Captive bubble method

Captive bubble method is a method for measuring contact angle between a liquid and a solid using drop shape analysis. In this method, a bubble of air is injected beneath a solid, the surface of which is located in the liquid, instead of placing a drop on the solid as in the case of the sessile drop technique.

The method is particularly suitable for solids with high surface free energy on which liquids spread out. Hydrogels, such as soft contact lenses for example, are likewise inaccessible for the standard arrangement; the captive bubble method is also used in such cases.