Mechanical‐Thermal Co‐Design of Flexible Thermoelectric Devices with Solid‐Liquid Electrodes for Enhanced Stretchability and Power Generation

Abstract The trade‐off between stretchability and power generation performance of flexible thermoelectric devices (FTEDs) hinders their practical applications in self‐powered wearable electronics. Herein, a novel mechanical‐thermal co‐design strategy is proposed based on a solid‐liquid electrode configuration to address this critical issue. This approach introduces a gravity‐assisted controllable encapsulation method that enables thin‐layer elastic confinement of liquid metal electrodes, simultaneously minimizing parasitic thermal resistance and achieving exceptional stretchability. Additionally, a tight‐binding arrangement of thermoelectric pairs mitigates interfacial stress concentration during mechanical deformation to significantly improve stretchability, while microstructured solid electrodes enhance heat dissipation to boost output power. The optimized device achieves over 100% stretchability (device resistance change does not exceed 10%) and a normalized output power density of 0.098 µW cm −2 K −2 under natural convection conditions without external heat sinks, with excellent stability maintained after over 10 000 cycles under large tensile and bending strains. As a proof of concept, the efficient applications of the FTEDs are demonstrated in harvesting heat from curved surfaces in various scenarios and powering LED bulbs. This work presents a breakthrough in achieving both high power generation performance and high stretchability in FTEDs, providing a new pathway for developing devices to harvest heat from highly deformable surfaces.