High precision CO2 dynamic sensing method based on cyclic microfluidic fluorescence response

The excessive emission of industrial CO 2 seriously threatens the living environment of human beings. In this paper, we propose a CO 2 sensing method based on cyclic microfluidic and dynamic flow detection technology. Firstly, a microflow permeation model was established to describe the numerical relationship between CO 2 permeation flux and gas phase inlet concentration and velocity. Secondly, we designed a microfluidic chip with coupled gas–liquid circulation and optimized its channel structure. Based on this, a microflow fluorescence response sensing system was built to analyze the fluorescence response spectral characteristics under different CO 2 permeation fluxes. Then, the optimal gas flow rate selection strategy for different CO 2 concentrations was proposed, and the CO 2 dynamic sensing model was established. Finally, the reliability of the proposed detection method is verified by comparing the detection results of commercial sensors with standard gases. The results indicate that the linear correlation coefficient between the relative fluorescence intensity and CO 2 concentration of the proposed CO 2 dynamic sensing method is 0.9987, the detection error of low concentration range is 193.3 ppb, and the detection error of high concentration range is less than 193.3 ppm. Compared with the parallel flow mixing device, the gas–liquid circulation-coupled microfluidic chip designed in this paper has better gas–liquid mixing effect. The system can operate continuously in the air for 40 weeks. Compared with commercial sensors, it has the advantages of better reusability, high linearity and low detection error in the whole range.