Entropy 2015, 17(7), 4684-4700; https://doi.org/10.3390/e17074684
Geometric Interpretation of Surface Tension Equilibrium in Superhydrophobic Systems
Department of Mechanical Engineering, University of Wisconsin-Milwaukee, 3200 N Cramer St, Milwaukee, WI 53211, USA
*
Author to whom correspondence should be addressed.
Academic Editor: George Ruppeiner
Received: 18 June 2015 / Revised: 24 June 2015 / Accepted: 30 June 2015 / Published: 6 July 2015
(This article belongs to the Special Issue Geometry in Thermodynamics)
Abstract
Surface tension and surface energy are closely related, although not identical concepts. Surface tension is a generalized force; unlike a conventional mechanical force, it is not applied to any particular body or point. Using this notion, we suggest a simple geometric interpretation of the Young, Wenzel, Cassie, Antonoff and Girifalco–Good equations for the equilibrium during wetting. This approach extends the traditional concept of Neumann’s triangle. Substances are presented as points, while tensions are vectors connecting the points, and the equations and inequalities of wetting equilibrium obtain simple geometric meaning with the surface roughness effect interpreted as stretching of corresponding vectors; surface heterogeneity is their linear combination, and contact angle hysteresis is rotation. We discuss energy dissipation mechanisms during wetting due to contact angle hysteresis, the superhydrophobicity and the possible entropic nature of the surface tension. View Full-TextKeywords:
surface tension; entropic force; superhydrophobicity; Neumann’s triangle; Antonoff’s rule; hysteresis
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).