m8ta
you are not logged in, login. new entry
text: sort by
tags: modified
type: chronology
{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?

{1352}
hide / edit[1] / print
ref: -0 tags: Charles Lieber syringe-injectable electronics SU-8 chronic flexible date: 10-14-2016 23:30 gmt revision:1 [0] [head]

PMID-27571550 Stable long-term chronic brain mapping at the single-neuron level.

  • Fu TM, Hong G1, Zhou T1, Schuhmann TG, Viveros RD2, Lieber CM.
  • 8 months with only 800nm of Su-8 (400nm of insulation!!). This is both surprising and very impressive; we have to step up our game!
  • In a mouse, too - their surgical technique must be very good. Mice only live ~ 2 years anyway.
  • Figure 3 -- stability -- incredible.
  • Recording sites were bare platinum, 20um diameter; stimulation sites were also bare Pt, 150um dia.
    • No plating or mircowire-fets, so far as I can see; electrode impedances were stable at 200 - 600k (supplementary figure 12).

{1204}
hide / edit[6] / print
ref: Linsmeier-2011.01 tags: histology lund electrodes immune response fine flexible review Thelin date: 12-08-2015 23:57 gmt revision:6 [5] [4] [3] [2] [1] [0] [head]

PMID-21867803[0] Can histology solve the riddle of the nonfunctioning electrode? Factors influencing the biocompatibility of brain machine interfaces.

  • We show results from an ultrathin multichannel wire electrode that has been implanted in the rat cerebral cortex for 1 year.
    • 12um Pt-Ir wires in a 200um bundle coated with gelatin. See PMID-20551508[1]
    • Electrode was left in the rat cortex for 354 days
    • no clear GFAP staining or ED1 positive cells at the electrode tips.
  • To improve biocompatibility of implanted electrodes, we would like to suggest that free-floating, very small, flexible, and, in time, wireless electrodes would elicit a diminished cell encapsulation.
  • Suggest standardized methods for the electrode design, the electrode implantation method, and the analyses of cell reactions after implantation
  • somewhat of a review -- Stice, Biran 2005 [2] 2007 [3].
  • 50um is the recording distance Purcell 2009.
  • See also [4]
  • Study of neuronal density and ED1 reactivity / GFAP:
    • Even at 12 weeks the correlation between NeuN density and GFAP / ED1 was small -- r 2=0.12
    • Note that DAPI labels many unknown cells in the vicinity of the electrode.

____References____

[0] Linsmeier CE, Thelin J, Danielsen N, Can histology solve the riddle of the nonfunctioning electrode? Factors influencing the biocompatibility of brain machine interfaces.Prog Brain Res 194no Issue 181-9 (2011)
[1] Lind G, Linsmeier CE, Thelin J, Schouenborg J, Gelatine-embedded electrodes--a novel biocompatible vehicle allowing implantation of highly flexible microelectrodes.J Neural Eng 7:4, 046005 (2010 Aug)
[2] Biran R, Martin DC, Tresco PA, Neuronal cell loss accompanies the brain tissue response to chronically implanted silicon microelectrode arrays.Exp Neurol 195:1, 115-26 (2005 Sep)
[3] Biran R, Martin DC, Tresco PA, The brain tissue response to implanted silicon microelectrode arrays is increased when the device is tethered to the skull.J Biomed Mater Res A 82:1, 169-78 (2007 Jul)
[4] Thelin J, Jörntell H, Psouni E, Garwicz M, Schouenborg J, Danielsen N, Linsmeier CE, Implant size and fixation mode strongly influence tissue reactions in the CNS.PLoS One 6:1, e16267 (2011 Jan 26)

{1306}
hide / edit[2] / print
ref: -2008 tags: tantalum chromium polyimide tungsten flexible neural implants adhesion layer date: 06-24-2015 22:53 gmt revision:2 [1] [0] [head]

PMID-18640155 Characterization of flexible ECoG electrode arrays for chronic recording in awake rats.

