Dewetting

Article summary

In fluid mechanics, dewetting is one of the processes that can occur at a solid–liquid, solid–solid, or liquid–liquid interface. Generally, dewetting describes the process of retraction of a fluid from a non-wettable surface it was forced to cover. 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 liquid placed on a solid substrate with ambient gas, is the so-called spreading coefficient : , due to Laplace pressure : S\ = \gamma_\text{SG} - \gamma_\text{SL} - \gamma_\text{LG} where is the solid-gas surface tension, is the solid-liquid surface tension and is the liquid-gas surface tension (measured for the mediums before they are brought in contact with each other). When , the spontaneous spreading occurs, and if , partial wetting is observed, meaning the liquid will only cover the substrate to some extent. The equilibrium contact angle \theta_\text{c} is determined from the Young–Laplace equation. 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 liquid film.…

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