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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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Publication details

The article was received on 19 Jun 2019, accepted on 29 Sep 2019 and first published on 01 Oct 2019


Article type: Paper
DOI: 10.1039/C9SM01224A
Soft Matter, 2019,15, 8175-8183
  • Open access: Creative Commons BY license
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    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

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