Adhesion instability of thin liquid films

We are interested in the dynamics of propagation of an adhesion front between two solid surfaces. A recent study has shown how putting in contact of two glass plates both covered with a viscous liquid film results into a fingering instability distinct from classical Saffman-Taylor viscous fingering. In this configuration, the instability mechanism involves a depletion of the viscous film ahead of the propagation front.

In numerous practical applications, only one surface is coated with an adhesive layer, which brings fundamental questions on contact line dynamics. Experiments on coated/non-coated configuration exhibit a front instability with different morphologies. Fingers are also observed, but in the transverse direction. These patterns rely on an original cascading nucleation mechanism.

In practice, most surfaces display roughness of finite amplitude. We finally present model experiments with grooved surfaces obtained by micro-machining. In the explored configuration, the rough surface is coated with a thick viscous layer while the facing one is smooth. Surprisingly fingers are also observed in a direction perpendicular to the grooves.