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Films, layers and droplets: The effect of near-wall fluid structure on spreading dynamics

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journal contribution
posted on 02.02.2017 by Hanyu Yin, David Sibley, Uwe Thiele, Andrew Archer
We present a study of the spreading of liquid droplets on a solid substrate at very small scales. We focus on the regime where effective wetting energy (binding potential) and surface tension effects significantly influence steady and spreading droplets. In particular, we focus on strong packing and layering effects in the liquid near the substrate due to underlying density oscillations in the fluid caused by attractive substrate-liquid interactions. We show that such phenomena can be described by a thin-film (or long-wave or lubrication) model including an oscillatory Derjaguin (or disjoining/conjoining) pressure, and explore the effects it has on steady droplet shapes and the spreading dynamics of droplets on both, an adsorption (or precursor) layer and completely dry substrates. At the molecular scale, commonly used two-term binding potentials with a single preferred minimum controlling the adsorption layer height are inadequate to capture the rich behaviour caused by the near-wall layered molecular packing. The adsorption layer is often sub-monolayer in thickness, i.e., the dynamics along the layer consists of single-particle hopping, leading to a diffusive dynamics, rather than the collective hydrodynamic motion implicit in standard thin-film models. We therefore modify the model in such a way that for thicker films the standard hydrodynamic theory is realised, but for very thin layers a diffusion equation is recovered.

History

School

  • Science

Department

  • Mathematical Sciences

Published in

Physical Review E

Citation

YIN, H. ...et al., 2017. Films, layers and droplets: The effect of near-wall fluid structure on spreading dynamics. Physical Review E, 95(2): 023104.

Publisher

© American Physical Society

Version

AM (Accepted Manuscript)

Publisher statement

This work is made available according to the conditions of the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0) licence. Full details of this licence are available at: https://creativecommons.org/licenses/by-nc-nd/4.0/

Acceptance date

10/01/2017

Publication date

2017

Notes

This paper was accepted for publication in the journal Physical Review E and the definitive published version is available at http://link.aps.org/doi/10.1103/PhysRevE.95.023104

ISSN

2470-0053

Language

en

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