Scalable wet-spinning of wearable chitosan-silica textile for all-day radiative cooling

Passive radiative cooling for cost-effective personal thermal management (PTM) has received tremendous attention as it permits continuous subambient temperatures without energy consumption. Enhancing emission in the mid-infrared wavelength range and minimizing solar heat absorption are two independent processes that impart materials with effective radiative cooling performance. However, scalable all-day subambient cooling for PTM has been limited for wide applications due to the compromise between complex manufacturing and effective broadband radiative cooling. Herein, this work reports spectrally selective fabrics consisting of chitosan (CS) fibers and silica microparticles (SiO2) for all-day PTM using a scabble and easy wet-spinning technique. Along with the porosity of the fiber, woven CS/SiO2 textiles provide high reflectivity (82.3 %) in the solar window (wavelength lambda, 0.3-2.5 mu m) and high infrared emissivity (95.6 %) within the atmospheric transparency window (wavelength lambda, 8-13 mu m). Additionally, the textiles exhibit great cloth comfort due to the physical properties of fibers including flexibility, breathability, and strength. The cooling power of wearable textiles during daytime and nighttime is 95.7 W m- 2 and 103.3 W m- 2. Comparing the outdoor thermal test results of nylon and cotton all day, the temperature difference of 11.2 degrees C and 5.4 degrees C proved the passive radiation cooling ability of the material. This effective radiative property arises from the chemical bond vibrations of the CS fabric matrix and phonon polarization resonance of SiO2 microparticles. Our scalable and inexpensive radiative cooler could be an excellent wearable textile for practical all-day PTM.