Self-ejections of multiple isolated slushes on disorderly grooved superhydrophobic surfaces

Zhengyong Huang,Feipeng Wang,Wenjie Xu,Ruiqi Zhang,Jian Li

doi:10.1063/1.5115454

Abstract

In this Letter, we developed a sprayable superhydrophobic coating with micro-sized disorder indentations to survey the self-ejections of isolated slushes on it during the defrosting process. The microstructures, chemical composition, hydrophobic characteristics, and self-ejection phenomenon of melting slushes on grooved superhydrophobic surfaces are presented. The grooved superhydrophobic surface demonstrates that multiple self-ejections of isolated melting slush off the original locations with no ice bridges or great surface energy release. In addition, the self-ejection of multiple isolated slushes observed generates enough kinetic energy and removes the residual melting slushes in ways of sweeping off. It is also found that the irregular melting slush with a greater deformation energy and surface contact area demonstrates shorter jumping distances compared to that with a spherical shape and low surface contact area. The observed short-distance self-ejection results from the defects of micro-pores on the indentations, leading to great dissipation in vapor pressures and reduced impact from volume fluctuations. Both the volume fluctuation of slush and the evaporation of intermediate liquid generate the pressure gradient in the upward direction and contribute to the self-ejection behavior of isolated melting slush. The results demonstrate the necessity of fabricating grooved superhydrophobic surfaces without micro-pores and conceptual feasibility of employing volume fluctuation of slush for the self-ejection of isolated single melting slush in the case of slushes with no ice bridges, small surface energy, and low inner vapor pressures.

Highlights

Superhydrophobic surfaces have been studied to prevent ice and frost accretion.5–8 Water on hierarchical superhydrophobic surfaces typically exhibits spherical shapes.9–11 The intermediate air layer significantly reduces the contact area and adhesion force between superhydrophobic surfaces and water droplets.12 On hierarchical superhydrophobic surfaces, the condensate droplets are continuously removed by sliding off the inclined surface at millimetric length scales or by coalescence-induced jumping at micrometric length scales.2,13,14 In our previous studies, we prepared one kind of durable superhydrophobic methyl silicone resin(MSR)/SiO2 coating by suspension air spraying,15 and transparent superhydrophobic coatings using atmospheric arc discharge.16 the de-wetting performance of horizontal superhydrophobic coating under a tangential AC electric field was studied.17,18 new condensate that nucleates at the original locations will eventually freeze into frost due to a surfacedefect-induced frost front and subsequent inter-droplet freezing wave propagation.14 Under subzero conditions, the superhydrophobic surface demonstrates gradual damage in surface microstructures and poor durability during icing/deicing cycles.19 In an ambient environment with high humidity and low temperature, the freezing of water droplets on the superhydrophobic surface is inevitable in the end.7,20–22 In one way, there have been reports on preparation of durable coatings with ice-phobic properties to deal with the problem of poor durability.23–26 In the other way, the superhydrophobic surface shows potential applications in energy-efficient de-icing for the case of emergency response
In this Letter, we developed a sprayable superhydrophobic coating with micro-sized disorder indentations to survey the self-ejections of isolated slushes on it during the defrosting process
The results demonstrate the necessity of fabricating grooved superhydrophobic surfaces without micro-pores and conceptual feasibility of employing volume fluctuation of slush for the self-ejection of isolated single melting slush in the case of slushes with no ice bridges, small surface energy, and low inner vapor pressures

Summary

Introduction

Superhydrophobic surfaces have been studied to prevent ice and frost accretion.5–8 Water on hierarchical superhydrophobic surfaces typically exhibits spherical shapes.9–11 The intermediate air layer significantly reduces the contact area and adhesion force between superhydrophobic surfaces and water droplets.12 On hierarchical superhydrophobic surfaces, the condensate droplets are continuously removed by sliding off the inclined surface at millimetric length scales or by coalescence-induced jumping at micrometric length scales.2,13,14 In our previous studies, we prepared one kind of durable superhydrophobic methyl silicone resin(MSR)/SiO2 coating by suspension air spraying,15 and transparent superhydrophobic coatings using atmospheric arc discharge.16 the de-wetting performance of horizontal superhydrophobic coating under a tangential AC electric field was studied.17,18 new condensate that nucleates at the original locations will eventually freeze into frost due to a surfacedefect-induced frost front and subsequent inter-droplet freezing wave propagation.14 Under subzero conditions, the superhydrophobic surface demonstrates gradual damage in surface microstructures and poor durability during icing/deicing cycles.19 In an ambient environment with high humidity and low temperature, the freezing of water droplets on the superhydrophobic surface is inevitable in the end.7,20–22 In one way, there have been reports on preparation of durable coatings with ice-phobic properties to deal with the problem of poor durability.23–26 In the other way, the superhydrophobic surface shows potential applications in energy-efficient de-icing for the case of emergency response. In this Letter, we developed a sprayable superhydrophobic coating with micro-sized disorder indentations to survey the self-ejections of isolated slushes on it during the defrosting process.

Results

Conclusion