Bioinspired Hierarchical Composites

Abstract

The structural design of composite materials at multiple length scales is a widespread strategy found in biological materials to optimize opposing properties or to combine multiple functional properties in a unique material system. The combination of this hierarchical structuring approach with the vast chemical repertoire available in synthetic systems is expected to lead to man-made composites with unprecedented functionalities. Alternatively, hierarchical materials can potentially achieve sufficient strength and toughness even if made out of weaker environmentally-friendly or bioresorbable building blocks. Replicating the hierarchical design principle of biological systems in synthetic materials is an exciting challenge that has been tackled by researchers across different scientific communities. In this chapter, we present state-of-the-art examples on attempts to identify fundamental design principles of hierarchical natural materials and to then mimic these bioinspired concepts in man-made materials. Three selected structural features that can be independently designed at multiple length scales in biological materials are described as examples: (i) mechanical reinforcement, (ii) porosity, and (iii) topography. By comparing biological and man-made materials exhibiting these hierarchical features, we provide an overview on the limitations of currently exploited top-down and bottom-up manufacturing technologies and on the opportunities for the future development of hierarchical composites inspired by the unique multiscale structure of biological materials.