A new artificial structure that may have applications in foldable electronics, space travel and more takes its inspiration from the ingenious, origami-like design of the wing of an earwig.
Researchers at ETH Zürich and Purdue University have been studying the unusual insect, which has wings that can be retracted to a compact size that allows the creature to tunnel underground. When open, those same wings become 1,000 percent larger — representing one of the highest folding ratios in the animal kingdom. Making use of those wings also does not require much energy on the earwig’s part: In their open, locked state they remain stiff without needing muscle power to provide stability. And with a single “click,” the wings fold easily into themselves.
A computer simulation run by the researchers showed that the wing design goes beyond the classical principle of origami, which relies on rigid, straight folds with intersections that add up to a 360-degree angular sum. In the earwig, the wing joints are made from layers of a special elastic biopolymer, resilin, the arrangement and thickness of which determines whether the joint will operate as an extensional or rotational spring. In some instances, both extensional and rotational functions are combined in the same joint. There is also a central mid-wing joint that is responsible for stability in both the open and closed states.
The researchers transferred their simulation findings to a multi-material 3D printer. This allowed them to manufacture a 4D object comprising four stiff plastic plates connected to one another by a soft elastic joint. The spring functions of the connecting folds were programmed into the material to enable them to perform extensional or rotational movements, mimicking the biological model.
The same principle was also transferred to larger elements, which allowed the team to create a spring origami gripper. Much like the earwig wing, the structure self-folds and locks. It is then able to grip objects without the need for external actuation.
The self-folding origami elements are currently in the prototype stage. But they could find numerous applications in the future such as solar sails for satellites or space probes which would be transported within a very small space, then — unfolded to their full size at their destination. More mundane uses are also possible — foldable tents, maps, package inserts and so on. Unlike most of their current analogues, however, these could automatically fold back into their original shape.
The research appears in a recent issue of the journal Science.
