Gel‐Free Capture of Microvolt‐Level Neural Signatures Via a 3D Monolithic Carbon Fiber Dry Electrode

ABSTRACT Gel‐based wet electrodes remain the gold standard for electrophysiology, but gel dehydration limits recordings. Existing dry electrodes partially address this limitation but suffer from high interfacial impedance. Here, a carbon fiber‐based porous electrode (CFPE) is reported, comprising a three‐dimensional conductive network coated with poly(3,4‐ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS). The CFPE establishes contact at hairy‐scalp sites with an impedance of approximately 10 kΩ·cm 2 . On the forearm, its impedance at 10 Hz without skin preparation is 11.09 ± 1.03 kΩ·cm 2 , compared with 13.57 ± 2.07 kΩ·cm 2 for wet electrodes. After 6 h of wear, CFPE impedance reaches 1.3 times its initial value without skin preparation or gel, whereas wet‐electrode impedance reaches 56 times its initial value when applied with skin preparation and conductive gel. High‐fidelity electrocardiography, electromyography, and electroencephalography signals are captured with correlation coefficients exceeding 90% and signal‐to‐noise ratios comparable to wet electrodes. The CFPE further resolves microvolt‐level speech‐evoked frequency‐following responses (FFR) and long‐latency responses (LLR), with fidelity comparable to wet electrodes and significantly higher LLR SNR. These results demonstrate gel‐free acquisition of weak neural biomarkers, opening a pathway toward prolonged, preparation‐free neurophysiology.