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Issue 40, 2019
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Bubbles nucleating on superhydrophobic micropillar arrays under flow

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Abstract

When a supersaturated aqueous solution flows over a microstructured, hydrophobic surface, bubbles tend to nucleate. Here, we control heterogeneous nucleation of gas bubbles from supersaturated CO2 solution. By designing the shape, size, and arrangement of hydrophobic micropillars and by adjusting the flow we obtain uniform nucleation patterns. It is possible to selectively turn nucleation on and off. We use laser scanning confocal microscopy to resolve nucleation in early stages at the micropillar–substrate intersection. Numerical simulations show a correlation between minute pressure drops behind micropillars and nucleation sites. Bubbles nucleate uniformly behind pillars of the same size. The flow profile further contributes to the uniform growth of the bubbles. We control heterogeneous nucleation by varying micropillar geometry or size, flow direction and rate. While nucleation behind square pillars is independent of the flow direction, nucleation behind round micropillars is coupled with the direction. Nucleation behind triangular micropillars is bifurcated. These observations pave the way for the replenishment of the gas layer entrapped in between hydrophobic surface features, needed for superhydrophobicity.

Graphical abstract: Bubbles nucleating on superhydrophobic micropillar arrays under flow

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Supplementary files

Article information


Submitted
19 Jun 2019
Accepted
29 Sep 2019
First published
01 Oct 2019

This article is Open Access

Soft Matter, 2019,15, 8175-8183
Article type
Paper

Bubbles nucleating on superhydrophobic micropillar arrays under flow

B. Pinchasik, F. Schönfeld, M. Kappl and H. Butt, Soft Matter, 2019, 15, 8175
DOI: 10.1039/C9SM01224A

This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. Material from this article can be used in other publications provided that the correct acknowledgement is given with the reproduced material.

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    [Original citation] - Published by The Royal Society of Chemistry.

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