Simulations And Experimental Studies Of Valve-less Micropumps Based On MEMS

In order to realize the demand of the quantitative transportation in the microfluidic system, the theoretical analysis, simulations and experimental studies of valve-less micropumps based on MEMS are developed. Diffuser-nozzle micropumps are typical valve-less micropumps. They use diverging and converging micro channels instead of one way valves. These micropumps utilize the different pressure drop characteristics of flow through a nozzle and a diffuser to direct the flow in one preferential direction, and hence cause a net pumping action. Additional benefits of diffuser-nozzle micropumps include the simple geometry and the mature manufacture technologies, so people draw much attention to these pumps. Numerical simulations about the effects of angle, length, minimum width and depth of the diffuser-nozzle to the mass flow and efficiency are done using the computational Fluid Dynamics program Ansys/Flotran. The vibration modes of the membrane are studied. And the fluid-membrane coupling vibration process is analyzed theoretically, the approximate analytical solution for the coupling vibration equation is given. On these basis, the variation rules of membrane amplitude and the mass flow of the pump are analyzed under different damping coefficients, different forces and different natural frequencies. The dynamic working process of valve-less micropumps and the variation rule of mass flow and accumulative mass flow under different amplitude and frequencies are analyzed with CFX. The mass flow results of simulations and the experimental studies match basically. The valve-less micropumps are made by micromaching technologies with silicon. And the membranes are made of PDMS. Glass-silicon-glass makes up the sandwich structure of the pump. The output abilities of the valve-less micropumps under different voltages, different frequencies and different membrane stiffness are measured through the experiments. The experiments also show that the valve-less pump can be used both as a liquid pump and as a gas pump. The mass flow of the gas pump is higher than the liquid pump under the same voltage, but back pressure of the gas pump is lower. The maximum mass flow of the liquid pump is 0.44ml/min when the voltage is 8V and the frequency is 15Hz. The maximum back pressure can reach 17.5 cmH2O.