Eur. Phys. J. E (2016) 39: 15
https://doi.org/10.1140/epje/i2016-16015-8

Regular Article

Revisiting the effect of hierarchical structure on the superhydrophobicity

¹ Functional Soft Matter & Materials Group, Key Laboratory of Space Applied Physics and Chemistry of Ministry of Education, School of Science, Northwestern Polytechnical University, 710129, Xi’an, China
² NPU-UM II joint Lab of Soft Matter, School of Science, Northwestern Polytechnical University, 710129, Xi’an, China

^* e-mail: dyzang@nwpu.edu.cn

Received: 13 July 2015
Revised: 26 September 2015
Accepted: 5 October 2015
Published online: 25 February 2016

Abstract

We have studied the wetting behaviors of surfaces with a single micro-scale structure and a double micro/nano hierarchical structure, respectively. We have found the delayed wetting phenomenon on the single micro scale surface, which indicates that the wetting state transits from the initial Cassie state to the Cassie impregnating one. Furthermore, the droplet rebound becomes incomplete on the single micro scale surface when the impact velocity exceeds a critical value. On the contrary, complete rebound can still be observed when impacting on the micro/nano hierarchical structure. We proposed that, under static deposition the wetting transition occurs though the contact line depinning mechanism, whereas it occurs via sagging mechanism under a dynamic impact. Our results may be helpful for the understanding of superhydrophobicity and the wetting transition on complex structures.