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

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·cm². On the forearm, its impedance at 10 Hz without skin preparation is 11.09 ± 1.03 kΩ·cm², compared with 13.57 ± 2.07 kΩ·cm² 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.