Weaving-based wearable sensing instrument designed for the joint motion monitoring of the elbow and knee flexion angle

This work presents a wearable optical fiber sensing scheme based on an eight-figure macro-bend fiber configuration. The wearable sensor scheme utilizes a single-mode fiber deformed on an eight-figure configuration. The fabricated optical fiber sensor is mounted onto a wearable woven fabric and then garment on the elbow and knee joints of different healthy volunteers' bodies. The proposed wearable biomechanical sensor shows an excellent sensitivity correlated with the human knee and elbow joints' range of motion 0 degrees-90 degrees which is about -0.963 nm/degrees, with good regression coefficients (R2) exceeding 99.6%, for elbow joint flexion and sensitivity of 0.874 nm/degrees with a high R2 exceeding 99.4% for knee flexion. Besides, this sensor also displays high repeatability and stability and a fast response time of 1.66 ms, combined with a small standard deviation of about 2.321%. So, the planned wearable optical fiber sensor system is a practicable option for monitoring joint motion, human movement analysis, and soft robots.