Metal Hydrogel‐Based Integrated Wearable Biofuel Cell for Self‐Powered Epidermal Sweat Biomarker Monitoring

Abstract Wearable sensors for continuous monitoring of biomarkers in body fluids have gained significant attention for their potential in disease diagnostics and health management, but lack sustainable power supply and advanced sensing strategies. Herein, sweat wearable biofuel cells (w‐BFCs) based on metal hydrogels are demonstrated with high output and outstanding stability, which harvest energy directly from human sweat and simultaneously enable self‐powered sensing of epidermal biomarkers. Experimental and computational results elucidate that the highly porous and flexible metal hydrogels exhibit superior electrocatalytic capabilities for oxidizing ascorbic acid (AA), a sweat metabolite at the anode, and reducing O 2 at the cathode. Consequently, the assembled AA/O 2 BFC delivers a high and stable power output, with a maximum output power density of 35 µW cm −2 at an ultralow AA concentration and long‐term stability over 30 days, and a self‐powered, sensitive sensing for AA detection. When applied to the skin of the volunteers, this integrated w‐BFC powers the biosensor using human sweat AA as fuel and allowing real‐time monitoring of AA sensing signal via smartphone. This work not only advances energy harvesting for wearable sensors but also paves new avenues for real‐time, online monitoring of epidermal sweat biomarkers.