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{1176}
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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?

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ref: -0 tags: alumina utah array electrode parylene encapsulation date: 10-23-2015 21:28 gmt revision:1 [0] [head]

Utah/blackrock group has been working on improving the longevity of their parlyene encapsulation with the addition of ~50nm Al2O3.

  • PMID-24771981 '''Self-aligned tip deinsulation of atomic layer deposited Al2O3 and parylene C coated Utah electrode array based neural interfaces
    • Process:
      • Normal Utah array dicing saw / glass frit / thinning and etch fabrication for the Utah probe.
      • Sputtered Ti, Sputtered Pt. (not sure how they mask this?)
      • Sputtered iridium oxide (SIROF, sputtered in an Ar + O2 plasma) electrode tips (again, not sure about the mask..)
      • ALD Al2O3 passivation, 50nm. Cambridge Fiji system, same as nanolab. Must take a long time!
      • A-174, aka 3-Methacryloxypropyltrimethoxysilane adhesion promoter (which presumably acts by pulling hydroxy groups off the alumina substrate; Al-O bonds have higher energy than Si-O)
      • 6um parylene.
      • Laser ablation of tips with 1000 pulses from KrF 5ns 100Hz excimer laser. Works much better than poking the electrode tips through thin aluminum foil.
      • O2 plasma descum / removal of carbon residues.
      • BOE removal of Al2O3 above the SIROF
    • Of note, ALD Al2O3 has included hydroxy bonds, which means that it gradually etches in PBS. (Pure Al2O3, as passivates aluminum parts exposed to seawater, does not?)
    • PBS also etches Si3N4, and crystaline Si.
  • IEEE-6627006 (pdf) Bi-layer encapsulation of utah array based neural interfaces by atomic layer deposited Al2O3 and parylene C
    • Atomic layer deposited (ALD) alumina is an excellent moisture barrier with WVTR at the order of ~ 10e-10 g·mm/m2·day [10-13]. But alumina alone is not suitable for encapsulation since it dissolves in water [14].
    • Demonstrated stable power-up of RF encapsulated devices for up to 600 equivalent days in 37C PBS.
      • Actual testing carried out at 57C, 4x accelerated.
  • PMID-24658358 Long-term reliability of Al2O3 and Parylene C bilayer encapsulated Utah electrode array based neural interfaces for chronic implantation.
    • Demonstrated good barrier longevity with wired Utah probes, active probes with flip-chip (Au/Sn eutectic reflow) record/stimulate circuits, and ones with bonded RF stimulation chips, INIR-6. (6th version!)
    • PBS etching of Si lead to undercutting & eventual flake-off of the SIROF, leading to dramatic impedance increase. (Figure 5 and 7).
      • no Pt under the SIROF?

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ref: -0 tags: Peter Ledochowitsch ECoG parylene fabrication MEMS date: 09-25-2014 16:54 gmt revision:0 [head]

IEEE-5734604 (pdf) Fabrication and testing of a large area, high density, parylene MEMS µECoG array

  • Details 5-layer platinum parylene process for high density ECoG arrays.

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ref: Seymour-2011.06 tags: PEDOT Seymour electrode recording parylene date: 08-06-2014 22:39 gmt revision:3 [2] [1] [0] [head]

PMID-21301965[0] Novel multi-sided, microelectrode arrays for implantable neural applications.

  • There are problems with parylene multielectrode arrays:
    • water and salts will rapidly diffuse into the various interfacial boundaries
    • Interfacial delamination due to poor wet adhesion of parylene on metal
      • This possibly due to mechanical stress
      • causes excessive cross-talk or noise.
    • Parylene-C devices are prone to poor adhesion at either the dielectric to dielectric interface or at the dielectric to metal interface *** (Sharma and Yasuda 1982; Yasuda et al 2001)
  • solution: PPXCH 2NH 2 and PPXCHO -- reactive parylene (amine bonds?!)
  • PEDOT is absolutely essential for attaining reasonable performance / impedance from the 85um^2 gold electrodes.
    • Thermal noise on 280um^2 and 170um^2 Au electrodes was too high to record neurons.
    • AU thickness 0.5um.
  • Performed soak tests on their electrodes; the reactive parylene is good, but not sure if it's a worthy improvement.

____References____

[0] Seymour JP, Langhals NB, Anderson DJ, Kipke DR, Novel multi-sided, microelectrode arrays for implantable neural applications.Biomed Microdevices 13:3, 441-51 (2011 Jun)

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ref: -0 tags: parylene plasma ALD insulation long-term saline PBS testing date: 04-02-2014 21:32 gmt revision:0 [head]

PMID-23024377 Plasma-assisted atomic layer deposition of Al(2)O(3) and parylene C bi-layer encapsulation for chronic implantable electronics.

