A Fiber-Tip Laminar Flow Rate Sensor With Temperature Compensated Based on Three-Beam Interferometer

The widespread utilization of microfluidics has increased the demand for flow rate precisely sensing in channel. In this paper, we propose a fiber-tip laminar flow rate sensor with temperature compensated based on three-beam interferometer, which is composed by a piece of polydimethylsiloxane (PDMS) and air in a section of hollow core fiber (HCF) sealed by graphene oxide (GO) film. Fluid with different flow rate will cause different impacts on the GO film, causing changes of the length of the air cavity. PDMS in the bottom of the cavity serves as a temperature-compensated portion because of the high thermo-optical coefficient (TOC) for testing the flow rate of microfluidics with different temperatures. The change of the length of the air cavity and the refractive index (RI) of the PDMS both will cause the shifting of the interference dips in the spectrum of the flow rate sensor. The ultra-thin GO film indicates that the sensor has a high-rate sensitivity, which can be used for the laminar flow rate measuring. The flow rate sensitivity can reach −44.679 nm/(mL/min) in the range of 0.01 to 0.1 mL/min. The actual flow field rate in the channel is obtained because the influence of the probe sensor embedding on the flow rate field is compensated during the calibration process. In addition, the sensor demonstrates a high-temperature compensated sensitivity of 30.963 nm/°C. This work provides a compact all-optical solution for laminar flow rate monitoring, which can also be applied to flow rate measuring in drug delivery, blood osmometry and bioanalysis.