Monitoring shoulder flexion-extension movements using a 3D-printed wearable sensor based on fiber Bragg grating technology

Recently, musculoskeletal disorders (MSDs) are considered the world's leading cause of pain and physical disability. Wearable devices can play a significant role in managing and preventing MSDs due to their numerous advantages like high unobtrusiveness, comfortability, and usability. Different types of sensors (e.g., electrical, mechanical, and optical) can be used to instrument garments like t-shirts and elastic straps to make them smart. Among others, wearable strain sensors are devices designed to measure the deformation or stretching experienced by the human body due physical activities and can be a valuable solution for monitoring MSDs.The purpose of this study is to propose the use of a novel wearable strain sensor for MSDs. In more details, a fiber optic sensor (i.e., fiber Bragg grating sensor) integrated into a 3D-printed structure with a dumbbell shape was used for detecting shoulder flexion/extension (F/E) movements. First, we described the sensor design and fabrication stage. Then, we detailed its metrological properties. Finally, we performed a pilot test on two healthy volunteers to assess the system capability of monitoring consecutive F/E movements in the range 0° - 90° in three different planes (i.e., sagittal, frontal and scapular planes).The system showed the best performance in monitoring F/E in the sagittal plane in real-time, followed by the frontal and the scapular plane. Moreover, the duration of F/E movements was estimated showing promising capacities in monitoring movement rate. The achieved findings suggest the potential use of the proposed wearable system in healthcare contexts such as MSDs for rehabilitation purposes to enhance patient outcomes, monitor progress, and provide personalized care.