Assisted dynamic wetting in liquid coatings

During forced wetting above a critical speed, visible amounts of air are entrained between a liquid and a moving solid, regardless of the wettability of the surface. The present article reviews how hydrodynamic and electrostatic forces, as well as the colloidal particle motion and the surface roughness, delay the onset of air entrainment to higher surface speeds. The onset velocities of air entrainment are compared with that in a filler-free, plunging tape flow on a smooth, uncharged surface in order to access how the dynamic wetting is assisted on a macroscopic length scale. The combined effect between different wetting assistances is also discussed.