Systematic Benchmarking of a Noise-Tolerant Conductive Hydrogel Electrode for Epidermal Bioelectronics

Conventional Silver/Silver Chloride (Ag/AgCl) electrodes remain the clinical standard for electrophysiological monitoring but are hindered by poor skin conformity, mechanical rigidity, and signal degradation, particularly under motion or sweat. Here, two hydrogel-based alternatives are presented and benchmarked using a wireless commercial platform: a porous poly(3,4-ethylenedioxythiophene):polystyrene sulfonate scaffold infused with hydrogel (PPSCF), and an all-hydrogel, crosslinker-free electrode (PPHG) synthesizes via a scalable, one-pot process. PPHG demonstrates intrinsic stretchability, self-adhesion, and biocompatibility, forming stable, low-impedance contacts with skin. Electrochemical measurements reveal that PPHG maintains a capacitive interface with reduced resistive losses, low loss tangent, high dielectric constant, and fast relaxation dynamics, features that enable intrinsic signal smoothing and noise suppression. In a cohort of 39 participants, PPHG electrodes outperform Ag/AgCl in electrocardiography (ECG), showing reduced motion artifacts, higher signal-to-noise ratios, and clear preservation of P-, R-, and T-waves. Electroencephalography (EEG) recordings demonstrate enhanced alpha-delta separation, while electrooculography (EOG) and electromyography (EMG) signals exhibit greater amplitude and sharper features. Machine learning analysis of ECG signals reveals a 2.2-fold improvement in inter-lead classification accuracy. These findings position PPHG as a soft, adhesive, and sustainable alternative for high-fidelity, multimodal bioelectronic interfaces, with strong potential for wearables and clinical monitoring systems.