Static (Equilibrium) Contact Angle, θ_e

(find instruments that measure contact angle here)

Definition:

The contact angle measured of a Sessile drop / Captive bubble on a solid substrate when the three phase line is not moving.

Summary/Description:

Static contact angle is the contact angle when all participating phases i.e gas (or liquid), liquid, solid, have reached their natural equilibrium positions and the three phase line is not moving anymore. The Static Contact Angle can be measured in a sessile drop or captive bubble configuration. In the sessile drop case a liquid droplet is placed on a solid sample and the contact angle is then determined. In the captive bubble method the solid sample is completely immersed in a liquid and an air bubble is brought in contact with the solid sample from below.