ABSTRACT
The angle formed at a stationary liquid front is termed the static contact angle. The angle formed at a moving liquid front is termed the dynamic contact angle. Static contact angles are determined by the equilibrium of interfacial energies. Dynamic contact angles are determined by the balance of interfacial driving force and viscous retarding force. There are two types of dynamic contact angles: those in spontaneous motion (where the liquid front moves spontaneously, driven by interfacial forces) and those in forced motion (where the motion is imposed externally).
