These Robotic Grippers Are Delicate Enough to Lift Egg Yolk

Delicacy and precision have long been barriers in robotics development, but lately, engineers have been making advancements in leaps and bounds and with a variety of approaches. Most recently, researchers from North Carolina State University have developed robotic grippers with a touch delicate enough to lift egg yolks without breaking them and precise enough to grip and lift a human hair. Drawing on the art of kirigami, the design has potential applications in both soft robotics and biomedical technologies.

Kirigami, a traditional paper-cutting art, informed the team’s strategy for 2D-to-3D shape morphing, using cut-guided deformation to produce novel material properties. In essence, kirigami uses cuts that divide the original material into discrete units without sacrificing global structural integrity. A thin sheet of patterned cuts can morph into a variety of 2D and pop-up 3D structures, imparting new properties to the material, including stretchability, multistability, and optical chirality, which have broad applications in mechanical metamaterials, stretchable devices, soft machines, and more.

In past studies, working backwards has proven difficult, but the approach used at NC State enables users to do just that. The shape of a 3D structure is in large part determined by the outer boundary of the material — for instance, a 2D object with a round boundary shape deforms into a sphere. Using this new process, users can determine the boundary shape and pattern of slits needed on the 2D material to create the desired final 3D shape.

The utility of the technique, which is a bit simpler than past developments and allows for a wide variety of customized structures, is demonstrated as the grippers grasp a raw egg yolk, a live fish, human hair, and more on video. While conventional grippers grab things by exerting pressure on them, these deform to surround an object and lift it, similar to how someone might cup their hands to lift a fragile object. The grippers are the first demonstration of the technique in action, but the researchers envision a host of possible applications, such as biomedical devices that can conform to the shape of a joint, bending and moving as a knee or elbow does. The team is now working toward exploring other possible applications and transitioning the research from the lab to practical use.