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Oct. 21 (UPI) -- Like the boss at the end of a video game, California's diabolical ironclad beetle is seemingly indestructible. Getting run over by a car is no sweat for the resilient beetle. And the species' more common enemies, hungry birds, lizards and rodents, are regularly frustrated by the hardy beetle.
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According to a new study, published Wednesday in the journal Nature, the diabolical ironclad beetle's near-invincibility is thanks to the insect's touch exoskeleton and its remarkable ability to play dead.
Using high-resolution microscopic and spectroscopic imaging surveys, researchers were able to pinpoint the nanoscale characteristics that make its exoskeleton so sturdy.
"The ironclad is a terrestrial beetle, so it's not lightweight and fast but built more like a little tank," study co-author David Kisailus said in a news release.
"That's its adaptation: It can't fly away, so it just stays put and lets its specially designed armor take the abuse until the predator gives up," said Kisailus, a professor of materials science and engineering at the University of California, Irvine.
Lab tests showed the beetle can survive forces up to 39,000 times its body weight.
Imaging scans showed the beetle's exoskeleton yields much of its strength from the elytra. Among flying beetles, the elytra operate as forewing blades, a kind of sheath for a beetle's wings. The diabolical ironclad beetle's elytra have evolved into a super strong, stationary shield.
The beetle's elytra are composed of layers of a fibrous material called chitin and supported by a protein matrix. Compared to flying beetles, the ironclad's exoskeleton feature 10 percent more protein by weight, lending an extra level of durability.
When scientists looked at how the ironclad's two elytra are sutured together, they found the shields fit together like a jigsaw puzzle. When compressed, the components don't shatter, but instead experience delamination, or layered fracturing.
"When you break a puzzle piece, you expect it to separate at the neck, the thinnest part," Kisailus said. "But we don't see that sort of catastrophic split with this species of beetle. Instead, it delaminates, providing for a more graceful failure of the structure."
Closer examination revealed the presence of rodlike elements called microtrichia that researchers estimate work like friction pads, preventing layers from slipping when they experience delamination.
Using powerful X-ray imaging technology, researchers observed the behavior of the beetle's nanoscale exoskeleton features while getting crushed. The imagines revealed what scientists suspected -- the layers of the elytra and surrounding exoskeleton slowly delaminate, but avoid structural failure.
Researchers used a 3D printer to create a similar structural arrangement with synthetic materials. Models showed the design maximized the material's strength and durability.
Tests showed the beetle's structural genius -- and the 3D-printed material it inspired -- outperforms the traditional rivets and fasteners used for aircraft segments and reinforce stress points.
Scientists estimate their research will have a variety of applications in structural and material engineering.
"This study really bridges the fields of biology, physics, mechanics and materials science toward engineering applications, which you don't typically see in research," Kisailus said. "Luckily, this program, which is sponsored by the Air Force, really enables us to form these multidisciplinary teams that helped connect the dots to lead to this significant discovery."
