1. Introduction
Any object with a temperature higher than absolute zero will emit thermal radiation as stated in Planck’s law[1]. According to the Stefan–Boltzmann law, the total thermal energy radiated from the surface of an object is proportional to the emissivity and the fourth power of the temperature. Thus, the infrared (IR) imaging can be controlled by either regulating the emissivity or changing the surface temperature. In nature, many organisms achieve better survival by adjusting their own IR radiation[2–4]. Inspired by natural creatures, imitate biological regulation of surface heat radiation to achieve personal thermal management[5,6], IR camouflage[7,8], IR radiation cooling[9,10], and other functions[11–13] has received widespread attention.