Fabrication and Cooling Performance Optimization of Stretchable Thermoelectric Cooling Device

Abstract

Stretchable electronic devices are known as elastic electronics or circuits. They are typically built by deposition or embedding of devices and circuits onto stretchable substrates, which can sustain large strains without failure. The research on this emerging technology has focused on the development of components based on insulators, conductors, or semiconductors to overcome inherent difficulties of generating mechanically stable layers and interconnections. In addition to the mechanical challenges, the heat-dissipation problem, remains yet to be solved, since stretchable electronics are generally fabricated using materials with poor thermal conductivities. To simultaneously address stretchability and heat dissipation, novel cooling platforms are required. As one promising pathway, this paper presents the fabrication and performance optimization of a thermoelectric device that is stretchable and effectively dissipates heat. The device is easy to fabricate and has a relatively simple structure, consisting of a silicone elastomer (Ecoflex), liquid metal, and thermoelectric legs. It is mechanically stable over 1000 stretching-and-releasing cycles with 30% strain. A thermal analysis reveals that the Ecoflex substrates impose significant thermal resistances to the entire device, degrading its cooling performance. To address this issue, alumina powder is added into the Ecoflex substrates. For the case of Ecoflex/alumina composite substrates with 60 wt % alumina, the maximum temperature drop is enhanced by 80 and 50% at 0 and 30% strains, respectively, under no heat load conditions. The devices with alumina addition also show a highly improved cooling per unit electrical power input, suggesting their potential merit in cost and energy saving. The cooling capability of the stretchable thermoelectric devices is further confirmed under both conductive and convective heat load conditions.