Joule Heating of a 4D-Printed Multi-Material Origami Gripper

This paper presents the development of a four-dimensional (4D)-printed soft origami gripper. The gripper's design consists of flat plates that are connected together using hinges that allow folding the structure into a three-dimensional structure. These folding panels form a cage that can grip and enclose objects of different sizes and shapes. The folded structure is attached to holders for the 4D-printed actuator to allow its deformation to close the fingers of the gripper. Fused deposition modeling technique is used to fabricate the structure of the origami gripper and its actuator. The structure of the gripper is printed using a combination of polylactic acid (PLA), conductive PLA (CPLA), and thermoplastic polyurethane (TPU), while the actuator is completely printed using CPLA. The TPU gives elasticity and flexibility to allow adaptive motion and better grasping, while the CPLA gives rigidity to the structure and allows the actuator to be activated by a direct current (DC) power supply. Gripping is achieved by activating the actuator using a DC power supply with a power of 36 mW to generate Joule heating that increases the temperature of the actuator from room temperature to 85°C. Three different ratios of active-to-passive layers of the actuator were used, including 25%, 50%, and 75%. Maximum performance is achieved when the ratio is set to 50%, causing the actuator to bend by 58.90° and the gripping distance to reach 6.38 mm, which is 53.20% of the original distance before activation. The results show that the proposed gripper can perform gripping tasks while its fingers are at room temperature, demonstrating that it is suitable for handling temperature-sensitive objects in areas like soft robotic and surgical tools.