Wetting of fine wires and fibers by a liquid film

Abstract

When a fine wire or fiber is coated with a liquid film, the latter breaks up spontaneously into beads. Such unusual wetting behavior is a particular manifestation of the general phenomenon of liquid column instability first studied by Plateau and Rayleigh. In this work various physical factors that influence the instability and the subsequent beading are examined in detail. In the first part hydrodynamic equations are solved to obtain the rate of growth of disturbances and the wavelength of the most rapidly growing disturbance. These quantities are governed primarily by the viscosity of the liquid and the thickness of the liquid film as compared to the wire radius. In the second part the static equilibrium configuration of the beads attained at the completion of the dewetting process is derived. The bead shape is determined by the contact angle of the liquid on wire and the volume of liquid available per bead. It is shown that even when the contact angle is zero, not more than three quarters of the wire surface is covered by the liquid beads.