Research On PZT Energy Harvester With D₃₁ Mode Based On MEMS

Energy harvester can convert the working environment energy of various types into electrical energy, so as to realize automatic energy supply of the devices. It has a profound influence on the development of the portable and intelligent devices, especially the application of low power consumption of milliwatt of wireless sensors nodes and portable electronies. The piezoelectric vibration energy harvester which has the advantages of simple structure, good compatibility with MEMS technology, easy integration, etc. has been becoming noticeable among energy harversters and has a good prospect in the research. In this thesis, the author discussed the research progress of piezoelectric energy harvester, proposed the structure of the suspend interdigital piezoelectric cantilever energy harvester and fabricated the prototype of device by the integrated production with the piezoelectric layer and substrate. This design fully embodied the idea about the integrated production and pitch production using MEMS technology. In this paper, some issue is discussed, such as the modeling of suspend interdigital piezoelectric cantilever energy harvester, the prepared technology influencing the performance of piezoelectric layer, MEMS technology of device.For the theory of modeling, the suspend interdigital piezoelectric cantilever is proposed based on the analysis type of the piezoelectric energy harvester: a discrete bottom beam, a top beam and the mass. There is a gap between the bottom beam and top beam, and the discrete bottom beam is composed of two support beam. And the PNZT is coated on the top beam and the bottom material is silicon. Compared the two coupling modes, the d₃₁ mode is designed to improve the output charge efficiency and simplify the technology complexity. The electromechanical coupling model of the suspend interdigital piezoelectric energy harvester is created. And the theoretical formulas for the output voltage, power, inherent frequency and efficiency of the interdigital piezoelectric vibration energy harvester are obtained. By the anlysis of theoretical formulas, the effects of structure parameters of the interdigital piezoelectric vibration energy harvester on the devices and the relationship between the structural parameters are discussed. These work provid the theoretical basis for structure design and experiment research.For the preparation of piezoelectric layer, the performance of PZT material is discussed including the design scheme, fabrication technology, material proportion and characterization. Based on the analysis, the performance of the piezoelectric thin film can be improved by the addition of niobium into the fabrication process of PZT, and created PNZT piezoelectric thin films with high performance parameters. And the performance of PNZT material is characterized. These work provided the experimental basis to the integrated process of film.The prototypes of energy harvesters are produced on the basis of theoretical analysis and simulation optimization. The test system is established to test the prototypes. The results show that the resonant frequency of the prototypes are 376 Hz, and the voltages of VP-P is 25.9V under 1.0g acceleration. The maximum output voltage is 6.5V and the maximum output power of 29.5μW in the case of loading. These work offered the experience basis for the fabrication of MEMS energy harvester potopyte. The fabrication process of the integrative Si-based PZT films energy harvestors based on MEMS technology is desighed. And the structure of MEMS prototype is completed which achieve the design target. The integrative MEMS prototypes of the Si-based PZT films energy harvestors are tested in the self-constructed test system. The results show that the law obtained from the theoretical value, the simulation value and the experimental value are consistent, and their numerical results are basically consistent. The frequency of prototype is 9500 Hz, and the voltage of VP-P is 290 mV. This paper provided the theory and expermential exploration on the mass production of MEMS energy harvester.