Fabrication And Testing Of Micro Piezoelectric Power Generator For Collecting Ambient Vibration Energy

In recent years, with the development of the integrated circuit and micro/nano electric-mechanical technology, the demand for wireless sensors nodes and portable electronics has been spreading speedily, but how to power them becomes one of the most important problems.In order to solve the problem which the traditional battery is bulky, short-lived and unable to meet the wireless sensor networks and embedded systems etc. which require new technologies for energy supply, people start to research the technology of environmental energy acquisition which is the use of the environment that exist in a variety of energy and converts it into electricity and stores up to provide power for electronic systems. The ambient energy which can be used for energy collection and conversion includes solar energy, vibration of mechanical energy, temperature gradient and so on. Vibration of mechanical energy is a kind of energy forms which exists a wide range of energy, especially in many places where people are more difficult to access. The study of the vibration energy harvesting technology is provided with more general significance.The working principle of micro piezoelectric power generation driven by environmental vibration is to use the environmental vibration to incent piezoelectric cantilever beam power generation system to produce the forced vibration, and to cause piezoelectric generating mechanical strain under the action of the exciting force. The mechanical strain is converted to electrical energy by the electromechanical coupling of piezoelectric material, and charge is generated in the piezoelectric film's surface. We collect and process the charge through the external circuit. Thus micro piezoelectric power generation device can be regarded as a micro-battery powered micro-power device.The relation of geometric parameters of the cantilever beam vs. natural frequencies and output voltage is simulated by finite element method (FEM). The analysis models were done using ANASYS because of its capability to work with coupled-field elements. The simulation results can give us a reference to make sure the dimension of the structure and manufacture the cantilever beam in the future.The micro fabrication processes are investigated for the piezoelectric cantilever power generator on the basis of literature [17] in this paper. Firstly to improve heat treatment process of piezoelectric thin film by Sol-Gel method in order to improve the piezoelectric properties of piezoelectric thin film, and characterize the performance of PZT piezoelectric thin film. The remnant polarization of the piezoelectric thin film which is made by the improved heat treatment process is higher than that which is made in literature [17], and its coercive electric field is more stable. So this preparation of piezoelectric thin film is more suitable as a memory; Secondly to improve the micro fabrication processes and solve the issues of beam-mass production. The beam-mass greatly reduces the natural frequency of the cantilever. And then, the wet and dry bulk micromachining techniques and film graphic technology are adopted to prepare the silicon-based piezoelectric cantilever structure. The natural frequency of the cantilever which is prepared by the improved MEMS process is down to around 300Hz. Compared to the piezoelectric cantilevers made in literature [17] which is around 1000Hz, this preparation of piezoelectric cantilevers are easier to pick up vibration energy in the environment.Finally, the natural frequency of piezoelectric micro-cantilevers is measured and the static and quasi-static calibration is carried out. The output power and voltage characters of micro prototype generators are surveyed.