Design Of Microfluidic Control System Based On Micropump Drive

The microfluidic system achieves the distributing,controlling,and mixing of liquids through narrow channels,and will be broadly applied in the fields of chemical synthesis and biological detection.Microfluidic systems are usually composed of microfluidic sensors,micropumps,micromixers and other components.As the driving component of the system,the micro pump provides the source power for fluid transportation.As the output component of the system,the micromixer is responsible for the control and mixing of fluids.However,due to the limitation of the size of micropumps,there is often a problem,that is,insufficient transportation capacity.Besides,the flow of liquid in narrow channels of the micromixer is usually at low Reynolds coefficient,which means it is in a laminar flow state.If only relying on the diffusion between molecules,the mixing period will be very long.Based on the above two problems,this paper introduces liquid crystal elastomer as a power element for the micropump,and optimizes the structure of the core components of the micropump and the model of pump body to improve the output capacity of the micropump;by introducing mixing units of different structures into the micro mixer inside,the fluids of different concentrations are crossed,stretched,and collided at the mixing unit,so as to achieve efficient and rapid mixing between the fluids.The research content includes the following aspects:(1)The structure of the cantilever beam valve micropump is designed.On the basis of theoretical analysis,in order to fasten the response speed and increase the energy transmission efficiency of the check valve,the relationship between the natural frequency and opening of the cantilever beam valve and its structural size was studied according to the simulation results,and the initial size of the cantilever beam valve was determined.The inlet valve and the nearby fluid were modeled;the actual working ability of the cantilever beam valve in a liquid environment was explored through twoway fluid-solid coupling;the influence of the cantilever beam valve structure and installation clearance on the output capacity was studied;the cavity and the structure size of the cantilever beam valve was further refined.Comparing the results of the flow field analysis,the structure of the outlet channel is determined.Combined with the above-mentioned finite element analysis process,single-chamber and double-chamber micropumps are designed.(2)The valveless micropump based on diffuser/nozzle is designed.The pressure distribution and flow resistance characteristics of the diffuser/nozzle as well as the theoretical flow rate of the valveless micropump are analyzed and calculated.A simulation model of a valveless micropump is established.This model is simulated and analyzed by two-way fluid-solid coupling,and the calculation results of the flow field and the pump membrane are observed to verify the rationality of the design.The influence of the diffuser/nozzle structure parameters and load factors on the output flow is studied,and the optimal structure of the diffuser/nozzle is determined according to the calculation results.It is found that increasing the load frequency and amplitude can increase the output flow of the micropump.Combined with the above-mentioned finite element analysis process,a valveless micropump is designed.(3)The model of a new type of micromixer is designed.Based on the traditional Y-type micro-mixer,a new type of micro-mixer model is designed by introducing different mixing units.The mixing process is simulated and analyzed by COMSOL to obtain the concentration field and velocity field data of the model.The results show that the rectangular obstruction type micromixer has a best mixing effect.The mixing efficiency at the outlet reaches 0.961.The fluid crosses,stretches and entangles at the mixing unit,forming a secondary flow at the bottom of the pipe,which effectively improves the mixing efficiency.The influence of the input flow on the mixing effect was studied.It was found that increasing the input flow aggravated the turbulence of the streamline,and expanded the secondary flow range at the bottom of the obstacle,which effectively improved the mixing efficiency.The obstacle structure was designed as a trapezoid.Compared with the rectangular obstacle-type structure,thus,the final mixing index is increased to a higher level of 0.984.