Bending Angle Sensor Based on Double-Layer Capacitance Suitable for Human Joint

Goto, Daisuke; Sakaue, Yusuke; Kobayashi, Tatsuya; Kawamura, K; Okada, Shima; Shiozawa, Naruhiro

doi:10.1109/ojemb.2023.3289318

Cited by 5 publications

(3 citation statements)

References 30 publications

(61 reference statements)

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“…Specifically: Tests were reported on one human subject. This small sample is similar to several other studies performed in the literature during the first stages of wearable sensor validation [ 27 , 28 , 31 , 32 , 33 ]. It is herewith justified by our goal to study how the sensor system performs over the course of time and for different activities as relying upon a certain calibration curve.…”

Section: Discussionsupporting

confidence: 86%

“…Bending sensors, on the other hand, are both bendable and stretchable. Nevertheless, resistive-type bending sensors are prone to hysteresis from stretching and bending deformations [ 23 , 24 , 25 , 26 ], while capacitive-based bending sensors may encounter errors due to capacitive coupling when skin contacts the sensors, potentially compromising accuracy [ 27 , 28 ]. Additionally, the direct placement of these sensors upon the joints makes them uncomfortable and somewhat limits movement.…”

Section: Introductionmentioning

confidence: 99%

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Wearable Loop Sensor for Bilateral Knee Flexion Monitoring

Zhang,

Caccese,

Kiourti

2024

Sensors

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We have previously reported wearable loop sensors that can accurately monitor knee flexion with unique merits over the state of the art. However, validation to date has been limited to single-leg configurations, discrete flexion angles, and in vitro (phantom-based) experiments. In this work, we take a major step forward to explore the bilateral monitoring of knee flexion angles, in a continuous manner, in vivo. The manuscript provides the theoretical framework of bilateral sensor operation and reports a detailed error analysis that has not been previously reported for wearable loop sensors. This includes the flatness of calibration curves that limits resolution at small angles (such as during walking) as well as the presence of motional electromotive force (EMF) noise at high angular velocities (such as during running). A novel fabrication method for flexible and mechanically robust loops is also introduced. Electromagnetic simulations and phantom-based experimental studies optimize the setup and evaluate feasibility. Proof-of-concept in vivo validation is then conducted for a human subject performing three activities (walking, brisk walking, and running), each lasting 30 s and repeated three times. The results demonstrate a promising root mean square error (RMSE) of less than 3° in most cases.

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Section: Discussionsupporting

confidence: 86%

Section: Introductionmentioning

confidence: 99%

Wearable Loop Sensor for Bilateral Knee Flexion Monitoring

Zhang,

Caccese,

Kiourti

2024

Sensors

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“…Strain sensors show even better results of measuring knee flexion of 1.2°± 0.87° RMSE [25] . Optical fiber sensors have shown to achieve a 5.3° ± 1.13° RMSE during walking [26] , while capacitive bending sensors have shown to achieve a RMSE 5.8° ± 1.2° during robotic arm bending tests [27] . Although other approaches may achieve slightly better results, they are bulky, restrict movement, suffer from drift, or are prone to wear and tear.…”

Section: Discussionmentioning

confidence: 99%

Wearable Loop Sensors for Knee Flexion Monitoring: Dynamic Measurements on Human Subjects

Anderson,

Cosma,

Zhang

et al. 2024

IEEE Open J. Eng. Med. Biol.

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Goals: We have recently introduced a new class of wearable loop sensors for joint flexion monitoring that overcomes limitations in the state-of-the-art. Our previous studies reported a proof-of-concept on a cylindrical phantom limb, under static scenarios and with a rigid sensor. In this work, we evaluate our sensors, for the first time, on human subjects, under dynamic scenarios, using a flexible textile-based prototype tethered to a network analyzer. An untethered version is also presented and validated on phantoms, aiming towards a fully wearable design. Methods: Three dynamic activities (walking, brisk walking, and full flexion/extension, all performed in place) are used to validate the tethered sensor on ten (10) adults. The untethered sensor is validated upon a cylindrical phantom that is bent manually at random speed. A calibration mechanism is developed to derive the sensor-measured angles. These angles are then compared to gold-standard angles simultaneously captured by a light detection and ranging (LiDAR) depth camera using root mean square error (RMSE) and Pearson's correlation coefficient as metrics. Results: We find excellent correlation (≥ 0.981) to gold-standard angles. The sensor achieves an RMSE of 4.463° ± 1.266° for walking, 5.541° ± 2.082° for brisk walking, 3.657° ± 1.815° for full flexion/extension activities, and 0.670° ± 0.366° for the phantom bending test. Conclusion: The tethered sensor achieves similar to slightly higher RMSE as compared to other wearable flexion sensors on human subjects, while the untethered version achieves excellent RMSE on the phantom model. Concurrently, our sensors are reliable over time and injury-safe, and do not obstruct natural movement. Our results set the ground for future improvements in angular resolution and for realizing fully wearable designs, while maintaining the abovementioned advantages over the state-of-the-art.

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