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Financial disclosures:

Patent: PCT/US2008/072662-Coating neural electrodes with carbon nanotubes and variations

Licensed technology covered by PCT/US2008/072662 to Plexon Inc for use in research products

Applications of carbon nanotube neural interfaces

Edward W Keefer

UT Southwestern Medical School

Dallas, TX

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Motivation for an improved electrode coating

Critical functional properties of an electrode interface for recording purposes include low

noise, low impedance, and stability of the neuron/electrode interface for prolonged periods.

Strategies to optimize that coupling must balance the conflicting goals of a highly selective

electrode with the need for high sensitivity. An ideal electrode will maximize both

sensitivity and selectivity; sensitivity increases with decreasing impedance, selectivity

increases as electrode size decreases. However, impedance increases as the area of theelectrode decreases, making the design of most microelectrodes a compromise between

these two parameters.

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3 ways of depositing dispersed CNT mixtures onto neural electrodes

1)Codepositing at cathode with gold or platinum2)Codepositing at anode with conductive polymers

3)Covalent attachment to functionalized metal electrodes

Interactions of neurons with CNTs arranged in 2 different,

distinct structures

1) Dispersed mixtures electroplated onto metal electrodes

2) CNT yarn electrode recordings from rat and chronic tissue reaction

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3 ways of depositing dispersed CNT mixtures onto neural electrodes

CNT/Au electroplated onto

planar MEAs

CNT/polypyrrole on SS

microwire

CNT covalent attachment to

tungsten sharp electrodesLow

voltage

High

voltage

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Keefer et al. (2008) Nat. Nano. 3:434-439

SEM and electrochemical

characterization of CNT/Au

coated MEA electrodes

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Functional benefits of CNT coated MEA electrodes-

increased efficacy of electrical stimulation

to elicit neural responses

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Performance of CNT coatings in vivo

Stereotrode recording from rat HC

1-8000 Hz

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Examples of other electrode types we have coated

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Unfiltered recording from rat hippocampus

60 61 62 63 64 65 66 67 68 69 70

ch 08

ch 07

ch 06

ch 05

ch 04

ch 03

ch 02

ch 01

Time (sec)

-1.25

1.25

CNT coated

CNT coated

CNT coated

CNT coated

Reduction in artifacts on CNT coated electrodes during in vivo recording

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50 ms

4.0 mv

1.0 mv

Tungsten sharp wire electrode

Z= 10 k

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Action potentials

Multi-unit activity

Field potentials

1-8000 Hz

300-8000 Hz

0.5 sec

1000s-1,000,000s

1 neuron

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anesthetized

euthanized + 12 minutes

electronic noise +

electrode noise +

biological noiseelectronic noise +

electrode noise +

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Reduced in vivo low frequency noise at CNT coated electrodes

1000 1001 1002 1003 1004 1005 1006 1007 1008 1009 1010

ch 08

ch 07

ch 06

ch 05

ch 04

ch 03

ch 02

ch 01

Time (sec)

-0.136

0.137

CNT coated

CNT coated

CNT coated

CNT coated

Unfiltered recording from rat hippocampus

euthanized

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Neuron Noise: 500 700 uV^2

Electrode Interface Noise: 80 100 uV^2

Electrode bulk noise + circuit thermal noise + 1/f noise

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Ray BaughmanUTD Nanotech Institute

Carbon nanotube sheet drawnfrom a CNT forest (Science 309:1215-1219)

Carbon nanotube yarn drawn and twisted from a CNT forest

Hierarchal structures from CNTs

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Fibroblasts growing on glass

or CNT sheet substrate.

Dorsal root ganglion neuron

on a carbon nanoyarn stained

with -tubulin.

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Nanoyarn electrodes

approximate exposed area 150 m2

Cyclic Voltammetry

.1-1000 V/sec scan rate

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Nanoyarn recording from rat cortex

RED- unfiltered 1-8000 Hz

BLUE- highpass 300-8000 Hz

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TEM Nanoyarn

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H & E stained frozen section 60 day after insertion

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Nanoyarn

DAPI

Tujs100

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Thank you for your attention