uning Optical Properties of Metamaterials by Mie Scattering for Efficient Sub-ambient Daytime Radiative Cooling

he management of the abundant eggshell biowaste produced worldwide hasbecome a problematic issue due to the generated odor and microorganisms afterdirectly disposing eggshell biowaste in landfills. Herein, we propose a novelmethod to convert the hazardous eggshell biowaste to valuable resources forenergy management applications. Eggshell-based films are fabricated byembedding eggshell powders into polymer matrix to achieve highly efficientsub-ambient daytime radiative cooling. Benefiting from the Mie scattering ofeggshell particles/air pores in the solar spectrum and strong emission ofeggshell in the mid-infrared (mid-IR) range, the eggshell-based films presenthigh reflection of 0.96 in the solar spectrum and high emission of 0.95 in themid-IR range, resulting in significant average temperature drop of 5{\deg}C and12{\deg}C below the ambient temperature during daytime and nighttime,respectively. Moreover, the eggshell-based films exhibit excellent flexibilityand self-cleaning properties, which are beneficial for practical long-termoutdoor applications. Our proposed design provides a novel means for anenvironmentally friendly and sustainable management of the eggshell biowaste.