Origami à la Earwig
An earwig's wing grows tenfold when it opens, and it is highly stable without the earwig having to exert muscular effort to stabilise it. The earwig does not require any effort to rapidly fold it closed either. Researchers at ETH Zürich and Purdue University have now discovered the secret to the earwig’s origami, and have created an artificial structure that functions according to the same principle.
Jakob Faber from Professor André Studart's group at ETH cooperated with Professor Andres Arrieta from Purdue University to analyse the wing’s structure and functional principle using a computer simulation of the wing. This simulation shows that if the wing were to function according to the traditional origami principle involving rigid, straight folds with an angular sum of 360 degrees at their intersections, the insect would be able to fold it to no less than one-third of its original size. In fact, it is essential for the earwig wing to possess elastic folds that can act as tension or torsion springs.
Faber and his colleagues also studied the earwig wing's central joint, which is responsible for stability in both the unfolded and folded states. Fold lines intersect here at angles that are incompatible with traditional origami. The researchers transferred their findings from the computer experiments to a multi-material printer, producing a 4D element comprising four hard plastic plates interconnected by soft, elastic plastic. The joint folds' spring functions were "programmed" into the material, allowing them to perform pulling or rotating movements as in the example from nature.
Space-saving solar sails
The element that the researchers produced is stable like the insect wing in its unfolded state, and folds together automatically when tapped lightly. The researchers have transferred this principle to larger elements, and have printed an origami gripper. It closes automatically, locks into place, and can hold objects without the gripper opening. The 3D printed origami elements are still prototypes. Applications for them could include folding electronics, for example. The space industry is also interested in providing satellites or space probes with solar sails that can be transported in confined spaces and then unfolded over a large area at the place of use. Self-locking origami structures based on the example of the earwig's wing would save space, weight and energy because they require neither a drive nor additional stabilisers. The researchers' work was published in the journal "Nature".