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

Abstract

Stretchablethermoelectric generators (s-TEGs) have beenregardedas promising energy harvesters for self-powered wearable electronics.However, previous s-TEGs show low power generation capacity due totheir high module resistances, originating from the poor electromechanicalinterfaces between rigid-soft components and the high electricalresistances of stretchable interconnects. Herein, we report strategiesto boost thermoelectric performance, which allows us to operate wirelesscommunication systems from body heat by generating a power of 2.6mW. Electromechanically graded interlayers that mediate discrete functionalitiesat the interfaces effectively reduce junction resistances, and solution-basedwelding that transforms scattered networks into mesh-like structuresproduces highly conductive and strain-resilient interconnects, respectively.Soft heat conductors are included to improve thermal interfaces, minimizingthermal impedance of elastomeric substrates. Consequently, the powergeneration capacity is significantly enhanced, exhibiting the highestnormalized power density of 1.48 mu W cm(-2) K-2 among reported high-performance s-TEGs. Our s-TEGsprovide realistic solutions for sustainable self-powered electronics.