Constructing electronic-ionic bicontinuous networks for high-fidelity bioelectrical monitoring with 24-hour stable interfaces

An electronic–ionic bicontinuous conductive network is designed to overcome the trade-off between conductivity and hydration stability in hydrogel electrodes. • The composite electrode maintains low skin–electrode impedance (<5 kΩ @ 10 Hz) for over 24 h (EEG) and 48 h (ECG), ensuring long-term interface stability. • Superior signal fidelity is achieved with an ECG signal-to-noise ratio of 50.4 dB, surpassing commercial Ag/AgCl electrodes by 8–10 dB. • Multimodal bioelectrical monitoring is demonstrated, including exercise ECG, dynamic EMG, and EEG (α rhythm and SSVEP analysis). • The work provides a generalizable materials strategy integrating high conductivity, flexibility, and long-term hydration for next-generation wearable bioelectronics. Developing high-performance electrodes for long-term, high-fidelity physiological monitoring remains a critical challenge in wearable healthcare. Here, we report a composite electrode formed by infiltrating a low-eutectic gel (choline chloride/glycerol/gelatin) into a nickel-coated polyurethane (PU@Ni) sponge, thereby establishing an electronic–ionic bicontinuous conductive network. The resulting electrode exhibits skin-adaptive mechanics (modulus of 0.21 MPa and fracture strain of 70%) and excellent environmental stability, retaining 95% of its initial mass after 48 h. Electrochemical characterization reveals a skin–electrode impedance below 5 kΩ at 10 Hz. In practical demonstrations, the electrode delivers high-quality ECG recording with a signal-to-noise ratio (SNR) of up to 50.4 dB, which is 8–10 dB higher than that of commercial Ag/AgCl electrodes, and maintains reliable performance during 48 h of continuous monitoring. Furthermore, EEG measurements show performance comparable to conventional wet electrodes, enabling stable, high-fidelity acquisition over 24 h. Overall, this work provides a scalable composite-engineering strategy to reconcile conductivity, mechanical compliance, and long-term durability, offering a promising platform for next-generation wearable bioelectronics.