Dynamic contact angles and hydrodynamics near a moving contact line

The contact angle is an important boundary condition needed to predict the shape of menisci. However, its measurement and use under dynamic conditions are not well understood. We have measured the shape of menisci very close to moving contact lines over a suite of geometric shapes for the macroscopic menisci. The excellent agreement between theory and experiment establishes that the proposed boundary condition characterizes only the materials of the system. Implications for the microscopic physics controlling the dynamic contact angles are explored.