The contact angle is a tangent angle between the interfaces formed when a phase contacts
tothe other immiscible phase. As the interfaces are equilibrated, the contact angle is called
to the equilibrated (or static) contact angle. The contact angle is applied to adhesive
materials, coating technology, polymer area, thin film technology, and surface treatment as
well as the interface science and technology.
As shown in Figure 1, when a liquid drop is settled on a solid surface, the contact angle of
the drop on the solid surface is defined by the mechanical equilibrium, of the drop under the
action of three interfacial tensions. The equilibrium relation is known as Young’sequation:
where qYis the Young contact angle, which is suited in the Young’s equation. The Young’s
equation represents that the contact angle measured in the field should be Young contact
angle if one used the Young equation or any other equation connect to the Young equation.