Free-standing iridium oxide nanotube array for neural interface electrode applications

It has been established that IrO₂ can improve the recording and stimulating efficiency of electrodes for neural activities. In this work, we have employed chemical bath deposition to fabricate an IrO₂ nanotube array using an anodic alumina (AAO) template. We determined the optimal chemical bath condition including a suitable pH value to preserve the AAO template. After exploring various chemical bath deposition parameters, we produced a uniform, ordered, and high-aspect-ratio IrO₂ nanotube array. We developed an acidic chemical bath for conformal IrO₂ deposition at a thickness of 60 nm per batch. The results from grazing incidence X-ray diffractometer (GIXRD) suggest the successful formation of IrO₂ film. The images obtained via scanning electron microscopy and qualitative elemental chemical analysis reveal free-standing iridium oxide nanotubes 400 nm in length after the removal of the AAO template by phosphoric acid. Electrochemical analysis of this IrO₂ nanotube array in charge storage capacity (CSC) was performed to evaluate its potential as a neural-electronic interface electrode.