Soft and stretchable liquid metal transmission lines as distributed probes of multimodal deformations

Abstract

Mechanical sensing is a key functionality in soft electronics intended for applications in health monitoring, human–machine interactions and soft robotics. Current methods typically use intricate networks of sensors specific to one type of deformation and one point in space, which limits their sensing capabilities. An alternative approach to distributed sensing is electrical reflectometry, but it is challenging to build the necessary transmission lines out of soft materials. Here, we report the scalable fabrication of microstructured elastomeric fibres that integrate tens of liquid metal conductors and have the length and cross-sectional integrity necessary to successfully apply time-domain reflectometry. Our soft transmission lines allow the detection of the mode, magnitude and position of multiple simultaneous pressing and stretching events. Furthermore, as a result of the dynamically responsive conductors, the pressure sensitivity is improved by a factor of 200 compared to rigid line probes. By integrating a single soft transmission line with a single interface port into a larger fabric, our technique can be used to create an electronic textile that can decipher convoluted mechanical stimulation.

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Fig. 1: Fabrication and structure of the soft transmission lines.
Fig. 2: Time-domain reflectometry set-up and evaluation of transmission line performance.
Fig. 3: Pressing on soft transmission lines.
Fig. 4: Stretching of soft transmission lines.
Fig. 5: Electronic textile for multiplexed deformation sensing.

Data availability

Source data for Figs. 1–5 are available with the paper. The datasets generated and analysed within this paper and other findings of this study are available from the corresponding author upon reasonable request.

Code availability

The code for the real-time data processing of the electronic textile and other findings of this study are available from the corresponding authors upon reasonable request.

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Acknowledgements

We thank L. Riemer, Z. Wang, H. Karami and F. Rachidi-Haeri for experimental support. We acknowledge Kraton Polymers for providing the material SEBS. We also acknowledge the European Research Council (ERC Starting Grant 679211 ‘FLOWTONICS’) for funding this project.

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Authors

Contributions

A.L. and F.S. conceived the idea. A.L. and N.B. designed and fabricated the soft transmission lines. A.L., C.D., R.C. and T.D.G. designed and carried out the experiments to characterize the lines. A.L. analysed the data and the results were discussed with all authors. A.L. and R.C. designed and fabricated the electronic textile, which was tested with the help of C.D. A.L. and F.S. wrote the manuscript, and all authors contributed to the revisions.

Corresponding author

Correspondence to Fabien Sorin.

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Supplementary information

41928_2020_415_MOESM2_ESM.mp4

Demonstration of pressing on electronic textile.

41928_2020_415_MOESM3_ESM.mp4

Demonstration of stretching and pressing on electronic textile.

Supplementary Information

Supplementary Notes 1–6 and Figs. 1–17.

Supplementary Video 1

Demonstration of pressing on electronic textile.

Supplementary Video 2

Demonstration of stretching and pressing on electronic textile.

Source data

Source Data Fig. 1

Statistical Source Data

Source Data Fig. 2

Statistical Source Data

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Statistical Source Data

Source Data Fig. 4

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Statistical Source Data

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Leber, A., Dong, C., Chandran, R. et al. Soft and stretchable liquid metal transmission lines as distributed probes of multimodal deformations. Nat Electron 3, 316–326 (2020). https://doi.org/10.1038/s41928-020-0415-y

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