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{1250}
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ref: -0 tags: polyimide electrodes thermosonic bonding Stieglitz adhesion delamination date: 03-06-2017 21:58 gmt revision:7 [6] [5] [4] [3] [2] [1] [head]

IEEE-6347149 (pdf) Improved polyimide thin-film electrodes for neural implants 2012

  • Tested adhesion to Pt / SiC using accelerated aging in saline solution.
  • Targeted at retinal prostheses.
  • Layer stack:
    • 50nm SiC deposited through PECVD @ 100C using SPS, with low frequency RF modulation.
    • 100nm Pt
    • 100nm Au
    • 100nm Pt
      • These layers will alloy during cure, and hence reduce stress.
    • 30nm SiC
    • 10nm DLC (not needed, imho; PI sticks exceptionally well to clean SiC)
  • Recent studies have concluded that adhesion to PI is through carbon bindings and not through oxide formation.
    • Adhesion of polyimide to amorphous diamond-like carbon and SiC deteriorates at a minimal rate.
  • Delamination is caused by residual stress, which is not only inevetable but a major driving force for cracking in thin films.
    • Different CTE in layer stack -> different contraction when cooling from process temperature.
  • Platinum, which evaporates at 1770C, and is deposited ~100C (photoresists only withstand ~115C) results in a high-stress interface.
    • Pt - Carbon bonds only occur above 1000C
  • After 9 and 13 days of incubation the probes with 400 nm and 300nm of SiC, respectively, which were not tempered, showed complete delamination of the Pt from the SiC.
    • 60C, 0.9 M NaCl, 1 year.
    • The SiC remained attached to the PI.
      • Tempering: repeated treatment at 450C for 15 min in a N2 atmosphere.
    • All other probes remained stable.
  • Notably, used thermosonic bonding to the PI films, using sputtered (seed layer) then 12um electroplated Au.
  • Also: fully cured the base layer PI film.
  • Used oxygen plasma de-scum after patterning with resists to get better SiC adhesion to PI.
    • And better inter-layer adhesion (fully cured the first polyimide layer @ 450C).
  • Conclusion: "The fact that none of the tempered samples delaminated even after ~5 years of lifetime (extrapolated for 37 C) shows a tremendous increase in adhesion.

{1253}
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ref: -0 tags: polyimide stieglitz stability date: 01-22-2017 05:35 gmt revision:1 [0] [head]

PMID-20144477 In vitro evaluation of the long-term stability of polyimide as a material for neural implants

  • PI degrades at 85C in PBS; otherwise, it's stable.
  • mechanical tests only; no electrical tests.
  • Durimide 7510 contains a photo-initiator and an adhesion promoter. Spin-coatable.
    • Adhesion can be inhibited with C4F8
    • notably softer.
  • Dupont Kapton is PMDA-ODA (phenol linkage in the amide); PI-2611 is BPDA-PPD (aromatic carbon-carbon in the dicarboxcylic acid). The latter resists water uptake better.

{1266}
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ref: -0 tags: polyimide adhesion delamination Stieglitz date: 08-18-2015 22:19 gmt revision:1 [0] [head]

Thin films and microelectrode arrays for neuroprosthetics

  • Juan Ordonez, Martin Schuettler, Christian Boehler, Tim Boretius and Thomas Stieglitz
  • Discussion of adhesion & ideas of using siliconcarbides as opposed to adhesion promoters (Silane A-174) to maintain good metal-polymer adhesion even with an equilibrium water vapor pressure.
  • Transition metals form carbide bonds with polyimide, but noble metals do not.
  • A one-metal (preferably noble) system is advantageous, as two metals will form a galvanic cell and eventually corrode.
  • Therefore it's best to develop non-metallic non-toxic adhesion promotion technologies.

{1316}
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ref: -0 tags: polyimide adhesion chromium copper tie layer upilex date: 06-24-2015 23:14 gmt revision:3 [2] [1] [0] [head]

Adhesion Evaluation of Adhesiveless Metal/Polyimide Substrate for MCM and high density packaging

  • Adhesion degradation after thermal and humidity stresses can occur for a number of reasons.
    • Copper diffusion can promote adhesion loss at elevated temperatures and can be inhibited by coating a barrier layer of metal – tie layer2.
    • Oxygen diffusion through polyimide film to the metal/polyimide interface plays a critical role in promoting degradation too3. Adhesion of Cr/polyimide interface is degraded significantly upon exposure to high temperature and humidity environment due to the hydrolysis of polyimide4,5 .
    • Catastrophic adhesion loss has been linked to moisture induced oxidation of chromium interfaces based on studies using radioactively tagged water4, 5.
  • That said, most of these vendors use Cr (20nm) as and adhesion layer, and Cu (200nm) as the conductor.
  • Upilex A faired very well after the pressure cooker test -- > 60% retention after 192 hours.
  • Seemingly Ta and Cr both adhere similarly to PI -- {1317}
    • Though Ta is much more ductile, and forms a stronger carbide, Cr is preferred... cheaper?

{1251}
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ref: -0 tags: microflex interconnect polyimide Stieglitz date: 03-03-2015 00:33 gmt revision:1 [0] [head]

IEEE-938305 (pdf) High Density Interconnects and flexible hybrid assemblies for active biomedical implants

  • Idea: make vias in your metallized PI film. Bump-bond through these vias to a chip below.
  • Achieve center-to -center distances of 100um.
  • No longer using this? See {1250}, which uses thermosonic bonding.

{1259}
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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.

{1252}
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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.

{1229}
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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.

