A bioinspired and scalable near-ideal broadband coating for radiative thermoregulation

Passive daytime radiative cooling has been widely acknowledged to be an environment-friendly pathway to realize considerable cooling effects. A broadband radiative coating is more favorable for thermoregulations where the temperature is close to or higher than that of the ambient environment. However, how to fabricate a near-ideal broadband radiative coating in a facile and low-cost way has been rarely reported. Herein, a biologically inspired dual-layer polymer-based near-ideal broadband radiative coating is fabricated by mimicking the microstructure of the scales of the white beetle Goliathus goliatus. The proposed coating, characterized as a near-ideal broadband radiative cooler with similar to 0.96 solar reflectance and similar to 0.95 broadband emissivity beyond 2.5 mu m, has been demonstrated to achieve an average temperature drop of similar to 7.1 degrees C and an average cooling power of similar to 118 W m(-2) under direct sunlight in outdoor tests, along with the verified notable advantage for radiative thermoregulation above the ambient temperature. As stepwise heating power is applied to heat the dual-layer coating and another contrastive porous monolayer coating, respectively, the dual-layer coating shows a temperature of 7.2 degrees C lower than that of the porous monolayer coating at a heating power of 1000 W m(-2). Moreover, with the presence of a dense layer, the dual-layer coating exhibits strong mechanical strength and functional expansibilities, like Ag deposition and colour painting. Overall, due to the notable radiative cooling capability, compatibility with large-scale production and multiform expansibilities, it is believed that the proposed coating has a promising future in radiative thermoregulation.