Abstract
Engineered systems are typically based on a large variety of materials differing in composition and processing to provide the desired functionality. Nature, however, has evolved materials that are used for a wide range of functional challenges with minimal compositional changes. The exoskeletal cuticle of spiders, as well as of other arthropods such as insects and crustaceans, is based on a combination of chitin, protein, water and small amounts of organic cross-linkers or minerals. Spiders use it to obtain mechanical support structures and lever systems for locomotion, protection from adverse environmental influences, tools for piercing, cutting and interlocking, auxiliary structures for the transmission and filtering of sensory information, structural colours, transparent lenses for light manipulation and more. This paper illustrates the ‘design space’ of a single type of composite with varying internal architecture and its remarkable capability to serve a diversity of functions.This article is part of the theme issue ‘Bio-derived and bioinspired sustainable advanced materials for emerging technologies (part 1)’.
Highlights
Materials have always been a driver of technological progress in human history, from copper and iron to plastics, magnets and semiconductors
Materials are characterized by their properties that are chosen for applications according to their property profile, as displayed for example in Ashby maps [2]. This led to the multiplication of materials with specific properties, each of them tuned to a given application. This diversity of material compositions is increasingly recognized as a sustainability problem, since among other difficulties, it impedes reuse in a different function and complicates separation into components and, recycling [3]
The cuticle is not just a skin-like protection, but represents the lever system needed for locomotion and acts as a support structure for numbers of tools for piercing, cutting and interlocking, for the reception, transmission and filtering of sensory information, for structural colours, transparent lenses, light manipulation and more. This is all achieved by variations of the same theme based on identical building blocks, which enables the chitin–protein composite to locally acquire the properties needed for each of these tools [7]
Summary
Materials have always been a driver of technological progress in human history, from copper and iron to plastics, magnets and semiconductors. This is all achieved by variations of the same theme based on identical building blocks, which enables the chitin–protein composite to locally acquire the properties needed for each of these tools [7] In this way, the chitin protein material of the arthropod cuticle is able to fill large portions of an Ashby map without major variations in chemical composition. With the abstraction that fibres do not necessarily need to be made of chitin, the examples shown here could inspire new ways of generating multiple material properties and fine-tuned functional structures without increasing the diversity of material compositions. We discuss the mechanical design space available to the spider to build its cuticle as shown by the remarkably fine structures, which serve a large spectrum of functions. The subsequent sections will exemplify various regions in these design spaces demonstrating the structural flexibility inherent to the material ‘design’ of the cuticle
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