Magnetron-sputtered thin films enabling heat transfer enhancement in electrocaloric heat pumps

Solid-state cooling devices offer a cleaner and more sustainable alternative to traditional refrigeration methods. The present work addresses a critical challenge in these systems: effective heat transfer through enhanced surface wettability. In this study, ceramic electrocaloric components were coated with magnetron-sputtered (Ti, Si)O2/WO3 thin films. A long-lasting superhydrophilic behavior of their surface has been achieved thanks to the mesoporous morphology of the coatings, which promotes capillary effects at the nanometric scale. Investigations on the wetting properties of coated and uncoated components, as well as studies on droplet dynamics at low pressures, demonstrate that the superhydrophilic coatings facilitate faster and more uniform water vapor condensation, thereby enhancing the heat transfer rate related to droplet growth. These findings suggest that optimizing the surface properties of electrocaloric materials with such coatings can lead to the development of high-performance electrocaloric heat pumps, potentially replacing traditional compressor-based systems and eliminating the need for harmful refrigerants.