Research ArticleAPPLIED SCIENCES AND ENGINEERING

Machine-knitted washable sensor array textile for precise epidermal physiological signal monitoring

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Science Advances  13 Mar 2020:
Vol. 6, no. 11, eaay2840
DOI: 10.1126/sciadv.aay2840
  • Fig. 1 Fabrication and structure of all-textile pressure sensors.

    (A) Two TATSAs integrated into a shirt for the monitoring of pulse and respiratory signals in real time. (B) Schematic illustration of the combination of TATSA and clothes. The inset shows the enlarged view of the sensor. (C) Photograph of the conductive yarn (scale bar, 4 cm). The inset is the SEM image of the cross section of the conductive yarn (scale bar, 100 μm), which consists of stainless steel and Terylene yarns. (D) Photograph of the nylon yarn (scale bar, 4 cm). The inset is the SEM image of the nylon yarn surface (scale bar, 100 μm). (E) Image of the computerized flat knitting machine carrying out the automatic weaving of the TATSAs. (F) Photograph of TATSAs in different colors (scale bar, 2 cm). The inset is the twisted TATSA, which demonstrates its excellent softness. (G) Photograph of two TATSAs completely and seamlessly stitched into a sweater. Photo credit: Wenjing Fan, Chongqing University.

  • Fig. 2 Demonstration of the working principle of TATSA.

    (A) The TATSA with the front, right, and top sides of the knit loops. (B) Simulation result of the force distribution of a TATSA under an applied pressure of 2 kPa using the COMSOL software. (C) Schematic illustrations of the charge transfer of a contact unit under short-circuit conditions. (D) Simulation results of the charge distribution of a contact unit under an open circuit condition using the COMSOL software.

  • Fig. 3 Performance of the TATSA.

    (A) Output voltage under nine knitting patterns of the conductive yarn (150D/3, 210D/3, and 250D/3) combined with the nylon yarn (150D/6, 210D/6, and 250D/6). (B) Voltage response to various numbers of loop units in the same fabric area when keeping the loop number in the wale direction unchanged. (C) Plots showing the frequency responses under a dynamic pressure of 1 kPa and pressure input frequency of 1 Hz. (D) Different output and current voltages under the frequencies of 1, 5, 10, and 20 Hz. (E) Durability test of a TATSA under a pressure of 1 kPa. (F) Output characteristics of the TATSA after washing 20 and 40 times.

  • Fig. 4 Pulse wave measurements at various artery positions and analysis of the pulse signals.

    (A) Illustration of the WMHMS. (B) Photographs of the TATSAs stitched into a wristband, fingerstall, sock, and chest strap, respectively. Measurement of the pulse at the (C1) neck, (D1) wrist, (E1) fingertip, and (F1) ankle. Pulse waveform at the (C2) neck, (D2) wrist, (E2) fingertip, and (F2) ankle. (G) Pulse waveforms of different ages. (H) Analysis of a single pulse wave. Radial augmentation index (AIx) defined as AIx (%) = P2/P1. P1 is the peak of the advancing wave, and P2 is the peak of the reflected wave. (I) A pulse cycle of the brachial and the ankle. Pulse wave velocity (PWV) is defined as PWV = D/∆T. D is the distance between the ankle and the brachial. ∆T is the time delay between the peaks of the ankle and brachial pulse waves. PTT, pulse transit time. (J) Comparison of AIx and brachial-ankle PWV (BAPWV) between healthy and CADs. *P < 0.01, **P < 0.001, and ***P < 0.05. HTN, hypertension; CHD, coronary heart disease; DM, diabetes mellitus. Photo credit: Jin Yang, Chongqing University.

  • Fig. 5 Respiratory wave measurements and analysis of SAS.

