Research On A New Microfluidic Method For Droplet Mixing Based On Electro-rotation Effect

With the rapid development of emerging integrated circuits and electronic information in recent years,the machining accuracy of micromachining technology has also been greatly improved,and integrated microfluidic devices have also appeared in large numbers.Since the 1950s,the basic idea of using small droplets to separate reactions has emerged.With the help of droplet microfluidics,routine laboratory operations can be performed using droplet as unit,and large amounts of data can be analyzed simultaneously.Therefore,droplet digital microfluidics is of great research and practical value,and droplet-based microfluidic device is also widely used in various applications,which uses microdroplet as reaction device for efficient mixing.In the natural state of micro-scale and no external disturbance,the fluid mainly maintains a stable laminar flow state,and its mixing depends heavily on the natural diffusion between molecules.Moreover,a large volume of fluid is not convenient to operate,but also causes waste of samples.Therefore,it is necessary to find a fast and efficient mixing method based on microdroplet.This thesis innovatively proposes a new method of micro fluidic driving with electrorotation effect,which utilizes dielectric polarization and induced electroosmotic flow to realize controllable rotational flow inside droplets,developing a droplet microfluidic chip integrating drive,rotation and mixing.Through systematic theoretical research,this thesis clarifies the formation mechanism of electro-rotation effect in microdroplet,enriching the theory of fluid mechanics at microscale.The numerical simulation software COMSOL was used to design a droplet mixing microfluidic model based on the electro-rotation effect,optimize the structural parameters of this model,and analyze the rotating flow characteristics inside the droplet and the mixing efficiency.The numerical analysis results show that the droplet mixing microfluidic chip proposed in this paper can improve obviously the mixing efficiency of droplets compared with the free diffusion.The droplet mixing microfluidic chip is fabricated by micromachining technology,and the droplet mixing efficiency of the chip is detected by the mixing of dyed droplets,and the mixing efficiency of the droplet mixing microfluidic chip is evaluated.This new method does not need large amounts of incompatible continuous flow,no external electrode plates,and no moving parts.The droplet generation is simple,and the speed and direction of the eddy current in the droplet can be precisely controlled by controlling the voltage.The temperature change is small and will not cause the evaporation of droplets.It overcomes the related deficiencies of existing droplet mixing techniques.