A new robotic gripping device has been developed by scientists at North Carolina State University.
Robotic grippers are gentle enough to turn book pages. Image Credit: North Carolina State University
The newly developed device is gentle enough to pick up a drop of water, strong enough to pick up a 6.4 Kg (14.1 pounds) weight, dexterous enough to fold a cloth, and sufficiently accurate to pick up microfilms that are nearly 20 times thinner compared to a human hair.
Besides possible manufacturing applications, the scientists also combined the device with technology that enables the gripper to be regulated by the electrical signals that have been produced by muscles in the forearm, thereby illustrating its ability for use with robotic prosthetics.
It is difficult to develop a single, soft gripper that is capable of handling ultrasoft, ultrathin, and heavy objects, due to tradeoffs between strength, precision, and gentleness. Our design achieves an excellent balance of these characteristics.
Jie Yin, Study Corresponding Author and Associate Professor of Mechanical and Aerospace Engineering, North Carolina State University
The design for the new grippers relies on an earlier generation of adaptable, robotic grippers that drew on the art of kirigami. This involves both cutting and folding two-dimensional sheets of material to develop three-dimensional shapes.
“Our new grippers also use kirigami, but are substantially different, as we learned a great deal from the previous design. We’ve been able to improve the fundamental structure itself, as well as the trajectory of the grippers—meaning the path at which the grippers approach an object when grabbing it,” states Yaoye Hong, co-author of the paper and a recent Ph.D. graduate from NC State.
The new design has the potential to achieve high degrees of strength and gentleness due to how it distributes force across the gripper’s structure.
The strength of robotic grippers is generally measured in payload-to-weight ratio. Our grippers weigh 0.4 grams and can lift up to 6.4 kilograms. That’s a payload-to-weight ratio of about 16,000. That is 2.5 times higher than the previous record for payload-to-weight ratio, which was 6,400. Combined with its characteristics of gentleness and precision, the strength of the grippers suggests a wide variety of applications.
Jie Yin, Study Corresponding Author and Associate Professor, Mechanical and Aerospace Engineering, North Carolina State University
One more advantage of the new technology is that its appealing characteristics are driven mainly by its structural design instead of by the materials that are utilized to fabricate the grippers.
Hong stated, “In practical terms, this means that you could fabricate the grippers out of biodegradable materials, such as sturdy plant leaves. That could be particularly useful for applications where you would only want to use the grippers for a limited period of time, such as when handling food or biomedical materials. For example, we’ve demonstrated that the grippers can be used to handle sharp medical waste, such as needles.”
Also, the scientists combined the gripping device with a myoelectric prosthetic hand, thereby implying the prosthesis is regulated with the help of muscle activity.
This gripper provided enhanced function for tasks that are difficult to perform using existing prosthetic devices, such as zipping certain types of zippers, picking up a coin, and so on.
Helen Huang, Study Co-Author and Jackson Family Distinguished Professor, Joint Department of Biomedical Engineering, North Carolina State University
Huang added, “The new gripper can’t replace all of the functions of existing prosthetic hands, but it could be used to supplement those other functions. And one of the advantages of the kirigami grippers is that you would not need to replace or augment the existing motors used in robotic prosthetics. You could simply make use of the existing motor when utilizing the grippers.”
As far as proof-of-concept testing is concerned, the scientists illustrated that the kirigami grippers could be utilized collectively with the myoelectric prosthesis to pluck grapes off a vine and turn the pages of a book.
Yin stated, “We think the gripper design has potential applications in fields ranging from robotic prosthetics and food processing to pharmaceutical and electronics manufacturing. We are looking forward to working with industry partners to find ways to put the technology to use.”
The study was co-authored by Yao Zhao and Yanbin Li, postdoctoral researchers at NC State; Joseph Berman, a Ph.D. student at NC State; and Yinding Chi, a former Ph.D. student at NC State.
The study was financially supported by the National Science Foundation under grants 2005374 and 2221479.
Journal Reference
Hong, Y., et al. (2023) Angle-programmed tendril-like trajectories enable a multifunctional gripper with ultradelicacy, ultrastrength, and ultraprecision. Nature Communications. https://doi.org/10.1038/s41467-023-39741-6.