  • Yeager JD1, Phillips DJ, Rector DM, Bahr DF.
  • We tested several different adhesion techniques including the following: gold alone without an adhesion layer, titanium-tungsten, tantalum and chromium.
  • All films were DC magnetron sputtered, without breaking vacuum between the adhesion layer (5nm) and gold counductor layer (300nm).
  • We found titanium-tungsten to be a suitable adhesion layer considering the biocompatibility requirements as well as stability and delamination resistance.
  • While chromium and tantalum produced stronger gold adhesion, concerns over biocompatibility of these materials require further testing.
    • Thought: use tantalum directly, no Ti needed.
    • Much better than Cr -- much more ductile and biocompatible.
    • Caveat: studies showing reduction to stociometric Ta results in delamination.
  • Ta conductivity: 1.35e-7 Ohms * m; Ti 4.2e-7; 3x better (film can be 3x thinner..)

{1302}
hide / edit[0] / print
ref: -0 tags: kevlar electrodes flexible polymer 12um McNaughton Utah date: 10-11-2014 00:19 gmt revision:0 [head]

PMID-8982987 Metallized polymer fibers as leadwires and intrafascicular microelectrodes

  • McNaughton TG1, Horch KW.
  • Ti/W, Au, Pt metalization via sputtering.
  • 12um core diamater.
  • demonstrate 8 month reliability.
  • 1um dipped silicone elastomer insulation.
  • note difficulty in manufactuing the fibers. No kidding!
  • Tensile strength the same as a 25um Pt-Ir wire, 90x more flexible.

{1274}
hide / edit[0] / print
ref: -0 tags: flexible neural probe polyimide silicon polyethylene glycol dissolvable jove livermore loren frank date: 03-05-2014 19:18 gmt revision:0 [head]

http://www.jove.com/video/50609/insertion-flexible-neural-probes-using-rigid-stiffeners-attached-with

  • details the flip-chip bonding method (clever!)
  • as well as the silicon stiffener fabrication process.

{1203}
hide / edit[5] / print
ref: Cheung-2007.03 tags: flexible electrode array Michigan probe histology Vancouver current source density EPFL polyimide date: 12-21-2013 21:07 gmt revision:5 [4] [3] [2] [1] [0] [head]

PMID-17027251[0] Flexible polyimide microelectrode array for in vivo recordings and current source density analysis.

  • Polyimide -- PI-2611 precusor.
  • 50nm Ti adhesion, 200nm Pt, both sputtered.
  • Electrodes etched via RIE in Cl2.
    • Sputtered and photo-patterned SiO2 etch mask.
  • Used regular solder to connect to a Samtec.
  • 15um total thickness.
  • 25um electrode diameter.
  • They were inserted directly (no carrier nor guide) into the brain; can be re-used.
  • Tested to 8 weeks.
  • No figure comparing silicon and polyimide, though they claim minimal GFAP response to the electrodes.

____References____

[0] Cheung KC, Renaud P, Tanila H, Djupsund K, Flexible polyimide microelectrode array for in vivo recordings and current source density analysis.Biosens Bioelectron 22:8, 1783-90 (2007 Mar 15)

{1259}
hide / edit[0] / print
ref: -0 tags: polyimide flexible cable frontiers florida date: 10-04-2013 01:55 gmt revision:0 [head]

PMID-24062716 A highly compliant serpentine shaped polyimide interconnect for front-end strain relief in chronic neural implants.

  • Sankar V, Sanchez JC, McCumiskey E, Brown N, Taylor CR, Ehlert GJ, Sodano HA, Nishida T.
  • 20um polyimide / gold / 20um polyimide.
    • No tie layer; then again, no longevity testing either.
  • Used sacrificial aluminum coating to release polyimide.

{1236}
hide / edit[8] / print
ref: -0 tags: optogenetics micro LED flexible electrodes date: 06-27-2013 19:31 gmt revision:8 [7] [6] [5] [4] [3] [2] [head]

PMID-23580530 Injectable, cellular-scale optoelectronics with applications for wireless optogenetics.

