Issue 5, 2017

Universal wetting transition of an evaporating water droplet on hydrophobic micro- and nano-structures

Abstract

Water-repellent, rough surfaces have a remarkable and beneficial wetting property: when a water droplet comes in contact with a small fraction of the solid, both liquid–solid adhesion and hydrodynamic drag are reduced. As a prominent example from nature, the lotus leaf—comprised of a wax-like material with micro- and nano-scaled roughness—has recently inspired numerous syntheses of superhydrophobic substrates. Due to the diverse applications of superhydrophobicity, much research has been devoted to the fabrication and investigations of hydrophobic micro-structures using established micro-fabrication techniques. However, wetting transitions remain relatively little explored. During evaporation, a water droplet undergoes a wetting transition from a (low-frictional) partial to (adhesive) complete contact with the solid, destroying the superhydrophobicity and the self-cleaning properties of the slippery surface. Here, we experimentally examine the wetting transition of a drying droplet on hydrophobic nano-structures, a previously unexplored regime. In addition, using a theoretical analysis we found a universal criterion of this wetting transition that is characterized by a critical contact angle. Different from previous results showing different critical droplet sizes, our results show a universal, geometrically-dependent, critical contact angle, which agrees well with various data for both hydrophobic micro- and nano-structures.

Graphical abstract: Universal wetting transition of an evaporating water droplet on hydrophobic micro- and nano-structures

Supplementary files

Article information

Article type
Paper
Submitted
08 Oct 2016
Accepted
22 Dec 2016
First published
22 Dec 2016
This article is Open Access
Creative Commons BY license

Soft Matter, 2017,13, 978-984

Universal wetting transition of an evaporating water droplet on hydrophobic micro- and nano-structures

A. Bussonnière, M. B. Bigdeli, D. Chueh, Q. Liu, P. Chen and P. A. Tsai, Soft Matter, 2017, 13, 978 DOI: 10.1039/C6SM02287A

This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. You can use material from this article in other publications without requesting further permissions from the RSC, provided that the correct acknowledgement is given.

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