Simulation And Experiment Design Of Particle Separation Equipment Driven By Surface Acoustic Wave

As a non-contact particle separation technology,surface acoustic wave(SAW)technology has many advantages,such as good directivity,strong penetration,good biocompatibility,small device size,flexible controllability and so on.There are good application advantages in medical,pharmacy,biochemistry,material preparation and other fields.In a SAW field,particles with different diameters have different acoustic radiation forces,according to this,they can be separated.Particle separation based on SAW technology can be divided into two categories: one-dimensional standing wave separation and traveling wave separation.The theory of saw standing wave(SSAW)and traveling wave(TSAW)is analyzed,128°YX-Li Nb O3 is selected as piezoelectric substrate material.The influence of the number of fingers of interdigital transducers(IDTs)on the output waveform and relative bandwidth is analyzed.The expressions of step response and frequency response of interdigital transducer are derived.Based on the theory of induced current,the relationship between the free wave velocity and the surface acoustic wave velocity affected by the disturbance on the piezoelectric substrate is derived.The arrangement distance of the standing wave interdigital transducer in two different arrangements is derived.The displacement equation of the particles in the standing acoustic wave field is derived,and the relationship between the diameter of the separated particles and the moving time of the particles in the microchannel is analyzed.The relationship between the diameter of particles and the resonance frequency of SAW is analyzed.The energy concentration area of SAW,the condition of suppressing the generation of body acoustic wave,the position of sound pressure node in standing wave field and the modal of acoustic wave in microfluid in traveling wave field are simulated and analyzed.Four kinds of standing wave interdigital transducers are designed,which are broken-line standing wave IDT based on sheath flow aggregation,standing wave IDT array based on transducer aggregation,standing wave IDT with variable node position and variable node standing wave IDT based on focused traveling wave propulsion,their sound pressure and characteristics are simulated,analyzed and compared.Three kinds of traveling wave interdigital transducers are designed,which are parallel traveling wave IDT with different number of fingers,focused traveling wave IDT and slanted traveling wave IDT with stepless frequency modulation,their sound pressure and characteristics are simulated,analyzed and compared.Eight interdigital transducers for standing wave and traveling wave particle separation experiments are made.The corresponding microchannels of PDMS are designed and manufactured.The resonance frequencies of each experimental device are measured,and they are verified that the actual SAW velocity is affected by periodic disturbance of interdigital electrode,and its value is smaller than the free SAW velocity.The reason why the voltage at the detection end of the focused IDT and the slanted IDT is smaller than that of the parallel IDT is analyzed.A program is written to make the slanted IDT produce high amplitude excitation in a certain frequency range.