  • This report presents an encapsulation scheme that combines Al(2)O(3) by atomic layer deposition with parylene C.
  • Al2O3 layer deposited using PAALD process-500 cycles of TMA + O2 gas.
  • Alumina and parylene coating lasted at least 3 times longer than parylene coated samples tested at 80 °C
    • That's it?
  • The consistency of leakage current suggests that no obvious corrosion was occurring to the Al2O3 film. The extremely low leakage current (≤20 pA) was excellent for IDEs after roughly three years of equivalent soaking time at 37 °C.
    • Still, they warn that it may not work as well for in-vivo devices, which are subject to tethering forces and micromotion.

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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: parylene metal adhesion Stieglitz date: 08-15-2013 17:22 gmt revision:0 [head]

PMID-20119944 Characterization of parylene C as an encapsulation material for implanted neural prostheses.

  • On Si3N4, platinum, and a first film of parylene-C, satisfactory adhesion was achieved with silane A-174, even after steam sterilization. (>1 N/cm)
  • higher adhesion for the parylene that was deposited at lower pressures.
  • but: higher deposition pressures results in lower crystalinity.
  • [33] parylene can be used to build freestanding nanowires.
  • Parylene does not stick to polyimide.
  • Parylene sticks to parylene well if left untreated.
  • Annealing parylene dramatically increased crystalinity / decreases elongation to break.
  • The deposited parylene C layers on untreated and with oxygen plasma-treated samples delaminated immediately after contact with saline. The behavior was also observed at two out of three samples of the A-174 treated wafers, but not in this magnitude.
    • A potential reason for these results could be contamination of the samples during assembly or excessive treatment with the adhesion promoter.

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ref: -0 tags: ACF chip bonding parylene field's metal polyimide date: 07-10-2013 18:34 gmt revision:10 [9] [8] [7] [6] [5] [4] [head]

We're making parylene electrodes for neural recording, and one critical step is connecting them to recording electronics.

Currently Berkeley uses ACF (anisotropic conductive film) for connection, which is widely used for connecting flex tape to LCD panels, or for connecting driver chips to LCD glass. According to the internet, pitches can be as low as 20um, with pad areas as low as 800um^2. source

However, this does not seem to be a very reliable nor compact process with platinum films on parylene, possibly because ACF bonding relies on raised areas between mated conductors (current design has the Pt recessed into the parylene), and on rigid substrates. ACF consists of springy polymer balls coated in Ni and Au and embedded in a thermoset epoxy resin. The ACF film is put under moderate temperature (180C) and pressure (3mpa, 430psi), which causes the epoxy to cure in a state that leaves the gold/nickel/polymer balls to be compressed between the two conductors. Hence, even if the conductors move slightly due to thermal cycling, the small balls maintain good mechanical and electrical contact. The balls are dispersed sufficiently in the epoxy matrix that there is little to no chance of conduction between adjacent pads.

(Or so I have learned from the internet.) Now, as mentioned, this is an imperfect method for joining Pt on parylene films, possibly because the parylene is so flexible, and the platinum foil is very thin (200-300 nm). Indeed, platinum does not bond very strongly to parylene, hence care must be taken to allow sufficient overlap to prevent water ingress. My proposed solution -- to be tested shortly -- is to use a low-melting temperature metal with strong wetting ability -- such as Field's metal (bismuth, tin, indium, melting point 149F, see http://www.gizmology.net/fusiblemetals.htm) to low-temperature solder the platinum to a carrier board (initially) or to a custom amplifier ASIC (later!). Parylene is stable to 200C (392F), so this should be safe. One worry is that the indium/bismuth will wet the parylene or polyimide, too; however I consider this unlikely due to the difficulty in attaching parylene to any metal.

That said, there must be good reason why ACF is so popular, so perhaps a better ultimate solution is to stiffen the parylene (or ultimately polyimide) substrate so that it can support both the temperature/pressure of ACF bonding and the stress of a continued electrical/mechanical bond to polyimide fan-out board or ASIC. It may also be possible to gold or nickel electroplate the connector pads to be slightly raised instead of recessed.


Update: ACF bond to rigid 1/2 oz copper, 4mil trace / space connector (3mil trace/space board):

Note that the copper traces are raised, and the parylene is stretched over the uneven surface (this is much easier to see with the stereo microscope). To the left of the image, the ACF paste has been sqeezed out from between the FR4 and parylene. Also note that the platinum can make potential contact with vias in the PCB.


