Fish scales: Primitive basis for modern metamaterials

Scales are a path breaking evolutionary adaptation that accompanied vertebrate evolution for the past 500 million years. Inherently lightweight with diverse shapes, sizes, materials, and distribution, they provide remarkable architecture-material enhancement, typical of metamaterials. Here we provide a perspective on mechanical behavior of fish scale inspired structures and explain the origins of some of their striking mechanical properties that include directional nonlinearity, interlocking behavior, and multiple penetration modes. We outline and explain the progress in understanding the complexities of these structures in global and local deformation modes and conclude by offering future perspectives and challenges.