Figure 1: Dip-coating experiment and definitions of the contact angles.
From: A moving contact line as a rheometer for nanometric interfacial layers
In a dip-coating experiment, the meniscus is seen to contact the surface at a so-called apparent or macroscopic contact angle, which depends on the velocity of the contact line, θMacro(v). Due to the viscous bending of the liquid–vapour interface, this is not the same as the microscopic contact angle θmicro in the vicinity of the contact line (zoom). In addition, on a viscoelastic surface, the force exerted by the fluid produces a deformation of the layer immediately below the contact line. The dynamics θmicro(v) reflect the response of the cusp-shaped deformation when the contact line is moving.
