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Omnidirectional printing of elastic conductors for three-dimensional stretchable electronics

Nature Electronics volume 6, pages 307–318 (2023)Cite this article

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Abstract

Three-dimensional printing could be used to create complex and multifunctional soft electronic devices. However, printing solid-state elastic conductors with three-dimensional geometries is challenging because the rheological properties of existing inks typically only allow for layer-wise deposition. Here we show that an emulsion system—consisting of a conductive elastomer composite, immiscible solvent and emulsifying solvent—can be used for the omnidirectional printing of elastic conductors. The viscoelastic properties of the composite provide structural integrity to the printed features—allowing freestanding, filamentary and out-of-plane three-dimensional geometries to be directly written—and pseudo-plastic and lubrication behaviours that provide printing stability and prevent nozzle clogging. Printed structures of the intrinsically stretchable conductor exhibit a minimum feature size less than 100 μm and stretchability of more than 150%. The vapourisation of the dispersed solvent phase in the emulsion results in the formation of microstructured, surface-localized conductive networks, which improve the electrical conductivity. To illustrate the capabilities of our approach, we create a skin-mountable temperature sensor with a matrix-type stretchable display based on omnidirectionally printed elastic interconnects.

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Fig. 1: Ink design for omnidirectional printing of elastic conductors.
Fig. 2: Rheological properties of omnidirectionally printable inks.
Fig. 3: Omnidirectional printing of elastic conductors.
Fig. 4: Morphologies and electrical characteristics of dilution-based and emulsion-based composites.
Fig. 5: Electromechanical characteristics.
Fig. 6: Direct writing of 3D-structured on-skin electronics.

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Data availability

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

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Acknowledgements

This work was supported by the Nano & Material Technology Development Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science and ICT (NRF-2020M3D1A2101799), the Korea Institute of Science and Technology (KIST) Future Resource Research Program (grant no. 2E32501) and KU-KIST School Project. B.L. also appreciates support from the NRF grant funded by the Korea government (MSIT) (no. 2021R1C1C2091957).

Author information

Author notes

  1. These authors contributed equally: Byeongmoon Lee, Hyunjoo Cho.

Authors and Affiliations

  1. Soft Hybrid Materials Research Center, Korea Institute of Science and Technology, Seoul, Republic of Korea

    Byeongmoon Lee, Hyunjoo Cho, Sooyeon Moon, Youngpyo Ko, Heesuk Kim & Seungjun Chung

  2. School of Biomedical Engineering, Korea University, Seoul, Republic of Korea

    Yong-Sang Ryu

  3. School of Information and Communication Engineering, Chungbuk National University, Cheongju, Republic of Korea

    Jaewook Jeong

  4. KU-KIST Graduate School of Converging Science and Technology, Korea University, Seoul, Republic of Korea

    Seungjun Chung

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Contributions

B.L., H.C., S.M. and S.C. conceived the idea. B.L. and S.C. designed the materials and experiments. B.L., H.C. and S.M. fabricated and characterized the printable inks and elastic conductors. Y.K., Y.-S.R. and H.K. assisted with the materials design and characterization. B.L. carried out the FEA in discussion with S.C. B.L. and H.C. designed and fabricated the skin-mountable devices. B.L., H.C. and S.C. wrote the manuscript with input from all the authors. H.K. and J.J. reviewed and revised the manuscript. All the authors discussed the results and approved the manuscript.

Corresponding authors

Correspondence to Byeongmoon Lee or Seungjun Chung.

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Peer review information

Nature Electronics thanks Lixue Tang, Hyunwoo Yuk and Nanjia Zhou for their contribution to the peer review of this work.

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Supplementary information

Supplementary Information

Supplementary Figs. 1–27, Tables 1 and 2 and references.

Supplementary Video 1

Three-dimensional spiral structure printed with emulsion-based ink.

Supplementary Video 2

Elasticity of omnidirectionally printed self-supporting conductors.

Supplementary Video 3

Single-step writing of self-supporting and out-of-plane geometries.

Supplementary Video 4

On-skin temperature visualization system based on omnidirectionally printed elastic conductors.

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Lee, B., Cho, H., Moon, S. et al. Omnidirectional printing of elastic conductors for three-dimensional stretchable electronics. Nat Electron 6, 307–318 (2023). https://doi.org/10.1038/s41928-023-00949-5

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