A robust and flexible wearable hydrogel thermocell driven by body heat fabricated by a one-step process at room temperature

Emerging flexible hydrogel thermocells (HTCs), which leverage thermoelectric (TE) technology, convert body heat into electricity and provide new opportunities for wearable electronics due to their high power density, stability, and environmental friendliness. However, practical wearable HTCs still face challenges such as complex manufacturing processes and a continuous power supply. Here, a robust and wearable HTC with continuous power supply is fabricated via a simple and feasible technique of a one-step room-temperature process. The HTC is fabricated by the ingenious combination of carboxymethyl chitosan with K3Fe(CN)6/K4Fe(CN)6, simultaneously forming a hydrogel framework and introducing redox couples. The optimized HTC can achieve an improved output power density of 1471.56 μW·m−2·K−2 and a Seebeck coefficient of 4.6 mV·K−1. Remarkably, it can directly and continuously convert body heat into electricity without depletion, effectively powering electronic watches and thermometers. This research demonstrates the broad practical potential of HTCs in everyday wearable applications.