Skin‐Interfaced Wearable Device for Synchronically Harvesting High‐Entropy Body Energy and Monitoring Deep Tissue Temperature

Efficiently harvesting thermal energy from human skin poses formidable challenges owing to its high‐entropy characteristics. While Seebeck‐effect wearable thermoelectric devices can convert skin heat flux into electrical voltage, prevailing generators remain constrained in delivering sustainable energy and multifunctionality. This limitation stems from a fundamental trade‐off where the output voltage falls below the effective charging threshold, leaving the ultra‐low skin heat flux underexplored for physiological sensing. In this study, we report a skin‐interfaced wearable thermoelectric sensor and generator that synchronously harvests body high‐entropy energy and monitors deep tissue temperature (< 0.2°C). This dual functionality is enabled by a thermal meta‐design that guides inherently dispersed cutaneous heat flux into a vertical, one‐dimensional path through geometric confinement, ensuring signal fidelity for both sensing and energy conversion. To overcome the limited skin‐ambient temperature gradient, we introduce a reusable cooling hydrogel patch based on a dual‐mode evaporation mechanism, boosting the electrical output to 120 mV and power density to 45.7 μW cm –2 . Furthermore, during daily wear under an approximate 10 K skin‐environment temperature differential, the system achieved a sustained output of up to 34 mV. The integrated voltage boost‐storage circuit maintained the capacitor voltage at around 1.044 V, facilitating a sustainable power supply to electronic loads, and stabilized at approximately 5.2 V near full charge. The integrated system demonstrates continuous, multi‐parameter health monitoring powered solely by body heat. This research establishes a co‐design paradigm for concurrent deep body temperature monitoring and high‐entropy energy recovery, paving the way for self‐powered, multimodal integrated wearable devices.