Fingering instability in adhesion fronts

The adhesion of two surfaces relies on the propagation an front. What is dynamics front when both are coated with a thin layer viscous liquid? Standard criteria from fingering instabilities would predict stable since fluid pushes away air low viscosity. Surprisingly, may be unstable and generally leads to growing fingers. We demonstrate model experiments where adhering slightly tilted by angle $\alpha$ that origin this interfacial instability feeding surrounding film. show experimentally typical wavelength mainly dictated thickness oil layers $h$ . In wedge geometry, found follow $t^{1/2}$ dependence saturate for extension length order $h/\alpha$