A Magnetically Responsive Flexible Thermal Switch for Reversible Thermal Regulation

Dynamic regulation of thermal conductivity is fundamental to smart thermal management and energy conservation. As a key component, a thermal switch enables smart thermal regulation by reversibly toggling thermal conductivity between high and low states. However, achieving flexible and continuous thermal switches remains a significant challenge. Here, a magnetically responsive flexible thermal switch composed of magnetic liquid metal, graphene films, and polydimethylsiloxane is developed. The flexible thermal switch exhibits a reversible and dynamic variation in thermal conductivity between 0.261 and 3.426 W·m^-1·K^-1, with a thermal switching ratio of 13.1. At different heat flux densities, the temperature difference between device and environment in the "on" state of flexible thermal switch is reduced by approximately 57.9% compared with that in the "off" state. Furthermore, a flexible thermal switch reduces the temperature deviation of a foldable smartphone heat source by 10.2%. It demonstrates excellent temperature regulation capability that can be applied to planar, curved, and wearable devices. This work provides promising opportunities for smart thermal management in curved and wearable devices such as soft robotics and foldable smartphones.