The wetting of liquids on rough surfaces has been explained in terms of a balance of the interfacial free energies of the three involved media (substrate, liquid, vapor) by Wenzel and Cassie andBaxter . Two wetting states have a minimum in the free
energy landscape :Wenzel wetting is characterized by a
complete contact of the liquid with all microscopic surface
features, while in Cassie-Baxter (CB) the wetting liquid
makes contact only with a small area fraction of protruding
roughness peaks, trapping an air film (plastron) between
the liquid and the substrate.