Ultraflexible Transparent Oxide/Metal/Oxide Stack Electrode with Low Sheet Resistance for Electrophysiological Measurements

Flexible, transparent electrodes are a crucial component for future implantable and wearable systems. For practical applications, conductivity and flexibility should be further improved to prevent signal attenuation, heat generation, and disconnection. Herein, we fabricate an ultraflexible transparent electrode with low sheet resistance (8.6 Ω/sq) using an indium-tin-oxide/Au/indium-tin-oxide (ITO) multilayer on a 1 μm thick parylene substrate. The electrodes were foldable and when compared to pristine ITO displayed greater mechanical robustness. Applicability for large-area applications was confirmed through electrochemical impedance measurements, and the compatibility of electrode arrays for in vivo applications was demonstrated with an optogenetic experiment. As a result of the ultraflexible transparent electrode's excellent conformity to soft tissue, voltage signals induced by light stimulation directly below the electrode were successfully recorded on the moving muscle.