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ref: -0 tags: electrode area review impedance date: 04-28-2017 17:55 gmt revision:9 [8] [7] [6] [5] [4] [3] [head]

Quick review of electrode area / impedance within m8ta:

  • {895} 500um^2
  • {311} 490um^2 nominal; 900k
  • {1040} 108um^2, plated from 5M to 1M.
  • Neuronexus: 177, 413um, 700um, and 1250um.
    • Suggest 177um for SUA, 413um for MUA.
    • Community consensus seems to be that these electrodes don't last as long, though.
    • Electroplating 177um^2 sites with PEDOT:PSS reduces impedance to 23k {1388}
  • {823} 122um^2 nominal
  • {736} 500um^2
  • {1027} (Utah) 1600um^2
    • Impedance: ~ 220K +-91K (in vivo -- large variance)
    • Blackrock site lists impedance @ 400k
  • SIrOF Utah array -- 3100um^2 (3.1e-5cm^2) -- large!
    • Impedance ~50K according to [www.blackrockmicro.com/userfiles/file/Microelectrode%20Arrays.pdf Blackrock product brochure].
  • PMID-20124668 (Utah again) 2000um^2, 125k Pt, 6k SIROF.
  • Neuropixel: 144um^2 acid-etched TiN
  • Carbon fiber: ~38 um^2, PEDOT:PSS or PEDOT:pTS started ~ 4M, plated down to ~ 130k initial, went up to 2M pSS, 840k pTS.

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ref: -0 tags: gold micrograin recording electrodes electroplating impedance date: 10-17-2016 20:28 gmt revision:5 [4] [3] [2] [1] [0] [head]

PMID-23071004 Gold nanograin microelectrodes for neuroelectronic interfaces.

  • We report a single-cell sized microelectrode, which has unique gold nanograin structures, using a simple electrochemical deposition method.
  • Fabricated microelectrode had a sunflower shape with 1-5 (um of micropetals along the circumference of the microelectrode and 500 nm nanograins at the center.
  • The nanograin electrodes had 69-fold decrease of impedance and 10-fold increase in electrical stimulation capability compared to unmodified flat gold microelectrodes.
  • images/1270_1.pdf pdf
  • The deposition was conducted with an aqueous solution containing 25 mM HAuCl (HAuCl · 3H O, Sigma-Aldrich, MO, 4 4 2USA) and 20 g/L polyvinylpyrrolidone (surfactant, stabilizing agent)

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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: Williams-2007.12 tags: electrode impedance spectroscopy histology date: 01-28-2013 19:12 gmt revision:3 [2] [1] [0] [head]

PMID-18057508[0] Complex impedance spectroscopy for monitoring tissue responses to inserted neural implants.

  • In general, impedance magnitude at 1 kHz was significantly increased in extensive reactions, starting about 4 days post-implant
    • Impedance is hence predictive of performance.
  • Electrodes with extensive reactions also displayed impedance spectra with a characteristic change at high frequencies. This change was manifested in the formation of a semi-circular arc in the Nyquist space, suggestive of increased cellular density in close proximity to the electrode site.
    • Interesting! Usefull!


[0] Williams JC, Hippensteel JA, Dilgen J, Shain W, Kipke DR, Complex impedance spectroscopy for monitoring tissue responses to inserted neural implants.J Neural Eng 4:4, 410-23 (2007 Dec)

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ref: -0 tags: impedance digital transmission line date: 03-14-2012 22:20 gmt revision:0 [head]

http://web.cecs.pdx.edu/~greenwd/xmsnLine_notes.pdf -- Series termination will work, provided the impedance of the driver + series resistor is matched to the impedance of the transmission line being driven.

School has been so long ago, I've forgotten these essentials!

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ref: Kim-2007.08 tags: Hyun Kim muscle activation method BMI model prediction kinarm impedance control date: 01-06-2012 00:19 gmt revision:1 [0] [head]

PMID-17694874[0] The muscle activation method: an approach to impedance control of brain-machine interfaces through a musculoskeletal model of the arm.

  • First BMI that successfully predicted interactions between the arm and a force field.
  • Previous BMIs are used to decode position, velocity, and acceleration, as each of these has been shown to be encoded in the motor cortex
  • Hyun talks about stiff tasks, like writing on paper vs . pliant tasks, like handling an egg; both require a mixture of force and position control.
  • Georgopoulous = velocity; Evarts = Force; Kalaska movement and force in an isometric task; [17-19] = joint dependence;
  • Todorov "On the role of primary motor cortex in arm movement control" [20] = muscle activation, which reproduces Georgouplous and Schwartz ("Direct cortical representation of drawing".
  • Kakei [19] "Muscle movement representations in the primary motor cortex" and Li [23] [1] show neurons correlate with both muscle activations and direction.
  • Argues that MAM is the best way to extract impedance information -- direct readout of impedance requires a supervised BMI to be trained on data where impedance is explicitly measured.
  • linear filter does not generalize to different force fields.
  • algorithm activity highly correlated with recorded EMG.
  • another interesting ref: [26] "Are complex control signals required for human arm movements?"


[0] Kim HK, Carmena JM, Biggs SJ, Hanson TL, Nicolelis MA, Srinivasan MA, The muscle activation method: an approach to impedance control of brain-machine interfaces through a musculoskeletal model of the arm.IEEE Trans Biomed Eng 54:8, 1520-9 (2007 Aug)
[1] Li CS, Padoa-Schioppa C, Bizzi E, Neuronal correlates of motor performance and motor learning in the primary motor cortex of monkeys adapting to an external force field.Neuron 30:2, 593-607 (2001 May)

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ref: bookmark-0 tags: microdrilling surgery craniotomy impedance date: 0-0-2006 0:0 revision:0 [head]


Pathformer is an electrosurgical hand-held meidcal device that cuts holes in nails and skin. It operates on mesoscissioning technology, cutting the nail/skin with a microcutting tool, using skin impedance as a feedback for stopping the cutting intervention. Pathformer is approved by FDA for creating holes in nails for treating subungual hematoma (black toe).