Design And Experiment Research Of Particle Sorting Microfluidic Chip Based On Focused Surface Acoustic Wave

Microfluidic chips have received extensive attention from scholars in the fields of biology,chemistry,materials science,and medicine due to their advantages of miniaturization,portability,low cost and low reagent consumption.At present,with the maturity of microfluidic technology,microfluidic chips have gradually shown the trend of replacing various functions achieved by traditional biochemical and medical laboratories,such as sorting,mixing,cell culture,reaction and detection.As one of the important functions,sorting is of great significance to the fields of drug synthesis,medical testing,drug development and diagnostics.Therefore,based on the microfluidic technology,a focused traveling wave surface acoustic wave(SAW)microfluidic sorting chip with infiltration treatment on the surface of the flow channel is proposed in this paper,and by studying the influence of flow rate and input power on particle migration to achieve the interparticle separation.The research work includes the following:The composition of the SAW device and its working principle are discussed.After comparing the material properties,128°Y-X lithium niobate is finally selected as the base material of the SAW device,and then the inter-finger width,finger spacing,interdigitated pair,focusing angle,focusing length and interdigital transducer materials of the focused interdigital transducer is preliminarily determined.Subsequently,the force analysis of suspended particles in the sound field is carried out,and finally the infiltration theory is introduced.Based on the simulation software,modal,harmonic response and transient analysis are carried out for the SAW device.Then,according to the parameters of the focused interdigital transducer,the finger pairs,focusing length and focusing angle are analyzed.Then,the flow channel inlet flow rate ratio is simulated to determine the optimal flow speed ratio at the three inlets.Finally,the movement of particles in the flow channel is analyzed by changing the flow speed,and the optimal average flow rate of the sorting flow channel is finally determined to be 4mm/s.Based on theoretical and simulation results,particle sorting chips are designed and fabricated for two and three kinds of particle sorting.Firstly,the SAW device and the runner bottom mold are fabricated by MEMS manufacturing technology.Then,the micro-channel system mold is designed,and three PDMS micro-channel systems are fabricated by molding technology,and the surfaces of three PDMS micro-channel systems treated with nothing,super-hydrophilic treatment and super-hydrophobic treatment,respectively,and then the natural bond method is used to complete the bonding of the micro flow channel and the SAW device,and finally the microfluidic chip is obtained through subsequent processing.In this paper,the SAW device and microfluidic chip designed and fabricated are used for experiment research.Firstly,design the experiment plan and set up the experiment platform.Then the acoustic streaming effect and the particle adhesion on the flow channel surface are tested.Based on the experiment,the particle deflection experiment with particle diameter of 10μm under different input power and average flow rate is studied,and particle sorting experiments of 1 μm,10 μm and 1 μm,5 μm,and 10 μm are finally performed by adjusting the input power.The experiment results show that as the input energy is constant,the deflection distance 10 μm particles increases as the average flow speed of the sorting channel decreases.Similarly,when the average flow speed of the sorting channel is constant,the deflection distance of 10 μm particles gradually increases as the input energy increases.In addition,the surface acoustic wave sorting chip has almost no effect on small-diameter particles,and the surface acoustic wave will deflect the particles only when the particle size is large.Furthermore the sorting chip designed in this paper can realize the separation of 1μm and 10μm particles at the working frequency f =131.83 MHz,the input power P=200m W,and the average flow rate of the sorting channel va =4mm/s,and the sorting efficiency is as high as 91.9%,which is also verified that the chip has good working performance.