Gel‐Based Polyacrylamide/Reduced Graphene Oxide Composite Thermocells for Body Heat Harvesting in Wearable Safety Devices

In this work, polyacrylamide (PAM)‐based hydrogels are engineered as flexible matrices for ionic thermoelectric (i‐TE) energy harvesting. Reduced graphene oxide (rGO) is incorporated as a functional filler to simultaneously strengthen the mechanical properties and enhance electronic transport. The degree of rGO reduction is precisely controlled via high‐temperature annealing to enable systematic tuning of the structural and electrochemical characteristics of the composite hydrogels. Further, PAM/rGO thermocells are fabricated via photocrosslinking and subsequently infused with an Fe(CN) 6 3−/4− redox electrolyte to form i‐TE active materials. Among the variants, PAM‐rGO150 exhibits a high ionic Seebeck coefficient of 1.38 mV K −1 along with a tensile strength of 23.32 kPa, achieving a favorable balance between TE performance and mechanical durability. To demonstrate practical applicability, an i‐TE module helmet (ITMH) is assembled using 36 series‐connected thermocells. The device successfully powers an LED indicator under a temperature difference as low as 8.8°C, thereby validating its capability to harvest human body heat. These results highlight the potential of rGO‐reinforced thermocells as lightweight, robust power sources for next‐generation self‐powered wearable safety systems.