Novel fiber-tip micro flowmeter based on optofluidic microcavity filled with silver nanoparticles solutions

A novel fiber-tip micro flowmeter based on optofluidic microcavity filled with silver nanoparticles solutions (SNS) is proposed. CW fiber laser was used to heat SNS that can emit heat obviously due to the excellent optic-thermo effect. The heat generated by the silver nanoparticles would be taken away as the microfluidic flows over the fiber microcavity until thermal balance is established under different velocity. The effective refractive index (RI) of the SNS changed followed by temperature of the thermal balance. The dips of the Fabry–Perot interference spectrum shift and the flow velocity can be demodulated. Moreover, the sensor can measure the flow rate with a high sensitivity due to the superior thermal conductivity and specific heat capacity of sidewalls. The max flow rate sensitivity can reach 1.5 nm/(μL/s) in the large range of 0–5 μL/s with a detection limitation (DL) of 0.08 μL/s. The Micron scale probe-type flowmeter has strong robustness and can be used to measure flow rate in tiny space. The heating medium also has an excellent biological compatibility and is not contact with the fluidics directly. As such, we believe that the proposed fiber-tip micro flowmeter has great application potentials in haematology, oil prospecting, ocean dynamics and drug research.