Droplet motion and oscillation on contrasting micro-striated surfaces

Spontaneous motion of liquid droplets can occur on hydrophobic, micro-structured, solid surfaces comprising a structural gradient. In this study, we examine such motion experimentally and explain our observations by invoking variable droplet–surface interactions (both actuation and resistance forces...

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Bibliographic Details
Published in:Journal of fluid mechanics 2021-06, Vol.916, Article A54
Main Authors: Zhao, Hongyu, Orejon, Daniel, Sefiane, Khellil, Shanahan, Martin E.R.
Format: Article
Language:English
Subjects:
Actuation
Droplets
Hydrophobic surfaces
Hydrophobicity
JFM Papers
Model testing
Movement
Qualitative analysis
Silicon wafers
Solid surfaces
Vertical oscillations
Wetting
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Summary:Spontaneous motion of liquid droplets can occur on hydrophobic, micro-structured, solid surfaces comprising a structural gradient. In this study, we examine such motion experimentally and explain our observations by invoking variable droplet–surface interactions (both actuation and resistance forces) arising from the structural gradient. The oscillatory motion of the droplet constitutes an integral aspect of the behaviour and this is incorporated into the overall modelling. The theoretical model features a truncated spheroid for the drop shape (flattened in the region of solid contact) coupled with the oscillatory and alternate leading and trailing motion of the contact line. Results from the model and experiments provide good qualitative and quantitative agreement. The component of the vertical oscillation is found to help overcome wetting hysteresis and actuate the motion, this being a key element for the completeness of the model.
ISSN:0022-1120
1469-7645
DOI:10.1017/jfm.2021.211