Tunable stiffness Kirigami gripper based on shape memory polymer and supercoiled polymer artificial muscle for multi-mode grasping

In this article, a tunable stiffness soft gripper based on Kirigami structure and shape memory polymer (SMP) is proposed. The Kirigami gripper uses SMP as variable stiffness element and employs Nichrome heating wires laid inside the gripper as heating element. Due to the segmented layout of the heating wires, the gripper possesses segmented stiffness modulation capability. As a result, programmable deformation trajectories are achieved, enabling multi-mode grasping functionality by adjusting its bending shape to accommodate different object contours. Using the thermally activated supercoiled polymer artificial muscle as the actuator, the gripper can achieve a silent and pumpless actuation and whole robotic system can be compact. The gripper mainly offers three different grasping modes—pinching, wrapping and hooking, to meet the requirements of complex tasks. Experimental results show that the Kirigami gripper can achieve a 13 times stiffness variation within 16 s, and each Kirigami gripper with different heating patterns exhibits different trajectories during the deformation process, capable of adapting and locking its shape to objects with different contours during grasping.