    (A) Photograph showing the display of the TATSA placed on the chest for measuring the signal in the pressure associated with respiration. (B) Voltage-time plot for the TATSA mounted on the chest. (C) Decomposition of the signal (B) into the heartbeat and the respiratory waveform. (D) Photograph showing two TATSAs placed on the abdomen and wrist for measuring respiration and pulse, respectively, during sleep. (E) Respiratory and pulse signals of a healthy participant. HR, heart rate; BPM, beats per minute. (F) Respiratory and pulse signals of a SAS participant. (G) Respiratory signal and PTT of a healthy participant. (H) Respiratory signal and PTT of a SAS participant. (I) Relationship between PTT arousal index and apnea-hypopnea index (AHI). Photo credit: Wenjing Fan, Chongqing University.

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/6/11/eaay2840/DC1

    Section S1. Definition of AIx and PWV

    Fig. S1. A geometrical model for loop structure.

    Fig. S2. Structure of the conductive yarn.

    Fig. S3. Structure of the nylon thread.

    Fig. S4. Compatibility of the TATSAs.

    Fig. S5. Photograph of TATSAs in different colors.

    Fig. S6. Photographs demonstrating that the TATSA has remarkable endurance.

    Fig. S7. Computerized flat knitting machine carrying out automatic knitting of a cloth.

    Fig. S8. Details of the TATSA.

    Fig. S9. Simulation result of the force distribution of a TATSA under applied pressures at 0.2 kPa using the COMSOL software.

    Fig. S10. Simulation results of the force distribution of a contact unit under the applied pressures at 0.2 and 2 kPa, respectively.

    Fig. S11. Complete schematic illustrations of the charge transfer of a contact unit under short-circuit conditions.

    Fig. S12. Schematic illustration of the experimental setup.

    Fig. S13. Continuous output voltage and current of TATSA in response to the continuously applied external pressure in a measurement cycle.

    Fig. S14. Voltage response to various numbers of loop units in the same fabric area when keeping the loop number in the wale direction unchanged.

    Fig. S15. A comparison between the output performances of the two textile sensors using the full cardigan stitch and plain stitch.

    Fig. S16. Plots showing frequency responses at the dynamic pressure of 1 kPa and pressure input frequency of 3, 5, 7, 9, 10, 11, 13, 15, 18, and 20 Hz.

    Fig. S17. The durability test of a TATSA under a pressure of 1 kPa.

    Fig. S18. The output voltages of the TATSA at different tension in the wale and course direction.

    Fig. S19. The output voltages after different twisting times.

    Fig. S20. The output voltages of the sensor at various relative humidity from 10 to 90%.

    Fig. S21. The pulse waveforms at ankle of different individuals.

    Fig. S22. The pulse waveforms of different age groups.

    Fig. S23. Different tightness was achieved by tightening the wristbands at both ends of the sensor.

    Fig. S24. The pulse waveforms on different measuring positions.

    Fig. S25. The output voltages of the sensor when the subject was in the static and motion conditions.

    Fig. S26. Photograph showing the TATSAs placed on the abdomen and wrist simultaneously for measuring respiration and pulse, respectively.

    Table S1. Performances and applications of smart textiles for wearable devices.

    Table S2. Data of AIx and PWV of the healthy, HTN, CHD, and DM groups.

    Table S3. Rating criteria for OSAS.

    Movie S1. Fabrication of the TATSA.

    Movie S2. Fabrication of the clothes.

    Movie S3. Monitoring of the pulse signal at the neck.

    Movie S4. Monitoring of the pulse signal at the wrist.

    Movie S5. Monitoring of the pulse signal at the fingertip.

    Movie S6. Monitoring of the pulse signal at the ankle.

    Movie S7. Monitoring of the pulse and respiratory signals at the chest.

    Movie S8. Comparison of the pulse waveforms measured by the medical instrument and the TATSA.

    Movie S9. Comparison of the respiratory waveforms measured by the medical instrument and the TATSA.

    Movie S10. Monitoring of the pulse and respiratory signals while sleeping.

