Silk fibroin microsphere-enabled passive radiative cooling ability for cotton fabrics

Passive radiative cooling has attracted extensive attention owing to its great potential in reducing energy consumption. Endowing common fabrics with radiative cooling ability is an effective personal cooling strategy to manage skin microenvironment and improve thermal comfort. Herein, we report the use of silk fibroin microspheres to impart cotton fabrics with radiative cooling ability, taking advantages of both the high infrared emittance of silk fibroin and the high solar reflectance of microspherical structure. The silk fibroin microspheres were prepared from an aqueous solution of regenerated silk fibroin through a simple ethanol-induced self-assembly approach. The diameter of microspheres (0.37–1.52 μm) and thus, the solar reflectance, can be easily adjusted by varying the ethanol amount. The general dip-coating method was used to apply the silk fibroin microspheres onto cotton fabrics. Remarkably, compared to pristine cotton fabric and pure silk fabric, the cotton fabric coated with silk fibroin microspheres achieved an average temperature drop of 5.1 °C and 2.3 °C, respectively, during daytime outdoor test. Moreover, the washing resistance of the silk fibroin microsphere coating can be greatly improved by applying an additional thin layer of polyacrylate adhesive, thereby demonstrating the practical application feasibility of coated cotton fabric for personal thermal management.