Insect wing tougher than man-made substances

Dublin, Aug 23 (IANS) The seemingly fragile insect wings are much tougher than many man-made substances that combine the best of technology and the latest advances in science.

The finding may potentially inspire the design of more durable and lightweight artificial ‘venous’ wings for micro-air-vehicles. It might also heighten interest in the winged properties of extinct insect species.

“The desert locusts are the marathon flyers of the insect world,” says Jan-Henning Dirks, who studied the properties of their wings together with David Taylor, professor of mechanical and manufacturing engineering at Trinity College, Dublin.

“These grasshoppers can fly for days across deserts and oceans with wings 10 times thinner than a human hair,” says Taylor.

During these long journeys the wings of the grasshoppers have to withstand hundreds of thousands of wing beats without failure. What is their secret? The journal Public Library of Science ONE reports.

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Like all insect body parts, the wings are made from cuticle, which is the second-most common natural material in the world.

“We recently showed that the cuticle of the grasshopper legs is one of the toughest natural materials in the world,” says Taylor. “Now we wanted to know whether this is true for the locust wings, too.”

To measure the toughness of the wings, the team cut small notches into the wing’s membrane and measured the force needed to drive the crack through the wing, according to a Trinity statement.

“We were quite surprised when our first experiments showed that the membrane of the wings alone was not very tough.” said Dirks. “We were expecting the membrane to be at least as tough as the legs.”

However, when Dirks and Taylor looked at the videos they recorded, they found that most cracks were effectively stopped once they ran into a cross vein. These minute crack barriers increased the wing’s toughness by 50 percent. So if these veins are so good in stopping cracks, why not have more of them?

“Compared to the thin wing membrane, the wing veins are relatively heavy. Therefore, you want as few veins as possible to keep the weight of the wing low,” said Dirks.

However, as the videos demonstrate, with fewer veins in the wing, there is less protection against cracks. “It is like the watertight compartments in a ship. With too many compartments, the ship gets too heavy. With too few, a single hole can sink the entire ship,” explained Dirks.