Design And Analysis Of An EWOD-driven Micropump

Microfluidics is widely used in many disciplines and fields because of its characteristics that macroscopic fluidics do not have.The micropump is an important part of the microfluidics,which provides power for the work of microfluidics and plays the role of fluidics transmission and distribution.As an important branch of micropump,EWOD micropump is generally used to drive discrete droplets by EWOD phenomenon.But as the study deepening,it is found that when microfluidics needs to achieve more complex functions,the number of electrodes will increase exponentially.At this time,difficulties are encountered in the arrangement of electrodes and leads,the complexity of electrode control,the processing technology of the micropump and other aspects.Therefore,some scholars have proposed a scheme to use the EWOD phenomenon to drive continuous microfluidics,which is the scope of the EWOD micropump discussed in this paper.Through research,it is found that the method of using EWOD to drive continuous microfluidics still has serious drawbacks of causing macroscopic reflux.Therefore,this paper aims to improve the shortcomings of the original EWOD micropump by designing the "multi-chambers structure" EWOD flexible-valves micropump,and the structural parameters and flow parameters of the EWOD flexible-valves micropump are analyzed in depth.The main work contents are as follows:(1)Schematic design of EWOD flexible-valves micropump.The principle of droplet vibration by using EWOD and the principle of micropump unidirectional flow by using flexible-valves are analyzed theoretically.The effectiveness of the EWOD phenomenon in making droplets vibrate is verified by experiments,the experimental results obtained are in agreement with the existing data,and by observing the change process of contact angle and the movement of droplets,the precautions of using EWOD phenomenon to drive droplets are learned and applied to subsequent simulation modeling.The unidirectivity of flexible-valve is verified by experiments,and the experimental results are good agreement with the theoretical analysis.The validity of the numerical model is verified by the experimental data,which ensures the rationality of the subsequent simulation analysis.(2)Structure design of EWOD flexible-valves micropump.A kind of parallel EWOD flexible-valves micropump is selected from four kinds of multi-chambers structure EWOD flexible-valves micropump,with the fluctuation of pumping volume and the presence of macroscopic backflow as the main evaluation indexes.And the fluidics flow in the parallel EWOD flexible-valves micropump is analyzed in detail by using COMSOL Multiphysics.It is concluded that the main reason for the small pumping fluctuation of the parallel micropump is the generation of the left and right inner circulation,and some relevant conclusions are drawn.(3)Structural parameters analysis of EWOD flexible-valves micropump.According to the information obtained,some important structural parameters are analyzed.Discuss its influence on the performance of the micropump,propose a better combination of structural parameters through the matching of different structural parameters.The pumping volume of the EWOD flexible-valves micropump with optimized structural parameters is about 3.5 times that before the optimization.(4)Flow parameters analysis of EWOD flexible-valves micropump.Based on the model of optimal structural parameter combination obtained,the influence of some main flow parameters on the performance of the micropump is discussed.Finally,according to the physical properties of the actual fluidics,a better combination of flow parameters is proposed.The pumping volume of EWOD flexible-valves micropump with flow parameter optimization is about 26 times that before structural parameter optimization,and about 7.6 times that after structural parameter optimization.