Dynamic Analysis And Acoustic-Structure Analysis Of Ultrasonic Travelling Wave Microfluid Driving Model

With the extensive application of Micro-electromechanical System (MEMS) in the domain of BME, fluid driving and controlling technique has become one research hotspot. Aiming at this research status for mocrofluidics, it is necessary to study the micro fluidic mechanisms in the domains of micro-scale, micro-structures and micro functional devices, and find a suitable modeling methodology for the study of microfluidics, then investigate on the optimization of the structures and parameters for the microfluidic devices. These studies need to be solved urgently.Ultrasonic travelling wave micro-fluid driving technique is different from the present kinds in principle. Using the anti-piezoelectric effect of piezoelectric ceramics, the ultrasonic vibration generated excites the travelling wave on the bottom surface of micro-channel, and acoustic field is generated simultaneously. The fluid medium in the micro-channel moves along the direction of travelling wave because of the effect of acoustic streaming, acoustic radiation pressure. As a new micro-fluid driving technique, ultrasonic travelling wave driving technique has no movable components, needs lower driving voltage, has convenient controlling method and is fit for miniaturization. So it will have extensive application in the future.Firstly, the dissertation summarizes the development of MEMS and micro-fluid. It retrospects to the status of micro-fluid driving technique inside and outside the country, and makes an introduction of the present kinds of micro-fluid driving technique.Secondly, the anti-piezoelectric effect, material character and frequency character of piezoelectric ceramics are introduced. The synthesis of travelling wave is analyzed in detail. By the research on the mechanism of acoustic radiation pressure and acoustic streaming, the relation between driving mechanism and model parameters is obtained, which is the base of the ultrasonic travelling wave driving technique.Thirdly, the annular driving model is modeled using finite element analysis software ANSYS and the dynamic characteristic of the model is analyzed. By the modal analysis, the relation between model natural frequency and elastic body structural parameters, such as the inner radius, outer radius and elastic body thickness, is discussed. The effect of channel size on the frequency is analysed, too. By the harmonic response analysis, the desired vibration modal is excited and the frequency characteristic is identified. The displacement variety along with the frequency is obtained. These offer the guidance for model structure design.Finally, the acoustics basic knowledge and acoustic-structure coupling theory are introduced. The acoustic-structure analysis is carried through with ANSYS software. The effect of acoustic field on model natural frequency is obtained by comparing the coupling model with uncoupling model. The effects of fluid density, velocity of sound on model natural frequency are also discussed.