A dual-mode MXene/CA-PSPDN hydrogel thermocell for complementary body-heat and photothermal energy harvesting

A dual-mode hydrogel integrates passive body-heat and active photothermal harvesting. • Electrospun CA fibers enable interfacial interlocking (250% strain, >95% retention). • High Seebeck coefficient of 1.8 mV K −1 from SO 4 2− /SO 3 2− thermogalvanic effect • Photothermal effect generates ΔT of 13.8 K under one-sun irradiation to boost output. • Continuous capacitor charging and LED operation under both body heat and solar light Continuous micropower is critical for next-generation wearable electronics. However, ionic thermoelectric hydrogels relying solely on body heat are limited by the inherently small skin-air temperature gradient (ΔT), leading to inadequate and fluctuating output. We propose a dual-mode harvesting strategy employing a hierarchical MXene/cellulose acetate (CA)-polyvinyl alcohol (PVA)/PEDOT:PSS (PSPDN) hydrogel thermocell. This 3D porous hydrogel exhibits high stretchability (250%) and sustained water retention, ensuring uninterrupted thermogalvanic ion transport. In passive mode, it harvests body heat to generate a stable baseline voltage, maintaining >95% output after 100 deformation cycles. Under illumination, the MXene/CA membrane acts as a broadband solar absorber to activate an active enhancement mode. Photothermal amplification of the thermogalvanic output enlarges the localized ΔT to 13.8 K under one-sun irradiation, boosting the estimated output power by more than an order of magnitude over the body-heat baseline and yielding a Seebeck coefficient of ~1.8 mV K −1 . With stable low-voltage output, the device charges capacitors and supports LED demonstrations of its thermovoltage response under various environmental triggers. This dual-mode concept—the passive body-heat mode guarantees a weather-independent baseline while the active mode adds solar gain whenever irradiation is available—offers a practical route toward uninterrupted self-powered wearable systems. A dual-mode MXene/CA-PSPDN hydrogel enables complementary body-heat and photothermal energy harvesting by combining passive body-heat thermoelectric generation with active solar-driven photothermal amplification. An electrospun nanofiber interlocking interface ensures 250% stretchability and 95% voltage retention after 100 cycles. The thermocell achieves a high Seebeck coefficient of 1.8 mV K −1 , with ΔT reaching 13.8 K under one-sun irradiation, delivering continuous output for self-powered wearables. Download: Download high-res image (237KB) Download: Download full-size image