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An on-skin platform for wireless monitoring of flow rate, cumulative loss and temperature of sweat in real time

Nature Electronics volume 4, pages 302–312 (2021)Cite this article

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Abstract

Monitoring the flow rate, cumulative loss and temperature of sweat can provide valuable physiological insights for the diagnosis of thermoregulatory disorders and illnesses related to heat stress. However, obtaining accurate, continuous estimates of these parameters with high temporal resolution remains challenging. Here, we report a platform that can wirelessly measure sweat rate, sweat loss and skin temperature in real time. The approach combines a short, straight fluid passage to capture sweat as it emerges from the skin with a flow sensor that is based on a thermal actuator and precision thermistors, and that is physically isolated from, but thermally coupled to, the sweat. The platform transfers data autonomously using a Bluetooth Low Energy system on a chip. Our approach can also be integrated with advanced microfluidic systems and colorimetric chemical reagents for the measurement of pH and the concentration of chloride, creatinine and glucose in sweat.

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Fig. 1: Design features and operating principles of a miniaturized, flexible module for remote, on-skin sensing of sweat rate.
Fig. 2: Experimental studies and FEA of key characteristics of the thermal flow sensor.
Fig. 3: A skin-interfaced, wireless system for continuous monitoring of sweat rate, sweat loss and temperature.
Fig. 4: On-body measurements of sweat flow rate and total loss for physical activity and dehydration monitoring.
Fig. 5: Multimodal sensing of sweat rate and loss, skin temperature and various sweat biomarkers.

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Data availability

Supporting data are available from the corresponding author upon reasonable request. Source data are provided with this paper.

Code availability

Custom-developed firmware for BLE SoCs and Android applications (user interfaces) for use on smartphones are available from the corresponding author upon reasonable request. All requests for source code will be reviewed by the corresponding author to verify whether the request is subject to any intellectual property or confidentiality obligations.

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Acknowledgements

This work made use of the NUFAB facility of Northwestern University’s NUANCE Center, which has received support from the Soft and Hybrid Nanotechnology Experimental (SHyNE) Resource (NSF ECCS-1542205), the MRSEC programme (NSF DMR-1720139) at the Materials Research Center, the International Institute for Nanotechnology (IIN), the Keck Foundation and the State of Illinois, through the IIN. J.U.K. and T.K. were supported by the Brain Research Program of the National Research Foundation (NRF) funded by the Korean government (MSIT; NRF-2019M3C7A1032076). J.C. acknowledges support from the National Research Foundation of Korea (NRF) grant funded by the Korean government (MSIT; NRF-2019R1A2C1084419). J.A.R. acknowledge support from the National Institute on Aging of the National Institutes of Health (NIH R43AG067835). We thank the Querrey-Simpson Institute for Bioelectronics for support of this work.

Author information

Author notes

  1. These authors contributed equally: Kyeongha Kwon, Jong Uk Kim, Yujun Deng.

Authors and Affiliations

  1. School of Electrical Engineering, Korea Advanced Institute of Science and Technology, Daejeon, Republic of Korea

    Kyeongha Kwon & Injae Yoo

  2. Querrey-Simpson Institute for Bioelectronics, Northwestern University, Evanston, IL, USA

    Kyeongha Kwon, Jong Uk Kim, Siddharth R. Krishnan, Hokyung Jang, Chun-Ju Su, Derek Wu, Yoonseok Park, Roozbeh Ghaffari, Stephen Lee, Yonggang Huang & John A. Rogers

  3. School of Chemical Engineering, Sungkyunkwan University, Suwon, Gyeonggi-do, Republic of Korea

    Jong Uk Kim & Tae-il Kim

  4. State Key Laboratory of Mechanical System and Vibration, Shanghai Jiao Tong University, Shanghai, China

    Yujun Deng

  5. Department of Civil and Environmental Engineering, Northwestern University, Evanston, IL, USA

    Yujun Deng & Yonggang Huang

  6. Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL, USA

    Siddharth R. Krishnan

  7. School of Mechanical Engineering, Kookmin University, Seoul, Republic of Korea

    Jungil Choi

  8. Department of Electrical & Computer Engineering, University of Wisconsin, Madison, WI, USA

    Hokyung Jang

  9. Department of Materials Science and Engineering, Northwestern University, Evanston, IL, USA

    KunHyuck Lee, Yixin Wu, Yonggang Huang & John A. Rogers

  10. Department of Biomedical Engineering, Northwestern University, Evanston, IL, USA

    Lindsay Lipschultz, Ted S. Chung, Roozbeh Ghaffari & John A. Rogers

  11. Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, Champaign, IL, USA

    Jae-Hwan Kim

  12. Department of Mechanical Engineering, Northwestern University, Evanston, IL, USA

    Derek Wu, Yonggang Huang & John A. Rogers

  13. Department of Biomedical Engineering, and Biomedical Institute for Convergence, Sungkyunkwan University, Suwon, Gyeonggi-do, Republic of Korea

    Tae-il Kim

  14. Departments of Neurological Surgery, Chemistry, Electrical Engineering and Computer Science, Northwestern University, Evanston, IL, USA

    John A. Rogers

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  1. Kyeongha Kwon
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Contributions

K.K., J.U.K. and J.A.R. conceived the idea, designed the research, analysed data and wrote the manuscript. K.K., J.U.K. and S.R.K. performed and were involved in the manufacturing of the sensors. K.K. designed the hardware for the wireless electronics platform. K.K., K.L. and I.Y. performed software design and software validation. Y.D. and Y.H. performed thermal and mechanical modelling. J.C., H.J., C.-J.S., Y.W., L.L., T.S.C., D.W. and J.-H.K. assisted with device fabrication. K.K. and J.U.K. performed research and led the experimental works with support from H.J., Y.P., T.K., R.G. and S.L.

Corresponding author

Correspondence to John A. Rogers.

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Competing interests

J.A.R., S.L. and R.G. are cofounders and/or employees of Epicore Biosystems, Inc., a company that pursues commercialization of microfluidic devices for wearable applications.

Additional information

Peer review information Nature Electronics thanks Tolga Kaya, Christopher Proctor and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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

Supplementary information

Supplementary Information

Supplementary Figs. 1–21, Tables 1–3 and notes 1–4.

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Source Data Fig. 1

Source data for Fig. 1c (inset).

Source Data Fig. 2

Source data for Fig. 2c–i.

Source Data Fig. 4

Source data for Fig. 4c–i.

Source Data Fig. 5

Source data for Fig. 5d,e.

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Kwon, K., Kim, J.U., Deng, Y. et al. An on-skin platform for wireless monitoring of flow rate, cumulative loss and temperature of sweat in real time. Nat Electron 4, 302–312 (2021). https://doi.org/10.1038/s41928-021-00556-2

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