Review on condensation frosting and defrosting experiments for superhydrophobic surfaces

Frosting is a natural phase change phenomenon which happens frequently in nature and industry and has negative effects on a variety of applications. As a passive anti-frosting strategy, superhydrophobic surfaces have been paid more and more attention. To shed light on the process and space–time characteristics of frosting on superhydrophobic surfaces, the preparation methods of superhydrophobic surfaces were introduced first. Then, the internal mechanisms of anti-frosting for superhydrophobic surfaces were revealed from two perspectives of condensation frosting and defrosting. For the preparation of superhydrophobic surfaces, previous studies have shown that laser etching could obtain ideal surface parameters, but there is still a lack of a preparation scheme with low cost and good reliability. For the condensation frosting on superhydrophobic surfaces, the surface with regular surface morphology could realize the spontaneous wettability transformation of the droplets and maintain the size of the condensed droplets within 10–20 μm. The freezing time of droplets on the surface with a regular micro-nano structure is about 4.42 times longer than that on the surface without a regular micro-nano structure. The condensation stage and droplet freezing stage are the keys to preventing frost on superhydrophobic surfaces. For the defrosting on superhydrophobic surfaces, the photothermal defrosting method using metal nanowires, graphene, and carbon nanotubes has a broad application prospect. The results of this study summarized the achievements, problems, and challenges of the current research, so as to provide a reference for the anti-frosting technology of superhydrophobic surfaces in practical applications.