High-performance wearable flexible thermoelectric generator enabled by moisture-adaptive GO@Agar-PAM hydrogel and copper foam cooling layer

Flexible thermoelectric generators (f-TEGs) are promising for harvesting low-grade body heat to power wearable electronics, but their output is often limited by insufficient cold-side heat dissipation under weak natural convection. Here, we report a moisture-adaptive cold-side thermal management strategy for wearable f-TEGs by integrating copper foam, graphene oxide-modified agar-polyacrylamide hydrogel (GO@Agar-PAM hydrogel), and lithium chloride (LiCl). Copper foam provides porous heat spreading and mechanical support, GO enhances thermal transport within the hydrogel network, and LiCl enables hygroscopic moisture replenishment to compensate for evaporative water loss. The optimized hydrogel with 0.6 wt% GO achieves a thermal conductivity of 0.6152 W m⁻¹ K⁻¹, while 30 wt% LiCl provides a favorable balance between water retention and atmospheric moisture absorption. Simulations show that the effective temperature difference across the thermoelectric legs increases from 0.98 °C to 7.3 °C after integrating the copper foam/GO@Agar-PAM hydrogel cooling layer. The optimized f-TEG delivers 208.3 mV, 3682.3 μW, and 157.4 μW cm⁻² under natural convection, increasing to 263.4 mV, 5626.5 μW, and 240.4 μW cm⁻² at 3 m s⁻¹ airflow. Stable electrical responses are demonstrated during repeated bending, skin-attached motion, humidity-regulated operation, and short-term thermal cycling. This work provides an effective cold-side thermal management strategy for body-heat-powered wearable thermoelectric systems.