Wearable stretchable sensor based on conductive textile fabric for shoulder motion monitoring

Wearable stretchable sensors are gaining significant interest in application related to joint motion monitoring. Stretchable strain sensors are a promising technological solution to develop wearable systems for several applications (e.g., sports, rehabilitation, health science) thanks to their flexibility, lightweight, compliance, and ease to wear. The aim of this study is twofold: i) to perform the metrological characterization of a stretchable sensing element based on a conductive textile fabric for developing a wearable sensor intended for joint motion monitoring and ii) to provide a preliminary assessment of the developed sensor in shoulder motion monitoring. The static characterization and the hysteresis analysis at different speeds (i.e., 50 mm.min−1, 100 mm.min−1, 200 mm.min−1, 400 mm.min−1and 600 mm.min−1) were carried out to assess the sensor's characteristics to mechanical strain. An explorative test to assess the sensor feasibility in monitoring horizontal flexion-extension of the shoulder was performed on one healthy volunteer. Results showed that the sensor's resistance decreased from $75 k \Omega$ at 0% strain level to $52 k \Omega$ at 10% strain level during static characterization. Moreover, the maximum hysteresis error $e_{H}\%$ was always lower than 2.59% during loading-unloading hysteresis cycles at different speeds. The developed stretchable sensor seems to be a promising solution for monitoring shoulder range of motion in applications were unobtrusiveness and wearability are key factors.