Eur. Phys. J. Special Topics 197, 163-178 (2011)
https://doi.org/10.1140/epjst/e2011-01453-8

Regular Article

Universality in the dependence of the drop contact angle on liquid-solid interactions and temperature obtained by the density functional theory

Department of Chemical and Biological Engineering, State University of New York at Buffalo, Buffalo, NY 14260, USA

^a e-mail: feaeliru@buffalo.edu

Received: 2 June 2011
Revised: 15 June 2011
Published online: 30 August 2011

Abstract

A nonlocal density functional theory is employed to calculate the contact angles of nano- and macrodrops on smooth solid surfaces in wide ranges of temperature and parameters of the Lennard-Jones potentials representing the fluid-fluid and fluid-solid interactions. For both types of drops, simple linear dependencies of the contact angle on the fluid-solid energy parameter ∊_fs was found for various temperatures and hard core fluid-solid parameters σ_fs. Expressions are suggested that relate the contact angle θ to the parameters of the interaction potentials and temperature. The most intriguing feature was that for each considered σ_fs there is a value ∊⁰_fs of ∊_fs for which the contact angle θ = θ₀ becomes independent of temperature and of σ_fs. It is shown that ∊_fs = ∊⁰_fs divides the materials for which θ increases from those for which θ decreases with increasing temperature.