Partially Air-Filled Skin-Attachable Deformable Gasket with Negative Poisson's Ratio for Highly-Efficient Stretchable Thermoelectric Generators

Wearable thermoelectric generators (WTEGs) have relied on soft encapsulation materials typically used for the structural support of thermoelectric legs. Heat loss through the filler and low heat transfer via the mismatched contact with the skin causes a small temperature gradient between the human body (hot side) and the natural environment (cold side). Instead of using soft encapsulation materials, a partially air-filled deformable gasket is purposed for leg support, achieving the thermal isolation of thermoelectric legs by preventing parasitic heat transfer. The WTEG comprising the deformable gasket exhibits a 30% larger temperature gradient than that with conventional encapsulant structures filled with soft materials. Additionally, the deformable gasket shows an auxetic metastructure owing to its negative Poisson's ratio, reversibly responding to changes in their environment, which is suitable for skin-like stretchable wearable devices. The band type of WTEG with the optimized leg geometry and fill factor shows a power output of 2 uW cm(-2 )for eight pairs of thermocouples, a record-high value among the stretchable TEGs obtained indoors at room temperature (23 ?) without wind. This approach paves the way for the efficient conversion of thermal energy into electrical energy and broadens potential applications for self-powered wearable electronics.