Polymer-encapsulated flexible strain sensors to monitor scapular movement: a pilot study

Strain sensors based on conductive and flexible textiles are gaining great relevance in research applications, rehabilitation, and sports medicine for monitoring human joints movements, thanks to their flexibility, negligible weight, and easy integration into substrates and wearable systems. The purpose of this work was twofold: i) to carry out the static characterization and to analyze the hysteresis of two textile-based strain sensors integrated into a polymeric matrix, and ii) to evaluate the feasibility of these sensors in monitoring scapular movements during bilateral arms abduction-adduction and flexion-extension. Results showed a comparable range of resistance variation at 0-20% strain during static characterization, with a mean absolute gauge factor of 2.65 (sensor A) and 2.12 (sensor B). The maximum hysteresis error was always lower than 31% for sensor A and lower than 27% for sensor B. Both sensors showed promising results in monitoring scapular motion during the two selected single-plane upper limb movements.