Naturally twisted to sieve stress

Abstract

Architected metamaterials—artificial structures with unusual properties that arise from tailored geometry—can guide deformation and energy flow in desirable ways. A subset of metamaterials called phononic bandgap materials can reflect, scatter, or absorb energy by manipulating the way mechanical waves interact with the periodic structures of the material. Waves within a specific frequency range cannot travel through such a material, creating a phononic bandgap. This effect is useful for technologies such as acoustic imaging, acoustic cloaking, shock proofing, and energy harvesting. Architected metamaterials are artificially made; does a similar phenomenon exist in nature? On page 659 of this issue, Alderete et al. (1) report that a mantis shrimp’s dactyl club has phononic bandgaps in which stress waves of specific frequency ranges are filtered. This demonstrates that natural ma terials can exhibit phononic behavior that is observed in artificial metamaterials, opening the possibility for designing bioinspired and biohybrid phononic bandgap materials.