Re-derivation of Young’s Equation, Wenzel Equation, and Cassie-Baxter Equation Based on Energy Minimization

Abstract

Recently, Young’s equation, the Wenzel equation, and the Cassie-Baxter equation have been widely used with active research on superhydrophobic surfaces. However, experiments showed that the Wenzel equation and the Cassie-Baxter equation were not derived correctly. They should be reviewed on a firm physical ground. In this study, these equations are re-derived from a thermodynamic point of view by em‐ ploying energy minimization and variational approach. The derivations provide a deeper understanding of these equations and the behavior of a contact angle. Also, in applying these equations, the limitations and considerations are discussed. It is ex‐ pected that this study will provide a theoretical basis fo