| Micro-flow system is an important branch of Microelectromechanical system (MEMS) The researches of microsensors and microvalves components have been made great progress in recent years. Because the microactuator is small in size, the invalid volume of fluid is low, the power consumption and sample dosage are decreased, and the microactuator response is also fast. So the microactuator is applied extensively. For instance, it can be used in the pressure, flow rate and directional controls, and the micro-fluid composition analysis.According to the operation principle of valveless micropump, a new type microactuator which driven by PZT is designed and proposal. The PZT film, valveless structure and characteristic of actuator are studied. The software of MEMS of Intellisuite CAD is used to design the processing technology and the main structural parameters also obtained.Based on the basic structural design, the principle of reverse piezoelectric effect of microactuator is explained, and the relationship between the deflection and effective pressure is analyzed, the theoretical foundation for square PZT film is submitted. Nozzle-diffuser elements are utilized in the valveless micropump. From the theory of hydrodynamics, the relationships between the loss efficient and the opening angle are given. The optimized angle is approximately 5°~7°. At the same time, the diffuser efficiency, which reflects the performance of the nozzle-diffuser elements, is determined by the opening angle and the ratio of throat area and outlet area.The fabrication process is also simulated by the software of MEMS of Intellisuite CAD. From the simulation of square compound sheet of PZT and silicon, the relationships between driving voltages and flexibility, thicknesses and flexibility, thicknesses and natural frequencies are submitted. It provides reference to further theory analyzing and experiment for micro-system with square silicon cup structure. According to the theory analyzing and fabrication processessimulation, we find that the opening angle and the length of nozzle-diffuser elements are the important factors. The relationship between the diffuser efficiencies and opening angles, lengths and Reynolds number was also given, respectively.The MEMS technologies, i.e. the film fabrication technology, the two-sided photoengraving technology, the silicon etch technology and the interface auxiliary bond technology, are introduced. The optimized dimensions and the photographs of pump membrane and nozzle-diffuser elements fabricated by micromechanical technologies are given.Study shows that the relationships between the rates of silicon anisotropic etching and temperature, the rates of silicon anisotropic etching and the concentrations of KOH. Sol-Gel method fabricating PZT film is also researched. The selection of bottom electrode material and the transition layer material, Sol-Gel method for PZT and 0-3 mixing method are all studied by experiments. Through SEM photographs observing, we find the PZT film fabricated by Sol-Gel method is homogeneous with no crackle. The cross section and the surface are flawless. The film thickness is about 2μm. The interfaces of SiO2/Ti/Au/PZT layers are clear. The XRD analysis of PZT shows that the perovskite structure PZT films with (110) prefer orientation.The operation principle that PZT polarize and the polarized condition are given in the microactuator test. In the PZT deformation test, the relationships of voltage, frequency, deflection and the variety of displacement relating to the deflection and the volume are obtained. The relationship between flow rate and frequency is reached and the back-pressure value is also obtained.All the results prove that the valve-less micropump driving by PZT fabricated by MEMS technology is feasible. It is easy to be integrated and produced in a large scale. It is suitable to be used in micro-flow control system.
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