Thermal control for flexible/wearable devices using radiative cooling

Abstract

The field of thermal control for wearable devices is undergoing significant advancements in order to facilitate the widespread adoption of advanced devices that possess characteristics such as miniaturization, integration, and ultrathin designs, thereby enabling ubiquitous applications. Recently, Contemporary methodologies employed in the creation of transformative electronic systems (TES) have incorporated gallium liquid metal as a means of achieving malleability regulation through temperature-induced liquid-solid phase transitions. The present design, unfortunately, lacks the ability to endure high temperatures in outdoor settings, resulting in an unfavorable softening of the device when the rigid mode of operation is preferred. We introduce a gallium-based thermal transformative system that is integrated with a flexible and stretchable radiative cooler. This innovative system provides efficient thermal management with zero power consumption, enabling reliable operation in high-temperature outdoor environments. The radiative cooler exhibits dual functionality in terms of reflecting solar heat transfer and emitting thermal energy. Consequently, the utilization of a TES in the air enables the device to sustain a temperature that is lower than the melting point of gallium (29.8 ℃) during periods of high temperatures and intense solar radiation, thereby averting undesired device softening. The reliability of the design approach for integrating radiative coolers with thermal energy storage has been verified through comprehensive studies on the optical, thermal, and mechanical characteristics of the system. Additionally, a proof-of-concept demonstration conducted in hot outdoor conditions further supports the potential for expanding the application of TES in diverse environments.