Dynamic wetting behavior of a triple-phase contact line in several experimental systems

Dynamic wetting behavior was investigated experimentally. First, the movement of a liquid column in a capillary tube was observed. Using the measured dynamic contact angles dependent on the contact line velocity, the solution of the modified Lucas-Washburn equation predicts the time variance of the liquid height in the capillary efficiently. Second, the dynamic contact angles were measured for a two-dimensional meniscus and an axisymmetric droplet to detect the influence of contact line curvature. The measured angles coincide well with each other for a two-dimensional meniscus and droplets of various radii. The dynamic wetting behavior is independent of the triple-phase contact line curvature. The dynamic contact angles measured in this study distribute widely from 10° to 170°. The results cannot be arranged by a single function of contact line velocity proposed by Hoffmann. It is suggested that the roughness or impurities on the solid surface could play an important role on the dynamic wetting behavior.