The Gecko's Toe: Scaling Directional Adhesives for Climbing Applications

In this paper, a bioinspired mechanism is presented that allows large patches of directional dry adhesives to attain levels of adhesion previously seen only for small samples in precisely aligned tests. The mechanism uses a rigid tile supported by a compliant material and loaded by an inextensible tendon, and is inspired by the tendon system and the fluid-filled sinus in gecko toes. This mechanism permits the adhesive to make full contact with the surface and have uniform loading despite significant errors in alignment. The single-tile mechanism is demonstrated on the StickybotIII robot and the RiSE climbing robot (gross weight 4 kg). A tiled array of these mechanisms is also presented, with a total adhesive area of 100 cm(2). This uses a pressurized sac to equalize adhesive forces among the tiles, and exhibits a comparable adhesive pressure and range of loading angles to those of single tiles. These results suggest that the tiled array can be scaled to larger areas and loads.