Wearable Flexible Hydrogel Optical Fibers Applied for Finger Morphology Analysis

The optical fiber-based wearable curvature sensor shows great potential for real-time monitoring of human joint motion and smart gesture interaction. However, its limited detection range (typically below 10 m −1 ) and the significant mismatch with the dynamic, large-curvature movements of human joints (> 100 m −1 ) have emerged as critical bottlenecks restricting its practical application. To address this challenge, this study proposes for the first time a hydrogel optical fiber flexible curvature sensor with ultra-wideband response. A fine-core hydrogel flexible optical fiber is fabricated using a drawing-spinning process, and its ultra-flexible characteristics successfully overcome the mechanical constraints of traditional optical fibers, enabling reversible bending deformation with a curvature range from 0 to 139.84 m −1 . To the best of the knowledge, this detection range is the largest curvature detection range in the field of optical fiber curvature sensing. By utilizing the displacement of interference valleys (sensitivity of 0.04 nm m −1 ) and the output light intensity attenuation (sensitivity of 1.97 µW m −1 ) when bending in the hydrogel multimode optical fiber, dual-parameter curvature sensing is achieved. By constructing a multi-joint monitoring platform and combining neural network algorithms, gesture recognition is achieved. This work provides an innovative solution for large curvature detection.