Design And Experimental Research Of Micromixer Based On Rayleigh Surface Acoustic Wave

Microfluidic chip is widely used in the fields of biology,chemistry,medicine and material synthesis because of its miniaturization,low cost and portability,which can reduce the system volume and energy consumption.As one of the functions of microfluidic chip,micromixing has great potential and market in the fields of chemical synthesis,biochemical analysis and drug development.Therefore,micromixing with high efficiency and rapid mixing of microfluidic plays an important role in the research of contemporary microfluidic chip.In this paper,a micromixer driven by Rayleigh surface acoustic wave(SAW)is proposed,which has good biocompatibility and nonintervention.The micromixer has simple structure and excellent mixing effect.The mixing performance is verified by numerical simulation and color reaction experiment.The silver nanoparticles are synthesized by micromixer to verify its application in chemical synthesis.The specific contents of this paper are as follows:(1)This paper summarizes the surface acoustic wave and its characteristics.The principle,structure and material of the surface acoustic wave device is introduced.Then acoustic flow effect caused by acoustic wave propagating into fluid is analyzed.Finally,acoustic flow force,which is the force of the fluid under the action of the surface acoustic wave,is deduced.(2)COMSOL and MATLAB are used to simulate the mode,harmonic response and transient state of SAW devices.The process of the generation,propagation and action of traveling wave surface acoustic wave(TSAW)and standing wave surface acoustic wave(SSAW)is analyzed.The overall simulation of TSAW micromixer and SSAW micromixer is carried out to analyze the micromixer mixing effect at different peak-peak voltage and at different entrance flow rate.(3)According to the theoretical analysis and simulation results,the TSAW micromixer and SSAW micromixer are designed and manufactured.First,the SAW devices are fabricated by MEMS technology;Then,the microchannel system mold is designed according to the size of SAW devices and the acoustic wave action area,and the microchannel is processed by molding method;The micromixer prototype is obtained by bonding SAW devices and microchannel system by natural bonding method.(4)The mixing performance of the micromixer is characterized by the color reaction of red and blue ink.Firstly,the experimental scheme is designed and the experimental platform is built to characterize and test the acoustic flow effect of acoustic diffraction into the fluid.Finally,the color reaction experiment is carried out by adjusting the injection pump and signal generator.Based on TSAW micromixer and SSAW micromixer,the color reaction of red and blue ink is carried out.The experimental results show that the mixing of red and blue ink becomes better with the increase of peak-peak voltage,when the inlet flow rate is constant;And the mixing effect of red and blue ink becomes worse with the increase of inlet flows rate(the action time of acoustic surface wave decreases),when the peak-peak voltage is constant.(5)The redox reaction degree of silver nitrate and glucose is controlled to realize controllable synthesis of silver nanoparticles.By adjusting the the experimental parameters of TSAW micromixer and SSAW micromixer such as peak-peak voltage and inlet flow rate,silver nanoparticles with good morphology,good monodispersity and small size deviation were successfully prepared.