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.

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。在探索与自然界多功能性相关的结构 - 功能关系时，解决生物材料中不同功能的性能协同、权衡和相对重要性可能是一项具有挑战性的任务，这反过来又会阻碍我们成功开发的能力他们合成的仿生同类产品。在这里，我们研究了在花甲虫Torynorrhina flammea的高度保护但显眼的彩色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这种关系. 结合实验、计算和理论方法，我们证明甲虫外骨骼中的微柱增强光子多层同时增强了机械强度和光学外观，从而提高了光学损伤容限。与普通多层结构相比，更硬的垂直微柱增加了刚度和弹性恢复，抑制了剪切带的形成，并增强了抗分层能力。微柱还以更大的极角散射反射光，增强第一级光学衍射级，这使得从更广泛的视角范围内可以看到反射的颜色。改进的角反射率和损伤定位能力的协同效应有助于光学损伤容限。我们系统的结构分析T. flammea的不同颜色多晶型物以及参数化光学和机械模型进一步表明，甲虫的微结构经过优化，可以最大限度地提高一级光学衍射，而不是其机械刚度。这些发现阐明了生物系统中用于实现多功能性的材料级设计策略，从而可以为受生物启发的材料创新提供信息。