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 (≈5800 K) as a heating source and outer space (≈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 °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 °C, respectively. The fabricated devices exhibit effective heating/cooling on diverse surfaces.