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Roughness-induced wetting Roland R. Netz* and David Andelman
 

Summary: Roughness-induced wetting
Roland R. Netz* and David Andelman
School of Physics and Astronomy, Raymond and Beverly Sackler Faculty of Exact Sciences,
Tel Aviv University, Ramat Aviv 69978, Tel Aviv, Israel
Received 8 February 1996; revised manuscript received 29 July 1996
We investigate theoretically the possibility of a wetting transition induced by geometric roughness of a solid
substrate for the case where the flat substrate does not show a wetting layer. Our approach makes use of a
closed-form expression that relates the interaction between two sinusoidally modulated interfaces to the inter-
action between two flat interfaces. Within the harmonic approximation, we find that roughness-induced wetting
is indeed possible if the substrate roughness, quantified by the substrate surface area, exceeds a certain
threshold. In addition, the molecular interactions between the substrate and the wetting substance have to
satisfy several conditions. These results are expressed in terms of a lower bound on the wetting potential for a
flat substrate in order for roughness-induced wetting to occur. This lower bound has the following properties.
A minimum is present at zero or very small separation between the two interfaces, as characteristic for the
nonwetting situation in the flat case. Most importantly, the wetting potential needs to have a pronounced
maximum at a separation comparable to the amplitude of the substrate roughness. These findings are in
agreement with the experimental observation of roughness-induced surface premelting at a glass-ice interface
as well as the calculation of the dispersion interaction for the corresponding glass-water-ice system.
S1063-651X 97 07101-8
PACS number s : 68.45.Gd, 68.15. e, 68.35. p

  

Source: Andelman, David - School of Physics and Astronomy, Tel Aviv University

 

Collections: Materials Science; Physics