Stability Regimes of Thin Liquid Films

Stability Regimes of Thin Liquid Films. Mezic, A. M. I. Microscale Thermophysical Engineering, 2:203-213, August 1, 1998, 1998.

Paper abstract bibtex

The stability of thin liquid films on solid surfaces is fundamental to many phenomena such as dropwise and filmwise condensation, evaporation and boiling, as well as self-assembly of clusters and molecules. The free energy of a liquid film consists of a surface tension component as well as highly nonlinear volumetric intermolecular forces resulting from van der Waals, electrostatic, hydration, and elastic strain interactions. Athermodynamic stability analysis showed that surface tension always stabilizes a film, whereas van der Waals force with positive values of Hamaker constant (A 0) tends to destabilize. The competition between the electrostatic and surface tension stabilizing forces on one hand and van der Waals force (A 0) on the other leads to a wide variety of stability maps for different ion concentrations, which contain thickness ranges where the films are unconditionally stable. A case study of water films on glass surfaces was used to investigate the effects of short-range hydration and strain interactions as well as negative values of the Hamaker constant (A 0). The analysis showed that a water film on glass is unconditionally stable if its thickness is either less than 3 nm or more than 10 nm, and unstable in between. It is suggested that the instability at 3 nm ruptures the water film resulting in droplet formation, and is the key to dropwise condensation of water on glass. In addition, stable films thicker than 10 nm, which are formed by coalescing droplets, lead to filmwise condensation.

@article {831,
	title = {Stability Regimes of Thin Liquid Films},
	journal = {Microscale Thermophysical Engineering},
	volume = {2},
	year = {1998},
	month = {August 1, 1998},
	pages = {203-213},
	abstract = {The stability of thin liquid films on solid surfaces is fundamental to many phenomena such as dropwise and filmwise condensation, evaporation and boiling, as well as self-assembly of clusters and molecules. The free energy of a liquid film consists of a surface tension component as well as highly nonlinear volumetric intermolecular forces resulting from van der Waals, electrostatic, hydration, and elastic strain interactions. Athermodynamic stability analysis showed that surface tension always stabilizes a film, whereas van der Waals force with positive values of Hamaker constant (A 0) tends to destabilize. The competition between the electrostatic and surface tension stabilizing forces on one hand and van der Waals force (A 0) on the other leads to a wide variety of stability maps for different ion concentrations, which contain thickness ranges where the films are unconditionally stable. A case study of water films on glass surfaces was used to investigate the effects of short-range hydration and strain interactions as well as negative values of the Hamaker constant (A 0). The analysis showed that a water film on glass is unconditionally stable if its thickness is either less than 3 nm or more than 10 nm, and unstable in between. It is suggested that the instability at 3 nm ruptures the water film resulting in droplet formation, and is the key to dropwise condensation of water on glass. In addition, stable films thicker than 10 nm, which are formed by coalescing droplets, lead to filmwise condensation.},
	isbn = {1089-3954},
	url = {http://dx.doi.org/10.1080/108939598199973},
	author = {Mezic, A. Majumdar I.}
}

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