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

Abstract

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.