Design And Experimental Study Of A Micromixer Driven By The Valveless Piezoelectric Pump

As an important branch of microfluidic technology applications,micromixers have the advantages of short mixing time,low sample consumption,easy integration,and ability to mix high-viscosity fluids,which has a significant impact on the biological and chemical fields.Different from the macro mixer,because the flow channel size in the micro mixer is micro-nano level and the fluid Reynolds number is very low,there is a big difference in the mixing mechanism between the two.Based on this,this paper design a new micromixer driven by the valveless piezoelectric pump.The micromixer consists of a driving unit and a mixing unit.The driving unit consists of two innovatively designed valveless piezoelectric pumps.The mixing unit consists of a Y-shaped mixing flow channel.Each piezoelectric pump can pump two liquids at the same time and has certain mixing ability.The piezoelectric pump firstly mixes the liquids to be mixed first,and then pumps them into the Y-shaped mixing channel for pulsating mixing.The micromixer can achieve fast,efficient and controllable mixing effects.The specific research contents is as follows:The working mechanism and micro-hybrid technology of the valveless piezoelectric pump are theoretically studied.First,based on the traditional expansion / contraction port valveless pump,a new valveless piezo pump with an expansion / contraction port structure is designed.The equivalent circuit model greatly simplifies complex problems in the system.Subsequently,the mixing mechanism of the pulsating mixing method in this paper was studied and analyzed,and it was proved that it has a reliable and efficient mixing effect.Based on the flow rate and the degree of mixing,the COMSOL software was used to simulate the driving unit and the mixing unit,and the MATLAB software was used to process the data results.Combined with the overall layout design and production process in the later stage,the optimal structure parameters and control parameters are obtained.The driving unit results show that the optimal structural parameters of the new expansion / contraction mouth are: 4mm in length,0.25 mm in width of the shrinking mouth,7 ° expansion angle,and 2mm from the shrinking mouth of the Tesla structure.The results of the mixing unit show that in the selection of the mixing mode,the mixing effect in the valveless pump driving mode is better than the valve pump driving mode,and the pumping order of "ABBA" is better than "ABAB";The best structural parameters and control parameters are: the inlet angle is 70 °,the runner width is 0.3mm,the mixing length is 5mm;Under the best output performance of the valveless piezoelectric pump(65Hz,0.31 ml / min),the mixing degree of the micro mixer can reach 97.56%;When the driving parameters are: output flow rate 0.1ml / min,driving frequency 50 Hz,the mixing effect of the micro mixer is the best,and the mixing degree can reach 99.39%.The structural parameters obtained by simulation analysis laid the foundation for the later instrument production and performance experiments.The overall layout design of the micromixer was determined based on the size of the accessories and the processing technology,and the final overall size was determined to be 34 mm × 32 mm × 4mm.Based on the PMMA bonding process,the prototypes of valveless piezoelectric pumps and micromixers were fabricated,and then an experimental platform was set up to conduct drive performance experiments on valveless piezoelectric pumps.The results show that when the pump cavity depth is 150 um,the driving performance is the best.With a square wave voltage of 140 V and a frequency of 65 Hz,the flow rate of the valveless piezoelectric pump reaches 0.31 ml / min.The new valveless piezoelectric pump has a certain mixing ability.A crescent-shaped pulsation layer appeared in the Y-shaped mixing flow channel,which proved that the mixing effect of the micromixer was good.