Biological optics, photonics and bioinspired radiative cooling

Radiative cooling with eco-friendly and zero-energy advantages is considered one of the most viable solutions to address the conflict between traditional energy-intensive cooling systems and global decarbonization. Despite significant advances, the development of radiative cooling still faces many challenges, such as fine-engineering of materials and structures to enhance solar reflection and mid-infrared emission, solar absorption caused by coloring for colorful radiative cooling, and spectral modulation for environmental-adaptative dynamic radiative cooling. Over millions of years of natural selection, utilizing a limited set of biomaterial palettes, optimized strategies, and micro-nano structural design, natural organisms have demonstrated fine control over light-matter interactions at different wavelength scales. Including broadband reflection of the sunlight to prevent solar heating, narrowband reflection of visible light to display brilliant colors, strong emission of mid-infrared wave to complete its cooling, and environmental-adaptative spectral modulation to achieve camouflage or thermal regulation. These biological structures and strategies provide extremely valuable inspiration for the development of advanced radiative cooling techniques. In this review, we systematically summarized the research progress of bioinspired radiative cooling technologies. Emphatically introducing the mechanism of key biological structures to achieve several optical functions, and discussing the various bioinspired radiative coolers and their application potential in different fields. Finally, we present the remaining challenges and outlook on the possible research directions in the future. It is hoped that this review will contribute to further research on bioinspired radiative cooling technology and make exciting progress.