Theoretical Analysis And Simulation Of Traveling Wave Micro-fluid Driving

With the development of MEMS technique, fluid driving and controlling technique in the micron components has become one research issue. The driving and controlling of microfluid is largely different from that of macrofluid. It is mostly because when the dimension decreases to micron level, the flow characteristic of fluid has changed a lot as a result of the influence of scale and surface effect. The change usually makes the transplantation of macrofluid driving and controlling technique to microfluid field unsuccessful or unfavorable, because microfluid driving and controlling technique is more complex and diversified. Ultrasonic traveling wave driving is different from the present microfluid driving techniques in principle. Using the anti-piezoelectric effect of piezoelectric ceramic, ultrasonic vibration is generated and the traveling wave is generated on the bottom surface of microchannel, and acoustic field is generated simultaneously. The liquid in the microchannel move along the direction of traveling wave because of the collective effect of shearing Reynolds stress, acoustic streaming, acoustic radiation pressure, viscous force and molecular force. As a new microfluid driving technique, ultrasonic traveling wave driving technique has no movable components, needs lower driving voltage, can adapt to all kinds of environment, so it will has extensive application in the future.This dissertation is supported by Nation Nature Science Foundation of china (No.10572078), Shandong Province Nature Science Foundation (No.Y2007A16). For the feasibility and driving model of ultrasonic traveling wave microfluid driving and controlling technique of the items, this paper has an embedded research from the view of acoustic and dynamics analysis.Firstly, the status of microflow driving technique inside and outside the country is introduced, the mechanism of traveling wave's generating are particularly analyzed, and the anti-piezoelectric effect, the character of material and frequency of piezoelectric ceramics, which makes a base for the driving and control of traveling wave microfluid, are also presented. The relation between driving mechanism and model parameters is given from the research on the forming mechanism of acoustic radiation pressure and acoustic streaming.Secondly, based on the analysis of the Finite Element Method (FEM), it discusses the relation between model's natural frequency and elastic body parameters. By the harmonic response analysis based on the anti-piezoelectric effect, the anticipated vibration mode is successfully excited at the point of resonance frequency, and the frequency characteristic of response amplitude is obtained. To the coupling field analysis, the following difficult issue, by the FSI in ANSYS, a model is built to accomplish the coupling between acoustic-fluid units with solid ones. The acoustic pressure distribution of circular panel channel is obtained, which make a great contribution to the study of acoustic streaming and pressure function in microfluidic driving.Finally, transient dynamic was made to the circle model, and the streamline in the fluid domain and velocity vector of the interface is obtained, which prove the feasibility of microfluidic driving and summarize my whole work.