Droplet Impact on the Super-Hydrophobic Surface with Micro-Pillar Arrays Fabricated by Hybrid Laser Ablation and Silanization Process.

Zhenyan Xia,Shibin Wang,Zhen Yang,Yuhe Xiao,Xianping Liu,Linan Li,Yanling Tian

doi:10.3390/ma12050765

Abstract

A super-hydrophobic aluminum alloy surface with decorated pillar arrays was obtained by hybrid laser ablation and further silanization process. The as-prepared surface showed a high apparent contact angle of 158.2 ± 2.0° and low sliding angle of 3 ± 1°. Surface morphologies and surface chemistry were explored to obtain insights into the generation process of super-hydrophobicity. The main objective of this current work is to investigate the maximum spreading factor of water droplets impacting on the pillar-patterned super-hydrophobic surface based on the energy conservation concept. Although many previous studies have investigated the droplet impacting behavior on flat solid surfaces, the empirical models were proposed based on a few parameters including the Reynolds number (Re), Weber number (We), as well as the Ohnesorge number (Oh). This resulted in limitations for the super-hydrophobic surfaces due to the ignorance of the geometrical parameters of the pillars and viscous energy dissipation for liquid flow within the pillar arrays. In this paper, the maximum spreading factor was deduced from the perspective of energy balance, and the predicted results were in good agreement with our experimental results with a mean error of 4.99% and standard deviation of 0.10.

Highlights

IntroductionInspired by natural lotus leaves [2], rose petals [3], and butterfly wings [4], super-hydrophobic surfaces (i.e., apparent contact angle above 150◦ and sliding angle below 10◦ ) have been successfully mimicked through the synergetic effects of micro/nanostructure fabrication and surface chemical modification [5,6,7,8,9,10]
Surface wettability is one of the significant properties for a particular solid substrate [1].Inspired by natural lotus leaves [2], rose petals [3], and butterfly wings [4], super-hydrophobic surfaces have been successfully mimicked through the synergetic effects of micro/nanostructure fabrication and surface chemical modification [5,6,7,8,9,10]
A super-hydrophobic aluminum alloy surface with pillar-array structure was successfully obtained by the hybrid laser ablation and post chemical modification

Summary

Introduction

Inspired by natural lotus leaves [2], rose petals [3], and butterfly wings [4], super-hydrophobic surfaces (i.e., apparent contact angle above 150◦ and sliding angle below 10◦ ) have been successfully mimicked through the synergetic effects of micro/nanostructure fabrication and surface chemical modification [5,6,7,8,9,10] Due to their enormous potential applications including anti-icing [11], drag reduction [12], self-cleaning [13], anti-bacteria [14], and corrosion resistance [15], super-hydrophobic surface mimicry has been extensively developed by state-of-the-art techniques, such as thermal imprinting [16,17], chemical vapor deposition [18], coating [19], electrochemical deposition [20,21], and laser texturing [22,23,24,25,26,27]. It has been proved that the contact time, surface interactions, internal energy dissipation, inertia, and capillarity of the droplet are of great importance to assess the performance of a super-hydrophobic surface for its anti-icing and self-cleaning functions [31,32]

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