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.

3D Printing of Emulsions and Foams into Hierarchical Porous Ceramics

“…SEM images of the interfaces between the different pore sizes/morphologies of the multiporosity alumina structures evidence the good bonding between the different inks (Figure C,D). Thus, hierarchical biomimetic structures exhibiting graded porosity analogous to those found in wood, bamboo, or bone could be achieved …”

Special wettable nanostructured copper mesh achieved by a facile hot water treatment process

“…XPS measurement on the mesh surface after HWT has been performed to verify the corresponding chemical state and composition. XPS spectra 7 in Figure 4 reveals the Cu2p state at 932.4 eV and an atomic composition of ~30% O and 70% Cu, which all indicate the formation of Cu2O [19,20,48].…”

“…Porous materials, such as foams, meshes, and sponges, can easily gain multiscale surface structures [19][20][21][22], which is the favorable surface topography for a materials to obtain superhydrophobicity or special wettability after reducing their surface energy. For example, mesh texture with sub-micrometer scaled pores (opening areas) and mesh wires serve as a micro level template for subsequent multiscale structures.…”

Hierarchical materials: Background and perspectives

“…12 Tough and strong alumina ceramic-based materials with a nacre-like brick-and-mortar structure have been made using freeze-casting of nanoparticle suspensions. 13 Polyurethane-based composites for stretchable electronics were developed using solvent-based hierarchical reinforcement approaches, with nanoclay and inorganic particles distributed in a polyurethane matrix.…”