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How a beetle is inspiring engineers to rethink aeroplane designs

If you think that conservation is just about observing animals, law enforcement or human/wildlife conflict, then think again. Researchers have been studying the diabolical ironclad beetle (Phloeodes diabolicus) whose shell is so tough it can be survive being run over by a car or stomped on by hikers in its native North American desert habitat.

This aptly named beetle can withstand compression of up to 150 newtons of force, which is 39,000 times their body weight – about 75% higher than comparable beetles can handle. The diabolical ironclad beetle has a shell which is incredibly crush resistant due to the architecture of its exoskeleton forewings (elytra). It has evolved without wings, therefore not being able to fly away from predators, so its incredibly strong ‘elytra’ enables it to survive attacks from birds and lizards.

Reporting in Nature, Rivera, et al. revealed the secret to the beetle’s incredibly tough structure. They used microscope images, 3-D printed models and computer simulations of the beetle’s armour to explore its ‘elytra’ and other body parts. Within the beetle’s tank-like physique, two key microscopic features help it to withstand crushing forces.

The first is a series of connections between the top and bottom halves of the exoskeleton, with ridges along the outer edges of the top and bottom that latch together. These ridge connections have different shapes across the beetle’s body. Those near the front and around its vital organs are highly interconnected, being stiff and resist bending under pressure. The connective ridges nearer its back are not as intricately interlocked, which allows the top and bottom halves of its exoskeleton to slightly slide past each other, giving flexibility which absorbs compression.

The second microscopic feature found was a rigid joint, or suture, that runs the length of the beetle’s back, connecting its right and left sides. A series of protrusions (called blades) fit together like a jigsaw puzzle, joining the two sides. These blades contain layers of tissue glued together by proteins and are highly damage resistant. So when the beetle is squashed, tiny cracks form in the protein glue between the blade layers and these small, healable fractures allow the blades to absorb impacts without completely snapping.

Rivera suggests that their “observations could be applied in developing tough, impact- and crush-resistant materials for joining dissimilar materials. We demonstrate this by creating interlocking sutures from biomimetic composites that show a considerable increase in toughness compared with a frequently used engineering joint.”

This opens up the possibility for engineers and architects to use beetle inspired designs that have superior mechanical properties – such as for far sturdier airplanes, bridges, buildings and vehicles. With the huge variety of insects we have on our planet who knows what else could inspire new designs for technology?

You can read more about the diabolic ironclad beetle and the resesarch techniques Rivera and his team used at nature.com and Berkeley Lab’s news centre.

Main photograph © David Kisalus (Science News 21 Oct 2020)