"Snap Instabilities," Which Make Popper Toys Pop, Could Let Future Robots Propel Themselves

Researchers at the University of Massachusetts at Amherst and Delft University of Technology, in partnership with the US Army, have published a paper detailing a way of giving materials the ability to propel themselves using only environmental energy flow — something the military is looking into for future robotics applications.

"Many plants and animals, especially small ones, use special parts that act like springs and latches to help them move really fast, much faster than animals with muscles alone," explains paper co-author Dr. Al Crosby, a professor of polymer science and engineering in the College of Natural Sciences at UMass Amherst. "Plants like the Venus flytrap are good examples of this kind of movement, as are grasshoppers and trap-jaw ants in the animal world."

The source of inspiration for the team's work: An experiment in watching a gel strip dry, which would have traditionally been a somewhat dull event — except for the observation that as the elastic strip lost moisture it moved, sometimes rapidly so as the result of "snap instabilities."

Snap instabilities themselves are nothing new: They've been used in everything from robotics to children's toys wherever sudden, rapid motion is required. Where the breakthrough comes is in discovering a way of creating a strip of material which would move repeatedly without being reset by motors or a user's hand. "With this discovery," Crosby notes, "there could be various applications that won't require batteries or motors to fuel movement."

"This work is part of a larger multi-disciplinary effort that seeks to understand biological and engineered impulsive systems that will lay the foundations for scalable methods for generating forces for mechanical action and energy storing structures and materials," says Dr. Ralph Anthenien, branch chief of the Army Research Office, regarding the work his office funded. "The work will have myriad possible future applications in actuation and motive systems for the Army and DOD."

The team's work has been published in the journal Nature Materials under closed-access terms.