Sliding induced adhesion of stiff polymer microfiber arrays: 2. Microscale behaviour

The adhesive pads of geckos provide control of normal adhesive force by controlling the applied shear force. This frictional adhesion effect is one of the key principles used for rapid detachment in animals running up vertical surfaces. We developed polypropylene microfiber arrays composed of vertical, 0.3 μm radius fibers with elastic modulus of 1 GPa which show this effect for the first time using a stiff polymer. In the absence of shear forces, these fibers show minimal normal adhesion. However, sliding parallel to the substrate with a spherical probe produces a frictional adhesion effect which is not seen in the flat control. A cantilever model for the fibers and the spherical probe indicates a strong dependence on the initial † To whom correspondence should be addressed. E-mail: [email protected]