A label-free infrared opto-fluidic method for real-time determination of flow rate and concentration with temperature cross-sensitivity compensation

Abstract

The ability to accurately measure the flow rate, concentration, and temperature in real-time in micro total analysis systems (μTAS) is crucial when improving their practical sensing capabilities within extremely small volumes. Our label-free infrared (1500–1600 nm) opto-fluidic method, presented in this study, utilizes a cantilever-based flow meter integrated with two parallel optical fiber Fabry–Perot interferometers (FPIs). The first FPI serves as an ultra-sensitive flow meter and includes a Fiber Bragg Grating (FBG) tip for localized temperature sensing. The second FPI has a fabricated photopolymer micro-tip for highly sensitive refractive index (RI) determination. In this work, we performed 3-D simulation analysis to characterize cantilever deflection as well as temperature distribution and its effect on the RI. The experimental results from temperature cross-sensitivity analysis lead to real-time measurement resolutions of 5 nL min⁻¹, 1 × 10⁻⁶ RIU and 0.05 °C, for the flow rate, refractive index, and temperature, respectively.