Bionic torus as a self-adaptive soft grasper in robots

For the development of advanced robots, there is an increasing demand to design self-adaptive envelope graspers that can take objects of unknown shapes, sizes, and softness. Inspired by the predation strategy of sea anemones, we propose a soft actuator by filling liquid into a torus. When a pulling force is applied at the interior skin of the torus, its exterior skin will roll inward and suck the target. Similar to the predation behavior of sea anemones, the inward crimping of the skin is able to grip and hold objects with different shapes, weights, and materials. By adjusting the rolling direction and length of the torus skin, the object could be engulfed, swallowed, and released. The prototype of such a gripper is fabricated, which demonstrates the versatility of application in various environments. This work provides an alternative route for designing self-adaptive graspers.