Electrochemical Principles of Safe Charge Injection

Cogan, Stuart F.; Garrett, David J.; Green, Rylie A.

doi:10.1002/9781118816028.ch3

Cited by 23 publications

(20 citation statements)

References 114 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Specifically, the PtIr electrodes have an area of 1.6 mm 2 and the SS electrodes have an area of 0.11 mm 2 . It is know that charge transfer on microelectrodes is usually higher than that of macroelectrodes due to edge effects that enable higher charge density accumulation at the border regions (Cogan et al, 2016a ). However, the PtIr electrodes have substantially higher CSC than both the smaller SS electrodes and macroelectrodes.…”

Section: Discussionmentioning

confidence: 99%

“…While CH coatings have been routinely applied to Pt or platinum/iridium (PtIr) electrodes used in sensory stimulating neuroprosthetics, it was recognized that by changing the material that interfaces with the neural tissue, it may not be necessary to use a conventional electrode material as the substrate. Stainless steel (SS) has a history in implantable electrodes for recording and also macroelectrodes in cardiac pacing (Bowman and Erickson, 1985 ; Peixoto et al, 2009 ; Cogan et al, 2016a ), however it is not commonly used in implantable neuroprosthetics. Recent studies by Aristovich et al ( 2016 ) have demonstrated that these arrays are capable of delivering high frequency signals (>1.7 kHz) required for imaging neural activity by electrical impedance tomography (EIT).…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Conductive Hydrogel Electrodes for Delivery of Long-Term High Frequency Pulses

et al. 2018

Self Cite

View full text Add to dashboard Cite

Nerve block waveforms require the passage of large amounts of electrical energy at the neural interface for extended periods of time. It is desirable that such waveforms be applied chronically, consistent with the treatment of protracted immune conditions, however current metal electrode technologies are limited in their capacity to safely deliver ongoing stable blocking waveforms. Conductive hydrogel (CH) electrode coatings have been shown to improve the performance of conventional bionic devices, which use considerably lower amounts of energy than conventional metal electrodes to replace or augment sensory neuron function. In this study the application of CH materials was explored, using both a commercially available platinum iridium (PtIr) cuff electrode array and a novel low-cost stainless steel (SS) electrode array. The CH was able to significantly increase the electrochemical performance of both array types. The SS electrode coated with the CH was shown to be stable under continuous delivery of 2 mA square pulse waveforms at 40,000 Hz for 42 days. CH coatings have been shown as a beneficial electrode material compatible with long-term delivery of high current, high energy waveforms.

show abstract

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Conductive Hydrogel Electrodes for Delivery of Long-Term High Frequency Pulses

et al. 2018

Self Cite

View full text Add to dashboard Cite

show abstract

“…Non-noble metals, such as titanium, tantalum, and stainless steel metals inject charge mainly through this double layer capacitance. [151] However, there are charge transfer limitations compared to faradaic electrode materials. [152–153] Irreversible faradic interactions occur when oxidized ions diffuse away from the electrode before they can be reduced and redeposited onto the electrode site, which is called electrode dissolution and can have harmful effects on the surrounding tissue.…”

Section: 0 Materials Considerations For Engineeringmentioning

confidence: 99%

A Materials Roadmap to Functional Neural Interface Design

Wellman

Eles

Ludwig

et al. 2017

Adv Funct Materials

298

328

View full text Add to dashboard Cite

Advancement in neurotechnologies for electrophysiology, neurochemical sensing, neuromodulation, and optogenetics are revolutionizing scientific understanding of the brain while enabling treatments, cures, and preventative measures for a variety of neurological disorders. The grand challenge in neural interface engineering is to seamlessly integrate the interface between neurobiology and engineered technology, to record from and modulate neurons over chronic timescales. However, the biological inflammatory response to implants, neural degeneration, and long-term material stability diminish the quality of interface overtime. Recent advances in functional materials have been aimed at engineering solutions for chronic neural interfaces. Yet, the development and deployment of neural interfaces designed from novel materials have introduced new challenges that have largely avoided being addressed. Many engineering efforts that solely focus on optimizing individual probe design parameters, such as softness or flexibility, downplay critical multi-dimensional interactions between different physical properties of the device that contribute to overall performance and biocompatibility. Moreover, the use of these new materials present substantial new difficulties that must be addressed before regulatory approval for use in human patients will be achievable. In this review, the interdependence of different electrode components are highlighted to demonstrate the current materials-based challenges facing the field of neural interface engineering.