Update 7/2: Fields metal (mentioned above) does stick to platinum reasonably well, but it also sticks to parylene (somewhat), and glass (exceptionally well!). In fact, I had a difficult time removing traces of field's metal from the Pyrex beakers that I was melting the metal with. These beakers were filled with boiling water, which may have been the problem.

When I added flux (Kester flux-pen 951 No-clean MSDS), the metal became noticeably more shiny, and the contact angle increased on the borosilicate glass (e.g. looked more like mercury); this leads me to believe that it is not the metal itself that attaches to glass, but rather oxides of indium and bismuth. Kester 951 flux consists of:

  • 2-propanol 15% (as a denaturing agent) boiling point 82.6C
  • Ethanol 73% (solvent) boiling point 78.3C
  • Butyl Acetate 7% boiling point 127C, flash point 27C
  • Methanol <3% b.p. 64.7C
  • Carboxylic acids < 3% -- proton donors? formic or oxalic acid?
  • Surfacants < 1% -- ?
Total boiling point is 173F.

After coating the parylene/platinum sample with flux, I raised the field's metal to the flux activation point, which released some smoke and left brown organic residues on the bottom of the glass dish. Then I dipped the parylene probe into the molten metal, causing the flux again to be activated, and partially wetting the platinum contacts. The figure below shows the result:

Note the incomplete wetting, all the white solids left from the process, and how the field's metal caused the platinum to delaminate from the parylene when the cable was (accidentally) flexed. Tests with platinum foil revealed that the metal bond was not actually that strong, significantly weaker than that made with a flux-core SnPb solder. also, I'm not sure of the activation temperature of this flux, and think I may have overheated the parylene.


Update 7/10:

Am considering electrodeless Ni / Pt / Au deposition, which occurs in aqueous solution, hence at much lower temperatures than e-beam evaporation Electrodeless Ni ref. On polyimide substrates, there is extensive literature describing how to activate the surface for plating: Polyimides and Other High Temperature Polymers: Synthesis ..., Volume 4. Parylene would likely need a different possibly more aggressive treatment, as it does not have imide bonds to open.

Furthermore, if the parylene / polyimide surface is *not* activated, the electrodeless plating could be specific to the exposed electrode and contact sites, which could help to solve the connector issue by strengthening & thickening the contact areas. The second fairly obvious solution is to planarize the contact site on the PCB, too, as seen above. ACF bonds can be quite reliable; last night I took apart (and successfully re-assembled) my 32" Samsung LCD monitor, and none of the flex-on-glass or chip-on-flex binds failed (despite my clumsy hands!).

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ref: -0 tags: Utah parylene cracking encapsulation electrode date: 06-28-2013 18:26 gmt revision:4 [3] [2] [1] [0] [head]

Characterization of parylene-C film as an encapsulation material for neural interface devices

  • Hsu, Jui-Meia; Kammer, Saschab; Jung, Erikc; Rieth, Lorend; Normann,A. Richarde; Solzbacher, Florianade (Utah)
  • lists Tg 35-80C for parylene-C;
  • 3um films applied.
  • Parylene samples were subjected to accelerated lifetime testing (85 % relative humidity (RH) and 85 ̊C) for 20 days, and the film did not show appearance changes as observed by optical microscopy. However, X-ray diffractograms show that the film crystallinity increased during this test.
  • 120C 100%RH for 2 hours released parylene from the silicon.
  • Soldering @ 350C backside of Utah array caused parylene to crack.
  • X-ray diffraction shows that heat causes parylene to crystalize:

___Low Dielectric Constant Materials for Ic Applications___ edited by Paul Shin Ho, Jihperng Leu, Wei William Lee

  • Aging and annealing increase crystalinity and thus lower the elongation to break and increase the modulus and mechanical strength of the films.
  • parylene-N is considerably more crystaline (57%), Tg 13C. (low!)
  • Bulk barrier properties are among the best of the organic polymeric coatings.

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ref: -0 tags: parylene microchannel micromolding glass transition temperature microfluidics date: 06-28-2013 17:34 gmt revision:3 [2] [1] [0] [head]

Parylene micromolding, a rapid low-cost fabrication method for parylene microchannel

  • doi:10.1016/j.snb.2003.09.038
  • Hong-Seok Noha∗ , Yong Huangb, Peter J. Hesketha Clemson
  • Parylene properties:
    • Glass transition temperature <90C; c.f. {1247}
    • Melting point 290C
    • Oxidation in air at 120C
    • Thermal bonding here at 200C in a vacuum oven @ 24MPa.

