Silk Acid-Mediated Phase Separation of PEDOT:PSS for Biocompatible, Flexible Neural Interfaces

Flexible multielectrode arrays (MEAs) are pivotal for elucidating the complex mechanisms of neural information transfer. A key challenge lies in developing ultrathin, highly compliant electrodes with high conductivity, low impedance, and excellent biocompatibility to establish conformal contact with organ surfaces. This enables precise recording of electrophysiological signal propagation with high spatiotemporal resolution, critical for deciphering physiological function. Conventional organic substrates, often thicker and possessing a higher Young's modulus, typically lack the necessary stretchability and conformability for dynamic interfaces. To overcome this, gold electrodes were modified by spin-coating a composite conductive layer of poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) doped with silk acid (SA) onto an ultrathin parylene substrate. Impedance of these flexible MEAs decreased with SA doping, indicating enhanced electrical conductivity. Furthermore, SA incorporation mitigated the intrinsic cytotoxicity of PEDOT:PSS. This optimized electrode design enables epileptic signal recording with a high signal-to-noise ratio (SNR) in the rat somatosensory cortex.