show abstract

“…This is accomplished using both capacitive mechanisms and a series of electrochemical reactions that convert the charge carriers from electrons (in the electrode) to ions (in the electrolyte). To ensure safe stimulation these reactions must be limited to reversible Faradaic reactions; these electrochemical reaction products remain localised to the electrode tissue interface and can therefore be readily reversed by a rapid charge recovery process (Fallon and Carter, 2016, Cogan, 2008, Cogan et al, 2016). Sequential stimulation ensures that charge recovery occurs soon after completion of the second phase of a biphasic current pulse.…”

Section: Discussionmentioning

confidence: 99%

“…Sequential stimulation ensures that charge recovery occurs soon after completion of the second phase of a biphasic current pulse. Long durations between the stimulus and the subsequent charge recovery allows the diffusion of the electrochemical reaction products away from to the electrode, reducing the potential for reversing the reaction and resulting in the formation of toxic electrochemical species being permanently released into the biological environment (Fallon and Carter, 2016, Cogan, 2008, Cogan et al, 2016, Shepherd et al, 2014). …”

Section: Discussionmentioning

confidence: 99%

Evaluation of focused multipolar stimulation for cochlear implants: a preclinical safety study

et al. 2017

View full text Add to dashboard Cite

Objective Cochlear Implants (CIs) have a limited number of independent stimulation channels due to the highly conductive nature of the fluid-filled cochlea. Attempts to develop highly focused stimulation to improve speech perception in CI users includes the use of simultaneous stimulation via multiple current sources. Focused multipolar (FMP) stimulation is an example of this approach and has been shown to reduce interaction between stimulating channels. However, compared with conventional biphasic current pulses generated from a single current source, FMP is a complex stimulus that includes extended periods of stimulation before charge recovery is achieved, raising questions on whether chronic stimulation with this strategy is safe. The present study evaluated the long-term safety of intracochlear stimulation using FMP in a preclinical animal model of profound deafness. Approach Six cats were bilaterally implanted with scala tympani electrode arrays two months after deafening, and received continuous unilateral FMP stimulation at levels that evoked a behavioural response for periods of up to 182 days. Electrode impedance, electrically-evoked compound action potentials (ECAPs) and auditory brainstem responses (EABRs) were monitored periodically over the course of the stimulation program from both the stimulated and contralateral control cochleae. On completion of the stimulation program cochleae were examined histologically and the electrode arrays were evaluated for evidence of platinum (Pt) corrosion. Main results There was no significant difference in electrode impedance between control and chronically stimulated electrodes following long-term FMP stimulation. Moreover, there was no significant difference between ECAP and EABR thresholds evoked from control or stimulated cochleae at either the onset of stimulation or at completion of the stimulation program. Chronic FMP stimulation had no effect on spiral ganglion neuron (SGN) survival when compared with unstimulated control cochleae. Long-term implantation typically evoked a mild foreign body reaction proximal to the electrode array; however stimulated cochleae exhibited a small but statistically significant increase in the tissue response. Finally, there was no evidence of Pt corrosion following long-term FMP stimulation; stimulated electrodes exhibited the same surface features as the unstimulated control electrodes. Significance Chronic intracochlear FMP stimulation at levels used in the present study did not adversely affect electrically-evoked neural thresholds or SGN survival but evoked a small, benign increase in inflammatory response compared to control ears. Moreover chronic FMP stimulation does not affect the surface of Pt electrodes at suprathreshold stimulus levels. These findings support the safe clinical application of an FMP stimulation strategy.

show abstract

Electrochemical Principles of Safe Charge Injection

Cited by 23 publications

References 114 publications

Conductive Hydrogel Electrodes for Delivery of Long-Term High Frequency Pulses

Conductive Hydrogel Electrodes for Delivery of Long-Term High Frequency Pulses

A Materials Roadmap to Functional Neural Interface Design

Evaluation of focused multipolar stimulation for cochlear implants: a preclinical safety study

Contact Info

Product

Resources

About