Experimental simulation of capillary effect on rough flat surfaces

Abstract The movement of the liquid column inside the slit was utilized to experimentally simulate the characteristics of the capillary force per unit length for different rough flat surfaces. The movement of the liquid column was achieved by continuously changing the slit interval. The maximum climb height and contact angle of the liquid column were observed during this process to study the relationship between capillary force and contact surface roughness. Based on the assumption that the microstructures on the rough surfaces are of the same form and continuously and uniformly distributed, it is shown that the capillary force per unit length under homogeneous wetting is independent of the roughness. For heterogeneous wetting, the capillary force per unit length is positively correlated with the roughness. The results also indicate that the appearance of “contact line pinning” is caused by insufficient capillary force along the direction of liquid column movement.