All-Season Passive Thermal Management Film with Multifunctionality for Efficient Radiative Cooling and Solar Heating

Thermal radiation management is an important aspect of thermal engineering and plays a crucial role in various industrial and environmental applications. However, either cooling or heating devices alone can exacerbate all-season consumption during hot summers or cold winters. We have designed a dual-mode thermal management device that can switch modes by a pull-out method, with femtosecond laser-induced graphene (LIG) on the surface of a polyimide membrane as the heating surface and a SiO2 hollow microsphere coating as the cooling surface. Due to the multi-interface reflection between SiO2 hollow microspheres and air, high reflectivity (93%) and 97% thermal infrared emissivity can be obtained. Under a solar irradiation intensity of 75 J/cm2, a temperature decrease of 6.3 °C can be realized. On the other hand, LIG can achieve an ultra-ambient temperature increase of 35 °C due to its excellent solar light absorption characteristics (ε ≈ 97%) and high thermal conductivity. Temperature regulation can be achieved by switching heating and cooling modes, which shows great promise in agriculture and for food and goods preservation. Also, this design is expected to offer a new approach to energy efficient cooling and heating in architecture.