4D Printing of a Modular Tweezer-Like Gripper

Grippers are end-effectors attached to micromanipulators to perform pick-and-place tasks using their ‘fingers'. The fabrication process of conventional grippers is time-consuming, costly, and involves various materials. On the other hand, four-dimensional (4D) printing is an emerging technology that adds another dimensional aspect to structures that are fabricated using three-dimensional (3D) printing by inducing shape changes through exposure to external stimuli. These 4D-printed structures incorporate the advantages of 3D printing, such as low wastage, fast prototyping, quick production, and customizability. This paper presents a 4D-printed modular tweezer-like gripper fabricated with polylactic acid (PLA) using fused deposition modeling (FDM) printing technique. The modular gripper uses a housing to hold interchangeable actuators for different applications. The actuators of the gripper are designed to be 30 mm long, 5 mm wide, and 0.8 mm thick. These actuators consist of a bilayer structure combining two different levels of pre-induced strain that are controlled using different printing speeds. The deformation of the actuators is achieved through heating in water, which releases the pre-induced strain stored in the printed layers of the actuators. In addition, the relationship between the bending angle of actuators and the FDM printing speed is studied. The deformation performance of the actuators is analyzed using Kinovea software. The standalone actuator with active layers printed at 80 mm/s is found to have a higher bending angle of 87.56˚, while the maximum bending angle of the actuator with active layers printed at 20 mm/s is found to be 23.32˚. As a proof of concept, the gripper is used to grip and hold a clip with a mass of 2214.3 mg, which is around 2.94 times the mass of the gripper. The proposed gripper shows promising performance, making it suitable to be used as an end-effector for robotics applications.