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ref: -2016 tags: Kozai carbon fiber microelectrodes JNE PEDOT PSS pTS date: 04-27-2017 01:42 gmt revision:6 [5] [4] [3] [2] [1] [0] [head]

PMID-27705958 Chronic in vivo stability assessment of carbon fiber microelectrode arrays.

  • showed excellent recording characteristics and nearly zero glial scarring.
  • 6.4um carbon fiber + 800nm parylene-C = 8.4um.
    • Cytec Thoronel T-650 CF, Youngs modulus = 255 GPa, tensile strength = 4.28 GPa, PAN-based.
  • Everything protected with our wonderful phenol epoxy 353NDT, heat-cure.
  • Used two coating solutions:
    • Solution of 0.01 M 3,4-ethylenedioxythiophene (483028, Sigma-Aldrich, St. Louis, MO): 0.1 M sodium p-toluenesulfonate (152536, Sigma-Aldrich, St. Louis, MO).
      • pTS is not that dissimilar from it's alkyl cousin, SPS, {1353}. Likely a soapy chemical due to the opposed methyl and sulfonic acid group; benzine will take up less room in the polymer c.f. SDS & may lower the oxidation potential of EDOT.
      • Tosylates have been explored as a EDOT counterion : PMID-22383043 Characterization of poly(3,4-ethylenedioxythiophene):tosylate conductive polymer microelectrodes for transmitter detection. and PEDOT-TMA
    • Solution was composed of 0.01 M 3,4-ethylene-dioxythiophene (483028, Sigma-Aldrich, St. Louis, MO):0.1 M polystyrene sulfonate (m.w. 70.000, 222271000, Acros, NJ).
    • For each solution the electrodeposition was carried out by applying 100 pA/channel for 600 s to form a layer of poly(3,4-ethylenedioxythiophene):sodium p-toluenesulfonate (PEDOT:pTS) or poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS).
      • Weird, would use voltage control here..
  • According to works by Green et al [45] and Hukins et al [46], equation (1) can be used to determine the aging time that
the fibers have undergone: t 37=t TQ10 T37)/10 where t 37 is the simulated aging time at 37 °C, t T is the amount of real time that the samples have been kept at the elevated temperature, T , and Q10 is an aging factor that is equal to 2, according to ASTM guidelines for polymer aging [47].
  • Show > 2MOhm impedance of the small-area electrodes. At the aging endpoint, PEDOT:pTS had about half the impedance of PEDOT:PSS.
    • 4M PSS, 7M pTS, both plated down to ~ 130k initial, went up to 2M pSS, 840k pTS.
  • Recording capability quite stellar
  • Likewise for the glial response.

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ref: -0 tags: NET probes SU-8 microfabrication sewing machine carbon fiber electrode insertion mice histology 2p date: 03-01-2017 23:20 gmt revision:0 [head]

Ultraflexible nanoelectronic probes form reliable, glial scar–free neural integration

  • SU-8 asymptotic H2O absorption is 3.3% in PBS -- quite a bit higher than I expected, and higher than PI.
  • Faced yield problems with contact litho at 2-3um trace/space.
  • Good recordings out to 4 months!
  • 3 minutes / probe insertion.
  • Fab:
    • Ni release layer, Su-8 2000.5. "excellent tensile strength" --
      • Tensile strength 60 MPa
      • Youngs modulus 2.0 GPa
      • Elongation at break 6.5%
      • Water absorption, per spec sheet, 0.65% (but not PBS)
    • 500nm dielectric; < 1% crosstalk; see figure S12.
    • Pt or Au rec sites, 10um x 20um or 30 x 30um.
    • FFC connector, with Si substrate remaining.
  • Used transgenic mice, YFP expressed in neurons.
  • CA glue used before metabond, followed by Kwik-sil silicone.
  • Neuron yield not so great -- they need to plate the electrodes down to acceptable impedance. (figure S5)
    • Measured impedance ~ 1M at 1khz.
  • Unclear if 50um x 1um is really that much worse than 10um x 1.5um.
  • Histology looks realyl great, (figure S10).
  • Manuscript did not mention (though the did at the poster) problems with electrode pull-out; they deal with it in the same way, application of ACSF.

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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: glassy carbon SU-8 pyrolysis CEC microelectrode stimulation stability platinum PEDOT date: 02-17-2017 00:05 gmt revision:2 [1] [0] [head]

A novel pattern transfer technique for mounting glassy carbon microelectrodes on polymeric flexible substrates

  • Use inert-atmosphere pyrolysis @ 900 - 1000 C of 20um SU-8 (which is aromatic) on a thermal oxide wafer.
  • Followed by spin & cure of PI.
  • Demonstrate strong carbonyl bonding of the glassy carbon with mechanical and FTIR testing.
  • Use of photosensitive PI allows through-vias to connect Cr/Au conductive traces.

