Skin Conformal Hydrogel Bioelectrodes for High-Fidelity Electrophysiology and Human–Machine Interfaces

Bioelectric interfaces used in electrophysiology must be capable of high-quality signal capture, mechanical conformance, and real-time interactivity. This research presents a conformable, reusable, and stretchable hydrogel bioelectrode composed of inkjet-printed PEDOT:PSS with a soft polyvinyl alcohol based substrate. This results in a strong, ion-conductive matrix 100 ± 16 kPa (n = 3) modulus, 660% ± 72% (n = 3) stretchability) and stable impedance (<6.4% drift over 72 h). The hydrogel bioelectrodes maintain <15% resistance drift after 50 strain cycles. The hydrogel bioelectrodes can effectively capture six bioelectrical signals, including heart, brain, muscle, ocular, electrodermal, and sympathetic skin nerve activities with outstanding signal-to-noise (SNR) ratios (up to 70 dB). Brain's alpha activity (8–12 Hz) is clearly detected, confirming the hydrogel bioelectrode's sensitivity to low-amplitude cortical signals. Sympathetic bursts in sympathetic skin nerve activity also show a 21% increase during the Valsalva maneuver, consistent with clinical observations. The hydrogel bioelectrodes also enable real-time human-computer interaction, where a subject-calibrated algorithm converts oculography signals from both eyes into directional drone control commands.