Transparent, metal-free PEDOT:PSS neural interfaces for simultaneous recording of low-noise electrophysiology and artifact-free two-photon imaging
Hyun Woo Kim, Jiwon Kim, Jong Youl Kim, Kyubeen Kim, Ju Young Lee, Taemin Kim, Shinil Cho, Jong Bin An, Hyun Jae Kim, Lulu Sun, Sunghoon Lee, Kenjiro Fukuda, Takao Someya, Mingyu Sang, Young Uk Cho, Jong Eun Lee, Ki Jun Yu
Abstract
Simultaneous two-photon imaging and electrophysiological recordings offer considerable potential for advancing neurological research and therapies. However, traditional metal-based neural interfaces suffer from photoelectric artifacts, while existing transparent implants rely on opaque interconnect lines to address conductivity limitations. Herein, we developed an optically transparent poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) neural electrode array with transparent electrodes and interconnect lines. Through a formamide, phosphoric acid, and ethylene glycol treatment, the metal-free PEDOT:PSS array achieved an impedance of 45.8 kΩ (at 1 kHz) even with a 20 × 20 µm² size. This advanced performance surpasses previous metal-free transparent neural interfaces and facilitates precise electrophysiological recordings, including extracellular action potentials and low-noise local field potentials. In vivo experiments demonstrated artifact-free two-photon imaging and reliable neural signal acquisition, while biocompatibility tests confirmed negligible cytotoxicity or immune responses. The developed metal-free PEDOT:PSS array provides a robust platform for neural recording and bioimaging, representing an advancement in transparent neural interface technology and integrated optical modalities. Metal-free neural electrodes enable simultaneous electrophysiological recording and optical imaging but often face challenges in impedance reduction. Here, Kim et al. develop a fully metal-free PEDOT:PSS neural interface with ultra-low impedance, high transparency, and compatibility with two-photon imaging.