Liquid metal-filled magnetorheological elastomer with positive piezoconductivity

Guolin Yun,Shi-Yang Tang,Weihua Li,Dan Yuan,Shuaishuai Sun,Lei Deng,Haiping Du,Qianbin Zhao,Sheng Yan,Michael D Dickey

doi:10.1038/s41467-019-09325-4

Guolin Yun, Shi-Yang Tang + Show 8 more

Open Access

https://doi.org/10.1038/s41467-019-09325-4

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Abstract

Conductive elastic composites have been used widely in soft electronics and soft robotics. These composites are typically a mixture of conductive fillers within elastomeric substrates. They can sense strain via changes in resistance resulting from separation of the fillers during elongation. Thus, most elastic composites exhibit a negative piezoconductive effect, i.e. the conductivity decreases under tensile strain. This property is undesirable for stretchable conductors since such composites may become less conductive during deformation. Here, we report a liquid metal-filled magnetorheological elastomer comprising a hybrid of fillers of liquid metal microdroplets and metallic magnetic microparticles. The composite’s resistivity reaches a maximum value in the relaxed state and drops drastically under any deformation, indicating that the composite exhibits an unconventional positive piezoconductive effect. We further investigate the magnetic field-responsive thermal properties of the composite and demonstrate several proof-of-concept applications. This composite has prospective applications in sensors, stretchable conductors, and responsive thermal interfaces.

Highlights

Conductive elastic composites have been used widely in soft electronics and soft robotics
We thoroughly explored the effects of particle, elastomer, liquid metal content, and curing process on the physical properties of the liquid metal-filled magnetorheological elastomer (LMMRE)
The unique property is that this LMMRE exhibits a positive piezoconductive effect, whose resistivity is maximum in the relaxed state, and drops drastically and exponentially with the application of any mechanical deformations, including stretching, compression, bending, and twisting

Summary

Introduction

Conductive elastic composites have been used widely in soft electronics and soft robotics These composites are typically a mixture of conductive fillers within elastomeric substrates. Most elastic composites exhibit a negative piezoconductive effect, i.e. the conductivity decreases under tensile strain. This property is undesirable for stretchable conductors since such composites may become less conductive during deformation. With the rapid development of soft electronics, attention to conductive elastic composites is rising These composites have a variety of applications such as sensors, wearables, and robots[1,2,3,4]. Conductive solid metals or carbon-based materials have been used as fillers for elastic conductors. The microdroplets can deform along with the matrix and retain its high conductivity at high strains, which can be used in soft robotics[21]

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