Research On Optical Detection Of Droplets In Microfluidic System

Microfluidic droplet detection technology is an important branch of microfluidics,which is widely used in biology,chemistry,medical and other fields.At present,microfluidic droplet detection technology mainly includes electrochemical detection,mass spectrometry detection,optical detection and other methods.Limited by the detection principle,it can only be applied to specific droplet detection,and its application scope is limited.The detection technology with low cost,simple structure and wide application range is needed in the current microfluidic applications.In this paper,the optical detection method of microfluidic droplets and the design of optical detection system are studied.The specific research contents are as follows:(1)In order to realize the measurement of droplet velocity and size in microfluidics,two kinds of optical detection systems,focusing detection and linear detection,are proposed respectively.The structure of optical path is designed and analyzed by theoretical calculation and ZEMAX simulation.According to the design scheme,an experimental device for droplet optical detection is built and verified.(2)Aiming at the problem of CCD strong light failure of the detection device,a solution of multi-stage attenuator superposition is proposed;And because of the problem of low signal discrimination in the direct detection,a detection method of biased CCD is proposed based on the principle of droplet refraction.The best offset angle is obtained from the light deflection model,and the accurate detection of micro droplets is realized.(3)Based on the principle and characteristics of flow focusing,a microfluidic experimental system was designed.A low-cost microfluidic pipeline was built by using micro four-way and capillary tube.The injection pump controlled by PLC was used as the fluid driving device to form a droplet microfluidic platform.The simulation of microfluidic pipeline is carried out by COMSOL software,and the range of fluid velocity of droplets generated in the pipeline is determined.The effect of droplet microfluidic system is verified by experiments.(4)Finally,the optical detection device and droplet microfluidic system are combined to form an experimental platform for the optical detection of micro droplets.In the experiment of micro droplet formation velocity,it is found that there is a positive correlation between the carrier velocity and the droplet formation velocity.For different kinds of droplets,the phenomenon that the detection signal intensity increases with the increase of refractive index is verified.The size detection experiment of a single micro-droplet is carried out,and the measured size results are basically consistent with the simulation.Through the research of this paper,the optical detection method of micro droplets based on the principle of optical refraction is proposed,and the micro droplet velocity and size detection are realized.It is of great significance to simplify the structure of the detection system of microfluidic,increase the application range of microfluidic detection,and promote the market application of microfluidic optical detection technology.