Flexible adhesion control by modulating backing stiffness based on jamming of granular materials

Most hands, feet, and talons of most creatures grasp objects with friction. However, the exceptional climbing capability of geckos relies on the synergetic effect of adhesion and friction. A switchable high normal adhesion strength is still a challenge. In this study, a gripper with adhesion-control was designed based on the jamming of granular materials filled inside a hemispherical adhesive membrane to control the backing stiffness of the contact. When the gripper approaches an object, a soft contact with unjammed granular materials leads to an intimate contact between the gripper and object. In gripping, a hard backing stiffness of the contact was achieved with vacuum-induced jamming of granular materials to realize a strong adhesion. The switching between soft/hard contact states leads to the change of adhesion force of over 40 times. The developed adhesion gripper can easily pick up large size smooth planar or curved objects, which could not be realized with friction-based grippers. This adhesion based grasping capability modulation by switching between soft/hard contact states might be used in many industrial applications.