Adhesion Characteristics of Polyurethane for Bionic Hairy Foot

Hairy adhesive pads are used by many animals and insects which can move on the ceilings and walls, such as gecko, spider, fly and some beetles. The effects of material properties and contact geometry were experimentally studied. The softest material has the highest adhesion and the surface roughness has hardly any effects on adhesion. The contact geometry and surface roughness influence adhesion heavily. The adhesion increases with the increase of normal force for a flat-to-flat contact, but does not get affected for a spherical sapphire ball to flat polyurethane contact. The adhesion is not affected by contact angles for soft connections, but heavily decreases for hard connections. The results are important data for bionic hairy foot design.