Model Description on the Interface Deformation after the Release of the Pinned Contact Line

Contact line can be easily stuck (pinned) on the defects or boundary of the different wettability regions.The contact line remains to be trapped until the contact angle increases beyond the advancing angle or decreases below the receding angle.Once such condition is satisfied, the contact line is released from the trapping site and rapidly proceeds or recedes with the contact angle changing toward the equilibrium contact angle.In this study theoretical description on the contact line motion and the contact angle after the release from the stuck condition at the groove edge is developed.The normal stress balance and the corresponding flow field adjacent to the surface are expressed under Stokes approximation.Since the interface deformation was limited within a certain distance from the solid surface, referred as 'boundary layer', the equation on the normal stress balance equation was solved with the boundary condition at the contact line and the outer boundary of the boundary layer.The results numerically obtained were compared with the experimental data, showing fairly good agreement between them.