Films, layers and droplets: The effect of near-wall fluid structure on spreading dynamics
| Autor: | Uwe Thiele, Hanyu Yin, Andrew J. Archer, David N. Sibley |
|---|---|
| Jazyk: | angličtina |
| Rok vydání: | 2016 |
| Předmět: |
Thin layers
Diffusion equation Materials science Statistical Mechanics (cond-mat.stat-mech) Fluid Dynamics (physics.flu-dyn) FOS: Physical sciences 02 engineering and technology Physics - Fluid Dynamics Condensed Matter - Soft Condensed Matter 021001 nanoscience & nanotechnology 01 natural sciences Surface tension Physics::Fluid Dynamics Condensed Matter::Soft Condensed Matter Adsorption Chemical physics 0103 physical sciences Lubrication Soft Condensed Matter (cond-mat.soft) Wetting 010306 general physics 0210 nano-technology Hydrodynamic theory Layer (electronics) Condensed Matter - Statistical Mechanics |
| Popis: | 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. 17 pages, 21 figures |
| Databáze: | OpenAIRE |
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