This article is from WeChat official account:Principle (ID: principle1687), author: Takeko, title figure from: vision China
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Ironclad beetle(common English name diabolical ironclad beetle, Latin scientific name Phloeodes diabolicus) lives in western North America, They often live under the bark of oaks and other trees and feed on fungi. Compared with many other beetles, this beetle has a flatter body, and its appearance seems to reveal an “uncrushable” temperament.
Is a beetle with certainty. | Image credit: David Kisailus / UCI
To some extent, the iron beetle can indeed be called a “miniature armored tank with six legs.” Because the biggest feature of this insect is that its exoskeleton is very hard, it can basically be regarded as a “jaw crusher” in nature. Many potential predators have no way of talking about them. Some animals may swallow the beetle whole, but for other predation methodsSuch as the pecking of birds or the biting of lizards, the structure of this exoskeleton is almost completely difficult to crack.
Entomologist Michael Caterino said that the iron beetle was “notorious” among entomologists for its extraordinary toughness. When making insect specimens, the shell of this beetle can also bend thin iron nails. They are not even afraid of cars, they can survive after being run over by cars.
This unique biological property not only attracts entomologists, it also arouses the curiosity of materials scientists and engineers. Through the analysis of microscopic images, three-dimensional printed models and computer simulations of the beetle’s exoskeleton, scientists have now discovered the secret of its exoskeleton strength. A new study published in Nature believes that the exoskeletons of beetles are connected by tightly interlocking impact-absorbing structures, which help them withstand huge squeezing forces. And these characteristics may inspire stronger new designs, such as the manufacture of body armor, buildings, bridges and vehicles.
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In this study, materials scientist David Kisailus and his team first performed compression experiments on the iron beetle. Researchers found that even though this beetle is only 2 cm long, it can withstand a compression force of up to 149 Newtons—this is about 15 kilograms of mass, which is about 39,000 times its own body weight. To put it vividly, this is equivalent to one person being able to carry about 40 M1 main battle tanks.
Subsequently, the team used high-resolution microscopy to explore the strength of the exoskeleton on a microscopic scale. They found that in the iron beetle’s own indestructible exoskeleton, there are two key microscopic features that help it resist squeezing forces.
Optical micrographs of cross-sections of the iron beetle at different scales. (E) and (f) show two key features. | Image source: Rivera,J. et al. / Nature (the picture is abbreviated, the original picture can be seen in the paper)
The first is a series of connections between the upper and lower parts of the exoskeleton. As you can imagine, the exoskeleton of this beetle is almost like two parts of a clam shell embedded together, with the jagged protrusions on the outer edges of the upper and lower parts interlocking with each other.
At the same time, in different areas of the entire body of the beetle, the interlocking methods of these protrusions are different, and there are three main types. For example, the front part of the beetle’s body has many important organs. The bulges around these organs are dense, showing a interlaced structure(blue in the picture below). This kind of connection is exceptionally hard and resists bending well under pressure.
On the other hand, the connecting bumps near the back of the beetle are not so dense, showing a lock structure (purple below) and independent The structure is (green), which allows a slight sliding space between the upper and lower halves of the exoskeleton. This flexibility also helps the beetle absorb the stress on the body.
On the entire body of the beetle, the connections of the upper and lower parts have different shapes. The figure shows the staggered structure (blue), the lock structure (purple) and the independent structure (green), and the corresponding body parts are marked with corresponding colors. | Picture source: Rivera, J. et al. / Nature (the picture is abbreviated, the original picture can be seen in the paper)
The second key feature is a rigid seam, also known as a seam(suture), it runs through the entire back of the beetle, connecting the left and right sides. Here are a series of bumps called pieces (blade), these pieces are put together like a puzzle, connecting the two sides together.
The photo of the back section of the iron beetle. It shows that the jagged part connects the left and right sides of its exoskeleton. These raised parts are tightly interlocking and can withstand tremendous pressure, providing a strong protection for the beetles. | Image credit: David Kisailus / UCI
These sheets contain tissue layers bonded together by proteins. This layered microstructure has high damage resistance. When the beetle is pressed, the protein glue between the tissue layers in each piece will form tiny cracks. These tiny, healable fractures can absorb impact without breaking the entire structure completely.
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In fact, in engineering applications, the joints between commonly used materials are often the weakest area, where tensile stress is concentrated, which may lead to unpredictable catastrophic damage, especially in engineering structures Connecting different materials in (such as plastic and metal) is still a big challenge. Although there are many reinforcement methods, they all have their own problems.
In the study, the team also used 3D printing to replicate these seams, and conducted high-stress tests in the laboratory. These tests show that the interlocking pieces will not suddenly break at the thinnest point to release the stress. On the contrary, the complex layered microstructure can gradually release the stress. The researchers also makeArtificial fasteners were designed and made with carbon fiber reinforced elements. In this way, parts made of different materials can be better integrated without rivets and other components.
Laminated fasteners with layered microstructures manufactured by researchers. | Picture source: Rivera, J. et al. / Nature (the picture is abbreviated, the original picture can be seen in the paper)
These results all prove the superior quality of this biologically inspired material. The research team hopes that these results can be used in the development of new materials that are tougher and more resistant to impact, and find stronger ways to connect different materials.
Reference source:
https://www.sciencenews.org/article/diabolical-ironclad-beetle-exoskeleton-armor-impossible-squish
https://www.nature.com/articles/s41586-020-2813-8
https://physicsworld.com/a/uncrushable-beetle-reveals-its-strengths-to-scientists/
https://www.nature.com/articles/d41586-020-02840-1
This article is from WeChat official account:principle (ID: principalia1687), author: Takeko