m8ta
you are not logged in, login. new entry
text: sort by
tags: modified
type: chronology
{1356}
hide / edit[6] / print
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.

{1176}
hide / edit[5] / print
ref: Gilgunn-2012 tags: kozai neural recording electrodes compliant parylene flexible dissolve date: 02-24-2017 19:14 gmt revision:5 [4] [3] [2] [1] [0] [head]

IEEE-6170092 (pdf) An ultra-compliant, scalable neural probe with molded biodissolvable delivery vehicle

    • Optical coherence tomography is cool.
  • Large footprint - 150 or 300um, 135um thick (13500 or 40500 um^2; c.f. tungsten needle 1963 (50um) or 490 (25um) um^2.)
  • Delivery vehicle is fabricated from biodissolvable carboxy-methylcellulose (CMC).
    • Device dissolves within three minutes of implantation.
    • Yet stiff enough to penetrate the dura of rats (with what degree of dimpling?)
    • Lithographic patterning process pretty clever, actually.
    • Parylene-X is ~ 1.1 um thick.
    • 500nm Pt is patterned via ion milling with a photoresist mask.
    • Use thin 20nm Cr etch mask for both DRIE (STS ICP) and parylene etch.
  • Probes are tiny -- 10um wide, 2.7um thick, coated in parylene-X.
  • CMC polymer tends to bend and warp due to stress -- must be clamped in a special jig.
  • No histology. Follow-up?

{1226}
hide / edit[1] / print
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!

{1057}
hide / edit[10] / print
ref: Kozai-2009.11 tags: electrodes insertion Kozai flexible polymer momolayer date: 01-30-2013 04:45 gmt revision:10 [9] [8] [7] [6] [5] [4] [head]

PMID-19666051[0] Insertion shuttle with carboxyl terminated self-assembled monolayer coatings for implanting flexible polymer neural probes in the brain.

  • This study investigated the use of an electronegative (hydrophillic) self-assembled monolayer (SAM) as a coating on a stiff insertion shuttle to carry a polymer probe into the cerebral cortex, and then the detachment of the shuttle from the probe by altering the shuttle's hydrophobicity.
    • Used 11-mercaptoundecanoic acid. Details included.
    • SAM atrtacts water once inserted, causing the hydrophobic polymer to move away.
      • Why not make the polymer hydrophillic?
      • Is this just soap?
  • Used agarose brain model.
  • Good list of references for the justification of soft electrodes, and researched means for addressing this, mostly usnig polymer stiffeners.
    • "Computer models and experimental studies of the probe–tissue interface suggest that flexible and soft probes that approach the brain’s bulk material characteristics may help to minimize micromotion between the probe and surrounding tissue ({737}; {1203}; {1102}; {1200}; LaPlaca et al., 2005; {1216}; Neary et al., 2003 PMID-12657694; {1198})"
  • "However, polymer probes stick to metallic and silicon surfaces through hydrophobic interactions, causing the polymer probe to be carried out of the brain when the insertion shuttle is removed. The solution is to use a highly hydrophillic, electronegative, self-assembled monolayer coating on the shuttle.
  • Biran et al 2005 suggests that incremental damage due to stab wounds from the shuttle (needle) should be minor.
  • Probes: 12.5 um thick, 196 um wide, and 1.2cm long, polymide substrate and custom designed lithographed PDMS probes.
  • Polymer probes were inserted deep - 8.5 mm.
  • PDMS probes inserted with non-coated insertion shuttle resulted in explantation of the PDMS probe.

____References____

[0] Kozai TD, Kipke DR, Insertion shuttle with carboxyl terminated self-assembled monolayer coatings for implanting flexible polymer neural probes in the brain.J Neurosci Methods 184:2, 199-205 (2009 Nov 15)