S. Varshney, E. Zolotovsky, Neri Oxman, M.C. Boyce, C. Ortiz

Abstract

The armored fish Polypterus senegalus possesses a mineralized ganoid squamation integrated with compliant tissue elements for an exoskeleton that is both protective and flexible. The mechanical, material, and morphometric design rules the exoskeleton were translated to macroscale, biomimetic models in four steps: (i) X-ray micro-computed tomography of mineralized fish scales, (ii) quantitative morphometric analysis of the reconstructed scale geometries, (iii) 3D geometric ion and associative modeling of the scale and tissue structures, and (iv) multi-material 3D printing of an articulated, composite assembly of rigid scales in a flexible substrate. Experimental testing of the synthetic prototypes quantified the mechanical behavior (curvature, flexibility, flexural stiffness) across multiple length scales. Variations in the prototype's composite structure, e.g. compliant connective elements between rigid subunits and rigid scale morphometry, illustrated that a combination of scale geometry and materiality control the anisotropic mechanical flexibility of the surface, which is composed of four degrees of freedom in scale-to-scale relative motion. Synthetic models that replicate the complex biomechanics of actinopterygian fish armor give insight into design rules for developing flexible, human-fit protection that maintains both full-body coverage and user mobility.