Correlation between Contact Line Pinning and Contact Angle Hysteresis on Heterogeneous Surfaces: A Review and Discussion

Micro- or nano-textured hydrophobic surfaces have attracted considerable interest due to their highly water-repellent property, and are called superhydrophobic. Although such superhydrophobic surfaces typically exhibit high contact angles for water droplets, their adhesion and frictional properties such as contact angle hysteresis are signifi cantly affected by the dynamics of contact line pinning at the droplet boundary. However, a clear correlation between the contact line pinning and the contact angle hysteresis has not been revealed yet. In this paper, we review the literature reporting on their correlation, both for chemically and physically patterned heterogeneous surfaces, including our recent discovery on superhydrophobic surfaces. Then, we propose and discuss an appropriate new physical parameter that shows close and consistent correlation between the dynamics of contact line pinning and the contact angle hysteresis.