Design And Simulation Of A Microfluidic Oscillator Based On A Novel Normally Closed Valve Structure

The microfluidic system completes sample injection,mixing,reaction,separation,detection and other processes through the manipulation of fluids in the microchannels.Microfluidic system has been widely used in biomedical,disease diagnosis and treatment,environmental detection and protection,military and space exploration and many other scientific fields because of its advantages of miniaturization,high integration,high efficiency,fast,little reagent consumption and low production cost.The micro valve,which is responsible for controlling and limiting the flow of fluid in the microfluidic chip channel,is the key control component in the microfluidic system.At present,the research of microvalve is one of the most active branches in the research of microfluidic system.In this paper,a new type of normally closed valve structure based on arc channel and trapezoidal valve seat structure is designed to solve the problems of excessive pressure threshold,large dead area and slow response speed of the existing normally closed valve.Based on the equivalent circuit theory,a microfluidic oscillator with a new normally closed valve structure is designed,and the working characteristics of the microfluidic oscillator are studied in depth.the work contents are as follows:Firstly,Using the equivalent circuit theory of microfluidic,the equivalent analysis of Check valve,normally closed valve,flow resistance series-parallel connection,flow resistance star triangulation,Kirchhoff's voltage law KVL and Kirchhoff's current law KCL in microfluidic control system is carried out.It is proved that the equivalent circuit theory is convenient,fast and efficient in the design of microfluidic system.Secondly,This paper introduces the knowledge of hydrodynamics of the mathematical model of microfluidic fluid and the theory of fluid incompressibility in microfluidic fluid,and compares and discusses the two description methods of fluid kinematics.The finite element weakening and linearization of the Navier-Stokes equation are presented.The finite element solution method for the fluid field is illustrated by the finite element discretization.Through the finite element weakening and linearization of Navier-Stokeses(N-S)equation,the finite element solution of the fluid field is obtained.At the same time,combining with the fluid-solid coupling,finite element analysis and boundary condition setting in COMSOL,the feasibility of simulation is verified theoretically.Then,A new type of normally closed valve based on arc channel and trapezoidal valve seat structure is proposed to solve the problems of excessive threshold,large dead area and slow response speed of micro-valve.At the same time,a microfluidic oscillator is designed based on the microvalve.Based on the equivalent circuit theory,the micro-oscillator is simplified,and the software Multisim is used to optimize the design of the micro-fluidic oscillator.The performance of the closed valve and the operating characteristics of the oscillator are studied by the simulation software COMSOL,and the effects of inlet velocity,threshold pressure and valve seat structure on the oscillation period are analyzed.According to the influence of inlet flow rate,threshold pressure and valve seat structure on the period of microfluidic oscillator,micro-flow controlled oscillator can be designed to meet the needs of different applications.