Generation Of O/W And W/O Type Microdroplets With Capillary Fracture

In recent years, droplet microfluidic chip is emerging as a novel chemical analysis platform due to its advantages in high-efficiency, high-throughput, fast reaction time and low consumption. Microfluidic technology based droplet generation and application are drawing more and more attention in many areas, such as chemical and life sciences. Previous works have shown that the different structure and material of microfluidic channels have an important influence on the generation of microdroplets. This thesis investigated the capability of microdroplet generation in microchannel device comprised of fused silica capillary, so as to obtain a simple, rapid method of droplet genration system.In the first chapter, the mechanism of droplet formation, the main parameters influncing the formation of droplet and the representative microfluidic devices for droplet generation are systematically summarized. And the applications of oil in water (O/W) and water in oil (W/O) droplet in biochemical analysis are also introduced. It is noticed from the review that a cheap chip processing technology is one of the trends of droplet microfluidic technology in the future.In the second chapter, a new type of droplet microfluidic chip was established based on fused silica capillary and the on-column micro-fracture, and successfully used for the generation of monodispersed O/W type microdroplet. In the experiment, deionized water was used as the continuous phase and was delivered through fracture channel; the dimethyl siliconeal oil was chosen as the dispersed phase and was delivered through capillary channel. The effects of the flow velocity of the two phases, the concentration of surfactant and the viscosity of continuous phase on the droplet size and droplet generation were investigated. When the concentration of surfactant was greater than its critical micelle concentration, the size of droplets remained unchanged. Statistics of50droplets of120μm gave a polydispersity index values of3.2%.In the third chapter, the capillary channel was firstly washed with silanized solution to make sure the channel surface was completely hydrophobic, and monodisperse water in oil droplets were successfully prepared. The effects of surfactant and flow rates of two phases on droplet formation were investigated. The results show that the size of droplets is mainly dependent on the flow ratio of two phase, And the polydispersity index values of fifty100μm droplets was3%. Combined with laser induced fluorescence system, the different concentration of the droplet of fluorescent sodium and the stability of droplets are detected, with which the potential application of the droplet system in the flow analysis was preliminarily demonstrated.The droplet microfluidic chip system is easy to establish, low cost and flexibile. Different types of microdroplet can be generated on-demand, and the homogeneous of droplet size is satisfactory. It may become an basic research platform for microdroplet based applications.