Dual-network phase-separation engineered conductive hydrogel with environment-adaptive adhesion and swelling resistance for underwater ECG

The application of electrocardiogram (ECG) monitoring in complex environments—such as underwater or under heavy perspiration—remains challenging due to interfacial instability and signal degradation in conventional electrodes. Developing flexible, environment-adaptive materials with cross-media compatibility is crucial for advancing wearable and subaquatic medical devices. Here, we report a novel strategy using aqueous PEDOT dispersion-induced phase separation to fabricate conductive hydrogels with robust underwater functionality. The resulting biphasic structure exhibits exceptional stretchability (up to 2500 % tensile strain), strong adhesion (40 kPa underwater), and intrinsic conductivity (16.7 S/m), without post-processing. These hydrogels maintain stable performance across air–water interfaces, enabling high-fidelity biopotential recording even in liquid environments. Demonstrated as ECG electrodes, they deliver clinical-grade signal quality underwater and resist interference from sweat during physical activity. This one-step fabrication method supports scalable, cost-effective production, facilitating integration into diving gear and marine protective suits. The material’s dual adaptability to both wet and dry conditions opens new pathways for reliable biosignal monitoring in extreme environments. These findings represent a significant step toward industrial deployment of hydrogel-based soft electronics in aquatic healthcare and sports physiology applications.