Robotic Soft Grippers
Engineers from North Carolina State University have developed robotic grippers based on the Japanese art of folding paper called Kirigami. The grippers were able to lift egg yolks and human hair. The work has wide applications, specifically in soft robotics and biomedical technologies, after valid testing in product testing labs.
Kirigami is the Japanese art of folding paper. In kirigami, the paper is cut as well as being folded, resulting in a three-dimensional design that stands away from the page. Kirigami offers a promising strategy for 2D-to-3D shape morphing through cut-guided deformation. However, existing kirigami for 3D curved shapes rely on intricate cut patterns in thin sheets, making the inverse design challenging. Instead of programming the cut patterns, the researchers programmed the curvature of cut boundaries for the target 3D curved morphologies through both forward and inverse designs. The strategy largely simplifies the inverse design and outcomes can be evaluated in product testing labs.
“We have defined and demonstrated a model that allows users to work backwards,” says Yaoye Hong, first author of a paper on the work and a Ph.D. student at NC State. “If users know what sort of curved, 3D structure they need, they can use our approach to determine the boundary shape and pattern of slits they need to use in the 2D material. And additional control of the final structure is made possible by controlling the direction in which the material is pushed or pulled”. All the properties of a new product can be determined in a product testing lab.
“Our technique is quite a bit simpler than previous techniques for converting 2D materials into curved 3D structures, and it allows designers to create a wide variety of customized structures from 2D materials,” says Jie Yin, corresponding author of the paper and an associate professor of mechanical and aerospace engineering at NC State.
To demonstrate the utility of their technique, researchers created grippers capable of grabbing and lifting objects ranging from egg yolks to a human hair. “We’ve shown that our technique can be used to create tools capable of grasping and moving even extremely fragile objects,” Yin says. “Conventional grippers grasp an object firmly — they grab things by putting pressure on them,” Yin says. “That can pose problems when attempting to grip fragile objects, such as egg yolks. But our grippers essentially surround an object and then lift it — similar to the way we cup our hands around an object. This allows us to ‘grip’ and move even delicate objects, without sacrificing precision.” This precision working can be evaluated in product testing labs.
According to the researchers, there are a host of other potential applications, for instance, we can design bionic parts such as a human knee. “Think of smart bandages or monitoring devices capable of bending and moving with your knee or elbow,” Yin says. “This is proof-of-concept work that shows our technique works,” Yin says. “We’re now in the process of integrating this technique into soft robotics technologies to address industrial challenges, after testing them in suitable product testing labs. We are also exploring how this technique could be used to create devices that could be used to apply warmth to the human knee, which would have therapeutic applications.
“We’re open to working with industry partners to explore additional applications and to find ways to move this approach from the lab into practical use.”
Video of the technology can be found at
Yaoye Hong, Yinding Chi, Shuang Wu, Yanbin Li, Yong Zhu, Jie Yin. Boundary curvature guided programmable shape-morphing kirigami sheets. Nature Communications, 2022; 13 (1) DOI: 10.1038/s41467-022-28187-x