Fish-inspired flexible protective material systems with anisotropic bending stiffness

Abstract Biological structures integrate morphometry (shape-based rules) with materials design to maximize organism survival. The exoskeleton of the armored fish, Polypterus senegalus , balances flexibility protection from predatory and territorial threats. Material properties are known; however, geometric rules underlying its anisotropic uncharacterized. Here, we show how scale shape, articulation, composite architecture produce mechanics using bio-inspired, multi-material 3D-printed prototypes. Passive loading (draping) shows that compliant connections between scales contribute mechanical anisotropy. Simulated experimental active (bending) orientation-dependent stiffness ranging over orders magnitude, including ‘mechanical invisibility’ where they do not add exoskeleton. results illustrate provides a powerful tool tune in architectures independent varying constituent composition. We anticipate introducing morphometric strategies will enable flexible, protective systems tuned complex shapes functions.