Design And Study Of Microfluidic Oscillator

Microfluidics is a science that focuses on the precise control of micro / nano-sized volumes of fluid by the micro / nano-scale structure.A critical need for enhancing the usability and capabilities of microfluidic technologies is the development of standardized,scalable and versatile control systems and alternating fluidic driver.The microfluidic oscillator driven by fluid can promote the development of device-embedded non-electrical flow-control systems and improve the convenience,scalability and robustness of microfluidics.This is the foundation for the microfluidic chip into the digital field.In this paper,a non-steady state multivibrator in circuits is used as the prototype,and a fluid driven microfluidic oscillator is designed and studied by using the microfluidic equivalent circuit theory.The microfluidic oscillator is made up of normally closed valves and micro-channels in symmetrical cascading.It just need simple external auxiliary device and is easy to transplant.Firstly,based on the theory of microfluidic equivalent circuit,the equivalent analysis of oneway valve,normal closed valve,the series and parallel of flow resistances,the star delta transformation of flow resistance,KVL and KCL in complex microfluidic system is carried out.All of them indicate that using the equivalent theory to assist in the design of microfluidic system is convenient,fast and efficient.Secondly,the feasibility and accuracy of the simulation are verified by the study of the characteristics of flow resistance,flow capacity,influenza and normally closed valve,which is the basis for the numerical simulation of microfluidic oscillators.Then,we get the relevant parameters of operating frequency from the working principle of the microfluidic oscillator.It is the built-in capacitance of normally closed valve and feedback flow resistance that influence the oscillation period.The simulation software is used to simulate the model of microfluidic oscillator.In this paper,we study the influence of inlet velocity,feedback flow resistance and the threshold pressure of the normally closed valve on the oscillation period of the microfluidic bistable oscillator.Additionally,we study the effects of inlet flow rate and normally closed valves on the rising and falling edge time of oscillation period.We also study how the duty cycle of the oscillation period varies with the valve seat.The results show that the oscillation period decreases as the inlet flow rate increases.The threshold of valve is providing the linear relationship with the oscillation period.With the widening of the normally closed valve seat,oscillation period increases;with the decrease of valve aspect ratio,oscillation period is reduced;with the increase of feedback flow resistance,oscillation period increases.The rising edge time can be shortened by increasing the inlet flow rate or reducing the fluidic capacitance of the normally closed valve.Moreover,asymmetrical design of the valves can adjust the duty cycle of the micro-oscillator.According to the results of the study,we can adjust the oscillator according to different requirements.