Exploration And Application Research Of Microfluidic Droplet Array Mechanism

The droplet microfluidic technology has developed rapidly in recent years.The static droplet array(SDA)microfluidic chip has been reported as an important research direction of droplet microfluidic technology.It can be used for particle or droplet capture,droplet generation and various biochemicals experiment.However,the current theoretical research on SDA microfluidic chips is not systematic enough,especially the mechanism for generating droplets using SDA microfluidic chips is very few.The widely used flow resistance theory does not consider the surface tension between twophase fluids,and the explanation is not comprehensive enough.Therefore,systematic research on the particle capture mechanism and droplet formation mechanism in SDA microfluidic chip,and on this basis,the relevant application research is particularly important at this stage.The specific research contents of this paper are as follows:(1)In this paper,the system theory analysis and simulation verification of particle capture mechanism and droplet generation mechanism in SDA microfluidic chip are carried out.This paper first uses flow resistance theory to explain the design of capturing particles using SDA structure.However,due to the two-phase interface in the process of generating droplets using the SDA structure,this paper proposes a capillary bursting valve and capillary restriction valve mechanism in the process of droplet formation.Through the VOF module of Ansys Fluent simulation software,the droplet generation process in the SDA microfluidic chip with circular,elliptical,diamond and rectangular shapes is simulated and analyzed.The function of the capillary bursting valve and the capillary restriction valve during the droplet formation process was initially verified.(2)The four SDA microfluidic chips with circular,elliptical,rhombic and rectangular trap structures were tested.The results show that there are obvious bursting valve phenomena in the three SDA microfluidic chips with circular,elliptical and diamond trap shapes.Since the chip with a rectangular trap structure has no expansion section,there is no bursting valve phenomenon caused by the expansion of the channel,and it is proved that the phenomenon of the capillary bursting valve is related to the opening size of the expansion section.The experimental video was processed in real time and further analyzed with SimpleCV image processing technology to verify the important role of the capillary bursting valve and capillary restriction valve in the droplet formation process.(3)The template method is used to prepare the particles which are substantially consistent with the shape of the trap structure,and the prepared particles can basically reproduce the morphology of the trap structure on the x-y horizontal plane.At the same time,250 μm diameter polystyrene particles were successfully captured using the capture array SDA microfluidic chip.It proves a wide range of application scenarios of SDA microfluidic chip.