Tannic acid-Ag+ activated ultrafast formation of adhesive, antibacterial, stretchable, and conductive hydrogels for flexible wearable sensors

The ideal flexible hydrogel sensor should combine excellent mechanical properties, high conductivity, and effective antibacterial activity to prevent bacterial growth. To address the limitations of traditional hydrogel sensors, such as insufficient flexibility, poor adhesion, and dependence on external energy during radical polymerization, this study developed a novel hydrogel based on a tannic acid-silver ion (TA-Ag + ) dynamic dual self-catalytic system. Through catalytic rapid radical polymerization, a double-network (DN) hydrogel was rapidly prepared at room temperature. This DN conductive hydrogel exhibits remarkable stretchability (up to 3000 % strain), high electrical conductivity (17.57 S/m), and self-adhesive capability, with measured maximum adhesion strengths on various substrates as follows: ceramic, 45.8 kPa; stainless steel, 43.62 kPa; glass, 43.43 kPa; aluminum, 37.07 kPa; acrylic plastic, 42.44 kPa; cardboard, 26.75 kPa; fresh porcine skin, 14.66 kPa. The TA and in situ generated silver nanoparticles within the system confer significant antibacterial properties to the hydrogel, with inhibition zones exceeding 20 mm against both Staphylococcus aureus and Escherichia coli . The introduction of LiCl enhances the water retention rate of the hydrogel by more than 20 %. The incorporation of methyl cellulose improves the biocompatibility of the material and promotes the formation of a denser cross-linked network and ion channels, thereby enhancing both tensile resistance and electrochemical performance. Experimental results demonstrate that the hydrogel can be applied in real-time monitoring of human joint movements, including finger, wrist, and elbow flexion, neck motion, and even large-range activities of the knee joint during vigorous exercise. These findings indicate that the material holds broad application prospects in the fields of wearable sensing and health monitoring.