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Soft electronic vias and interconnects through rapid three-dimensional assembly of liquid metal microdroplets

Nature Electronics volume 7, pages 1015–1024 (2024)Cite this article

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Abstract

The development of soft electronics requires methods to connect flexible and stretchable circuits. With conventional rigid electronics, vias are typically used to electrically connect circuits with multilayered architectures, increasing device integration and functionality. However, creating vias using soft conductors leads to additional challenges. Here we show that soft vias and planar interconnects can be created through the directed stratification of liquid metal droplets with programmed photocuring. Abnormalities that occur at the edges of a mask during ultraviolet exposure are leveraged to create vertical stair-like architectures of liquid metal droplets within the photoresin. The liquid metal droplets in the uncured (liquid) resin rapidly settle, assemble and then are fully cured, forming electrically conductive soft vias at multiple locations throughout the circuit in a parallel and spatially tunable manner. Our three-dimensional selective stratification method can also form seamless connections with planar interconnects, for in-plane and through-plane electrical integration.

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Fig. 1: LM-STAIR fabrication of LM soft interconnects and vias.
Fig. 2: Physical characterization of LM-STAIR vias and interconnects.
Fig. 3: Electromechanical characterization of LM-STAIR vias and interconnects.
Fig. 4: Multilayer circuit fabrication with crossing interconnects and adhesion characteristics.
Fig. 5: Multilayer magnetic sensing and indicating flexible circuit demonstration.

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Data availability

The data that support the findings of this study are available from the corresponding author upon reasonable request.

Change history

  • 30 October 2024

    In the version of the article initially published, Sungjune Park’s name appeared incorrectly (as Sujgjune Park) in the Peer review information section, and has now been corrected in the HTML and PDF versions of the article.

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Acknowledgements

D.H.H. and M.D.B. acknowledge support from the Office of Naval Research Young Investigator Program (ONR YIP) (grant no. N000142112699) and the National Science Foundation CAREER award (grant no. 2238754). C.H. and L.L. acknowledge support from Virginia Polytechnic Institute and State University through the COE Faculty Fellowship. C.H. and L.L. also thank D. Baum for the kind assistance in using random-work distance transforms for quantitative microCT analysis.

Author information

Author notes

  1. Dong Hae Ho

    Present address: Department of Energy Science and Engineering, Daegu Gyeongbuk Institute of Science and Technology (DGIST), Daegu, Republic of Korea

  2. Chenhao Hu & Ling Li

    Present address: Department of Materials Science and Engineering, University of Pennsylvania, Pennsylvania, PA, USA

Authors and Affiliations

  1. Department of Mechanical Engineering, Soft Materials and Structures Lab, Virginia Tech, Blacksburg, VA, USA

    Dong Hae Ho & Michael D. Bartlett

  2. Macromolecules Innovation Institute, Virginia Tech, Blacksburg, VA, USA

    Dong Hae Ho & Michael D. Bartlett

  3. Department of Mechanical Engineering, Virginia Tech, Blacksburg, VA, USA

    Chenhao Hu & Ling Li

Authors
  1. Dong Hae Ho
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  2. Chenhao Hu
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  4. Michael D. Bartlett
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Contributions

D.H.H. and M.D.B. conceived and designed research. D.H.H. conducted research. C.H. and L.L. contributed to measurement and analysis of the microCT scan data. M.D.B. supervised the work. D.H.H. and M.D.B. wrote the paper with contributions from all the authors.

Corresponding author

Correspondence to Michael D. Bartlett.

Ethics declarations

Competing interests

M.D.B. and D.H.H. are inventors on a patent application (US Patent Application no. 63/535,919) on the fabrication approach. The other authors declare no competing interests.

Peer review

Peer review information

Nature Electronics thanks Wedyan Babatain, Sungjune Park and Nanjia Zhou for their contribution to the peer review of this work.

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Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Supplementary information

Supplementary Information

Supplementary Notes, Figs. 1–21 and Videos 1–6.

Supplementary Video 1

Reconstructed microCT images of LM-STAIR vias.

Supplementary Video 2

LM-STAIR ultrasonic activation.

Supplementary Video 3

Real-time fabrication of LM-STAIR vias inside the photoresin.

Supplementary Video 4

Reconstructed microCT images of planar interconnect.

Supplementary Video 5

Circuit adhesion demonstration.

Supplementary Video 6

Magnetic field interface circuit demonstration.

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Ho, D.H., Hu, C., Li, L. et al. Soft electronic vias and interconnects through rapid three-dimensional assembly of liquid metal microdroplets. Nat Electron 7, 1015–1024 (2024). https://doi.org/10.1038/s41928-024-01268-z

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