A Human Finger-Inspired Shape-Locking Pneumatic Gripper Enabled by Folding Laminar Jamming Structure

Bio-inspired soft grippers based on impactive gripping with the advantages of flexibility and universality have been widely used in take-and-place tasks. However, this type of gripper has the risk of breaking fragile objects with deformable surfaces due to the inevitable impactive force applied to the objects. Inspired by the grasping method of human fingers, this article presents a gripper containing two shape-locking fingers that can simultaneously control the span and grasping force to reduce the impact and grasp fragile objects safely. The shape-locking finger composes of three parts, including a soft pneumatic actuator, a folding laminar jamming structure, and a typical laminar jamming structure and the function of the three parts are driving, locking the shape, and improving the stiffness of the finger, respectively. In addition, combined with finite element analysis, we establish a theoretical model to predict the finger's bending angle and tip force, and the experimental results demonstrate the reliability of the model. Through a specific grasping process: pregrasp, shape-locking, and improving the grasping force, the controllable span and force (CSF) gripper can safely grasp deformable objects, such as a plastic cup with a 100-g weight, tofu, cake, mochi, and jelly, which shows that the CSF gripper has the potential for fragile foods tasks.