A Stretchable Thermoelectric Device based on Direct Ink Writing of Liquid Metal and Multi‐Layer Lamination

Abstract Wearable thermoelectric devices are widely used due to their ability to generate heat and cool rapidly without the need for bulky external equipment. Researchers have explored methods to enhance flexibility and stretchability by incorporating liquid metal as an electrode. However, the challenge lies in the low thermal conductivity of the polymer, which hampers heating and cooling performance. Traditional methods, like molding and spraying, increase the thickness of both liquid metal and polymer channels, but this added thickness does not significantly improve the device's stretchability.[1, 2] To overcome these issues, this paper proposes a stretchable thermoelectric device (STED), which offers improved heating and cooling capabilities, as well as enhanced stretchability. To enhance the thermal conductivity of the polymer, Ag powder with varying particle sizes is mixed with the material. Additionally, the liquid metal is deposited using the direct ink writing (DIW) method, reducing the whole thickness of STED. The air layer is created by printing molten isomalt, which is subsequently removed using water. The proposed STED exhibits high stretchability, reaching up to 150 %, enabling flexible twisting in various directions. The double‐layer structure resulted in a maximum temperature decrease of 14 °C at room temperature.