Dynamical wetting transition: liquid film deposition and air entrainment

Abstract

The speed at which a liquid can move over a substrate is strongly limited when the surface is partially dry. The wetting dynamics is then governed by the motion of the contact line, which has remained a challenging problem in fluid mechanics. Such moving contact lines play a key role for printing and imaging techniques. The technology of Immersion Lithography, for example, uses a portion of water between a lens and a substrate in order to increase the resolution. When the substrate is moving too fast, droplets are emitted at the receding part of the water. Similarly, air bubbles can be observed in the advancing part, suggesting entrainment of air at the advancing contact line. The transition from a steady interface to drop emission or air entrainment is called a dynamical wetting transition, and originates from the maximum speed at which contact lines can move across a surface. This thesis therefore addresses the fundamentals of “dynamical wetting transitions”.