Super-hydrophobic surfaces to condensed micro-droplets at temperatures below the freezing point retard ice/frost formation

Retarding and preventing ice/frost formation has an increasing importance because of the significant energy and safety concerns nowadays. In this paper, super-hydrophobic surfaces with ZnO nanorod arrays were fabricated. These surfaces were super-hydrophobic not only to sessile macro-droplets at room temperature but also to condensed micro-droplets at temperatures below the freezing point. The effects of these ZnO surfaces towards ice/frost formation were investigated. The results show that the time of condensed droplets maintaining the liquid state (t) increases with the decrease of the growth time (t(ZnO)) of ZnO nanorods which determines the surface wettability, clearly indicating the retardation of ice/frost formation. An explanation is proposed based on classic nucleation theory and the heat transfer between condensed droplets and super-hydrophobic surfaces. These results make clear that superhydrophobicity to condensed micro-droplets at temperatures below the freezing point is desirable for effectively retarding ice/frost formation. In addition, they are significant for understanding the effect of superhydrophobicity at surface temperatures lower than the equilibrium freezing point on retarding and preventing ice/frost formation and will be beneficial for the design of effective anti-ice/frost materials.