Roughening Transition in a Moving Contact Line

TL;DR

This paper models the deformation dynamics of moving contact lines on disordered surfaces, unifying coating and pinning transitions as roughening phenomena, and proposes a phase diagram with implications for experimental observations.

Contribution

It introduces a unified theoretical framework for contact line transitions, incorporating both local and hydrodynamic dissipation mechanisms, and predicts a phase diagram with a junction point.

Findings

Coating and pinning transitions are unified as roughening transitions.

A phase diagram with a junction point for phase boundaries is proposed.

Recalling contact lines can leave a Landau–Levich film immediately after depinning.

Abstract

The dynamics of the deformations of a moving contact line on a disordered substrate is formulated, taking into account both local and hydrodynamic dissipation mechanisms. It is shown that both the coating transition in contact lines receding at relatively high velocities, and the pinning transition for slowly moving contact lines, can be understood in a unified framework as roughening transitions in the contact line. We propose a phase diagram for the system in which the phase boundaries corresponding to the coating transition and the pinning transition meet at a junction point, and suggest that for sufficiently strong disorder a receding contact line will leave a Landau--Levich film immediately after depinning. This effect may be relevant to a recent experimental observation in a liquid Helium contact line on a Cesium substrate [C. Guthmann, R. Gombrowicz, V. Repain, and E. Rolley, Phys. Rev. Lett. {\bf 80}, 2865 (1998)].