Abstract

Prof Ulrike Wegst

Natural structural materials are built at ambient temperature from a fairly limited selection of components. They usually comprise hard and soft phases arranged in complex hierarchical architectures, with characteristic dimensions spanning from the nanoscale to the macroscale. The resulting materials are lightweight and often display unique combinations of strength and toughness, but have proven difficult to mimic synthetically. Here, we review the common design motifs of a range of natural structural materials, and discuss the difficulties associated with the design and fabrication of synthetic structures that mimic the structural and mechanical characteristics of their natural counterparts.

Introduction

The technological development of humanity was supported in its early stages by natural materials such as bone, wood and shells. As history advanced, these materials were slowly replaced by synthetic compounds that offered improved performance. Today, scientists and engineers continue to be fascinated by the distinctive qualities of the elegant and complex architectures of natural structures, which can be lightweight and offer combinations of mechanical properties that often surpass those of their components by orders of magnitude. Contemporary characterization and modelling tools now allow us to begin deciphering the intricate interplay of mechanisms acting at different scales — from the atomic to the macroscopic — and that endow natural structures with their unique properties. At present, there is a pressing need for new lightweight structural materials that are able to support more efficient technologies that serve a variety of strategic fields, such as transportation, buildings, and energy storage and conversion. To address this challenge, yet-to-be-developed materials that would offer unprecedented combinations of stiffness, strength and toughness at low density, would need to be fashioned into bulk complex shapes and manufactured at high volume and low cost. It is an open question how this goal can be achieved. Although remarkable examples have arisen from the laboratory, it remains uncertain whether they can be scaled-up for use in practical applications.