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 togenerate heat and cool rapidly without the need for bulky external equipment.Researchers have explored methods to enhance flexibility and stretchability byincorporating liquid metal as an electrode. However, the challenge lies in thelow thermal conductivity of the polymer, which hampers heating and coolingperformance. Traditional methods, like molding and spraying, increase thethickness of both liquid metal and polymer channels, but this added thicknessdoes not significantly improve the device’s stretchability.[1, 2] To overcomethese issues, this paper proposes a stretchable thermoelectric device (STED),which offers improved heating and cooling capabilities, as well as enhancedstretchability. To enhance the thermal conductivity of the polymer, Ag powderwith varying particle sizes is mixed with the material. Additionally, the liquidmetal is deposited using the direct ink writing (DIW) method, reducing thewhole thickness of STED. The air layer is created by printing molten isomalt,which is subsequently removed using water. The proposed STED exhibitshigh stretchability, reaching up to 150 %, enabling flexible twisting in variousdirections. The double-layer structure resulted in a maximum temperaturedecrease of 14°C at room temperature.