Gecko-inspired directional and controllable adhesion

The fabrication of bio-inspired microscale fibrillar adhesives that exhibit similar shear adhesive strength to gecko lizard feet on smooth surfaces, was reported. Angled based fiber arrays were molded with a 1mm thick backing layer using a thin spacer to define the thickness and ensure uniformity. A thin film of liquid ST-1060 polyurethane was spun onto a polystyrene substrate for 45 seconds at 4000rpm. The liquid polyurethane wetted the tips of the fibers, and the samples were manually separated from the liquid film. A custom adhesion characterization was used for the adhesion and shear experiments. A smooth 6mm diameter glass hemisphere was moved into contact with the fibers at 25μm. The insignification of any pressure differential effect was found by observation of tip contact during detachment. The fibers were observed only to develop cavities in the last few milliseconds before detachment after approximately 40 seconds of extension, meaning that the air cavities are not stable and do not affect the adhesion.