Secret to the diabolical ironclad beetle's strength may lead to highly durable materials, researchers say

It's a bird!

It's a plane!

No, it's the diabolical ironclad beetle: Phloeodes diabolicus. The U.S. Southwest desert bug cannot fly to escape threats but it can survive being run over by a car, thanks to its remarkably strong exoskeleton.

Engineers from the University of California at Irvine and Purdue University say they've determined how the beetle survives high pressure and that knowledge may lead to developing equally durable materials.

Their findings were published in Nature on Oct. 21, citing David Kisailus, UC-Irvine materials science & engineering professor, as principle investigator and corresponding author of the study.

"The ironclad is a terrestrial beetle, so it's not lightweight and fast but built more like a little tank," Kisailus said in an Oct. 22 University of California article. "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."

Rather than being a beetle of steel, the secret to the diabolical ironclad beetle's super-durability is two "elytra" that run along the length of its abdomen.

These “elytra” are designed with an interlocking puzzle piece connection, a geometry that softens impact, and microtrichia that provide a reliable interface. Together these designs make the beetle "extremely impact-resistant," the study said.

The study's engineers used advanced microscopy, spectroscopy and in situ mechanical testing to identify multiscale architectural designs within the beetle's exoskeleton.

"We highlight a series of interdigitated sutures, the ellipsoidal geometry and laminated microstructure of which provide mechanical interlocking and toughening at critical strains, while avoiding catastrophic failure," the study said. "These observations could be applied in developing tough, impact- and crush-resistant materials for joining dissimilar materials."

Researchers, lead by UC-Irvine graduate student Jesus Rivera, investigated the diabolical ironclad beetle's features to discover what contributes to the beetle's ability to not be crushed as easily. The researchers found the beetle's elytra locked together when pressure is applied, making the beetle far more difficult to crush.

Rivera, who worked in Kisailus' lab during the research, collected the beetles from the Inland Empire campus for the study. Researchers found the diabolical ironclad beetle can survive pressure approximately 40,000 times its body weight — and doesn't need to change in a phone booth to do it, according to the UC-Irvine article.

A 200-pound man attempting to equal that feat would have to endure 7.8 million pounds of pressure.

Rivera has since earned his Ph.D.

Another researcher in the study, University of California-Riverside undergraduate Drago Vasile, recreated the interlocking pieces of the diabolical ironclad beetle's elytron with carbon fiber-reinforced plastics. Once recreated, researchers put the plastic version through the same paces as the diabolical ironclad beetle.

"Sure enough, the scientists found that the beetle-inspired structure was both stronger and tougher than current engineering fasteners," the UC-Irvine article said.

The study was not only a work of engineering, Kisailus said.

"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 in the UC-Irvine article. "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."