Reversible Solar Heating and Radiative Cooling Devices via Mechanically Guided Assembly of 3D Macro/Microstructures

Solar heating and radiative cooling are promising solutions for decreasing global energy consumption because these strategies use the Sun (approximate to 5800 K) as a heating source and outer space (approximate to 3 K) as a cooling source. Although high-performance thermal management can be achieved using these eco-friendly methods, they are limited by daily temperature fluctuations and seasonal changes because of single-mode actuation. Herein, reversible solar heating and radiative cooling devices formed via the mechanically guided assembly of 3D architectures are demonstrated. The fabricated devices exhibit the following properties: i) The devices reversibly change between solar heating and radiative cooling under uniaxial strain, called dual-mode actuation. ii) The 3D platforms in the devices can use rigid/soft materials for functional layers owing to the optimized designs. iii) The devices can be used for dual-mode thermal management on a macro/microscale. The devices use black paint-coated polyimide (PI) films as solar absorbers with multilayered films comprising thin layers of polydimethylsiloxane/silver/PI, achieving heating and cooling temperatures of 59.5 and -11.9 degrees C, respectively. Moreover, mode changes according to the angle of the 3D structures are demonstrated and the heating/cooling performance with skin, glass, steel, aluminum, copper, and PI substrates is investigated. Reversible solar heating and radiative cooling devices employing mechanically guided 3D architectures demonstrate dual-mode actuation with uniaxial strain. These devices, which are applicable on macro/microscales, utilize optimized 3D platforms that accommodate both rigid and soft materials. Heating/cooling layers achieve heating/cooling temperatures of 59.5 and -11.9 degrees C, respectively. The fabricated devices exhibit effective heating/cooling on diverse surfaces. image