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Hydrogen-doped viscoplastic liquid metal microparticles for stretchable printed metal lines

Nature Materials volume 20, pages 533–540 (2021)Cite this article

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Abstract

Conductive and stretchable electrodes that can be printed directly on a stretchable substrate have drawn extensive attention for wearable electronics and electronic skins. Printable inks that contain liquid metal are strong candidates for these applications, but the insulating oxide skin that forms around the liquid metal particles limits their conductivity. This study reveals that hydrogen doping introduced by ultrasonication in the presence of aliphatic polymers makes the oxide skin highly conductive and deformable. X-ray photoelectron spectroscopy and atom probe tomography confirmed the hydrogen doping, and first-principles calculations were used to rationalize the obtained conductivity. The printed circuit lines show a metallic conductivity (25,000 S cm–1), excellent electromechanical decoupling at a 500% uniaxial stretching, mechanical resistance to scratches and long-term stability in wide ranges of temperature and humidity. The self-passivation of the printed lines allows the direct printing of three-dimensional circuit lines and double-layer planar coils that are used as stretchable inductive strain sensors.

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Fig. 1: Characterization of the H-doped LM MPs.
Fig. 2: Computational modelling of the LM oxide.
Fig. 3: Viscoplastic deformability of the H-doped oxide skin.
Fig. 4: Electrical and mechanical stability of the printed LM MP circuit line.
Fig. 5: Printed 3D circuit line with autonomous self-passivation.

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Data availability

All the data that support this study are included in this article and its supplementary information files. Source data are provided with this paper.

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Acknowledgements

S.V. and U.J. acknowledge the support of a National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (no. NRF-2020R1A2C3012738), the Center for Advanced Soft-Electronics funded by the Ministry of Science, ICT and Future Planning as Global Frontier Project (CASE-2015M3A6A5072945) and the Korea Research Institute of Chemical Technology (KRICT). W.J., E.K. and A.S. gratefully acknowledge support from the Ministry of Science and ICT under the Creative Materials Discovery Program (2018M3D1A1058536) and computational resources from KISTI (KSC-2019-CRE-0024). H.W. and L.B. are thankful for the financial support of a Marie Sklodowska-Curie Individual Fellowship (‘3D-SITS’) from the European Union’s Horizon 2020 research and innovation programme (no. 799733). J.B.S. appreciates financial support from the Ministry of Science and ICT (MSIT) of the Korean government (no. 2018R1C1B6008585). The authors thank S. J. Park and J. M. Park (POSTECH) for supporting the rheology measurements.

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Author notes

  1. Woosun Jang

    Present address: Department of Inorganic Chemistry, Fritz-Haber Institute of the Max-Planck Society, Berlin, Germany

  2. Jae Bok Seol

    Present address: Department of Materials Engineering and Convergence Technology, Center for K-metal, Gyeongsang National University (GNU), Jinju, South Korea

  3. These authors contributed equally: Selvaraj Veerapandian, Woosun Jang.

Authors and Affiliations

  1. Department of Materials Science and Engineering, Pohang University of Science and Technology, Pohang, Korea

    Selvaraj Veerapandian, Minsik Kong, Kaliannan Thiyagarajan, Junghyeok Kwak, Gyeongbae Park, Gilwoon Lee, Wonjeong Suh, Insang You, Anupam Giri & Unyong Jeong

  2. Department of Material Science and Engineering and Center for Artificial Synesthesia Materials Discovery, Yonsei University, Seoul, Korea

    Woosun Jang, Mehmet Emin Kılıç & Aloysius Soon

  3. National Institute for Nanomaterials Technology, Pohang University of Science and Technology, Pohang, Korea

    Jae Bok Seol

  4. Center for Micro-BioRobotics (CMBR@SSSA), Istituto Italiano di Tecnologia, Pontedera, Italy

    Hongbo Wang & Lucia Beccai

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Contributions

S.V., H.W., L.B. and U.J. designed the experiment. S.V. carried out the fabrication and characterization of the LM MP circuit lines, analysed the data and wrote the manuscript along with U.J. A.S., W.J. and M.E.K. designed the theoretical part and wrote the corresponding part of the manuscript. J.B.S. performed the APT analysis. K.T., G.P. and I.Y. performed the electrical characterization of the conductive LM MPs and assisted the characterization of the die-hard properties of the circuit line. M.K., J.K., G.L., W.S. and A.G. assisted the characterization of the LM MP circuits.

Corresponding authors

Correspondence to Aloysius Soon or Unyong Jeong.

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Competing interests

Patent applications (Korean Patent application numbers 10-2020-0038722 and 10-2020-0033237) have been filed based on the results of this study.

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Peer review information Nature Materials thanks Michael Dickey and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Supplementary information

Supplementary Information

Supplementary Figs. 1–24, Discussion and Tables 1–3.

Supplementary Video 1

Die-hard interconnection with LED.

Supplementary Video 2

Hard to kill the electrical connection under strain and mechanical damage.

Supplementary Video 3

3D complex printed line.

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Veerapandian, S., Jang, W., Seol, J.B. et al. Hydrogen-doped viscoplastic liquid metal microparticles for stretchable printed metal lines. Nat. Mater. 20, 533–540 (2021). https://doi.org/10.1038/s41563-020-00863-7

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