Wearable Optical Fiber Sensors for Joint Motion and Muscle Activity Monitoring: An Optimization Study

Wearable sensors are rapidly revolutionizing healthcare and biomedical monitoring, often used for physical rehabilitation therapies, yet existing solutions continue to face challenges associated with stability, wearability, proper integration, and high cost. Traditional mounting methods often result in sensor displacement and inaccurate measurements, while rigid designs sacrifice user comfort. To address these limitations, a novel wearable solution was presented, which integrates polymer optical fiber (POF) sensors with Kinesio tape. The new wearable is employed for monitoring elbow movement and muscle contractions, as a case study, using varying fiber spacing configurations (1, 2, and 3 mm). The system demonstrated excellent repeatability during multiple flexion and extension cycles, maintaining consistent voltage patterns with minimal deviation. Experimental validation with goniometer measurements demonstrated that while 1 mm spacing provided high sensitivity, it experienced signal saturation, similarly the same behavior was observed for 2 mm fiber spacing; conversely, 3 mm spacing offered extended range but reduced sensitivity when compared to lower spacing values. The novel wearable effectively tracked the elbow joint angles and detected muscle contractions, with the 1 mm spacing configuration showing high sensitivity to subtle muscle movements at the skin level. This work lays the foundation for future development of wearable POF-based monitoring systems for healthcare monitoring and personalized medicine.