    Movie S11. Monitoring of the pulse and respiratory signals while sitting.

  • Supplementary Materials

    The PDF file includes:

    • Section S1. Definition of AIx and PWV
    • Fig. S1. A geometrical model for loop structure.
    • Fig. S2. Structure of the conductive yarn.
    • Fig. S3. Structure of the nylon thread.
    • Fig. S4. Compatibility of the TATSAs.
    • Fig. S5. Photograph of TATSAs in different colors.
    • Fig. S6. Photographs demonstrating that the TATSA has remarkable endurance.
    • Fig. S7. Computerized flat knitting machine carrying out automatic knitting of a cloth.
    • Fig. S8. Details of the TATSA.
    • Fig. S9. Simulation result of the force distribution of a TATSA under applied pressures at 0.2 kPa using the COMSOL software.
    • Fig. S10. Simulation results of the force distribution of a contact unit under the applied pressures at 0.2 and 2 kPa, respectively.
    • Fig. S11. Complete schematic illustrations of the charge transfer of a contact unit under short-circuit conditions.
    • Fig. S12. Schematic illustration of the experimental setup.
    • Fig. S13. Continuous output voltage and current of TATSA in response to the continuously applied external pressure in a measurement cycle.
    • Fig. S14. Voltage response to various numbers of loop units in the same fabric area when keeping the loop number in the wale direction unchanged.
    • Fig. S15. A comparison between the output performances of the two textile sensors using the full cardigan stitch and plain stitch.
    • Fig. S16. Plots showing frequency responses at the dynamic pressure of 1 kPa and pressure input frequency of 3, 5, 7, 9, 10, 11, 13, 15, 18, and 20 Hz.
    • Fig. S17. The durability test of a TATSA under a pressure of 1 kPa.
    • Fig. S18. The output voltages of the TATSA at different tension in the wale and course direction.
    • Fig. S19. The output voltages after different twisting times.
    • Fig. S20. The output voltages of the sensor at various relative humidity from 10 to 90%.
    • Fig. S21. The pulse waveforms at ankle of different individuals.
    • Fig. S22. The pulse waveforms of different age groups.
    • Fig. S23. Different tightness was achieved by tightening the wristbands at both ends of the sensor.
    • Fig. S24. The pulse waveforms on different measuring positions.
    • Fig. S25. The output voltages of the sensor when the subject was in the static and motion conditions.
    • Fig. S26. Photograph showing the TATSAs placed on the abdomen and wrist simultaneously for measuring respiration and pulse, respectively.
    • Table S1. Performances and applications of smart textiles for wearable devices.
    • Table S2. Data of AIx and PWV of the healthy, HTN, CHD, and DM groups.
    • Table S3. Rating criteria for OSAS.

    Download PDF

    Other Supplementary Material for this manuscript includes the following:

    • Movie S1 (.mp4 format). Fabrication of the TATSA.
    • Movie S2 (.mp4 format). Fabrication of the clothes.
    • Movie S3 (.mp4 format). Monitoring of the pulse signal at the neck.
    • Movie S4 (.mp4 format). Monitoring of the pulse signal at the wrist.
    • Movie S5 (.mp4 format). Monitoring of the pulse signal at the fingertip.
    • Movie S6 (.mp4 format). Monitoring of the pulse signal at the ankle.
    • Movie S7 (.mp4 format). Monitoring of the pulse and respiratory signals at the chest.
    • Movie S8 (.mp4 format). Comparison of the pulse waveforms measured by the medical instrument and the TATSA.
    • Movie S9 (.mp4 format). Comparison of the respiratory waveforms measured by the medical instrument and the TATSA.
    • Movie S10 (.mp4 format). Monitoring of the pulse and respiratory signals while sleeping.
    • Movie S11 (.mp4 format). Monitoring of the pulse and respiratory signals while sitting.

    Files in this Data Supplement:

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