Current Distribution on Capacitive Electrode-Electrolyte Interfaces

Chen, Zhijie Charles; Ryzhik, Lenya; Palanker, Daniel

doi:10.1103/physrevapplied.13.014004

Cited by 23 publications

(26 citation statements)

References 32 publications

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“…As expected for SIROF microelectrodes, the pseudo-capacitance is significantly higher compared with the double-layer capacitance. (22,24) The resulting capacitive current flow at a sweep rate of 0.1 V/s through a parallel circuit of C DL and C P has a value of 3.94 mA/cm 2 , which is in agreement with the measured CV data (see Fig. 5).…”

Section: Eissupporting

confidence: 85%

“…6(b). The circuit is a complete model of the electrodeelectrolyte interface (22) and includes the double-layer capacitance C DL , the pseudo-capacitance C P , the faradaic leakage resistance R F , the charge transfer resistance R CT , the Warburg impedance Z W , and the serial resistance R S . Additionally, a parallel stray capacitance C S was included, which is well-known to exist in three-electrode EIS measurements.…”

Section: Eismentioning

confidence: 99%

“…The pseudo-capacitance C P models the quasi-continuous, reversible faradaic reaction involving reduction and oxidation of Ir 3+ /Ir 4+ at the surface of the SIROF microelectrodes. (22,24) The Warburg impedance Z W accounts for mass-transfer limitation by diffusion. Similarly to what has been used for other SIROF microelectrodes, (10) we used the Warburg element for finite-length diffusion with a reflecting boundary, as given by Eq.…”

Section: Eismentioning

confidence: 99%

See 2 more Smart Citations

Sputtered Iridium Oxide as Electrode Material for Subretinal Stimulation

Haas¹,

Rudorf²,

Becker³

et al. 2020

Sensors and Materials

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The efficiency and safety of neuronal stimulation with implants strongly depend on the electrode material. Microelectrodes composed of iridium oxide are becoming increasingly important as they exhibit excellent charge injection capacity (CIC) as well as charge storage capacity (CSC). We present the development of a robust process for the fabrication of sputtered iridium oxide films (SIROF). This process has been used for the "RETINA IMPLANT Alpha AMS" for several years of subretinal stimulation. In this paper, we describe the full experimental investigation of the electrode material. The electrochemical and morphological properties were investigated by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), voltage transient measurements, and focused ion beam-scanning electron microscopy (FIB-SEM). The implementation on the CMOS chip of the retinal prosthesis is presented. The deposition process window was investigated extensively. Major changes in process parameters lead to a difference in impedance of only 10% of the mean. Accelerated aging tests revealed a long-term stability of the electrodes of at least 10 years under conditions of use. The SIROF electrodes (diameter 30 µm) show low impedance (15.9 kΩ), excellent CSC (50.9 mC/cm 2), and high CIC (4.2 mC/cm 2). In summary, the robustness of the presented deposition process and the large process window enable the integration of high-quality SIROF microelectrodes in active implants and thus long-term stability in a wide range of safe electrical stimulation.

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Section: Eissupporting

confidence: 85%

Section: Eismentioning

confidence: 99%

Section: Eismentioning

confidence: 99%

See 1 more Smart Citation

Sputtered Iridium Oxide as Electrode Material for Subretinal Stimulation

Haas¹,

Rudorf²,

Becker³

et al. 2020

Sensors and Materials

View full text Add to dashboard Cite

show abstract

“…For this scheme to work properly, T 1 − T 0 should be at least several times longer than the time constants of the electrode relaxation and charge redistribution calculated in [31].…”

Section: Transient Behaviormentioning

confidence: 99%

Harmonic-Balance Circuit Analysis for Electro-Neural Interfaces

Chen

Wang

Palanker

2020

Preprint

Self Cite

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AbstractObjectiveAvoidance of the adverse electrochemical reactions at the electrode-electrolyte interface defines the voltage safety window and limits the charge injection capacity (CIC) of an electrode material. For an electrode that is not ideally capacitive, the CIC depends on the waveform of the stimulus. We study the modeling of the charge injection dynamics to optimize the waveforms for efficient neural stimulation within the electrochemical safety limits.ApproachThe charge injection dynamics at the electrode-electrolyte interface is typically characterized by the electrochemical impedance spectrum, and is often approximated by discrete-element circuit models. We compare the modeling of the complete circuit, including a non-linear driver such as a photodiode, based on the harmonic-balance (HB) analysis with the analysis based on various discrete element approximations. To validate the modeling results, we performed experiments with iridium-oxide electrodes driven by a current source with diodes in parallel, which mimics a photovoltaic circuit.Main resultsApplication of HB analysis based on a full impedance spectrum in frequency domain eliminates the complication of finding the discrete-element circuit model in traditional approaches. HB-based results agree with the experimental data better than the discrete-element circuit analysis. HB technique can be applied not only to demonstrate the circuit response to periodic stimulation, but also to describe the initial transient behavior when a burst waveform is applied.SignificanceHB-based circuit analysis accurately describes the dynamics of electrode-electrolyte interfaces and driving circuits for all pulsing schemes. This allows optimizing the stimulus waveform to maximize the CIC, based on the impedance spectrum alone.

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“…To this sense, peripheral neural interface (PNI) devices have appeared to retrieve and send neural signals directly from and to the residual or existing peripheral nerves in this field [7]. Recently, thin film flexible polymeric devices are being used for measuring nerve impulse from the central or peripheral nerve systems [8][9][10][11][12][13]. Such flexible polymeric devices tend to be designed several µm in thickness and a few mm in length due to its nature of interfacing with neurons in human body.…”

Section: Introductionmentioning

confidence: 99%

Characterization and Analysis of Metal Adhesion to Parylene Polymer Substrate Using Scotch Tape Test for Peripheral Neural Probe

2020

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This paper presents measurement and FEM (Finite Element Method) analysis of metal adhesion force to a parylene substrate for implantable neural probe. A test device composed of 300 nm-thick gold and 30 nm-thick titanium metal electrodes on top of parylene substrate was prepared. The metal electrodes suffer from delamination during wet metal patterning process; thus, CF4 plasma treatment was applied to the parylene substrate before metal deposition. The two thin film metal layers were deposited by e-beam evaporation process. Metal electrodes had 200 μm in width, 300 μm spacing between the metal lines, and 5 mm length as the neural probe. Adhesion force of the metal lines to parylene substrate was measured with scotch tape test. Angle between the scotch tape and the test device substrate changed from 60° to 90° during characterization. Force exerted the scotch tape was recorded as the function of displacement of the scotch tape. It was found that a peak was created in measured force-displacement curve due to metal delamination. Metal adhesion was estimated 1.3 J/m2 by referring to the force peak and metal width at the force-displacement curve. Besides, the scotch tape test was simulated to comprehend delamination behavior of the test through FEM modeling.

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Current Distribution on Capacitive Electrode-Electrolyte Interfaces

Cited by 23 publications

References 32 publications

Sputtered Iridium Oxide as Electrode Material for Subretinal Stimulation

Sputtered Iridium Oxide as Electrode Material for Subretinal Stimulation

Harmonic-Balance Circuit Analysis for Electro-Neural Interfaces

Characterization and Analysis of Metal Adhesion to Parylene Polymer Substrate Using Scotch Tape Test for Peripheral Neural Probe

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