The role of material architecture to achieve functional hierarchy in the cuticle of the flower beetle, <i>Torynorrhina flammea</i>

Biological materials achieve outstanding multifunctionality through a hierarchical arrangement of material architecture at multiple length scales. To understand the multifunctionality of biological materials, “structure-properties” relationship instead of the conventional “structure-property” relationship should be considered, where “property-property” relationship must be discussed additionally. However, associating multiple individual functions and revealing the relative importance of each function are challenging, as different functions belong to different disciplines and the criteria of comparison have not yet been established. In this study, we address these challenges based on the cuticle of the flower beetle, Torynorrhina flammea. We combine multidisciplinary experimental, computational, and theoretical techniques to understand the “structure-optics-mechanics” relationship of the beetle’s cuticle. The relative importance of optical performance to the mechanical performance in the beetle’s cuticle is further demonstrated using concepts from biological evolution. Our results not only illustrate the mechanical and optical design principles of the beetle’s cuticle but also opens an avenue to understand the evolutionary driving force of multifunctional biological materials.