The mechanisms of detachment of mushroom-shaped micro-pillars: from defect propagation to membrane peeling

The detachment mechanisms of adhesive micro-structured surfaces based on mushroom-shaped micro-pillars are analyzed. The detachment of a single mushroom shaped pillar takes place as a consequence of destabilization of an interfacial void whose size increases following a crack-like propagation process. When the radius of the crack exceeds the pillar radius, the detachment process enters the so-called plate regime governed by bending effect in the plate. This regime is strongly unstable and characterized by strong reduction of adhesion strength. As the crack moves further, membrane stresses in the plate become dominant and the detachment process enters the so called membrane regime, which resembles the peeling of an axisymmetric membrane. During this process the peeling line linearly increases with the radius of the crack, thus leading to an almost proportional increase of the strength of adhesion