Milliwatt-Scale Body-Heat Harvesting Using Stretchable Thermoelectric Generators for Fully Untethered, Self-Sustainable Wearables

Stretchable thermoelectric generators (s-TEGs) have been regarded as promising energy harvesters for self-powered wearable electronics. However, previous s-TEGs show low power generation capacity due to their high module resistances, originating from the poor electromechanical interfaces between rigid–soft components and the high electrical resistances of stretchable interconnects. Herein, we report strategies to boost thermoelectric performance, which allows us to operate wireless communication systems from body heat by generating a power of 2.6 mW. Electromechanically graded interlayers that mediate discrete functionalities at the interfaces effectively reduce junction resistances, and solution-based welding that transforms scattered networks into mesh-like structures produces highly conductive and strain-resilient interconnects, respectively. Soft heat conductors are included to improve thermal interfaces, minimizing thermal impedance of elastomeric substrates. Consequently, the power generation capacity is significantly enhanced, exhibiting the highest normalized power density of 1.48 μW cm –2 K –2 among reported high-performance s-TEGs. Our s-TEGs provide realistic solutions for sustainable self-powered electronics.