Roles of discontinuities in bio-inspired adhesive pads.

Morphological intricacies of the biological attachment pads generate considerable interest owing to their remarkable ability to control adhesion to various surfaces. Motivated by the adhesive microstructures of insects, we examine the behaviour of adhesion and crack propagation in patterned adhesive films. These films are made of silicone elastomers that were patterned with lateral, longitudinal or crosswise incisions from which a thin silanized glass plate was removed in a displacement-controlled peel experiment. The behaviours of crack propagation on these patterned adhesive films are controlled by simple incision patterns, their depths and spacing. With the crosswise incisions, significant enhancement (x10-20) of fracture energy has been achieved. These findings point towards an important mechanism by which of biological organisms might enhance adhesion, and provide a simple design principle for manipulating the interfacial fracture in a variety of artificial attachment devices.