Electrochemical characterization of ZnO-based transparent materials as recording electrodes for neural probes in optogenetics

Abstract

In the elucidation of brain functions, neuroscience has garnered attention in the realization of brain-machine interfaces, deep brain stimulation, and artificial intelligence. Optogenetics is a biological technique used to control neural activities via optical stimulation. It is one of the most effective approaches used to investigate brain functions. This study proposed to employ the transparent recording electrode to enhance the performance of neural probes for optogenetics. Compared with conventional metal recording electrodes, the proposed transparent recording electrodes have the potential to obtain higher signal-to-noise ratios when placed over optical stimulation points. To develop transparent recording electrodes, we used ZnO-based materials with good biocompatibility and transparency for utilization as biomedical electrodes. Considering saline as one of the main components of living organisms, we investigated the fundamental electrochemical characteristics of ZnO-based electrodes in saline through electrochemical impedance spectroscopy and cyclic voltammetry. The results showed that nondoped ZnO and Al-doped ZnO, deposited by radio frequency magnetron sputtering, exhibited a broad potential window. An electrical double layer was found to strongly act on the interface between the electrodes and solution rather than a redox reaction. In addition, this study reports the effects of crystallization and dopant on the electrochemical characteristics of the ZnO-based electrodes. The transparent ZnO-based electrode developed herein is a promising candidate to enhance the performance of neural probes for optogenetics and can be effectively applied in biological devices.