Microstructural design for mechanical-optical multifunctionality in the exoskeleton of the flower beetle Torynorrhina flammea
Microstructural design for mechanical-optical multifunctionality in the exoskeleton of the flower beetle Torynorrhina flammea
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DOI：
10.1073/pnas.2101017118
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发表时间：
2021-06-22
影响因子：
11.1
通讯作者：
Li, Ling
中科院分区：
文献类型：
--
作者：
Jia, Zian;Fernandes, Matheus C.;Li, Ling
生物系统具有合成适应特定生理和生态需要的多功能材料的非凡能力。在探索自然界中与多功能性相关的结构-功能关系时，解决生物材料中性能协同、权衡和不同功能的相对重要性可能是一项具有挑战性的任务，而这反过来又会阻碍我们成功开发合成生物灵感对应物的能力。在这里，我们研究了在花甲虫（Torynorrhina flammea）高度保护性但颜色明显的外骨骼中发现的多功能生物材料的机械和光学特性之间的关系。结合实验、计算和理论方法，我们证明了甲虫外骨骼中的微柱增强光子多层同时增强了机械稳健性和光学外观，从而提高了光学损伤容忍度。与普通多层结构相比，竖向微柱刚度增大，弹性回复率提高，抑制剪切带的形成，抗分层能力增强。微柱还使反射光以更大的极角散射，增强了第一光学衍射阶，从而使反射的颜色在更大的视角范围内可见。提高的角反射率和损伤定位能力的协同效应有助于提高光学损伤容限。本研究通过对不同颜色多晶体的系统结构分析和参数化光学和力学建模进一步表明，甲虫的微结构优化是为了最大化一阶光学衍射而不是机械刚度。这些发现揭示了生物系统中用于实现多功能的材料级设计策略，从而可以为生物启发材料创新提供信息。
Biological systems have a remarkable capability of synthesizing multifunctional materials that are adapted for specific physiological and ecological needs. When exploring structure-function relationships related to multifunctionality in nature, it can be a challenging task to address performance synergies, trade-offs, and the relative importance of different functions in biological materials, which, in turn, can hinder our ability to successfully develop their synthetic bioinspired counterparts. Here, we investigate such relationships between the mechanical and optical properties in a multifunctional biological material found in the highly protective yet conspicuously colored exoskeleton of the flower beetle, Torynorrhina flammea. Combining experimental, computational, and theoretical approaches, we demonstrate that a micropillar-reinforced photonic multilayer in the beetle's exoskeleton simultaneously enhances mechanical robustness and optical appearance, giving rise to optical damage tolerance. Compared with plain multilayer structures, stiffer vertical micropillars increase stiffness and elastic recovery, restrain the formation of shear bands, and enhance delamination resistance. The micropillars also scatter the reflected light at larger polar angles, enhancing the first optical diffraction order, which makes the reflected color visible from a wider range of viewing angles. The synergistic effect of the improved angular reflectivity and damage localization capability contributes to the optical damage tolerance. Our systematic structural analysis of T. flammea's different color polymorphs and parametric optical and mechanical modeling further suggest that the beetle's microarchitecture is optimized toward maximizing the first-order optical diffraction rather than its mechanical stiffness. These findings shed light on material-level design strategies utilized in biological systems for achieving multifunctionality and could thus inform bioinspired material innovations.