Thermogalvanic hydrogels for low-grade heat harvesting and health monitoring.

Direct conversion of ubiquitous heat energy into electricity is crucial for the development of green and sustainable power sources and self-powered electronic devices. Compared with traditional semiconductor thermoelectric materials, emerging thermogalvanic hydrogels offer high thermopowers, excellent intrinsic flexibilities, and low manufacturing costs, making them highly promising for low-grade thermal energy harvesting, self-powered flexible electronics, and wearable health monitoring devices. This review summarizes the recent advancements in thermogalvanic hydrogels, focusing on the strategies employed to enhance their thermoelectric properties and mechanical performances and expand their operational temperature ranges. We also explore their potential applications in low-grade heat harvesting for powering electronic devices and wearable applications. This review will provide valuable insights and guidance for the development and application of high-performance thermogalvanic hydrogels by systematically analyzing the potential of thermogalvanic hydrogels for flexible energy supply systems, outlining the performance enhancement mechanisms, and further discussing the current challenges and opportunities.