Liquids on topologically nano-patterned surfaces
"Liquids on Topologically Nanopatterned Surfaces"
Oleg Gang, Kyle J. Alvine, Masafumi Fukuto, Peter S. Pershan, Charles T. Black, and Benjamin M. Ocko
Physical Review Letters 95(21) 217801 (2005)
Soft Matter Keywords
liquid thin film, wetting, laterally heterogeneous surface
Gang, et al. present experimental work performed to verify theory on the wetting of thin films. Working with a nanopatterned silicon surface and a film of methyl-cyclohexane (MCH), the authors should that film thickness has two different power law dependences on chemical potential offset from the bulk liquid-vapor equilibrium. These two dependences delineate two regimes of film growth. The first regime is characterized by constant film thickness on the surface and filling of the nanowells, while the second regime is characterized by growth of the surface film after the wells have been completely filled. The behavior of the film is studied using x-ray reflectivity (XR) and grazing incidence diffraction (GID).
Practical Application of Research
Though not all results from this paper fully explained by theory, the authors have shown that film thickness on a heterogeneous surface is controllable. Deposition of coatings will benefit from this work, and it is feasible that nanopatterning a surface before deposition can help give an extra bit of control over the liquid thin film.
Thin Film Thickness
With their patterned silicon/MCH system, the authors set out to validate theories on the dependence of liquid thin film thickness on chemical potential difference. From previous work in the Pershan lab and others, the thickness of a film on a flat surface with only van der Waals interactions, the authors expect a power-law of: <math>d \propto \Delta \mu^-\Beta</math>