Natures wonders: beetle tough exoskeleton (Introduction)

by David Turell , Sunday, July 04, 2021, 22:15 (1025 days ago) @ David Turell

Just analyzed and has incredible design:

https://www.sciencedaily.com/releases/2021/06/210629134309.htm

:Beetles are creatures with built-in body armor. They are tiny tanks covered with hard shells, also known as exoskeletons, protecting their soft, skeleton-less bodies inside. In addition to providing armored protection, the beetle's exoskeleton offers functions like sensory feedback and hydration control. Notably, the exoskeletons of many beetles are also brilliantly colored and patterned, which enhances visual communication with other beetles and organisms.

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"Li and his team launched their research from knowledge of a beetle's shell composition: their outer exocuticle layer contains a unique microstructure with only 1/30 of a millimeter thickness. Its composition is a stack of horizontal nanoscale layers inserted with vertical microscale pillars, providing the exoskeleton with optical coloration and mechanical strength at the same time.

"Unlike pigment-based colorations, the optical appearance of the flower beetle results from the exoskeleton's microstructure. The nanolayered region consists of two alternating material compositions, which selectively reflect light of certain colors. This phenomenon is called structural color or photonic color.

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"The flower beetle achieves this through reinforcement of its shell's vertical micropillars. When the microstructure is pierced, the shell's micropillars hold a seal around the site of the puncture. This prohibits the beetle's wing from tearing, cracking, or delaminating. The micropillars are also able to spring backward, thus reducing the size of the damage site intruded by the incoming object after unloading.

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"They found that the presence of micropillars, while reducing some degree of optical reflection, is able to redistribute the reflected light to a greater angular range. This contributes to the beetle's ability to "send out" the optical signals to its potential receivers.

"At the same time, mechanically, the presence of micropillars increases the stiffness, strength, and mechanical robustness of the structure by preventing the formation of shear bands, improving the damage resistance of the outer layer, and localizing damage to the exoskeleton.

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"The final objective was to determine which property, optical or mechanical, is more optimized when evolution "designs" the microstructure. To answer this question, the team examined the microstructure of flower beetles from the same species group, but with different colors.

"Optical function won the day. They found that the size and distribution of the micropillars in beetles of differing colors were indeed optimized for achieving the most efficient light redistribution. The improvement of mechanical properties, particularly the stiffness, appeared not to be optimized, since the microstructure was not entirely covered with the stiffer and stronger micropillars. This result indicated that optical performance took priority over mechanical performance during the evolution of this peculiar multilayer, micropillar structure."

Comment: This study shows how strength and coloration can be simultaneously achieved through proper design