PMID-28084398 Highly Stable Glassy Carbon Interfaces for Long-Term Neural Stimulation and Low-Noise Recording of Brain Activity

  • Use EIS to show superior charge-injection properties + stability of glassy carbon electrodes vs. Pt electrodes.
    • GC lasted > 5e6 pulses; Pt electrodes delaminated after 1e6 pulses.
    • Hydrogen bonding (above) clearly superior than neat PI-Pt interface
  • GC electrodes were, true to their name, glassy and much smoother than the platinum electrodes.
  • Further reduced impedance with PEDOT-PSS coating.
    • PEDOT-PSS coating on glassy carbon was, in their hands, far more stable than PEDOT-PSS on platinum.
  • All devices, GC, PEDOT:PSS, and Pt, had similar biocompatibility in their assay (figure 7)

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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: carbon fiber pitch based tensile strength date: 02-04-2017 00:07 gmt revision:4 [3] [2] [1] [0] [head]

Contenders for high-modulus pitch-based carbon fiber: "

CorpModelYoung's modulusTensile StrengthDiameter Elongation at break
Nippon Graphite Fiber CoGranoc XN-90860 GPa3.43 GPa10 um0.4%
Mitsubishi RayonK13D2U940 GPa3.21 GPa11 um0.36%
Cytec ThornelP-120830 GPa2.41 GPa??0.3-0.5%
Cytec ThornelK1100965 GPa3.10 GPa10 um??

Tensile and Flextural Prperties of single carbon fibers

  • High modulus pitch-based carbon fibers have quite low compressive and shear strengths. The flexural strength could be affected strongly by its low strength under compression and shear loading.

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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: carbon fiber electrode array parylene fire sharpening microthread date: 03-20-2014 19:57 gmt revision:5 [4] [3] [2] [1] [0] [head]

PMID-23860226 A carbon-fiber electrode array for long-term neural recording.

  • Guitchounts G1, Markowitz JE, Liberti WA, Gardner TJ.
  • We describe an assembly method for a 16-channel electrode array consisting of carbon fibers (<5 µm diameter) individually insulated with Parylene-C and fire-sharpened. The diameter of the array is approximately 26 µm along the full extent of the implant.
  • Fibers from http://www.goodfellowusa.com/
    • young's modulus of 380GPa vs. tungsten 400GPa.
    • Data available from Toho Tenax
  • The absence of any report of single neuron isolation in HVC with a fixed chronic electrode implant underscores the difficulty of recording small cells (8-15um soma) with an implant whose damage length scale is large relative to the target neurons. (!!)

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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: -0 tags: electrode carbon fiber MEA date: 04-22-2013 18:19 gmt revision:2 [1] [0] [head]

PMID-21228307 Ultrasmall and customizable multichannel electrodes for extracellular recordings

  • 7um carbon fiber electrodes.
  • It has been estimated that insertion of a 50 um wire in the adult rat hippocampus CA1 area could damage 90% of the neurons that would otherwise be recordable by the electrode (Claverol-Tinture and Nadasdy 2004)
  • Highlight the tetrode effect: it's like beam forming.
  • Carbon fibers from Goodfellow Cambridge.
  • Insulated with a pulled micropipette.
  • Added insulation with cathodic electrodeposition paint (Claerclad HSR)
  • focused ion beam milling (FIB) (Qiao et al 2005) -- working resolution below 10nm.
  • The carbon fibers were fond to be stiff enough to penetrate the fly 'dura'.

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ref: notes-0 tags: CO2 global warming carbon dioxide indonesia brazil date: 03-14-2008 21:34 gmt revision:0 [head]

From the New Yorker, Feb 25:

  • "Just two countries - Indonesia and Brazil - account for ten percent of the greenhouse gasses released into the atmosphere. "
  • "During the next twenty-four hours the effect of losing forests in Brazil and Indonesia will be the same as if eight million people boarded airplanes at Heathrow airport and flew en mass to New York. "

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ref: notes-0 tags: energy carbon CO2 hot water heater. date: 02-25-2008 23:36 gmt revision:2 [1] [0] [head]

How much carbon dioxide (CO2) is released to heat the water for a 5-minute shower?

  1. assumptions
    1. water enters your house at 45F, and you heat it to 100F.
    2. the energy efficiency of your hot water heater is 87%, and we ignore the cost of static thermal losses.
    3. you live in the southeast like me, which is predominantly powered by coal-fired plants. These plants release about 0.8kg/kwh of CO2 ref
    4. transmission of energy from the power plant to your home is 90% efficient
    5. you have a shower head that flows at a rate of 2.2 gallons/minute
  2. result: 2.2gpm -> 138.6 ml/sec -> * 31C temp rise -> 4.2kw -> 0.31kg CO2.
    1. that's about equivalent of driving 4 miles in a 30mpg car. (gasoline CO2 release = 2.4kg/gallon)

  • Interesting analysis. I'm surprised how much CO2 is used by those 5-minutes of delicious, delicious hot shower! --joeyo