Transparent and Flexible Electrocorticography Electrode Arrays Based on Silver Nanowire Networks for Neural Recordings

Abstract

This work explored hybrid films of silver nanowires (AgNWs) with indium zinc oxide (IZO) for developing high-performance and low-cost electrocorticography (ECoG) electrodes. The transparent hybrid films achieved a sheet resistance of 6 Ω/sq, enabling electrodes with a diameter of 500 μm to reach an impedance of 20 kΩ at 1 kHz and a charge storage capacity of 3.2 mC/cm2, an improvement in properties over IZO electrodes, whose performance is on par with classical tin-doped indium oxide (ITO). Characterization of light-induced artifacts was performed, showing that light intensities <14 mW/mm2 elicit minimum electrical potential variation, which falls within the magnitude of baseline noise. The validation of the electrodes in vivo was achieved by recording electrical neural activity from the surface of the rat cortex under anesthesia. Moreover, the presence of the hybrid films did not cause the distortion of light during fluorescence microscopy. This study highlighted the capabilities of transparent ECoG electrodes based on AgNWs with IZO. In the end, we leveraged available, yet affordable, techniques and materials to facilitate ease of production, creating a tool that is cost-effective and scalable for laboratories looking to record neural electrical activity on a large and fast scale with direct visualization of neurons.