  • Supplementary materials
  • 21 authors, University Illinois at Urbana-Champaign, Tufts, China, Northwestern, Miami ..
  • GaN blue and green LEDs fabricated on a flexible substrate with stiff inserter.
    • Inserter is released in 15 min with a dissolving silk fibrin.
    • 250um thick SU-8 epoxy, reverse photocured on a glass slide.
  • GaN LEDS fabricated on a sapphire substrate & transfer printed via modified Karl-Suss mask aligner.
    • See supplemental materials for the intricate steps.
    • LEDs are 50um x 50um x 6.75um
  • Have integrated:
    • Temperature sensor (Pt serpentine resistor) / heater.
    • inorganic photodetector (IPD)
      • ultrathin silicon photodiode 1.25um thick, 200 x 200um^2, made on a SOI wafer
    • Pt extracellular recording electrode.
        • This insulated via 2um thick more SU-8.
  • Layers are precisely aligned and assembled via 500nm layer of epoxy.
    • Layers made of 6um or 2.5um thick mylar (a polyester -- polyethylene terephthalate (PET))
    • Layers joined with SU-8 2.
    • Wiring patterned via lift-off.
  • Powered via RF scavenging at 910 Mhz.
    • appeared to be simple, power in = light out; no data connection.
  • Tested vs control and fiber optic stimulation, staining for:
    • Tyrosine hydroxylase (makes l-DOPA)
    • c-fos, a neural activity marker
    • u-LEDs show significant activation.
  • Also tested for GFAP (astrocytes) and Iba1 (activated microglia); flexible & smaller devices had lower gliosis.
  • Next tested for behavior using a self-stimulation protocol; mice learned to self-stimulate to release DA.
  • Devices are somewhat reliable to 250 days!

{1230}
hide / edit[2] / print
ref: -0 tags: dissertation interconnect parylene flexible electrodes date: 02-26-2013 00:30 gmt revision:2 [1] [0] [head]

http://docs.lib.purdue.edu/dissertations/AAI3444877/

  • Several different projects --
    • Stretchable PDMS electrodes
    • PDMS-parylene ECoG
    • Transmitting parallel neural data via free-space optical link
    • semi-flexible hydrogel-parylene neural electrode.
    • The parylene electrodes with selectively patterned hydrogel provide stiff mechanical properties for easy penetration into the brain tissues and subsequent flexibility after insertion upon swelling of the hydrogel.
    • advanced packaging system with using a composite inorganic parylene combination.
      • Atomic layer deposited alumina-zirconia (Al2O3–ZrO2) composite layer can provide a conformal and nano-laminated coating on parylene surface in neural packaging systems in order to improve the hermeticity for long term implantations
  • Can't get the entire PDF. annoying.

{1162}
hide / edit[3] / print
ref: -0 tags: polymide flexible electrode Rousche incision needle assist date: 01-30-2013 06:38 gmt revision:3 [2] [1] [0] [head]

PMID-11327505 Flexible Polyimide-Based Intracortical Electrode Arrays with Bioactive Capability

  • Use gold / polymide fabrication; electrode is 20um thick, 160um wide.
  • Still quite flexible -- buckles at 0.003 N.
  • Successfully recorded by inserting it in an incision in rat barrel cortex -- needle assist.
    • Well, not too successfully.
  • Suggest that bioactive components can be applied to the permeable polymide surface.

____References____

' ''' ()

{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)

{1191}
hide / edit[4] / print
ref: Wester-2009.04 tags: parylene flexible electrode gold Georgia date: 01-29-2013 03:14 gmt revision:4 [3] [2] [1] [0] [head]

PMID-19255461[0] Development and characterization of in vivo flexible electrodes compatible with large tissue displacements.

  • Device was 100um wide and 25um thick, and was stiff enough to enter directly.
    • carefully calibrated this stiffness -- good! we should do the same.
  • parylene composition.
  • brain tissue force on the order of 2mN.
  • No histology.
  • [http://www.ncbi.nlm.nih.gov/pubmed?term=LaPlaca%20MC[Author]&cauthor=true&cauthor_uid=19255461 laPlaca] has a good number of publications on shear stress in brain tissue.

____References____

[0] Wester BA, Lee RH, LaPlaca MC, Development and characterization of in vivo flexible electrodes compatible with large tissue displacements.J Neural Eng 6:2, 024002 (2009 Apr)

{1201}
hide / edit[1] / print
ref: Kato-2006.01 tags: bioactive neural probes flexible parylene japan Kato microspheres date: 01-28-2013 03:57 gmt revision:1 [0] [head]

PMID-17946847[0] Preliminary study of multichannel flexible neural probes coated with hybrid biodegradable polymer.

