Dynamics of moving, three phase contact line

When a liquid or a gas displaces or is displaced by another liquid from a solid surface, a dynamic contact line develops. Flow patterns near moving contact lines are the chief concern on the deposition of ultra-thin Lagmuir-Blodgett films and on a wide range of phenomena from coating operations to the performance of packed bed columns.; The main hypothesis in this work is that the dynamics of contact lines strongly depends on short and long-range molecular forces of submicrometer range. However, the classical formulation of the moving contact line problem ignores the contribution of molecular forces to shear stresses at the interface. Therefore, a surface force caused by unbalanced intermolecular forces at the interface was introduced to the classical analysis through the use of the jump momentum balance. The asymptotic series expansion develop by Cox (Cox 1986a; Cox 1986b) was revisited by including the effect of molecular forces on shear stresses at the fluid-fluid interface and on the slip velocity at the solid-fluid interface.; There are three basic macroscopic flow patterns in the vicinity of a moving contact line. These flow patterns were confirmed experimentally in this and previous works (Savelsky et al. 1995). Measurements of the flow patterns and velocity vectors were obtained by a particle tracking velocimetry technique. This was accomplished by using a digital video system and a computer program developed during this research.; A good agreement between the experimental measurements and the theoretical computations was obtained. Finally, this work shows that an accurate model for the three-phase contact line dynamics requires the inclusion of molecular level forces. These forces determine the dynamic contact angle, flow patterns, and slip lengths at the contact line.