The Study Of Physical Field And Characterization Methods On Acoustic Microfluidic Device

With the maturity of micro-fabrication technology and the popularizing concept of Lab on Chip(LOC),microfluidics has been a rapidly developing research hotspot dur-ing the past two decades.As an experiment platform of micron size,microfluidic chips are revolutionizing multiple research methods in many scopes.As a branch of acous-tic hydromechanics,the acoustic-driven microfluidic chip has attracted the attention of both researchers and engineers,with prevailing advantages of being non-invasive-high-strength,easy to manufacture,low cost and highly biocompatible.For exploration of micro-fluid field properties,Particle Image Velocimetry(PIV)is a widely accepted-measurement method which employs multi-frame particle position maps obtained by high-speed photography.Through calculating the particle motion field with a specific algorithm,the characteristic of the microfluidic field can thus be obtained.In this thesis,the PIV and acoustic microfluidics were combined to characterize microfluidic devices driven by either bulk acoustic wave(BAW)or surface acoustic wave(SAW).The physical images in the microfluidic devices were systematically ex-plored through the above-mentioned methods.With the help of existing and further deduced acoustic microfluidic theory,studies concerning microfluidic devices were carried out as:Firstly,the BAW device was fabricated and the particle motion in the one dimen-sional and two dimensional standing wave fields were recorded and analyzed using PIV.The accuracy of such measurement was then verified quantitatively using finite element method(FEM).The impact of particle radius on the particle motion was further explored in both simulation and experiment.Secondly,the SAW device was fabricated,and the energy evolution process as well as the particle distribution in the SAW device were quantitatively analyzed.By analyzing the obtained microscopic images in depth(averaging,calculating kinetic energy and exploring time dependent energy variation),the characteristics of particle motion,arrangement law and electroacoustic conversion efficiency coefficient in SAW devices were obtained.Based on the combination of PIV and acoustic microfluidic devices,a streaming and pressure field characterization method was proposed,with which the two-dimensional pressure field as well as stream-ing field could be obtained instantly without the need of mechanical scanning device.Proposed method of this thesis can serve as a boost to promote the application of mul-tiple microfluidic devices.Finally,this thesis proposed several expectations for future applications of acoustic microfluidics on the basis of a detailed investigation of the theory and characterization methods of the devices.The Ph.D.dissertation analyzed the physical field characteris-tics and particle motion law of the acoustic microfluidic chip.Meanwhile,a feasible,practical and yet highly-reliable characterization method was proposed,aiming at solv-ing theoretical and practical problems in actual microfluidics applications.The research results are expected to promot the standardization of microfluidic devices and provide more possible means for the application of microfluidics.