Soft and Strong, Powerless All Along

Robots employ a diverse array of gripper types to interact with objects in their environment with precision and versatility. Among the many types available, mechanical grippers stand as the most common and widely used. With their jaws or fingers, they grasp objects effectively, enabling simple pick-and-place operations or intricate manipulation tasks. Vacuum grippers, on the other hand, rely on suction to securely handle smooth and flat-surfaced objects, such as glass or electronic components, while minimizing physical contact to prevent damage. Magnetic grippers utilize electromagnetic forces to firmly hold ferromagnetic objects, proving particularly useful in challenging or hazardous environments.

And the list goes on and on, with a customized solution available for just about any use case. But when it comes to soft robotics in particular, the selection of grippers can be a bit limited. Manufacturing devices that are soft, and yet sturdy, is challenging enough. But to also add actuation and sensing systems without introducing any rigid components is harder still. And if the application requires that the gripper use no electronics at all, well, then good luck finding anything that is suitable.

Yet this is exactly what a team of roboticists at the University of California San Diego and the BASF corporation have recently achieved. They have developed a soft, 3D-printed robotic gripper that can pick up, hold, and release objects. It is also equipped with gravity and touch sensors. And absolutely no electronics are required to operate it.

A specialized fused filament fabrication 3D printing approach was developed to enable this technological advancement. In general, limitations in this printing method result in objects that have a high degree of stiffness, and they also tend to be leaky, which prevents them from being used for many applications. But the team’s approach involved drawing a continuous path during the creation of each layer. This avoided the introduction of any defects into the print. It also allowed for finer and more detailed structures to be created, which means that these prints can be an order of magnitude softer than normal prints.

The defect-free printing allowed for the integration of channels and pneumatic valves that control a high-pressure flow of air that triggers the actuation. When the touch sensor is activated by an object within the jaws of the gripper, compressed air is allowed into the internal channels to securely grasp the object. Rotating the hand in the correct manner triggers the gravity sensor, which in turn releases the air pressure and causes the jaws to open up.

The fabrication procedures can be utilized in producing other types of structures and grippers for soft robots as well. The researchers envision such devices being utilized in industrial, research, and exploration tasks in the future. The softness of the system could also have use in specialized applications where delicate handling is required, as is the case with food production and the handling of fruits and vegetables, for example. And since the fabrication procedures can be carried out on desktop 3D printing setups, this technology could be widely used for any number of applications.