Transcript Perfecting the Carbon Nanotubes Forest

James Harper
Robert Mifflin
Advisors:
Prof. Prab Bandaru
Prof. SungHo Jin
Prof. Frank Talke
June 7th, 2007
Jacobs School of Engineering
University of California – San Diego

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

Creating Pure Lines of Carbon Nanotubes

Conclusion
◦ Dielectrophoresis
◦ Flow Fractionalization Analysis and Improvement
◦ Pulsed dielectrophoresis
◦ Selection and Release
◦ The Perfect Carbon Nanotube Forest

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,
[2]
[3]
Flex displays
[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,
[5]
[6]
Composites
[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
[15]
[14]

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!
[19]
[18]
[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.
Bio Process
Select an species
Isolate the individual
Sequence the DNA
-------
Maps to
CNT – rough sort desired CNTs
CNT – individual capture
Check the Chirality – using Raman scattering
Release the individual
---
Release the individual CNT
Clone the individual
---
Clone the CNT
(into a controlled environment)
and conduction properties
[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

Creating Pure Lines of Carbon Nanotubes

Conclusion
◦ Dielectrophoresis
◦ Flow Fractionalization Analysis and Improvement
◦ Pulsed dielectrophoresis
◦ Selection and Release
◦ The Perfect Carbon Nanotube Forest

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
F     m Re( K f ) E

2
For CNTs,
where


6
r 2l ,
Kf 
 *p   m*
 m*
and
*  i


+++++++
-- -----
+ + + +
--- -
[22]
[23]

CNTs with dissimilar conductivities
and morphologies develop different
terminal velocities within a fluid flow,
as described by
vT 

Fdep
f
u
Separation is most efficient when vT
of different sizes of CNTs is most
dissimilar.
◦ Adjust friction factor f by changing orientation
[24]

Three possible orientations
◦ Parallel
f para 
8l
2 ln(2l / r )  1
◦ Perpendicular
f perp 
16l
2 ln(2l / r )  1
◦ Random
f random 
6l
ln(2l / r )
[25]

Because vT  Fdep f  u ,
vT α f -1
when u is constant.
f para 
8l
2 ln(2l / r )  1
f random 
f perp 
6l
ln(2l / r )
16l
2 ln(2l / r )  1
100 nm length
2 μm length
Difference
(s/kg)
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
Orientation

Inverse of Friction Factor (s/kg)
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)
Constant Conductivity
Variable Parameters
1
1
0.8
0.8
0.6
0.6
0.4
0.4
0.2
TextEnd
Re[f CM]
Re[f CM]
0.2
TextEnd
0TextEnd
-0.2TextEnd
0TextEnd
-0.2TextEnd
-0.4
-0.4
-0.6
-0.6
-0.8
-0.8
-1 3
10
10
5
7
10
Frequency,
Hz
Constant Radius
10
9
10
-1 3
10
11
1
1
0.8
0.8
0.6
0.6
5
7
10
Frequency, Hz
Constant Permittivity
10
9
10
11
0.2
TextEnd
Re[f CM]
0TextEnd
-0.2TextEnd
0TextEnd
-0.2TextEnd
-0.4
-0.4
-0.6
-0.6
-0.8
-0.8
-1 3
10
10
0.4
0.4
0.2
TextEnd
Re[f CM]

10
5
7
10
Frequency, Hz
10
9
10
11
-1 3
10
10
5
7
10
Frequency, Hz
10
9
10
11
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
F     m Re( K f ) E
2

   i




Complex Permittivity
  1 (
Permittivity of CNT
 Metallic = 2000
 Media = 18.6
0
0

Modified Clausius Mossotti

E field between electrodes
Eg
4 e 2 N a
)
m
 2 m ( p   m )   m ( m   p )
Re{k f }=
 2 m2   m2
2.5E 6 volts per meter
And the friction factor
8 l

2 ln(2l / r )  1

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 material
for sticktion and later lift off
[26]

Use Raman scattering and conduction parameters to
analyze the CNTs

Electronic and mechanically
stringency wash cartridge.

Decorate CNTs with bio-particles to ease
later handling.
CNTs are then released as
needed from the storage
cartridge.

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, A1040, Vienna, Austria, [email protected], 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.