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Stretchable and suturable fibre sensors for wireless monitoring of connective tissue strain

Nature Electronics volume 4, pages 291–301 (2021)Cite this article

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Abstract

Implantable sensors can be used to monitor biomechanical strain continuously. However, three key challenges need to be addressed before they can be of use in clinical practice: the structural mismatch between the sensors and tissue or organs should be eliminated; a practical suturing attachment process should be developed; and the sensors should be equipped with wireless readout. Here, we report a wireless and suturable fibre strain-sensing system created by combining a capacitive fibre strain sensor with an inductive coil for wireless readout. The sensor is composed of two stretchable conductive fibres organized in a double helical structure with an empty core, and has a sensitivity of around 12. Mathematical analysis and simulation of the sensor can effectively predict its capacitive response and can be used to modulate performance according to the intended application. To illustrate the capabilities of the system, we use it to perform strain measurements on the Achilles tendon and knee ligament in an ex vivo and in vivo porcine leg.

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Fig. 1: Design for a wireless fibre strain-sensing system.
Fig. 2: Working mechanism of the fibre strain sensor.
Fig. 3: Performance of fibre strain sensor.
Fig. 4: Characterization and ex vivo demonstration of a wireless fibre strain-sensing system.
Fig. 5: Biocompatibility and in vivo demonstration of a wireless fibre strain-sensing system.

Data availability

The raw data generated in this study are freely available from the corresponding authors on reasonable request.

Code availability

The custom code developed for recording data from the network analyser is available on Github at https://github.com/jaelee2020/suturable_fibre_strain_sensors.git.

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Acknowledgements

We thank T. Schlotter for his support with the numerical simulations. In addition, we thank T. Lee and K. Yoon of Yonsei University in South Korea for their help with the conductive fibres. This work was supported by the ETH Zurich Postdoctoral Fellowship Program, co-founded by the Marie Curie Actions for People COFUND Program, by ETH Zurich and SENESCYT and by the KRIBB (Korea Research Institute of Bioscience and Biotechnology) Research Initiative Program (KGM4252021), Korea. The work was also financed by the DGIST Start-up Fund Program of the Ministry of Science and ICT (2021010030), and the Korea Medical Device Development Fund grant, funded by the Korea government (the Ministry of Science and ICT) (project number 2020M3E5D8107020).

Author information

Authors and Affiliations

  1. Department of Robotics Engineering, Daegu-Gyeongbuk Institute of Science & Technology (DGIST), Daegu, Republic of Korea

    Jaehong Lee, Hwajoong Kim, Junwoo Yea, Chaewon Jin, Hongsoo Choi & Kyung-In Jang

  2. Laboratory of Biosensors and Bioelectronics, Institute for Biomedical Engineering, ETH Zürich, Zurich, Switzerland

    Jaehong Lee, Stephan J. Ihle, Guglielmo Salvatore Pellegrino, Byron Llerena Zambrano, Aline F. Renz, Csaba Forró & Janos Vörös

  3. Futuristic Animal Resource and Research Center & National Primate Research Center, Korea Research Institute of Bioscience and Biotechnology, Ochang, Republic of Korea

    Chang-Yeop Jeon & Hee-Chang Son

  4. Department of Urology, University Hospital of Zurich, University of Zurich, Zurich, Switzerland

    Daniel Eberli & Florian Schmid

  5. Institute of Signal Processing and Wireless Communications, Zurich University of Applied Sciences, Winterthur, Switzerland

    Roland Küng

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Contributions

J.L. designed the overall concept and experiments, and performed all the tasks including the fabrication, measurements, data analysis and mathematical analysis. S.J.I. contributed to building the Python code for wireless measurement in the ex vivo experiment. G.S.P. conducted the finite element method simulation on the working mechanism of the fibre sensor. H.K., J.Y., C.-Y.J., H.-C.S. and K.-I.J. contributed to the in vivo experiments. C.J. and H.C. conducted the cell viability tests for demonstrating the biocompatibility of the system. D.E. and F.S. provided the professional suturing technique for the ex vivo experiment. B.L.Z. and A.F.R. contributed to the measurement experiments and data analysis. C.F. contributed to the analytical model of the sensor. R.K. performed the wireless measurement of the sensing system. J.V. contributed to the development of the sensor concept, data interpretation, mathematical analysis and critical revisions of the article.

Corresponding authors

Correspondence to Jaehong Lee or Janos Vörös.

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The authors declare no competing interests.

Additional information

Peer review information Nature Electronics thanks Roozbeh Ghaffari, John Ho, Chwee Lim 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. 1–28 and six notes.

Reporting Summary

Supplementary Video 1

Behaviour of a double helical fibre strain sensor under tensile strain.

Supplementary Video 2

Suturing a fibre strain-sensing system on the Achilles tendon of a porcine leg.

Supplementary Video 3

Ex vivo demonstration of a fibre strain-sensing system.

Supplementary Video 4

In vivo demonstration of a fibre strain-sensing system.

Supplementary Video 5

X-ray video of an implanted fibre strain-sensing system during movements.

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Lee, J., Ihle, S.J., Pellegrino, G.S. et al. Stretchable and suturable fibre sensors for wireless monitoring of connective tissue strain. Nat Electron 4, 291–301 (2021). https://doi.org/10.1038/s41928-021-00557-1

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