Description
With the advent of reliable microfabrication techniques, the design and fabrication of micron scaled electrodes for the use of neural interfacing have seen great advances. Brain machine interfaces (BMI’s) hold the potential to revolutionize the treatment and diagnosis of a wide variety of neural diseases. Glassy carbon (GC) is a novel material that has shown to be a promising electrode material with several key characteristics that make it favorable for use in microelectrode fabrication. Traditionally metallic materials have been the standard choice due to their high conductivity. Carbon-based materials and metal-based materials fundamentally perform as electrodes differently. Carbon electrodes primary conduct current via capacitive mechanisms, where-as metallic electrodes conduct current via the faradaic mechanism. This study aims to characterize the electrochemical characteristics of glassy carbon and platinum microelectrodes by means of developing a comprehensive computational model that illustrates these behaviors. Microelectrode arrays fabricated with glassy carbon and platinum were analyzed via electrochemical impedance spectroscopy (EIS). The AC impedance responses of these microelectrodes were analyzed via EIS in phosophate buffered saline (PBS). The EIS output was then analyzed via equivalent circuit modeling. Using the modified-Randales circuit the relevant electrochemical parameters was determined for the two materials. EIS measurements and equivalent circuit modeling provided information about macro-behaviors of the electrochemical system. Using finite element analysis, a computational model describing the spatial and time domains of glassy carbon and platinum were determined. The outputs of the equivalent and FEA show that the behaviors of these two materials is remarkably similar despite using fundamentally different current-transfer mechanisms. This result implies that the rough surface of thin-film platinum electrodes used in this study results in a capacitive effect that matches the capacitive nature that glassy carbon has. This lends further credence to the use of glassy carbon in the use of neural prosthetics as the electrochemical performance is equivalent with the added benefit that that carbon-based materials inherently have.
