| Micro-Electro-Mechanical Systems (MEMS) is a micro system that including micro sensor, micro machine, micro actuator and signal processing and controlling, it is characterized by its small shape, light weight and low power consumption. Micro motor is an important actuator of MEMS, and it has a major impact on the whole system. Though there are several kinds of micro motors such as electromagnetic, electrostatic, piezoelectric and ultrasound micro motors currently, they all have their own limits. In recent years, an old driving method called electrohydrodynamics that has been discovered for a hundred years but not well understood attracted the attention of scientists, and they applied it to several fields including micro pumps and bio- particle separation chips. Now, there is a lot of research on micro pumps but little on micro motors overseas, and there is no research on both in our country. Electrohydrodynamic motor has advantages of simple structure, a few moving parts, greater energy density, small size and low cost. For the above reasons, we made a preliminary research on the electrohydrodynamic motor in theoretical, experimental and simulating work, and this laid the foundation for further work. We will describe what we have done in 6 chapters.In chapter 1, the back ground of MEMS was introduced, and research status of micro pumps and micro motors was analyzed, and the targets and contents of our work were described.In chapter 2, the theories of electrohydrodynamic including electrohydrodynamic in dc fields-electric body forces and electrohydrodynamic in ac fields- ac electrokinetic were introduced. In-depth discussions of their work forms and mechanisms were discussed.In chapter 3 the electric fields and force fields were simulated and compared with several kinds of electrode structures in the effect of dc and ac voltages. A further understanding of the theories of electrohydrodynamics and a series of conclusions were made, and this helped a lot because of the limits of experiment.Electrohydrodynamic motor in ac fields and other devices in dc fields were designed and manufactured in chapter 4 based on the theories in chapter 2and chapter 3. Six electrodes patterns were designed and four kinds of fluids including liquid crystals were chosen for the electrohydrodynamic motor in ac fields in order to study and compare their impacts.The experimental sequence, phenomenon and results were discussed in chapter 5. It was found that the micro rotors rotated unsteady when it was first started. Through the comparison and analysis, we can see the relationships between the rotating speed and the voltage, fluids, the inner diameter and the amounts of electrodes.In the last chapter, a final conclusion of this paper was made, and the future work was prospected. |
