Flow Rate Sensor Based On Optical Microfiber Embedded Soft Film

With the development of chemical,pharmacy,and energy engineering,traditional flow rate measurement based on electrical and mechanical techniques cannot meet the specific requirements in harsh environment gradually,especially the lack of sensitive and reliable method for the flow rate measurement in millimeter-scale pipelines.As a new type of optical waveguides,with diameters close to or below the wavelength of the guided light,microfibers not only inherit the advantages of standard optical fibers,such as immunity to electromagnetic interference,resistance to corrosion and multiplexing detection capability,but also have unique properties,including strong evanescent field,small size and high mechanical flexibility,which are attractive for developing compact flow rate sensors with fast response and high sensitivity.Here,we firstly reviewed the development of fiber-optic rate sensors and microfiber sensors,and introduced the fabrication and optical properties of microfibers.We developed a flow rate sensor based on optical microfiber embedded soft film.The microfiber is embedded in polydimethylsiloxane(PDMS)film to realize flow rate sensing in millimeter-scale pipelines.The PDMS fi lm is deflected by the flowing liquid,resulting in the leakage of guided modes of the embedded microfiber which is directly related to the flow rate of the liquid.We theoretically verified the feasibility of the PDMS film embedded with U-shaped microfiber for flow rate sensing in pipelines.Firstly,the deformation of the PDMS film at different flow rates is observed through simulation and experiment.The simulation results also show the bending angle of the PDMS film is related to the flow rate of the liquid.In addition,the optical simulation results show that the larger the bending angle of the microfiber,the smaller the output light intensity.Then we successfully fabricated an optical microfiber flow rate sensor with low detection limit(<0.05 L/min),high resolution(0.005 L/min)and fast response(12 ms).And we have experimentally verified that the thickness of the PDMS film,the diameter of the microfiber and the working wavelength can affect the sensitivity and working range of the sensor.In this paper we realized a compact and highly sensitive optical sensor with high flexibility for the accurate millimeter-scale pipeline flow rate measurement which also paves the way for the packaging and application of optical microfiber sensors.