On the ability of drops or bubbles to stick to non-horizontal surfaces of solids. Part 2. Small drops or bubbles having contact angles of arbitrary size

Abstract

The ability of small drops or bubbles to stick to non-horizontal solid surfaces is analysed. The principal results consist of identifying the critical value of the volume of a drop (or bubble) beyond which it will dislodge and move down (or up) the surface of the solid, and determining the speed at which it will move. In addition, the area of the solid wetted by the drop (or dried by the bubble) is calculated when its volume is at its critical value. All of the results are expressed in terms of experimentally measurable material properties. The most limiting restriction on the validity of the results is the assumption that the value of the contact angle hysteresis is small.