wettabilityhysterese

Wettability hysteresis refers to the phenomenon where the contact angle of a liquid on a solid surface depends on the direction of movement of the three-phase contact line. This means that the angle at which a liquid-solid interface is formed when advancing across the surface is different from the angle measured when the liquid recedes. This difference in contact angle is not observed on perfectly smooth and chemically homogeneous surfaces.

The primary cause of wettability hysteresis is the heterogeneity of the solid surface at a microscopic level. This heterogeneity can arise from variations in surface chemistry, surface roughness, or the presence of adsorbed contaminants or defects. As the contact line advances, it encounters these imperfections in a specific order, leading to one contact angle. When receding, the contact line traverses the same imperfections but in the reverse order, resulting in a different contact angle.

Wettability hysteresis has significant implications in various fields. In fluid flow through porous media, it affects capillary pressure curves and fluid displacement efficiency, influencing phenomena like oil recovery and water infiltration. In microfluidics, it can impact droplet manipulation and flow control. Understanding and quantifying wettability hysteresis is crucial for accurately modeling and predicting interfacial phenomena in many scientific and engineering applications.