Mechanism And Experiments For The Droplet Formation And Manipulation In Microfluidics

Fluid is an important existence form of objects, while microfluidics foucus onthe manipulation of fluids in micro scale. Droplet is a new branch of themicrofludics in recent years, which is regarded as an independent micro-reactor. Theresearch on the reaction in the droplet is crucial for the new microfluidic work.Compared with tranditional chemical reaction, droplet has many advantages, such aslow sample consumption, rapid response, and no pollution etc, resulting in its extendapplication on chemical sythesis, nanomaterial preparation, cell analysis and drugsorting. However, the formation and manipulation of droplets are the foundation ofabove research, but the previous work is not deep. Depending on this condition, thethesis will focus on the basic mechanism of the droplet formation and manipulation,in order to achieve the precise control of drolets, which is significant for themicrofluidics.Firstly, research actuality is reviewed, and the basic mechanism for the twophase flow is proposed, including the non-dimensional parameters in dropletdynamics, wall wetting properties, contact angle and marangoni effect etc. Thedroplet formation mechanisms for T shape microchannel, stream focusing, andcoaxial fluids are described, meanwhile the basic manipulation mechanisms areanalyzed.Secondly, the models for kinds of mirochannel are set up and simulated bysetting the suitable boundary conditions, and using the level set methods. Moreover,the manipulate models for transport, split and fusion are founded, and also obtainthe simulation results, providing parameters comparation for the experiments.Finally, the microchips for the droplet formation and manipulation arefabricated using standerd litography. The methods including the T shapemicrochannel, stream focusing, and coaxial fluids are employed to create steady andhomogeneous droplets. In addition, the yeast cells are packed by the droplets,achieving the droplets transport, split, fusion and mixing etc. The chips with theintegrated functions are carried out, in order to achieve the parallel fuctions, whichverify the theoretical and simulation results effectively.