Fabrication of Nanoporous IrO₂/Ir Films for Bioelectrode and Neural Prosthesis Applications

IrO₂ and Ir are attractive materials for bio-interface applications due to their desirable stability, electrochemical performance, and biocompatibility. Nanostructured IrO₂/Ir possesses several advantageous properties including large surface-to-volume ratio, light weight, super hydrophilic surface, desirable electrochemical capability, and cell adhesion. Herein, we employ a cost-effective process to fabricate uniform nanoporous IrO₂/Ir film by chemical bath deposition, high-vacuum annealing, and electrochemical activation. High-vacuum annealing can remove oxygen from an IrO₂ film to create a nanoporous structure, and we determine the optimized electrochemical activation to transform Ir to IrO₂/Ir. The surface morphology, roughness, hydrophilicity, crystallinity, oxidation state, and charge storage capacity (CSC) of the films were analyzed. The nanoporous IrO₂/Ir film showed a 25% increase of CSC compared to the dense IrO₂ film, and this excellent performance makes it a promising candidate for bio-interface applications. In addition, this fabrication route can be cost-effective process without wasting the expensive noble metal Ir material.