Magnetically Addressable Shape-Memory and Stiffening in a Composite Elastomer.

Paolo Testa,Eric R Dufresne,Claire Donnelly,Robert W Style,Peter M Derlet,Elena Borisova,Laura J Heyderman,Jizhai Cui

doi:10.1002/adma.201900561

Paolo Testa, Eric R Dufresne + Show 6 more

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https://doi.org/10.1002/adma.201900561

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Abstract

With a specific stimulus, shape-memory materials can assume a temporary shape and subsequently recover their original shape, a functionality that renders them relevant for applications in fields such as biomedicine, aerospace, and wearable electronics. Shape-memory in polymers and composites is usually achieved by exploiting a thermal transition to program a temporary shape and subsequently recover the original shape. This may be problematic for heat-sensitive environments, and when rapid and uniform heating is required. In this work, a soft magnetic shape-memory composite is produced by encasing liquid droplets of magneto-rheological fluid into a poly(dimethylsiloxane) matrix. Under the influence of a magnetic field, this material undergoes an exceptional stiffening transition, with an almost 30-fold increase in shear modulus. Exploiting this transition, fast and fully reversible magnetic shape-memory is demonstrated in three ways, by embossing, by simple shear, and by unconstrained 3D deformation. Using advanced synchrotron X-ray tomography techniques, the internal structure of the material is revealed, which can be correlated with the composite stiffening and shape-memory mechanism. This material concept, based on a simple emulsion process, can be extended to different fluids and elastomers, and can be manufactured with a wide range of methods.

Highlights

Shape-memory materials can assume a temporary shape through a programming step and can recover their original shape in response to a specific stimulus.[1]
The combination of various types of liquid inclusions with soft elastomeric matrices has been recently proposed as an effective way to create soft materials with novel functionalities, such as high electrical conductivity and temperature dependent color.[16,17,18,19]. We have extended this approach to our material, using instead a magneto-rheological fluid
At = 40%, the same magnetic field results in an almost 30-fold increase in the storage modulus. These values are remarkably high compared to previous results obtained for composites with magnetic particles dispersed directly in PDMS matrices where storage moduli increases of only 1.3-1.8 fold were reported at significantly higher iron contents.[23]

Summary

Introduction

Shape-memory materials can assume a temporary shape through a programming step and can recover their original shape in response to a specific stimulus.[1]. We dispersed magneto-rheological fluid droplets in PDMS prior to cross-linking at volume fractions, , ranging from 0% to 40%, as described in the Experimental Methods.

Results

Conclusion