New 3D-printed soft robotic gripper functions without electronics

The device is printed all in one go and can pick and release objects

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Soft robotics has a lot of potential when it comes to creating robots that can interact with humans and delicate objects without causing any harm or damage to them.

However, manufacturing devices that are both soft and sturdy is challenging. Creating soft robots can be a complex and time-consuming process, as most of them are pneumatically actuated and fabricated by molding and assembling processes that typically require many manual operations and limit complexity. Furthermore, complex control components must be added to achieve even simple functions.

Now, a team of roboticists at the University of California San Diego, in collaboration with researchers at the BASF corporation, has developed a soft robotic gripper that is 3D printed in one print and also doesn’t need any electronics to work.

The 3D-printed robotic gripper is equipped with built-in gravity and touch sensors and can pick up, hold, and release objects. The gripper can be mounted on the end of a traditional robotic arm for industrial manufacturing applications, food production, and the handling of fruits and vegetables.

Most 3D-printed soft robots often have a certain degree of stiffness and tend to be leaky, preventing them from being used for many applications. Also, they need a fair amount of processing and assembly after printing in order to be usable.

Close up photograph of part of the new robotic gripper that functions without electronics.
Close up photograph of part of the new robotic gripper Credit: UC San Diego

But the team’s approach used a new 3D printing method, which involves the printer nozzle tracing a continuous path through the entire pattern of each layer printed. This avoided the introduction of any defects into the print and allowed for finer and more detailed structures to be created. The method also reduced the likelihood of leaks and defects in the printed piece, which are very common when printing with soft materials.

The new approach enables printing thin walls as thin as 0.5 millimeters. The thinner walls and complex, curved shapes allow for a higher range of deformation, resulting in a softer structure overall.

Additionally, the fabrication process required no manual operation, such as assembly or adjustment. This means the process and design are easily reproducible using a similar desktop 3D printer.

While the gripper doesn’t require any electricity to operate, it does have to be hooked up to a source of compressed air. It is integrated with channels and pneumatic valves that control a high-pressure flow of air that triggers the actuation. The series of valves would allow the gripper to both grip on contact and release at the right time.

When the touch sensor is activated by an object in the gripper’s jaws, compressed air is allowed to enter the internal channels to grasp the object securely. Rotating the hand in the right direction activates the gravity sensor, which releases the air pressure and causes the jaws to open.

“It’s the first time such a gripper can both grip and release. All you have to do is turn the gripper horizontally. This triggers a change in the airflow in the valves, making the two fingers of the gripper release,” said Yichen Zhai, the leading author of the paper in a statement.

This fluidic logic allows the robot to remember when it has grasped an object and is holding on to it. When it detects the weight of the object pushing to the side, as it is rotating horizontally, it releases the object.

The gripper could be a useful manipulation tool in various applications such as manufacturing and farming, research, and exploration tasks in the future.

Journal reference:

  1. Yichen Zhai, Albert De Boer, Jiayao Yan, Benjamin Shih, Martin Faber, Joshua Speros, Rohini Gupta, Michael T. Tolley. Desktop fabrication of monolithic soft robotic devices with embedded fluidic control circuits. Science Robotics, 2023; DOI: 10.1126/scirobotics.adg3792
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