Flexible membrane curvature sensor based on multilayer polyimide substrate and optical fiber implantation

We report a flexible membrane curvature sensor with multilayer polyimide thin film substrate and embedded fiber Bragg gratings (FBGs). The major contribution is obtaining a membrane curvature sensor with extraordinary flexibility and repeatability for the measurement of soft mechanisms and complex structures. The approximate linear relation between the reflected wavelength shift and the bending curvature is analyzed using the pure bending model. The reflection spectra variation of the sensor with the curvature of the measuring object, and the effect of the embedded depth of the FBG sensitive element is analyzed experimentally. The optimal depth position for the implantation of the optical fiber, and the sensitivity and repeatability of the membrane sensor is obtained. The results proved that the proposed membrane curvature sensor is flexible enough to fit tightly on the molded surface of the object for real time measurement. In the curvature range of 0m−1-30m−1, the maximum sensitivity is up to 51.62pm/m−1, and the fluctuation coefficient in repeated measurements is negligible. The membrane sensor is simple in configuration, easy to fabricate and low cost. It has broad application prospects in the field of industrial measurement, medical detecting and monitoring.