Effect of an Insoluble Surfactant on the Moving Contact-Line of an Immersed Sessile Oil Drop

In this paper, the effect of an insoluble surfactant on the moving contact line of a sessile oil drop surrounded by another liquid is studied. The model involves parameters such as the density and viscosity of the fluids, the gravity, and the property of the surface which is characterized by so called the slip coefficient. The front-tracking method is used to solve numerically the free boundary motion of the interface. To maintain the conservation of mass during the numerical procedure, a weighted factor with a certain condition is introduced to calculate the update surfactant concentration, for each iteration. Results show that the surfactant affects the drop to accelerate its detachment from the solid substrate, and the slip coefficient turns out to be the crucial factor for the magnitude of the contact line movement.