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Size dependence of bubble wetting on surfaces: Breakdown of contact angle match between small sized bubbles and droplets

Abstract

For a bubble on a smooth and rigid substrate, its contact angle is always assumed to be the supplement to droplet contact angle under the same wetting conditions. Here we revisit bubble wetting on smooth solid surfaces via both free energetic analysis and molecular dynamics (MD) simulations. Our study shows a fundamental difference between bubble wetting and droplet wetting: the size dependence of isothermal compressibility of gas bubble leads to a size-dependent bubble contact angle. Based on theoretical analysis we develop a new relation between bubble contact angle and droplet contact angle, which is verified with MD simulations for nano-sized bubbles and droplets. In general, our studies show that for bubbles having a size greater than 10 micrometers, the traditional relation of bubble contact angle being the supplement to droplet contact angle holds. But, when bubble size decreases to several micrometers or even to a size of nanoscale, the relation of contact angle match breaks down, and the deviation from contact angle match increases with decreasing bubble size. This study reveals a unique wetting behavior of bubbles, implying that wetting of micro- and nano-bubble deserves serious consideration.

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Publication details

The article was received on 05 Nov 2018, accepted on 09 Jan 2019 and first published on 09 Jan 2019


Article type: Paper
DOI: 10.1039/C8NR08929A
Citation: Nanoscale, 2019, Accepted Manuscript
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    Size dependence of bubble wetting on surfaces: Breakdown of contact angle match between small sized bubbles and droplets

    H. Zhang and X. Zhang, Nanoscale, 2019, Accepted Manuscript , DOI: 10.1039/C8NR08929A

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