The "Pac-Man'' Gripper: Tactile Sensing and Grasping through Thin-Shell Buckling

Soft and lightweight grippers have greatly enhanced the performance of robotic manipulators in handling complex objects with varying shape, texture, and stiffness. However, the combination of universal grasping with passive sensing capabilities still presents challenges. To overcome this limitation, we introduce a fluidic soft gripper, named the ``Pac-Man'' gripper, based on the buckling of soft, thin hemispherical shells. Leveraging a single fluidic pressure input, the soft gripper can encapsulate slippery and delicate objects while passively providing information on this physical interaction. Guided by analytical, numerical, and experimental tools, we explore the novel grasping principle of this mechanics-based soft gripper. First, we characterize the buckling behavior of a free hemisphere as a function of its geometric parameters. Inspired by the free hemisphere's two-lobe mode shape ideal for grasping purposes, we demonstrate that the gripper can perform dexterous manipulation and gentle gripping of fragile objects in confined environments. Last, we prove the soft gripper's embedded capability of detecting contact, grasping, and release conditions during the interaction with an unknown object. This simple buckling-based soft gripper opens new avenues for the design of adaptive gripper morphologies with applications ranging from medical and agricultural robotics to space and underwater exploration.