Stability of polyimide integrated ITO electrodes.

Multi-modal devices combining several recording and stimulation techniques like optical and electrophysiological ones become more and more relevant. For optical applications, novel electrode materials providing high transparency and stability are required. Therefore, mechanical and electrochemical improvement of the transparent and highly conductive material indium-tin-oxide (ITO) was studied to examine future application in chronic implantable systems. Accelerated aging in vitro showed a possible sub-chronical operational time, whereas the ITO phase boundary underwent a transition from capacitive behavior to a Warburg impedance. Furthermore, an additional transparent adhesion layer of silicon carbide (SiC) between the polyimide substrate and the ITO layer was integrated. This greatly enhanced the thermal and mechanical stability of ITO on the flexible substrate, which enable many possibilities for future manufacturing processes and applications.