Composite process to fabricate low impedance and long electrical stability platinum gray microelectrodes using iridium oxide

The performances and stability of implantable microelectrodes for chronic neural stimulation heavily depends on the electrode surface materials. In this paper, we proposed that platinum (Pt) gray/iridium oxide (IrO_x) and IrO_x/Pt gray composite could be electroplated on the surface of Pt electrode. The surface morphologies of microelectrodes with four different electroplating methods were characterized by scanning electron microscopy (SEM). Consequently, the Pt microelectrode coated with IrO_x showed dendritic morphology while the one with Pt gray coating appeared granular. The electrochemical performances of these electrodes were measured by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) tests, showing that Pt microelectrode decorated with IrO_x/Pt gray had the best electrochemical characteristics and long-term stability.