3D printing soft robots integrated with low-melting-point alloys

Soft robots are developed and applied in aspects such as grasping delicate objects. Their inherent flexibility also enables applications that are unattainable by humans, especially those in life-threatening environments. However, the object grasping performed by most pneumatic soft robotics during transportation requires continuous external power/force, a highly energy-consuming process, particularly for long-distance transportation. In this paper, we propose a low-melting-point alloy (LMPA)-integrated soft robot, manufactured by material extrusion additive manufacturing, requiring no power/force for holding objects during the moving process and thus presenting energy-saving characteristics. The working principles of the LMPA-integrated soft robot are as follows: (1) The LMPA is injected inside the soft robot using material extrusion. (2) The LMPA is heated to above its melting temperature so that the soft robot can change its shape. (3) At this stage, the soft robot is able to grasp an object. (4) While the soft robot is holding or grasping the object, the LMPA is cooled down to room temperature so that it turns into a solid state, and from this point onward, the soft robot can hold the object without relying on extra power for object grasping. (5) Once the soft robot arrives at the destination, the LMPA will be melted again to change the shape of the soft robot for releasing the grip and/or getting ready for another object grasping. In summary, this paper presents a case study of soft grippers, using 3D printing, specifically material extrusion, for fabricating an LMPA-integrated soft robot.