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Instability of Air Films Trapped Between Liquid Drops and Solid Surfaces

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Friday, November 13, 2020, 1 pm

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This is a past event.

Chemical Engineering Seminar

Yuesheng Gao

PhD Candidate
Chemical Engineering
Michigan Technological University

Abstract: Wetting of solid surfaces occurs when water droplets spread on hydrophilic surfaces. On hydrophobic surfaces, water beads up and forms a finite contact angle. Although this phenomenon is well known, the interaction forces between water droplets and solid surfaces have not yet been studied. In this seminar, I will introduce our newly developed Synchronized Tri-wavelength Reflection Interferometry Microscopy (STRIM) technique for characterizing both the instability of air films and surface forces between water droplets and solid surfaces. It was found that a water droplet started to spread on a solid surface when the closest separation distance reached a critical separation distance. We have also shown that there was a strong attractive force between water droplets and hydrophilic surfaces originating from electrostatic force, pulling the water droplet to spread on the solid surface. The increases in the critical separation distance as a function of surface hydrophobicities was found to be applicable for a variety of natural mineral surfaces. In addition, STRIM technique has been also used to understand the mechanism involved in capture of micron-sized dust particles by water sprays used in the underground coal mines. The use of surfactant chemicals as wetting agents in water sprays enables an alternation of surface charges on coal surfaces, favoring for water-dust attachment. The microscopic mechanism involved in the capture of dust particles by water sprays was revealed.

Bio: Yuesheng Gao is a PhD candidate in the Department of Chemical Engineering at Michigan Tech. He received his BS and MS degrees in Mining Engineering from Central South University in 2014 and 2016, respectively. He has authored 18 journal articles. He serves as a reviewer for 15 international journals and serves as a session chair for the Society for Mining, Metallurgy, and Exploration. His research expertise involves interface science and mineral processing.

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