Fingering instabilities in adhesive failure

We study the fingering instabilities that occur in the debonding of model adhesives. We perform a linear analysis of the instability in the lifting Hele-Shaw cell, relevant for the failure of soft adhesives. The analysis is done for a Newtonian fluid but can be extended to shear-thinning fluids without any problem. When compared to experiment, significant differences are found between the linear theory and the experimental results. We therefore, discuss three-dimensional effects, that are found to improve the agreement; nevertheless significant differences between theory and experiment persist.