Optical and Electrochemical Methods for Determining the Effective Area and Charge Density of Conducting Polymer Modified Electrodes for Neural Stimulation

Harris, Alexander R.; Molino, Paul J.; Kapsa, Robert M. I.; Clark, Graeme M.; Paolini, Antonio G.; Wallace, Gordon G.

doi:10.1021/ac503733s

Cited by 22 publications

(42 citation statements)

References 34 publications

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“…where F is the Faraday constant and r is the electrode radius [22]. On a 2 mm diameter platinum electrode, voltammetry of 5 mM Ru(NH 3 ) 3+ 6 at 100 mV s −1 produced a response typical of linear diffusion with a reduction peak at −107 mV and an oxidation peak at −30 mV, giving a peak splitting of 77 mV ( figure 8(a)).…”

Section: Resultsmentioning

confidence: 99%

Measuring the effective area and charge density of platinum electrodes for bionic devices

et al. 2018

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The safe potential window, charge injection mechanism, charge injection capacity and charge density of platinum depends on electrolyte, size of the electrode, oxygen concentration and differences in electrode polishing method. The oxidation and reduction charge injection capacities are not equal. Careful control of a platinum electrodes surface may allow larger charge densities and safe use of smaller electrodes. New electrode materials and geometries should be tested in a consistent manner to allow comparison of potential suitability for neural stimulation.

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Section: Resultsmentioning

confidence: 99%

Measuring the effective area and charge density of platinum electrodes for bionic devices

et al. 2018

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“…The platinum electrodes were modified as described previously for PEDOT and PPy doped with sulphate, pTs, poly(styrenesulfonate) (PSS), dodecylbenzenesulfonate (DBSA) and chondroitin sulphate (CS) [11,13,16]. Uncoated platinum electrodes were bright silver, PEDOT-pTs and PEDOT- The total deposition charge also increased with time of conducting polymer growth (figure 2b).…”

Section: Resultsmentioning

confidence: 99%

“…Platinum is used for most human bionic devices, and the charge density can be determined by hydride reduction and stripping in acidic solutions using cyclic voltammetry [12]. This mechanism is not suitable for most other electrode surfaces, and we recently proposed reduction of a solution soluble redox species, Ru(NH3)6 3+ , as an alternative [13]. Mass transport of the redox species to the electrode surface is affected by voltammetric scan rate, and subsequently, a linear and radial diffusion profile (at fast and slow scan rates respectively) results in two different charge density values; measurement of a geometric area provides a third charge density value.…”

Section: Introductionmentioning

confidence: 99%

Effective Area and Charge Density of Iridium Oxide Neural Electrodes

Harris

Paolini

Wallace

2017

Electrochimica Acta

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The performance of neural electrodes over chronic periods is poor with degrading signal-to-noise ratio and low biocompatibility. Consequently, electrodes require modification to improve their performance, biostability and biocompatibility. A large variety of doped conducting polymers have been proposed for optimising neural electrodes, but to date, none have achieved the required biostability and biocompatibility necessary for human application. Dextran sulfate is used as an antithrombotic and may be of use in improving neural electrode biocompatibility. Poly-3,4-ethylenedioxythiophene was successfully doped with dextran sulfate (PEDOT-DS) by electropolymerisation on neural electrode arrays. Deposited films increased the electrode area and displayed a rough morphology compared to uncoated electrodes. Electrode area and charge density were obtained using microscopy and reduction of Ru(NH3)6 3+. Deposition charge, geometrical and linear diffusion electroactive areas were strongly correlated with deposition time. The charge density calculated from the geometrical area was greater on PEDOT-DS modified electrodes than unmodified and PEDOT-para-toluene sulfonate (PEDOT-pTs) modified electrodes. The charge density calculated from the linear diffusion electroactive area was smaller on PEDOT-DS modified electrodes than unmodified and PEDOT-pTs modified electrodes. The charge density of the PEDOT-DS modified electrodes was dependant on the electrode area.

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“…30 The charge injection capacity of an electrode for bionic applications is usually assessed by cyclic voltammetry. 22,31 This method can provide information on the reaction mechanisms available at the electrode/solution interface. However when these electrodes are used in vivo, electrical pulses rather than potential sweeps are applied.…”

Section: Discussionmentioning

confidence: 99%

Charge Injection from Chronoamperometry of Platinum Electrodes for Bionic Devices

Harris

Newbold

Carter

et al. 2018

J. Electrochem. Soc.

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The chronoamperometric response of platinum under biologically relevant conditions was investigated to understand how charge transfer across the electrode-tissue interface occurs during potential pulsing. Platinum behaves as a non-ideal electrode, passing capacitance and faradaic charge. The faradaic reactions are associated with oxide formation and removal, hydrogen and anion adsorption. The capacitance charge decayed within μs while the faradaic charge decay occurred over longer times. The total charge and the ratio of faradaic to capacitance charge was seen to vary with time, potential, electrode size, oxygen concentration, electrolyte and surface cleaning method. The charge transfer mechanisms result in an accumulation of charge during multiple potential pulses, mostly reductive charge under the conditions presented here. This modifies the composition of the electrode/solution interface. An accurate understanding of charge transfer at the electrode/tissue interface must subsequently be obtained under biologically relevant conditions (an artificial perilymph with low oxygen concentration for cochlear implants electrodes and artificial cerebrospinal fluid for neural implants) and with appropriate clinical electrodes.The chronoamperometric response of platinum under biologically relevant conditions was investigated to understand how charge transfer across the electrode-tissue interface occurs during potential pulsing. Platinum behaves as a non-ideal electrode, passing capacitance and faradaic charge. The faradaic reactions are associated with oxide formation and removal, hydrogen and anion adsorption. The capacitance charge decayed within μs while the faradaic charge decay occurred over longer times. The total charge and the ratio of faradaic to capacitance charge was seen to vary with time, potential, electrode size, oxygen concentration, electrolyte and surface cleaning method. The charge transfer mechanisms result in an accumulation of charge during multiple potential pulses, mostly reductive charge under the conditions presented here. This modifies the composition of the electrode/solution interface. An accurate understanding of charge transfer at the electrode/tissue interface must subsequently be obtained under biologically relevant conditions (an artificial perilymph with low oxygen concentration for cochlear implants electrodes and artificial cerebrospinal fluid for neural implants) and with appropriate clinical electrodes.

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Optical and Electrochemical Methods for Determining the Effective Area and Charge Density of Conducting Polymer Modified Electrodes for Neural Stimulation

Cited by 22 publications

References 34 publications

Measuring the effective area and charge density of platinum electrodes for bionic devices

Measuring the effective area and charge density of platinum electrodes for bionic devices

Effective Area and Charge Density of Iridium Oxide Neural Electrodes

Charge Injection from Chronoamperometry of Platinum Electrodes for Bionic Devices

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