechanicallystringency wash cartridge.

Decorate CNTs with bio-particles to ease later handling.

CNTs are then released asneeded from the storagecartridge.

Moved to cloning cell off chip

[27]

Sonicated into seeds Embedded into an LBL deposited layer Used to grow Final CNTs

Sorting of CNTs difficult, yet improvable◦ Flow fractionalization◦ Pulsed dielectrophoresis

Best solution: avoid problem of perfect sorting with capture and release of CNTs◦ The perfect carbon nanotube forest

Pictures◦ [1,2] “The Application of Vertically Aligned Carbon Nanotube Arrays in Electronics and Biosensors” by Dr. Jun Li, NASA

Ames Research Center, MS 229-1, Moffett Field, CA 94035

◦ [7] “Carbon nanotubes enter Tour de France.” CNet.com.

◦ [8-9] “ Carbon Nanotube Based Biosensors.” Massood Z. Atashbar1, Bruce Bejcek2, Srikanth Singamaneni1, and Sandro Santucci. Electrical and Computer Engineering Department, Western Michigan University, Kalamazoo, MI-49008, USA

◦ [10] “Drug Delivery and Biomolecular Transport.” Nanotubes Monthly.

◦ [17-20] “Simple model for dielectrophoretic alignment of gallium nitride nanowires.” Abhishek Motayeda et al. Material Science and Engineering Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland 20899 and Department of Electrical and Computer Engineering, University of Maryland, College Park, Maryland 20742

◦ [24] Dielectrophoresis of carbon nanotubes using microelectrodes: a numerical study.” Maria Dimaki and Peter Bøggild. MIC–Department of Micro and Nanotechnology, Building 345 East, Technical University of Denmark, DK-2800, Kgs. Lyngby, Denmark.

◦ [29] “High-Speed Integrated Particle Sorters based on Dielectrophoresis.” J.H. Nieuwenhuis1, A. Jachimowicz1, P. Svasek2, M.J. Vellekoop1, Industrial Sensor Systems, ISAS, Vienna University of Technology, Gusshausstrasse 27-29, A-1040, Vienna, Austria, nieuwenhuis@tuwien.ac.at, Ludwig Boltzmann Institute of Biomedical Microtechnology, Vienna, Austria

Articles◦ Dielectrophoresis of carbon nanotubes using microelectrodes: a numerical study.” Maria Dimaki and Peter Bøggild. MIC–

Department of Micro and Nanotechnology, Building 345 East, Technical University of Denmark, DK-2800, Kgs. Lyngby,◦ Morgan H and Green N G 2003 AC Electrokinetics: Colloids and Nanoparticles Research Studies Press Ltd p. 76-77.◦ Pohl, H. A. (1978) Dielectrophoresis, Cambridge University Press, Cambridge◦ Arnold, W. M. and Zimmerman, U. (1982) Z. Naturforsch. 37c, 908-915 ◦ Mischel, M., Voss, A. and Pohl, H. A. (1982) J. Biol. Phys. 10, 223-226.

More references available for this document upon request.