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ref: -0 tags: parylene silicon neural recording probes date: 06-07-2013 00:15 gmt revision:4 [3] [2] [1] [0] [head]

http://thesis.library.caltech.edu/4671/1/PhDThesisFinalChanglinPang.pdf

  • Notes: Michigan probes suffer from thickness limited to <15um, hence are often not stiff enough to penetrate the pia & arachnoid.
  • Likewise, utach arrays are fabricated through a substrate, so cannot be made longer than 1.5-2mm. Plus, they are connected with 25um gold wires, which is both rigid and requires a fair bit of work. (Perhaps with a wirebond machine?)
  • SiO2 suffers from high internal stress (formed at high temperature) and tends to hydrate over time, both making it a less than ideal insulator for biological applications.
    • Silicon is slowly attacked in saline.
  • Use Cr/Au traces, and Ti/Pt electrode sites on his probes.
    • 2.5um minimum trace width.
  • Importantly, they solve the problem of parylene to silicon interconnect by simply fabricating the wires on parylene -- like ours -- and only use silicon as a structural support.
    • Silicon is roughened via XeF2 for good parylene adhesion.
      • Alas, does not survive a long-term soak -- but maybe this is useful? (page 102)
        • This too can be solved via bringing the parylene in vacuum up to melting temperature to better bond with Si.
  • Metal pads on parylene are destroyed by wedge bonding -- heat and pressure are too high!
  • Their solution is to use conductive epoxy & fan the wires out to omnetics pitch (635um) in what they call parylene-PCB-omnetics connector (PPO).
  • Plated a 5um x 5um electrode with platinum black to reduce the impedance from 1.1M to 9.2k (!!)
    • Problem is that Pt black is fragile, and may be scraped off during insertion -- see figure on page 95.
  • Probe shanks are ~ 170um x 150um, tip spade-type patterned via DRIE.
  • To be able to sustain soaking and lifetime testing, thick parylene layers are needed for the flexible parylene cable. The total parylene thickness of our neural probes is about 13 μm which results in a long etching time. We use photoresist as a mask when etching parylene using RIE O2 plasma etching; the etching rate of parylene and photoresist in RIE is roughly 1:1. Thick photoresist (> 20 μm) with high resolution is needed. AZ 9260 thick-film photoresist is designed for the more-demanding higher-resolution thick-resist requirements. It provides high resolution with superior aspect ratios, as well as wide focus and exposure latitude and good sidewall profiles. A process of two spinning coats using AZ 9260 has been developed to make a high-resolution thick photoresist mask of about 30 μm. Figure 4-11 shows the thick photoresist on the probe tip to guarantee a sharp tip after plasma etching. The photoresist is hard baked in oven at 120 oC for 30 min; the thick photoresist needs to be carefully handled during baking to avoid thermal cracking.
  • Otline electrolysis-based actuators ... interesting but hopefully not needed.

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ref: -0 tags: plasma etch removal parylene DRIE date: 05-28-2013 18:47 gmt revision:2 [1] [0] [head]

Plasma removal of Parylene C

  • Ellis Meng, Po-Ying Li and Yu-Chong Tai USC / Caltech
  • Technics O2 plasma etch works, as do DRIE / RIE etch; all offer varying degrees of anisotropy, with the more intricate processes offering straighter sidewalls.
  • Suggested parameters for O2 etch is 200sccm / 200W.
  • Etch will be somewhat isotropic -- top of photoresist will be etched away, leading to ~15deg sloped sidewalls.
    • Hence, small parylene features will be narrowed by the 02 plasma.

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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.

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ref: -0 tags: parylene interconnect monolithic integration silicon DRIE date: 02-26-2013 00:29 gmt revision:1 [0] [head]

A New Multi-Site Probe Array with Monolithically Integrated Parylene Flexible Cable for Neural Prostheses

    • Use DRIE to etch the back of the wafer after patterning the front. Clever!

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ref: -0 tags: parylene PDMS material properties gold compliant date: 02-08-2013 22:38 gmt revision:2 [1] [0] [head]

PMID-21240559 Highly-compliant, microcable neuroelectrodes fabricated from thin-film gold and PDMS

  • he microcable electrodes were also electromechanically tested, with measurable conductivity (220 kΩ) at an average 8% strain (n = 2) after the application of 200% strain.

