This squishy ball, inspired by an equally cute kid’s toy, is a breakthrough in a new class of three-dimensional structures that can buckle reversibly. It starts out as an inflated sphere, and if you suck the air out of it, it buckles down along its dimples into a smaller ball 46 percent its original size. It looks sort of like a buckyball, so its creators at MIT nicknamed it a “buckliball.”
Structures that can predictably buckle have several useful applications. You could make a football stadium with an easily collapsible buckly dome, for instance. Or perhaps a soft robot with foldable joints or skin, or maybe small drug-delivering capsules that could morph and twist inside the body, or even synthetic molecules that can buckle just like viruses.
A team of engineers at MIT wanted to figure out the simplest 3-D structure that can do this, and they thought of the Hoberman Twist-O, a pretty fun little toy. It’s made of a network of struts connected by rotatable hinges and it can collapse in on itself. The MIT team wanted to make a shell that could do this. The resulting buckliball is made of soft rubber and has no moving parts, just 24 special dimples arranged in a specific pattern to induce optimal buckling. The dimple design inspired the new term “buckligami,” for the folding patterns required to make it buckle just so.
The buckliball and its design methods appear in this week’s issue of the Proceedings of the National Academy of Sciences.