| Passive radiative cooling technology can achieve a lower temperature without additional energy input by radiating heat to outer space in the transparent atmospheric spectral window.Rational photonic structure design can realize high reflectance/absorption efficiency with frequency selectivity.However,scalable nanomanufacturing of photonic structures with low-cost,controlled spectral reflection/absorption selectivity and desired properties remains a challenge.Some natural creatures with photonic structures have been reported to exhibit broadband reflectivity and thermal regulation ability,which motivated biomimetics.In this work,we discover indeed that the dual-scale triangular-shaped fluffs by morphology and optical properties,characteristic of the longicorn beetle Neocerambyx gigas(N.gigas).The fluffs enable the tropical beetles to decrease the body temperature by increasing the reflectivity in the vis-NIR region based on total internal reflection and Mie scattering and by enhancing the MIR emissivity to radiate heat to the surroundings,which contribute to thermal regulation ability in hot climates.Inspired by the finding,a photonic film consisting a micro-pyramid-arrayed polymer matrix with random ceramic particles is fabricated with high throughput.The film reflects?95%of solar irradiance and exhibits an infrared emissivity>0.96.The effective cooling power is found to be?90.8Wm-2 and a temperature decrease of up to 5.1°C is recorded under direct sunlight.Additionally,the film exhibits hydrophobicity,superior flexibility and strong mechanical strength,which is promising for thermal management in various electronic devices and wearable products. |
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