On surface roughness effects in wetting phenomena

Abstract

A survey of the literature which builds on concepts put forth by Good in 1952 relating to surface roughness effects in wetting phenomena is performed. Good proposed a thermodynamic equation which could be used to derive the relationship between the various interfacial energies in a solid/fluid/fluid system and the angle of interception at the three-phase line of contact. This formulation allowed the derivation of Young's equation and its variations, such as Wenzel's equation, which accounts for surface roughness effects on the equilibrium contact angle. In the same work, Good also proposed the free energy barrier concept as a possible cause for contact angle hysteresis as the three-phase line of contact undergoes contortion between mechanically stable configurations. Mechanistic arguments were needed to account for hysteresis effects not predicted in the strictly thermodynamic approach. Subsequent works which extended the global thermodynamic or mechanistic perspectives were examined. Common critical underlying assumptions were inspected in both the thermodynamic and the mechanistic views, such as local enforcement of Young's equation.

Keywords:

• Roughness
• wetting
• hysteresis
• thermodynamics
• contact angle