Dewetting

In fluid mechanics, dewetting is one of the processes that can occur at a solid–liquid or liquid–liquid interface. Generally, dewetting describes the rupture of a thin liquid film on the substrate (either a liquid itself, or a solid) and the formation of droplets. The opposite process—spreading of a liquid on a substrate—is called wetting. The factor determining the spontaneous spreading and dewetting for a drop of oil placed on a liquid substrate (water here) with ambient gas, is the so-called spreading coefficient :

where is the gas-water surface tension, is the gas-oil surface tension and is the oil water surface tension (measured on the fluids before they are brought in contact with each other)

When , the spontaneous spreading occurs, and if , dewetting occurs.

Spreading and dewetting are important processes for many applications, including adhesion, lubrication, painting, printing, and protective coating. For most applications, dewetting is an unwanted process, because it destroys the applied thin film.