Fig. 2: Programmable and controllable grasping trajectories of the gripper.
a The deploying trajectories at the end effector of petals in the grippers with different original intersecting angles γo. The color of the curves represents different γo. \({\bar{{{{{\kappa }}}}}}_{{{{{\max }}}}}\) denotes the normalized curvature of the trajectory curve at the maximum applied strain εmax. The inset shows the isometric view of the simulation results of the gripper with γo = 80°, with γ denoting the changing intersecting angle upon stretching. b, c Side-view (in the yz-plane) closure process of the grippers with γo = 150° and 80°. The deploying trajectories at the end effector of petals with an increasing applied strain ε. d The trajectory of the gripper with mimicking the cucumber tendril curve. The color bar represents the curvature \(\bar{{{{{\kappa }}}}}\) along the trajectory proportional to the applied strain ε. \({\bar{{{{{\kappa }}}}}}_{{{{{\max }}}}}\) and \({\bar{{{{{\kappa }}}}}}_{{{{{\min }}}}}\) are the maximum and minimum curvature along the trajectory. The inset shows a cucumber tendril. e The normalized curvature \({\bar{{{{{\kappa }}}}}}_{{{{{\max }}}}}\) of the trajectory curve at the maximum applied strain as a function of the variation (180°-γo) in the original intersecting angle. f The grasping/closing angle α as a function of the angle γo in different 2D precursors. The grasping angle α denotes the angle between the tangential direction at the end tip of the petal and the horizontal axis in the fully deployed state. Schematics show the side-view of different α demonstrated by grippers with γo = 80° and 150°. The error bars are the standard errors of the mean. Scale bars = 10 mm.
