Construction and properties of popcorn-structured nanofiber membrane for daytime radiative cooling

Over the past decade, passive radiative personal thermal management in hot, high-sunlight environments has become a research hotspot in the smart wearable field. It protects outdoor human health, improves external thermal comfort, and cuts CO₂ emissions. This study prepared core-shell structured BaSO₄@SiO₂ nanoparticles with radiative cooling effects. Then, using electrospinning, it developed a PAN/BaSO₄@SiO₂ nanofiber membrane with popcorn-like structure. It has high reflectivity, high emissivity, and good applicability. By incorporating core-shell nano-spheres for Mie scattering and multi-level solar reflection across the spectrum, the optimized PAN/BaSO₄@SiO₂ membrane achieved a solar reflectivity of 94.3% and a mid-infrared emissivity of 90.8%. In outdoor tests under sunlight, compared to pure PAN fiber membranes, the PAN/BaSO₄@SiO₂ membrane reduced the simulated human skin temperature by 6.2℃, staying 4℃ below the ambient temperature. Moreover, when worn on the human arm, it achieved a 5.8℃ temperature reduction on the inner surface compared to cotton fabric. This excellent passive radiative cooling effect requires no extra energy. The nanofiber membrane made by electrospinning has a cooling power of 59.4 W/m² and is highly scalable, showing potential in smart wearable cooling clothing.