Predictive flow rate measurement using self-mixing optical feedback interferometry for point-of-use microfluidic applications

Abstract

A precise knowledge of the flow rate in microscale fluidic devices is one of the key challenges in modern diagnostics. Flow rate has a direct impact on diffusion rates during chemical processing, which in turn minimizes the quantity of minute samples needed for testing. The flow rate measurement methods reported to date either require a relatively bulky optical arrangement, or maintaining their form factor at a low cost is not feasible. To address this issue, Self-Mixing Optical Feedback Interferometry (SM-OFI) is being widely explored for the design of microfluidic flowmetry devices, owing to its portability and cost-effective structure. However, measuring the variable flow rate is still a limitation for SM-OFI systems. In this paper, the authors present a predictive analysis-based measurement method to estimate the flow rate. The proposed method is based on an auto-regressive least mean square algorithm, and the variations in the flow rates are solved as a Quadratic Performance Surface (QPS) problem. The proposed method was experimentally verified using different test samples prepared with distilled water, benzyl chloride, and methylene iodide. The statistical analysis performed on the experimental results revealed a strong linear correlation with the true values, with an R-squared value of 0.9997 and a standard error of 0.0013. The proposed method achieves a resolution of 1.1828 μL/min with a standard uncertainty of 0.1860 μL/min. It also features a well-aligned, real-time measurement scheme integrated into a compact optical structure.