Morphology and adhesive characteristics of Cybister(male) fore-foot adhesive pads

The morphology，adhesive mechanism and adhesive characteristics on two different surfaces of Cybister (male) fore-foot‘s adhesive pads were studied. The SEM photos show that the adhesive padst ructure consists of three adhesive devices and many setae at the marginal side. Each adhesive device contains about 15 micro-adhesive discs like an insole，which form an array in parallel. Two adhesive mechanisms are vacuum adhesive force by the adhesive discs and the Van der Waals force by the setae. The normal and tangential adhesive forces of the adhesive pads were tested respectively on the elytra surface and the glass surface. The maximal normal force is 53.3 mN and the maximal tangential force is 213.5 mN. The results indicate that the tangential adhesive forces are 6～8 times larger than the normal ones on two different surfaces (dry or wet)，and the tangential adhesive forces on the wet surface are larger than those on the dry surface，while the results of the normal forces are contrary. The conclusions approve that the normal adhesive forces basically are equivalent to the Van der Waals forces and the tangential adhesive forces come into being because of the two adhesive mechanisms’ work. These works offer the theoretic references for designing the bionic robot‘s pads.