Heat Typed Fiber Liquid Flow Sensor With Wide Sensing Range and High Sensitivity

In this paper, a heat typed fiber sensor for microfluidic velocity measurement with large sensing range and high sensitivity is demonstrated. The single-mode fiber (SMF) end face and polymer cap form a Fabry Perot (FP) structure. The Au film layer on the surface of the polymer cap is heated by an infrared laser, and the heated Au film layer undergoes heat transfer to the polymer cap structure, causing it to expand upon heating. Due to the heat carried away by the polymer cap structure at the action of microfluidic rates, the cavity length of the polymer cap structure changes. Therefore, the flow rate can be measured by monitoring the wavelength drift of the interference spectrum. The experimental results indicate that the laser can induced heat and transfer to the probe because the Au film has excellent thermal conductivity. Furthermore, the probe has a good response to the flow rate. The probe has advantages of simple preparation, small size, and strong structure, which can be used for micro flow rate sensing with wide sensing range and high sensitivity.