Akash Singh, Banaras Hindu University
Armour is integrated into the body of beetles (Order Coleoptera). They’re minuscule tanks with exoskeletons, powerful shells that protect their soft, skeleton-less bodies inside. In addition to providing protective protection, the beetle’s exoskeleton provides sensory feedback and hydration management. Exoskeletons of many beetles are also highly coloured and patterned, which aids in visual communication with other beetles and organisms. Ling Li, the primary investigator, and his team discovered a multifunctional microstructure in the exoskeleton of a beetle that serves as both a mechanical and an optical framework. The results of their research were published in the Proceedings of the National Academy of Sciences.
Their attention was focused on a single species: the flower beetle, Torynorrhina flammea. This little scarab beetle dwells in Southeast Asia’s jungles and is known for its beautiful hues, which range from deep blue through green, orange, and red. These vibrant shells are made up of two layers that work together to provide protection, communication, and hydration.
Structure-Function relationship:
When compared to other members of the species, adaptation allows for improved survival and reproduction. Continually thriving to stay alive, biological systems have an amazing potential to create multifunctional materials that are tailored to certain physiological and ecological requirements. In the long run of evolution, multifunctional genes, proteins, and structures are frequently altered to minimize the energy expenditure load. It can be difficult to investigate structure-function correlations in nature that are connected to multi-functionality.
How a beetle’s coloured armour works:
Li and his colleagues began their research by studying the composition of a beetle’s shell: the outer exocuticle layer includes a unique microstructure with a thickness of only 1/30 of a millimetre. It is made up of a stack of horizontal nanoscale layers inserted with vertical microscale pillars, which gives the exoskeleton visual colour while also providing mechanical strength. Unlike pigment-based colourations, the optical appearance of the flower beetle is determined by the microstructure of the exoskeleton. The nanolayered region is made up of two alternating material compositions that selectively reflect different colours of light. Structural colour, or photonic colour, is the name given to these phenomena.
Beetles’ exoskeletal shells must be sturdy and damage-resistant in addition to giving colour, according to Li. The flower beetle achieves this by reinforcing the vertical micropillars in its shell. When the microstructure is breached, the micropillars of the shell form a seal around the puncture site. The wing of the beetle is prevented from tearing, breaking, or delamination as a result of this.
The multi-functional exoskeleton of Beetle:
The extremely protective coloured exoskeleton of the flower beetle Torynorrhina flammea contains a multifunctional biological substance that is claimed to determine mechanical and optical qualities. Ling Li and his colleagues show that a micro-pillar-reinforced photonic multilayer in the beetle’s exoskeleton simultaneously improves mechanical resilience and optical appearance, resulting in optical damage tolerance, using a combination of experimental, computational, and theoretical approaches. When compared to plain multilayer structures, stronger vertical micro-pillars improve stiffness and elastic recovery, reduce shear band development, and improve delamination resistance. These micro-pillars also scatter reflected light at larger polar angles, improving the initial optical diffraction order and allowing the reflected colour to be seen from a wider variety of viewing angles. The optical damage tolerance is in turn improved by the synergistic effect of improved angular reflectivity and damage localization capacity.
In a nutshell, the microarchitecture of the beetle is designed to maximize first-order optical diffraction rather than mechanical rigidity. Their findings give light to material-level design strategies for obtaining multi-functionality in biological systems.
Prospects:
Understanding the structural foundation for multi-functionality, as well as functional synergies and trade-offs in biological materials, could help designers create bio-inspired multifunctional materials with greater efficiency. In this paper, we show how a coordinated experimental, theoretical, and computational approach reveals the structure–mechanics–optics relationship of the cuticle of the beetle, paving the way for future research into biological materials and the development of photonic materials with strong mechanical properties.
Also read: Recent insights into myotendinous junction formation
References:
- Jia, Z., Fernandes, M. C., Deng, Z., Yang, T., Zhang, Q., Lethbridge, A., Yin, J., Lee, J.-H., Han, L., Weaver, J. C., Bertoldi, K., Aizenberg, J., Kolle, M., Vukusic, P., & Li, L. (2021). Microstructural design for mechanical–optical multifunctionality in the exoskeleton of the flower beetle Torynorrhina flammea. Proceedings of the National Academy of Sciences, 118(25), e2101017118. https://doi.org/10.1073/pnas.2101017118
- Eder, M., Amini, S., & Fratzl, P. (2018). Biological composites—Complex structures for functional diversity. Science, 362(6414), 543–547. https://doi.org/10.1126/science.aat8297
About author:
Akash Singh is a first year masters student of Biochemistry at Banaras Hindu University. He plans to pursue a PhD in the future. He aims to pursue his career in research and teach the young minds of the country.
Social media links : LinkedIn : https://www.linkedin.com/in/akash-singh-82b5811a2/
Some of his publications at BioXone are:
3 thoughts on “Multifunctional microstructure found in Beetle’s exoskeleton”