Tensiometric studies on wetting. II. Some effects of surface roughness (experimental)

The wetting of regularly rough solid bodies was investigated by means of capillarography. In this technique solid probes are immersed and withdrawn from liquid-fluid interfaces with steady velocities. Continuous observation of the three phase contact line (TPL) motion and recording of the capillary force are possible simultaneously. The effect of regular axisymmetric grooves on cylindrical rods on wetting hysteresis was found to follow theoretical predictions closely at large roughness dimensions (∼86 µm) in which case the TPL makes jumps from one equilibrium position to another while advancing. At lower rugosities (∼1 µm) the effect of regular roughness for a given concentric groove geometry is complicated by effects attributed to the dominant influence of chemical heterogeneity of the solid surface.