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{1383}
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ref: -0 tags: carbon nanotube densification conductivity strength date: 02-23-2017 02:52 gmt revision:2 [1] [0] [head]

Super-strong and highly conductive carbon nanotube ribbons from post-treatment methods

  • Conductivity of 1.2e6 S/m, about that of stainless steel.
    • 500 x 500nm wire, length 1cm will have a resistance of 40k.
  • Aerogel method: methane + ferrocene + thiophene + hydrogen.
    • Resulting in ~ 18% Fe, multi-walled carbon nanotubes, diameter 15nm, 15-20 walls.
  • Densified with a stainless-steel spatula on regular paper.
    • Resulting in ribbons 22um wide, 650nm thick.
  • Very high tensile strength, up to 5.2 GPa; moduls ~ 266 GPa.

High-strength carbon nanotube fibre-like ribbon with high ductility and high electrical conductivity

  • Slightly higher conductivity, 1.82 - 2.24e6 S/m.
  • Rolled until it was 500nm thick!
  • Spun from an aerogel (!!) using ethanol + ferrocent + thiophene.

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ref: -0 tags: iridium oxide nanotube intracellular recording electroplate MEA date: 02-22-2017 22:41 gmt revision:0 [head]

PMID-24487777 Iridium oxide nanotube electrodes for sensitive and prolonged intracellular measurement of action potentials.

  • Electrodeposition of IrOx "magically" forms 500nm tubes.
  • Holes in Si3N4 / SiO2 were formed via e-beam lithography; underlying Pt wires via liftoff.
  • Showed long (minutes) intracellular access, though it tended to dip with time.

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ref: -0 tags: carbon fiber thread spinning Pasquali Kemere nanotube stimulation date: 02-09-2017 01:09 gmt revision:0 [head]

PMID-25803728 Neural stimulation and recording with bidirectional, soft carbon nanotube fiber microelectrodes.

  • Poulin et al. demonstrated that microelectrodes made solely of CNT fibers22 show remarkable electrochemical activity, sensitivity, and resistance to biofouling compared to conventional carbon fibers when used for bioanalyte detection in vitro.23-25
  • Fibers were insulated with 3 um of block copolymer polystyrene-polybutadiene (PS-b-PBD) (polybutadiene is sythetic rubber)
    • Selected for good properties of biocompatibility, flexibility, resistance to flextural fatigue.
    • Available from Sigma-Aldrich.
    • Custom continuous dip-coating process.
  • 18um diameter, 15 - 20 x lower impedance than equivalently size PtIr.
    • 2.5 - 6x lower than W.
    • In practice, 43um dia, 1450um^2, impedance of 11.2 k; 12.6um, 151k.
  • Charge storage capacity 327 mC / cm^2; PtIr = 1.2 mC/cm^2
  • Wide water window of -1.5V - 1.5V, consistent with noble electrochemical properties of C.
  • Lasts for over 97e6 pulsing cycles beyond the water window, vs 43e6 for PEDOT.
  • Tested via 6-OHDA model of PD disease vs. standard PtIr stimulating electrodes, implanted via 100um PI shuttled attached with PEG.
  • Yes, debatable...
  • Tested out to 3 weeks durability. Appear to function as well or better than metal electrodes.

PMID-23307737 Strong, light, multifunctional fibers of carbon nanotubes with ultrahigh conductivity.

  • Full process:
    1. Dissolve high-quality, 5um long CNT in chlorosulfonic acid (the only known solvent for CNTs)
    2. Filter to remove particles
    3. Extrude liquid crystal dope through a spinneret, 65 or 130um orifice
    4. Into a coagulant, acetone or water
    5. Onto a rotating drum to put tension on the thread & align the CNTs.
    6. Wash in water and dry at 115C.
  • Properties:
    • Tensile strength 1 GPa +- 0.2 GPa.
    • Tensile modulus 120 GPa +- 50, best value 200 GPa
      • Pt: 168 GPa ; Au: 79 GPa.
    • Elongation to break 1.4 %
    • Conductivity: 0.3 MS/m, Iodine doped 5 +- 0.5 MS/m (22 +- 4 microhm cm)
      • Cu: 59.6 MS/m ; Pt: 9.4 MS/m ; Au: 41 MS/m
      • Electrical conductivity drops after annealing @ 600C
      • But does not drop after kinking and repeated mechanical cycling.
  • Theoretical modulus of MWCNT ~ 350 GPa.
  • Fibers well-aligned at ~ 90% the density (measure 1.3 g/cc) of close-packed CNT.