  • Conference proceedings. a little light.
  • :-)
  • probes made of parylene-C

____References____

[0] Kato Y, Saito I, Hoshino T, Suzuki T, Mabuchi K, Preliminary study of multichannel flexible neural probes coated with hybrid biodegradable polymer.Conf Proc IEEE Eng Med Biol Soc 1no Issue 660-3 (2006)

{1177}
hide / edit[2] / print
ref: -0 tags: magnetic flexible insertion japan neural recording electrodes date: 01-28-2013 03:54 gmt revision:2 [1] [0] [head]

IEEE-1196780 (pdf) 3D flexible multichannel neural probe array

  • Shoji Takeuchi1, Takafumi Suzuki2, Kunihiko Mabuchi2 and Hiroyuki Fujita
  • wild -- they use a magnetic field to make the electrodes stand up!
  • Electrodes released with DRIE, as with Michigan probes.
  • As with many other electrodes, pretty high electrical impedance - 1.5M @ 1kHz.
    • 20x20um recording sites on 10um parylene.
  • Could push these into a rat and record extracellular APs, but nothing quantitative, no histology either.
  • Used a PEG coating to make them stiff enough to insert into the ctx (phantom in IEEE conference proceedings.)

{1198}
hide / edit[5] / print
ref: Harris-2011.12 tags: mechanically adaptive electrodes implants case western dissolving flexible histology Harris date: 01-25-2013 01:39 gmt revision:5 [4] [3] [2] [1] [0] [head]

PMID-22049097[0] Mechanically adaptive intracortical implants improve the proximity of neuronal cell bodies.

  • See also [1]
  • Initial tensile modulus of 5GPa dropped to 12MPa. (almost 500-fold!)
    • Their polymer nanocomposite (NC) still swells 65-70% (with water?)
    • Implant size 100 x 200um.
  • Controlled with tungsten of identical size and coating.
  • Tethered to skull.
  • Interesting:
    • The neuronal nuclei density within 100 µm of the device at four weeks post-implantation was greater for the compliant nanocomposite compared to the stiff wire.
    • At eight weeks post-implantation, the neuronal nuclei density around the nanocomposite was maintained, but the density around the wire recovered to match that of the nanocomposite.
    • Hypothesis, in discussion: softer implants are affecting the time-course of the response rather that final results
  • The glial scar response to the compliant nanocomposite was less vigorous than it was to the stiffer wire
  • Cultured astrocytes have been shown to respond to mechanical stimuli via calcium signaling (Ostrow and Sachs, 2005).
  • Substrate stiffness is also known to shift cell differentiation in mesenchymal stem cells to be neurogenic, myogenic, or osteogenic (Engler et al., 2006).
  • In vivo studies which focus on the effects of electrode tethering have shown that untethered implants reduce the extent of the glial scar (Biran et al., 2007; Kim et al., 2004; Subbaroyan, 2007)
  • Parylene, polymide, and PDMS still each have moduli 6 orders of mangitude larger than that of the brain.
  • In some of their plots, immune response is higher around the nanocomposites!
    • Could be that their implant is still too large / stiff?
  • Note that recent research shows that vitemin may have neuroprotective effects --
    • Research has linked vimentin expression to rapid neurite extension in response to damage (Levin et al., 2009)
    • NG2+ cells that express vimentin have been proposed to support repair of central nervous system (CNS) damage, and stabilize axons in response to dieback from ED1+ cells (Alonso, 2005; Nishiyama, 2007; Busch et al., 2010)
  • Prior work (Frampton et al., 2010 PMID-20336824[2]) hypothesizes that a more compact GFAP response increases the impedance of an electrode which may decrease the quality of electrode recordings.

____References____

[0] Harris JP, Capadona JR, Miller RH, Healy BC, Shanmuganathan K, Rowan SJ, Weder C, Tyler DJ, Mechanically adaptive intracortical implants improve the proximity of neuronal cell bodies.J Neural Eng 8:6, 066011 (2011 Dec)
[1] Harris JP, Hess AE, Rowan SJ, Weder C, Zorman CA, Tyler DJ, Capadona JR, In vivo deployment of mechanically adaptive nanocomposites for intracortical microelectrodes.J Neural Eng 8:4, 046010 (2011 Aug)
[2] Frampton JP, Hynd MR, Shuler ML, Shain W, Effects of glial cells on electrode impedance recorded from neuralprosthetic devices in vitro.Ann Biomed Eng 38:3, 1031-47 (2010 Mar)

{1206}
hide / edit[0] / print
ref: -0 tags: flexible polymer electrode recording polypyrrole Bizzi date: 01-25-2013 00:39 gmt revision:0 [head]

PMID-19164034 Cortical recording with polypyrrole microwire electrodes.

