Bioinspired materials that self-shape through programmed microstructures

André R Studart,Randall M Erb

doi:10.1039/c3sm51883c

Abstract

Nature displays numerous examples of materials that can autonomously change their shape in response to external stimuli. Remarkably, shape changes in biological systems can be programmed within the material's microstructure to enable self-shaping capabilities even in the absence of cellular control. Here, we revisit recent attempts to replicate in synthetic materials the shape-changing behavior of selected natural materials displaying deliberately tuned fibrous architectures. Simple processing methods like drawing, spinning or casting under magnetic fields are shown to be effective in mimicking the orientation and spatial distribution of reinforcing fibers of natural materials, thus enabling unique shape-changing features in synthetic systems. The bioinspired design and creation of self-shaping microstructures represent a new pathway to program shape changes in synthetic materials. In contrast to shape-memory polymers and metallic alloys, the self-shaping capabilities in these bioinspired materials originate at the microstructural level rather than the molecular scale. This enables the creation of programmable shape changes using building blocks that would otherwise not display the intrinsic molecular/atomic phase transitions required in conventional shape-memory materials.

Highlights

Biological and synthetic materials that change shape upon external stimuli are of great scienti c interest and have been exploited in a range of different applications in biomedicine, aerospace, transportation and materials science.[1,2]
Synthetic shape-changing systems, known as shape-memory materials, typically exhibit phase transitions at the molecular and/or atomic scale which enable kinetic trapping of a temporary shape that is later restored to the original conformation under a selective thermal, chemical, magnetic or optical trigger.[1,2,3,4,5,6,7]
The shape-memory behavior of NiTi metallic alloys relies on the martensitic transformation of the crystalline structure of the metal at a well-de ned temperature.[6]

Summary

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Shape changes in biological systems can be programmed within the material’s microstructure to enable self-shaping capabilities even in the absence of cellular control. We revisit recent attempts to replicate in synthetic materials the shape-changing behavior of selected natural materials displaying deliberately tuned fibrous architectures. In contrast to shape-memory polymers and metallic alloys, the self-shaping capabilities in these bioinspired materials originate at the microstructural level rather than the molecular scale. This enables the creation of programmable shape changes using building blocks that would otherwise not display the intrinsic molecular/atomic phase transitions required in conventional shape-memory materials

Introduction

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Conclusions and outlook