Investigation of Coalescence-Induced Droplet Jumping on Mixed-Wettability Superhydrophobic Surfaces

Ming-Jun Liao,Li-Qiang Duan

doi:10.3390/pr9010142

Abstract

Coalescence-induced droplet jumping has received more attention recently, because of its potential applications in condensation heat transfer enhancement, anti-icing and self-cleaning, etc. In this paper, the molecular dynamics simulation method is applied to study the coalescence-induced jumping of two nanodroplets with equal size on the surfaces of periodic strip-like wettability patterns. The results show that the strip width, contact angle and relative position of the center of two droplets are all related to the jumping velocity, and the jumping velocity on the mixed-wettability superhydrophobic surfaces can exceed the one on the perfect surface with a 180° contact angle on appropriately designed surfaces. Moreover, the larger both the strip width and the difference of wettability are, the higher the jumping velocity is, and when the width of the hydrophilic strip is fixed, the jumping velocity becomes larger with the increase of the width of the hydrophobic strip, which is contrary to the trend of fixing the width of the hydrophobic strip and altering the other strip width.

Highlights

Coalescence-induced droplet jumping on a superhydrophobic surface has received more and more attention [1,2,3,4,5,6,7,8,9,10,11], because it has been applied to various fields, including condensation heat transfer [12,13], self-cleaning [14], anti-icing [15,16], anti-dew [17] and so forth
The result of this paper shows that the velocity limit is broken on the mixed-wettability superhydrophobic surfaces with equal width of Lb and Ll
Coalescence-induced droplet jumping on mixed-wettability superhydrophobic surfaces is studied numerically by using the molecular dynamics simulation method

Summary

Introduction

Coalescence-induced droplet jumping on a superhydrophobic surface has received more and more attention [1,2,3,4,5,6,7,8,9,10,11], because it has been applied to various fields, including condensation heat transfer [12,13], self-cleaning [14], anti-icing [15,16], anti-dew [17] and so forth. The jumping velocity affects the efficiency of these applications. Zhang et al [18] made a comprehensive analysis of the published papers of droplet self-jumping data. They demonstrated that vj had a definite relationship to the contact angle and droplet radius (r), where vj followed distinct laws for different contact angle ranges and was more sensitive to a smaller radius. With the development of micro–nano technology, many studies have focused on fabricating various micro-/nano-structured surfaces to discover the enhancement of droplets coalescence and jumping. It has been demonstrated that the microstructures make the apparent contact angle of the droplet increase, a faster jumping of merged droplets is achieved [1,5,6,20,21,22]

Methods

Results

Conclusion