Inflatable grippers

The coupling between elasticity and geometry in pressurized structures can lead to unexpected deformations. Elastic curved tubes made of two flat quasi-inextensible thin sheets sealed together respond in such a way that their reference curvature is amplified when they are inflated. Here we focus on V-shaped tubes with sharp corners that deform so the initial angle between the arms decreases upon inflation, acting as a hinge-like mechanism. We first characterize the kinematic and the mechanical response of an individual hinge through a combination of experiments and finite element modelling. This observation serves as a starting point for exploring several mechanism designs. We propose a star-shaped tube made of successive V-shaped tubes forming a closed loop as a mechanical actuator. Upon inflation, the structure contracts radially and provides a soft grasping solution with tunable grabbing force. Building on the mechanical description of individual hinges, we address the inverse problem and optimize the geometry of the closed loop and operational conditions to obtain a target grabbing force for the gripper.