Artifact-Minimizing Ultrathin Transparent Electrodes Fabricated via iCVD for In Vivo Optogenetic Stimulation and Neural Signal Monitoring of Primary Visual Cortex

Abstract

Simultaneous optical stimulation and electrical recording using neural interfaces remains challenging due to the inherent optical opacity of metallic electrodes. Here, we demonstrate transparent electrodes that overcome this limitation, achieving > 65% optical transmission while maintaining superior electrical performance through molecular-level control of ultrathin gold deposition. Using initiated chemical vapor deposition (iCVD) of poly(dimethylaminomethylstyrene) (pDMAMS), we transformed the 3D island growth of gold into 2D continuous films, enabling functional 10-nm-thick electrodes. The resulting transparent arrays exhibited a sheet resistance of 3.5 Ω sq−1 and an electrochemical impedance of 0.9 Ω·cm2, with a calculated electrical-to-optical conductivity ratio (figure of merit; FoM) of 223.7. In in vivo validation, the electrodes demonstrated a 74% reduction in photoelectric artifacts, enabling both optogenetic stimulation and low-noise recording from the cortical area beneath the electrode array. Moreover, optogenetically evoked cortical responses in a blind (rd10) mouse were quantitatively well matched to visually evoked cortical responses in a wild-type mouse, suggesting the potential for optogenetic vision restoration. The combination of optical transparency, low impedance for high-fidelity cortical response recording, mechanical durability with a thickness of <5 µm, and biocompatibility positions this platform to advance optogenetic applications, from visual prosthetics to neural interfaces that require integrated optical-electrical functionality.