Leaf-Inspired Layered Hydrogel with Spatially Selective Ag/Ag2S Formation for Photothermal Antibacterial Therapy and Strain Sensing

The overuse of antibiotics has accelerated the emergence and spread of drug-resistant microorganisms, creating an urgent need for anti-infective materials with integrated therapeutic and monitoring functions. Herein, a leaf-inspired porous layered hydrogel, HEVCTM, was developed for photothermal antibacterial treatment and flexible sensing. The precursor hydrogel, HEVCTM, was first prepared by one-pot free-radical polymerization of the hydrophilic functional monomer VIM-CAT, the hydrophobic monomer TBA-MA, and N-hydroxyethyl acrylamide (HEAA). After immersion in AgNO3 solution, spatially selective formation of Ag/Ag2S was induced within the hydrogel. Specifically, Ag+ was in situ reduced to metallic Ag by the surface-enriched hydrophilic VIM-CAT, while Ag2S was generated in the middle region under the induction of hydrophobic TBA-MA, leading to the spontaneous formation of a sandwich-like layered architecture. Owing to the introduction of Ag2S, the hydrogel exhibited an enhanced near-infrared (NIR) photothermal response and achieved antibacterial efficiencies of 99% against Escherichia coli and 98% against Staphylococcus aureus. Meanwhile, the surface Ag layer endowed the hydrogel with good electrical conductivity and stable strain sensitivity, enabling real-time monitoring of human motions, including finger bending, frowning, and wrist bending. This work provides a simple strategy for constructing layered hydrogels with integrated photothermal antibacterial and flexible sensing functions and offers new insight into anti-infective flexible electronics.