Wearable Multifunctional Hydrogel for Energy‐Autonomous Edema Monitoring

Abstract Recent advancements in wearable electronics highlight the importance of developing comfortable, fully self‐sustaining systems. Addressing this need, a highly environmentally stable multifunctional ionic hydrogel has been engineered specifically for integration into smart sock platforms, enabling simultaneous physiological monitoring, energy storage, and energy harvesting from daily activities. The hydrogel network, formed by polyvinyl alcohol (PVA), acrylic acid (AA), and calcium chloride (CaCl 2 ) via synergistic physical and chemical crosslinking, exhibits exceptional mechanical properties with stretchability up to 1375% and a toughness of 1.489 MJ m − 3 . Incorporation of CaCl 2 significantly enhances ionic conductivity (26 mS cm −1 ), sensitivity (Gauge Factor: 4.05), and low‐temperature tolerance (freezing point: −67 °C). Furthermore, the hydrogel serves effectively as an electrolyte in flexible supercapacitors and as a soft electrode in triboelectric nanogenerators (TENGs). The supercapacitors maintain high capacitance under extreme conditions, such as low temperatures and physical deformation, meeting critical requirements for wearable energy storage devices. Collectively, these properties position the developed hydrogel‐based smart sock as a comprehensive solution for chronic edema monitoring, energy harvesting, and storage, suitable for diverse self‐powered health monitoring applications.