The effects of velocity and viscosity on solid-liquid interfacial behavior during dynamic contact angle measurement

The effect of the relative solid-liquid velocity on the force measured in Wilhelmy plate experiments is described. Two cases are examined: (1) carbon fibers immersed in viscous fluids and (2) poly(hydroxyethylmethacrylate) immersed in water. In the first case, the velocity-dependent contribution of the shear stress exerted by the fluid on the fiber surface gives rise to a peculiar shape of the recorded force-distance curve. This contribution is modeled and discussed. In the second case, the relative solid-liquid speed has a great effect on the recorded force, which shows normal behavior at a low stage speed and a stick-jump motion as the speed is increased. These results are discussed by considering the dynamic nature of poly(hydroxyethylmethacrylate) surfaces.