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An electrically and mechanically self-healing composite with pressure- and flexion-sensitive properties for electronic skin applications

Nature Nanotechnology volume 7, pages 825–832 (2012)Cite this article

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Abstract

Pressure sensitivity and mechanical self-healing are two vital functions of the human skin. A flexible and electrically conducting material that can sense mechanical forces and yet be able to self-heal repeatably can be of use in emerging fields such as soft robotics and biomimetic prostheses, but combining all these properties together remains a challenging task. Here, we describe a composite material composed of a supramolecular organic polymer with embedded nickel nanostructured microparticles, which shows mechanical and electrical self-healing properties at ambient conditions. We also show that our material is pressure- and flexion-sensitive, and therefore suitable for electronic skin applications. The electrical conductivity can be tuned by varying the amount of nickel particles and can reach values as high as 40 S cm−1. On rupture, the initial conductivity is repeatably restored with ∼90% efficiency after 15 s healing time, and the mechanical properties are completely restored after ∼10 min. The composite resistance varies inversely with applied flexion and tactile forces. These results demonstrate that natural skin's repeatable self-healing capability can be mimicked in conductive and piezoresistive materials, thus potentially expanding the scope of applications of current electronic skin systems.

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Figure 1: Preparation of the self-healing composite.
Figure 2: Electrical and conductive healing efficiency characterization of self-healing composite.
Figure 3: Mechanical and healing efficiency characterization of the self-healing composite.
Figure 4: Characterization and application of the self-healing electronic sensor skin.

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Acknowledgements

The authors acknowledge funding support from the Air Force Office of Scientific Research (grant no. FA9550-12-1-01906). B.C-K.T. acknowledges support from the National Science Scholarship (NSS) from the Agency for Science, Technology and Research (A*STAR). R.A. acknowledges support from the Stanford Graduate Fellowship (SGF) and the Center for Advanced Molecular Photovoltaics (CAMP). Z.B. acknowledges support from LG Display. The authors thank D.J. Lipomi and J. Mei for fruitful discussions, and J.B-H. Tok, N. Liu and Y. Tan for proofreading the manuscript drafts. Thanks also go to I. Wong and Y. Ohkura for help with mechanical testing, and to Y. Diao for initial help with material characterization.

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Author notes

  1. Benjamin C-K. Tee and Chao Wang: These authors contributed equally to this work

Authors and Affiliations

  1. Department of Electrical Engineering, Stanford University, David Packard Building, Stanford, California, 94305, USA

    Benjamin C-K. Tee

  2. Department of Chemical Engineering, Stanford University, 381 North–South Mall, Stanford, California, 94305, USA

    Chao Wang, Ranulfo Allen & Zhenan Bao

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  1. Benjamin C-K. Tee
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  2. Chao Wang
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Contributions

B.C-K.T., C.W. and Z.B. conceived, designed and directed the project. B.C-K.T., C.W. and R.A. performed the experiments. C.W. synthesized and characterized the polymer materials. R.A. performed all the rheological measurements and analysis. B.C-K.T. and C.W. co-wrote the manuscript draft. All authors discussed the results and commented on the manuscript.

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Correspondence to Zhenan Bao.

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Tee, BK., Wang, C., Allen, R. et al. An electrically and mechanically self-healing composite with pressure- and flexion-sensitive properties for electronic skin applications. Nature Nanotech 7, 825–832 (2012). https://doi.org/10.1038/nnano.2012.192

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