Biomimetic core-shell fibril for enhanced adhesion

Fibrillar adhesive structures in nature are usually terminated by compliant plate-like elements that are critically important. We have fabricated a simple, model, core-shell fibrillar structure by coating an aluminum wire with (poly)dimethylsiloxane (PDMS). By partially etching the core metal, we obtain a compliant annular terminus. Measurements of the force required for this structure to detach from and slide against a glass substrate show that sliding is accommodated by a stick-slip mechanism and that substantial enhancement of adhesion can be achieved. A simple theoretical model, which is in good agreement with experimental data, shows that during the sticking phase the contact reduces in size and the mechanics of this process is controlled by the balance of energy release from the stretched PDMS and adhesion between it and the substrate.