Current technologies focused on manipulating heat flow primarily employ materials that exhibit metal-insulator transitions. However, for these materials to be efficient, the operating temperature of the device must be close to the transition temperature. Since the transition temperature is not easily tunable, the solution involves developing and studying new materials that have desirable transition temperatures which often is an inhibitor. Furthermore, as temperature and heat are strongly coupled, the ability to actively control heat flow can be limited.

We propose a solution for active control of heat flow that involves altering the thermal conductivity of a material through mechanical strain. Stretching (compressing) a material leads to an increase (decrease) in the spacing between the atoms, results in a decrease (increase) in thermal conductivity of the material. Our approach involves achieving the required strain by applying an electrical voltage, referred to as the piezoelectric effect. In this study, the relationship between mechanical strain and thermal conductivity is experimentally studied on thin films. Both inorganic and organic films, fabricated using solution processing and sputtering techniques will be used to explore this effect. Thermal conductivity measurements will be carried out using 3-omega, which is a well-established electro-thermal technique. There will also be a thrust to quantify anisotropy in thermal conductivities of the piezoelectric films. In this talk, we report data from preliminary experiments that demonstrate the reversible and tunable thermal conductivity of piezoelectric thin films such as ZnO.