  • http://web.mit.edu/bcs/bizzilab/publications/bae2008.pdf
  • Electropolymerization of PPy on a glassy carbon electrode in solution.
  • Polypyrrole microwires were prepared by mounting a PPy film perpendicular to the stage of a cryo-microtome and slicing it in 20um sections.
  • Electrode mounted inside a glass capillary tube.
  • Impedance: 1e5 @ 1kHz.

{1192}
hide / edit[0] / print
ref: -2002 tags: sea slugs flexible electrodes polymide Washington date: 01-04-2013 18:46 gmt revision:0 [head]

IEEE-1002325 (pdf) Silicon micro-needles with flexible interconnections

  • Implanted their isolated needles (see also {219}) in sea slugs Tritonia diomedea
    • Sea slug neurons are large -- up to 400um -- makes recording easier.
  • Silicon needles fabricated via reactive ion etching and SF6 sharpening.
  • 'intracellular recording!
  • Pretty advanced fabrication, I guess.

{1189}
hide / edit[0] / print
ref: -0 tags: microelectrode array flexible PDMS via interconnect Georgia date: 01-04-2013 00:33 gmt revision:0 [head]

IEEE-6197244 (pdf) A PDMS-Based Integrated Stretchable Microelectrode Array (isMEA) for Neural and Muscular Surface Interfacing

  • Targeted at e.g. ECoG; in this paper, they look at cat muscle (epimyscial recording).
  • MEA is directly fabricated with a stretchable substrate, such as a thin PCB or ASIC, through via bonding for built-in packaging.

{1188}
hide / edit[1] / print
ref: -0 tags: flexible micxrowire arrays electrode recording Georgia polymide date: 01-04-2013 00:13 gmt revision:1 [0] [head]

IEEE-906517 (pdf) Flexible microelectrode arrays with integrated insertion devices

  • 2001 MEMS Conference.
  • FMA = flexible microelectrode arrays.
  • Both for nerves (pass-through needle) and cortex (removeable needle).
    • Primarily tested in tissue proxies.
  • Anticipated the utility of photolithography for patterning the electrodes + rigid insertion devices.
  • The elastic modulus of polymers like polymide are two orders of magnitude less than metals, but still six orders of magnitude higher than brain tissue (46kPa).
  • Pass-through needle very similar to the threaded wire idea.
  • removable needle simply stops the thread & drives the needle a bit further to break the attachment site.
    • Did not test removable needle technique (?)
  • Defined electroplating with a thick photoresist mask, as Michel says.
  • Tested FMAs with movement and acceleration vs. rigid arrays. FMAs faired much better, of course!

____References____

' ''' ()

{1178}
hide / edit[1] / print
ref: -0 tags: parylene flexible neural recording drug delivery microfluidics 2012 inserter needle release date: 01-02-2013 22:41 gmt revision:1 [0] [head]

PMID-23160191 Novel flexible Parylene neural probe with 3D sheath structure for enhancing tissue integration

  • They seem to think that drugs are critical for success: "These features will enhance tissue integration and improve recording quality towards realizing reliable chronic neural interfaces."
  • Similar to Kennedy: "The sheath structure allows for ingrowth of neural processes leading to improved tissue/probe integration post implantation." 8 electrodes, 4 on the cone interior, 4 on the exterior.
    • opening is 50um at tip, 300 um at base.
  • Used a PEEK-stiffened parylene ZIF connection.
  • Only tested in agarose, but it did properly release from the inserter needle.
  • I wonder if we could use a similar technique..
  • "Lab on a chip" journal (Royal society of Chemistry). nice.

{1175}
hide / edit[0] / print
ref: -0 tags: flexible polymer neural probes compliant MIT EPFL 2008 date: 12-22-2012 01:28 gmt revision:0 [head]

Demonstration of cortical recording using novel flexible polymer neural probes

  • Two layer platinum process minimizes probe size -- nice. Might be useful for our purposes.
  • used electrochemical etching to release the lithographically patterned devices from the sacrificial aluminum layer.
  • Impedance looks pretty high -- 500k at 1kHz.
  • They talk about PCA as though it's unusual to them (?)
  • Histology uncontrolled and un-quantitiative.

{751}
hide / edit[3] / print
ref: work-0 tags: flexible kapton funny date: 05-12-2009 21:57 gmt revision:3 [2] [1] [0] [head]

-- from the Lenthor Engineering Design guide. Wow they are indeed everywhere!