Based On The Design Of Two-dimensional Normal Modes Of Mems Ultrasonic Separation And Flow Field Simulation Study

Particles suspending in fluid suffer acoustic radiation from the different physical characteristic (velocity and density) between suspended particle and host liquid, and particles may be moved to special positions with certain spatial distribution of the acoustic radiation forces. It shows the clue that ultrasound acts as a physical approach to separate suspended particles in the fluid. In a micro device such as MEMS (Micro Electro-Mechanical System), most of conventional processes and devices for removing small particles from a liquid are inconvenient. However, separation with ultrasound is valuable way as a non-contact manipulation method in micromachines. There is a great potentional application in microfluidic system for ultrasonic separation, so that there are more and more people to spend effort on it.The MEMS ultrasonic separator is a device which may control and move suspended particles in fluid by acoustic radiation forces, and it may be directly used in flow-through separation processes. According to multilayer structure model of micro separator, the theory of acoustic radiation forces and the normal vibration principle, a MEMS ultrasonic separator based on two-dimensional normal modes is designed in this paper. The simulation of the separator is carried out for optimization. The main contents are as follows:1. From the theory about acoustic radiation force and the formula, the separation technique with plane ultrasonic standing wave is studied. And it is operated to analyze the structure model of multi layered resonator for ultrasonic separation and the transmission of ultrasonic in multi medium. The equivalent circuit of micro separator is present. The characteristic of MEMS ultrasonic separator based on plane standing wave is discussed.2. The normal vibration modes of micro separator's chamber are introduced, and the characteristic of particles'agglomerate in chamber is analyzed. A MEMS ultrasonic separator based on two-dimensional normal modes is designed to remove particles from liquid. This separator operates on the typical structure model of multi layered resonance, and the excitation methods of the separator are discussed. A novel way is given to emit ultrasonic with reverse phase form double PZT transducers in series. The spatial distribution of acoustic pressure is simulated in the cross-section of the micro separator with ANSYS software. It is validated that the two-dimensional normal modes are existed in the micro separator chamber. Also, the series of spatial distribution of acoustic pressure is put forward with excitation method and side-wall conditions of the micro separator.3. The process of laminar flow is simulated with GAMBIT and FLUENT software, and the series of flow regime analysis are present with channel. At last, a MEMS separator with two-dimensional normal resonant modes is designed to suit the micro- fabrication.