Fabrication of fibrous nanofiber membranes for passive radiation cooling

Passive radiation cooling technology reflects sunlight and emits infrared thermal radiation into the cold outer space through the transparent window of the atmosphere (8–13  \(\mathrm{\mu m}\) ) without consuming any energy to cool objects. Therefore, it has potential application prospects in many fields and has attracted the wide attention of researchers. In recent years, photonic radiators and metamaterials have been studied in passive radiative cooling. However, they are usually not flexible, low ductility, complex shape and demand a high level of precision, which severely restricts large-scale manufacturing and limits their practical application. A simple and high-efficient electrospinning method with inexpensive raw materials is demonstrated for fabricating a high-performance fibrous and stretchable polymer nanofiber for daytime passive radiation cooling that consists of polyvinylidene fluoride and polydisperse silicon dioxide (SiO 2 ) microspheres. For effective scattering by nanofiber structures and silica microspheres, the membrane exhibits an average solar reflectivity of 92.3%. The molecular vibration of polyvinylidene fluoride and phonon polarization resonance of silica microspheres result in an average atmospheric window transmissivity of 0.86. The daytime cooling performance has experimentally demonstrated a maximum temperature decrease up to 5.8 °C under an average solar intensity of 700.8 W/m 2 . This work provides a promising method for the scale-up production of radiative coolers with high performance.