{1191}
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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)

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ref: Salcman-1976.01 tags: Salcman electrodes recording chronic microelectrode array MEA original parylene date: 01-28-2013 22:18 gmt revision:8 [7] [6] [5] [4] [3] [2] [head]

PMID-1256090[0] A new chronic recording intracortical microelectrode

  • maintain that tethering is the rational way to go: it "re-establishes the normal biomechanics of the intact cranial vault". (Salcman 1972, 1973) {1010}
    • have model of electrode tip motion in response to brain-skull displacements (Goldstein and Salcman 1973) {1011}
      • Electrode would have a tip displacement of about 5um in response to a 1mm displacement of the electrode's point of entry into the skull.
      • Exponential dependence on recording amplitude and distance (Rall, 1962). Gradient: 7.5uv/um; movements of more than 1-2um can radically alter the recordnig shape.
      • Probably our electrodes work because the dura & gliosis becomes firmly attached to the electrode shafts.
    • not really an array so much as a number (10-12) of single-unit electrodes.
  • Details the process of parylene-C deposition, electrode microwelding, etc. Pretty cool stuff -- what has happened to this technology?
  • Each bubble is glued with cyanocrylate to the pia. (they too question the safety of this).
  • arrays can be manually inserted via forceps.
  • 25um iridium wire electroplated in 1-2um of gold
    • then electo-etched until the desired tip geometry is achieved, 1-3um diameter
    • and vacuum coated in 3um of parylene-C.
    • Impedance 1-2M with a 1kHz sine wave at 10nA. Impedance is inversely related to the frequency of the test current, phase angle of 70-80deg.
      • Ref Robinson, 1968.
    • We must emphasize the extreme sensitivity of electrode measurements to the test conditions. Measured values of Z e are usually increased 1-3M when the electrode has been stored away for a few days. Removing the electrode from the test bath for a few minutes in air can lead to equally large increases when the electrode is tested upon remersion. [...] might be oxide.
    • Pinholes are the usual failure mechanism (KD Wise 2004), {149}; parylene is 'pinhole-free'.
  • The connecting 25um Au lead is very flexible and imposes little stress on the iridium electrode.
    • Connecting wire coated in 12um of parylene C
    • Would prefer even finer wire, 12um.
  • Perspex window over the craniotomy; had a vent in this window which they could open.
  • Opening the vent would cause the brain to pulse, moving the electrodes through the cortex and changing neural activity.
  • Size of an electrode is limited by ability to introduce it into the brain.
    • Electrode must be introduced through the pia; as the pial vessels supply the cortex (or drain the cortex).
    • For their electrodes, P crit=0.9g ; the force necessary to penetrate the pia is 0.05 - 0.2g.
  • pure iridium is stiffer than Pt-Ir by a factor of 3 or so. (521 G N/m^2 = 521 GPa, higher than tungsten, which is 400 Gpa)
    • Pure iridium is apparently the stiffest metallic element ref
  • Interesting: "Once again we are impressed by the fact that passive recording electrodes exhibit drops in impedance in the living system which they never show on in vitro testing in protein solutions at 37C.
    • Between 40 and 50 days, a slow downward trend becomes noticeable; this trend continues for the life of the animal and asymptotically approaches values below 500k. Electrodes still record.
    • See {999}
    • Surmise that pure iridium electrodes have a different metal-electrolyte interface than more conventional metals (Pl and W).
  • Mention that the ultimate purpose is for a neural prosthesis.
    • Their then use was for recordings from M1 in monkeys and V1 from cats. (Schmidt, Bak, McIntosh 1974)
  • Ref Wise et al {1012}.

____References____

[0] Salcman M, Bak MJ, A new chronic recording intracortical microelectrode.Med Biol Eng 14:1, 42-50 (1976 Jan)

{1201}
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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)

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ref: Seymour-2009.1 tags: Parylene MEA biocompatibility pin hole water saturation PPX date: 01-25-2013 01:19 gmt revision:2 [1] [0] [head]

PMID-19703712[0] The insulation performance of reactive parylene films in implantable electronic devices.

  • Describe the development and testing of a superior form of parylene: poly(p-xylylene) functionalized with reactive group X (PPX-X)
  • Heat-treated PPX-X device impedance was 800% greater at 10kHz and 70% greater at 1Hz relative to heated parylene-C controls after 60 days (in saline).
  • Better wet attachment to the metal.

____References____

[0] Seymour JP, Elkasabi YM, Chen HY, Lahann J, Kipke DR, The insulation performance of reactive parylene films in implantable electronic devices.Biomaterials 30:31, 6158-67 (2009 Oct)

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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.