Biomimicry — the practice of looking to nature for engineering solutions — may have a new source of inspiration. A flightless insect called the diabolical ironclad beetle (Phloeodes diabolicus) resists squashing, crushing and crunching like no other bug. Tests show it can withstand being run over by a car. Its durable exoskeleton, made of unique layers, joints and shapes, helps it survive much longer than other beetles, despite its inability to fly. Whereas most beetles live a few weeks, a diabolical ironclad’s life may span seven or eight years, according to Smithsonian Magazine.
Recent research published in the journal Nature used microscope images, 3D-printed models and computer simulations to investigate and partly explain the beetle’s armor. Its tough exterior could influence biomimicry applications, including indestructible composite materials for aircraft and buildings. Team member Pablo Zavattieri, professor of civil engineering at Purdue University, says the scientific analysis “shows that we may be able to shift from using strong, brittle materials to ones that can be both strong and tough by dissipating energy as they break. That’s what nature has enabled the diabolical ironclad beetle to do.”
Flat and Flightless
The inch-long beetle, which lives in the deserts of western North America, has developed several characteristics that make it invincible. For starters, its body is flat and low to the ground, as opposed to rounded, according to Science News.
It’s also flightless. That may seem like a disadvantage because the beetle can’t fly away from predators. But a part of the shell that other flying beetles use to protect their delicate wings — known as the elytra — has stayed with the ironclad beetle, even as it adapted to life on the ground. Now, it offers them a different kind of defense. The hard, armor-like structures fused together at the center of the beetle’s back at a line called a suture that runs the length of the insect’s abdomen. Using advanced imaging technology, including an electron microscope, the scientists viewed a cross-section of this suture. The unique joint resembled two interlocking puzzle pieces — one piece with a bulbous lobe and the other with a lobe-shaped dent.
In experiments, the scientists put this part of the shell into a tiny vise and then used an electron microscope to image the results when they put pressure on it. “Lo and behold, the interface at that suture, the jigsaw puzzle we’re talking about, did not fail,” University of California Irvine materials scientist David Kisailus told Wired.
The shell itself is also very strong, made of layers of fibrous material. When put under pressure, the material slightly fractures, spreading the force across the shell, which mitigates catastrophic failure. Compression tests revealed that the beetle could withstand around 39,000 times its own body weight.
The scientists didn’t stop at studying the unique strength of this beetle. They also explored how their observations could be applied to developing ultra-strong materials. In the Purdue University press release, team member David Restrepo, who worked on this project as a postdoctoral researcher in Zavattieri’s group and is now an assistant professor at the University of Texas at San Antonio, said that a big challenge in engineering involves joining different materials without reducing their ability to support loads. “The diabolical ironclad beetle has strategies to circumvent these limitations,” Restrepo said.
One example comes from turbines that power aircraft. There, metal and composite materials are connected with a fastener that not only adds weight but could cause stress that leads to fractures or corrosion.
Researchers at the University of California Irvine built a carbon fiber composite fastener inspired by the diabolical ironclad beetle’s puzzle-shaped suture. Through load testing, researchers found that this fastener was just as strong as a standard aerospace fastener but significantly tougher.
Kisailus told Wired that the diabolical ironclad beetle deserves more study. It’s still unclear what biological components, including proteins, make up the exoskeleton. “We don’t know what those proteins are,” says Kisailus. “Are they hyperelastic?” he says.
The answers could lead to indestructible aircraft that, unlike the beetle, can take to the skies to avoid enemies.