In an effort to turn such insights into engineered structures, Reis's lab is competing for one of the ODISSEI grants in partnership with Bertoldi and several others. One of their goals is to compile a lexicon of shapes: polyhedra that will buckle, bend, stretch, collapse and expand in predictable ways in response to specific stimuli. The shapes are based on spherical shells with holes cut in them. But surrounding the holes are ligaments designed to contain weak spots that buckle when stressed. In principle, these buckling polyhedra could be made in a range of sizes, whether it's a nanometer-scale sphere designed for drug delivery or a retractable roof for an athletics stadium. The team calls the resulting structures 'buckliballs' — the subject of Bertoldi's presentation at this year's APS meeting.
Buckliballs, with their geometric design and near-magical behavior, encapsulate the cleverness and beauty for which extreme-mechanics researchers yearn. Looking ahead, the more theoretically minded foresee a new set of general rules that could describe the behavior of any flexible solid as it crumples. Meanwhile, those with an engineering bent imagine robots with appendages that can transform into tools or squeeze, octopus-like, through tiny spaces; backpacks that expand into tents; and mobile phones that users can roll up and stick behind their ears like a pencil. They see a whole realm of devices that transmute failure into function. That could all be years in the making — but Bertoldi and her rapt audience already see far more in this field than engineers' toys.