{1085}
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ref: Parush-2011.01 tags: basal ganglia reinforcement learning hypothesis frontiers israel date: 01-24-2012 04:05 gmt revision:2 [1] [0] [head]

PMID-21603228[0] Dopaminergic Balance between Reward Maximization and Policy Complexity.

  • model complexity discounting is an implicit thing.
    • the basal ganglia aim at optimization of independent gain and cost functions. Unlike previously suggested single-variable maximization processes, this multi-dimensional optimization process leads naturally to a softmax-like behavioral policy
  • In order for this to work:
    • dopamine directly affects striatal excitability and thus provides a pseudo-temperature signal that modulates the tradeoff between gain and cost.

____References____

[0] Parush N, Tishby N, Bergman H, Dopaminergic Balance between Reward Maximization and Policy Complexity.Front Syst Neurosci 5no Issue 22 (2011)

{744}
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ref: Merletti-2009.02 tags: surface EMG multielectrode recording technology italy date: 01-03-2012 01:07 gmt revision:2 [1] [0] [head]

PMID-19042063[0] Technology and instrumentation for detection and conditioning of the surface electromyographic signal: state of the art

  • good background & review of surface EMG (sEMG) - noise levels, electrodes, electronics. eg. Instrumentation amplifiers with an input resistance < 100MOhm are not recommended, and the lower the input capacitance, the better: the impedance of a 10pf capacitor at 100hz is 160MOhm.
  • Low and balanced input impedances are required to reduce asymmetric filtering of common-mode power-line noise.

____References____

[0] Merletti R, Botter A, Troiano A, Merlo E, Minetto MA, Technology and instrumentation for detection and conditioning of the surface electromyographic signal: state of the art.Clin Biomech (Bristol, Avon) 24:2, 122-34 (2009 Feb)

{466}
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ref: notes-0 tags: Duke Licensing patents university royalty royalties intellectualproperty date: 10-12-2007 17:41 gmt revision:4 [3] [2] [1] [0] [head]

What I have learned about licensing & Duke (or really, licensing at universities in general), in no particular order:

  • Licensing fees split up: 50% to the inventors, 10% to the lab, 10% to the department, 30% to the dean
    • The 50% inventors' fees are split up based on what is determined fair by the inventors themselves, or if that fails, by the Office of Licensing & Ventures (OLV) itself. If there are several patents in a licensing, then it is split between patents based on relevance / contribution, then between each of the inventors. Royalties are split in the same way.
    • The OLV & patent's budget is indirectly paid through these licensing fees.
  • Universities are granted ownership of any intellectual property developed by graduate students & other employees under federal funding through the 1980/1984 Bayh-Dole Act. Universities assume ownership of IP developed through privately funded work, though there is no one law for this.
    • Graduate students are considered employees under the law, hence IP retained, even if no formal contract was signed.
  • Even if an independent inventor (e.g. me) files a invention disclosure form to Duke in good faith, and upon investigation the OLV agrees that the claim of independence is supported, this does not prevent future litigation.
    • If the fields of invention and research overlap, as is probably true for me, then OLV & Duke are likely to protest (money is at stake, after all).
  • Patents require a servicing fee every 3-5 years - have to learn more about this!
  • Almost certainly want a patent on a device. without it, it is very easy to steal :/
    • Can patent software 'ideas' or 'methods' that have utility, but not the actual software. The text of the software is copyrighted, like a book.
  • If a patent has people on it who were not involved in the invention, the patent can be legally contested and voided. Conversely, if the patent does not have all the inventors on it, then it can also be contested by an outside party, and voided.
  • Duke will pay the legal fees for patents & writing up a licensing contract
    • Duke will also pay the fees to patent in other countries (where the patenting fees are much higher), depending on market.
      • The European Union has no centralized patent office - patents must be filed in each country and translated to & from the official language. The legal and translation fees & time spent on this can be very high, so usually companies only file in a few largest markets, if at all.
    • Concerning the named inventors on a patent, above, Duke determines who is involved usually by asking the PI, without delving into the internal politics of a lab. This may or may not be an issue.
  • Typical licensing fees $25k - $1M, depending on what is being patented.
  • Duke can revoke the licensing agreement if the company is not using it / making progress within a period specified by the licensing contract, e.g. 6 - 9 months.
  • Duke typically licenses multiple patents at a time to startups; startups typically need more than one patent.
  • Duke typically pursues non-exclusive licenses on biological models (e.g. Gouping Feng's OCD mouse), and exclusive licenses on devices (like this, i suppose)
    • In some fields, device licensing is exclusive to a field - e.g. one company licenses for Parkinson's application, another for Alzheimer's, etc.
  • Once a patent is licensed to a company, it typically becomes gradually 'diluted' as the company & employees invests more in the idea/technology. If the initial royalty level was 5%, and the company makes significant changes & improvements, then the company will re-negotiate the royalty percentage.
    • Oftent the licensing agreement specifies the maximum amount of dilution / the minimum royalty level, as ultimately the university was involved in the first step to commercialization, without which anything else could have happened.
  • Similarly, if the company licensing University IP needs to give a certain royalty percentage to another patent holder & cannot remain solvent without decreasing University share, then the company and University will negotiate a lower royalty rate.

conclusions:

  • Everything is fluid & up for negotiation, depending on the desires and situations of each of the parties.
    • Typically, the university and inventor are on the same side, but that is not true for me.
  • Need a lawyer to navigate the maze!

{374}
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ref: notes-0 tags: entrepreneur MIT notes LLC tax law securities advice date: 05-22-2007 15:25 gmt revision:0 [head]

http://enterpriseforum.mit.edu/mindshare/startingup/index.html

  • many good articles on setting up a subchapter S corporation (only taxed once, with limitations), LLC, obtaining good employees, dealing with securities and investment, etc!