Neural stimulation electrodes charge injection

Structure can be readily modified to improve charge injection capability and promote biocompatibility. Such advantages make it an attractive candidate for further research as coatings for neural stimulation electrodes. 

Within a neural stimulation system, the electrodes are subjected to a harsh working environment. They may have to inject a large amount of charge, tolerate extreme local pH changes, and function for the duration of the device lifetime. To ensure longevity, the electrodes need to be thoroughly tested. 

The demand for high-resolution stimulation in neural prosthetic devices requires the development of high performance, high density microelectrode arrays. For such arrays, the choice of electrode materials has become increasingly important. Stimulation electrodes serve as the interface between electronic devices and neural systems. Since high levels of charge injection and electric fields are applied to functional and responsive tissues and electrode materials, it is critical that damage to tissues or nerves, as well as to electrode materials, from chronic stimulation be minimized or avoided [21]. 

Recently, we reported work on the evaluation of PEDOT for neural stimulation applications [33]. PEDOT was electrochemically deposited on thin-film Pt electrodes of stimulation electrode arrays to evaluate its properties for chronic stimulation. The coated electrodes demonstrated much lower impedance than thin-film Pt due to the high surface area and high ion conductivity across the film. The PEDOT film also presents intrinsic redox activity, which contributes to the low impedance as well as a much higher charge storage capacity. The charge injection limit of PEDOT electrodes was found to be 2.3 mC/cm, comparable to IrOx, and much higher than... 

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