General equation of wettability: A tool to calculate the contact angle for a rough surface

- Use of classical thermodynamics to integrate three distinct wetting states for a given surface.
- Common expression for the free energy of any wetting state.
- Deduction of a general equation of wettability that applies to any wetting state of any surface topology.
- Statement of a simplified method to determine Cassie and Wenzel contact angles for five surface topologies.
- Derivation of a predictive tool to determine Cassie or Wenzel contact angles based on surface topology and chemistry.