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ref: -0 tags: nanotube tracking extracellular space fluorescent date: 02-02-2017 22:13 gmt revision:0 [head]

PMID-27870840 Single-nanotube tracking reveals the nanoscale organization of the extracellular space in the live brain

  • Extracellular space (ECS) takes up nearly a quarter the volume of the brain (!!!)
  • Used the intrinsic fluorescence of single-walled carbon nanotubes @ 1um, 845nm excitation, with super-resolution tracking of diffusion.
    • Were coated in phospholipid-polyethylene glycol (PL-PEG), which display low cytotoxicity compared to other encapsulants.
  • 5ul, 3ug/ml injected into the ventricles of young rats; allowed to diffuse for 30 minutes post-injection.
  • No apparent response of the microglia.
  • Diffusion tracking revealed substantial dead-space domains in the ECS.
    • As compared to patch-clamp loaded SWCNTs
  • Estimate from parallel and perpendicular diffusion rates that the characteristic scale of ECS dimension is 80 to 270nm, or 150 +- 40nm.
  • The ECS nanoscale dimensions as visualized by tracking similar in dimension and tortuosity to electron microscopy.
  • Viscosity of the extracellular matrix from 1 to 50 mPa S, up to two orders of magnitude higher than the CSF.
  • Positive control through hyalurinase + several hours to digest the hyaluronic acid.
    • But no observed changes in morphology of the neurons via confocal .. interesting.
    • Enzyme digestion normalized the spatial heterogenaity of diffusion.

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ref: -0 tags: Kewame carbon nanotube yarn wet spinning CNT date: 03-26-2015 18:29 gmt revision:0 [head]

Neural Stimulation and Recording with Bidirectional, Soft Carbon Nanotube Fiber Microelectrodes

  • 43um diameter CTN yarn
  • Shows superior charge injection / surface area.
  • polystyrene-polybutadiene co-polymer insulation (like ABS, without the acrylonitrile)
  • https://chemistry.beloit.edu/classes/nanotech/CNT/nanotoday3_5_24.pdf -- details on the process of spinning these CNT yarns.
    • Tensile strength still far below commercial carbon fibers or high-strength polymers.

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ref: -0 tags: gold carbon nanotube electroplating impedance PEG date: 10-24-2014 22:25 gmt revision:1 [0] [head]

PMID-21379404 Creating low-impedance tetrodes by electroplating with additives

  • Electroplated tetrodes to 30-70 kΩ by adding polyethylene glycol (PEG) or multi-walled carbon nanotube (MWCNT) solutions to a commercial gold-plating solution.
  • Cui and Martin [12] showed that altering the concentration of gold-plating solution and electroplating current can change the morphology of a gold-plated microelectrode coating.
  • Additionally, Keefer et al. [13] found that adding multi-walled carbon nanotubes (MWCNTs) to a gold-plating solution created microelectrode coatings with a “rice-like” texture and very low impedances.
  • Au electroplating solution made of non-cyanide, gold-plating solution (5355, SIFCO Selective Plating, Cleveland, OH).
  • A one-second, reversed-polarity pulse helped to clean the surface of the tetrode tip and lowered the impedances to 2MΩ to 3 MΩ before electroplating.
  • Electroplating pulses were one to five seconds long and were repeated until the tetrodes reached the desired impedances. After electroplating, the tetrodes were soaked in DI, air dried, and checked for shorts.

Conclusion: 75% PEG, commercial electropating solution, 0.1ua current pluses to 250K or less.

  • Though the Caswell Au plating solution will likely behave differently ..

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ref: -0 tags: Kozai carbon nanotube electrode rcording histology date: 08-02-2013 05:42 gmt revision:1 [0] [head]

PMID-23142839 Ultrasmall implantable composite microelectrodes with bioactive surfaces for chronic neural interfaces.

  • Here, we report the development of an integrated composite electrode consisting of a carbon-fibre core, a poly(p-xylylene)-based thin-film coating that acts as a dielectric barrier and that is functionalized to control intrinsic biological processes, and a poly(thiophene)-based recording pad.
  • 7um diameter carbon nanotubes slide easily into cortex & yield good recording.
  • only 0.8um of parlyene-N coating.
    • Does it stick well? Does it crack?
  • Functionalized the parylene with 50nm of bromine / oxygen complex, bromoisobutyrate.
  • PEDOT recording surface drastically lowered impedance.
  • Difficult to assemble these little buggers!

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ref: bookmark-0 tags: muscle artifial catalyst nanotubes shape-memory alloy date: 0-0-2006 0:0 revision:0 [head]

http://www.newscientist.com/article/dn8859-methanolpowered-artificial-muscles-start-to-flex.html