Development Of Micro Energy Harvester With Frequency-up-conversion Mechanism Based On Piezoelectric Thick Film Technology

In recent years,with the rapid development of integrated circuits,MEMS(Micro-Electro-Mechanism System)and other technologies,ultra low power electronic devices(such as wireless sensor network nodes and portable electronic products)have been widely used.For example,the wireless sensors node is widely used in wireless sensor network that has large nodes and complexed environment.The nodes used the traditional power storage modules.However,the traditional power storage modules such as batteries have limited lifetime or need to be recharged periodically.So,the way to solve the power problem of the wireless sensors node is self power by energy harvester.In this paper,an up-frequency piezoelectric thick film micro energy harvester is proposed,aim to solve the problem that the lower output voltage and higher work frequency.The piezoelectric thick film is achieved through bonding of the PZT wafer and silicon wafer.The micro energy harvester size is small,because of the micro energy harvester is fabricated by MEMS.Thus,the micro energy work frequency is relatively high.So,by assembling low-frequency cantilever beam and High-frequency cantilever beam,the low-frequency beam can absorb the vibration of the environment and periodically collide high-frequency beam to realize the low-freuqncy to high-frequency,and improve the energy conversion efficiency.The main contents of this paper are as follows:(1)Study of the micro energy harvester's theoretical knowledge,and the commonly used piezoelectric materials are compared.The PZT wafer is selected as the piezoelectric material for subsequent process.The vibration and supporting mode of the piezoelectric vibrator are studied,and the voltage output and power output of cantilever piezoelectric energy harvester are theoretically calculated.The principle of the collision lifting mechanism is deeply studied,and the collision process of the cantilever beam is analyzed,which is divided into initial contact,cooperative motion and elastic release.(2)A micro energy harvester based on piezoelectric thick film is designed and simulated.The micro energy harvester is mainly composed of two cantilever beams which is "S" shaped low-freuqnecy cantilever beam and a high-freuqnecy cantilever beam.The cantilever beam simulation by COMSOL,and the reaonant frequency of the low-frequency are 44.078Hz and 86.023Hz,respectively,and the high-frequency cantilever is 2010.7Hz.(3)A new process flow of the fabricated up-frequency piezoelectric thick film micro energy harvester is proposed.The innovation of this process is the preparation of a piezoelectric thick film by bonding of PZT wafer and silicon wafer bonding,then mechanically thinning the PZT piezoelectric ceramic.(4)The output performance of the up-frequency piezoelectric thick film micro energy harvester is tested.The experimental process is designed,which is divided into the output performance test of a single high-frequency cantilever and the output performance test of the up-frequency piezoelectric thick film micro energy harvester.The resonant frequency of a single high frequency cantilever beam is 1995Hz,and the output voltage is 286mV at the 0.5g acceleration.The maximum average output power is 2.694?W,and the maximum power output density is 224.5?W/cm3,The up-frequency piezoelectric thick film micro energy has the maximum output voltage is 341.3mV at the 1g acceleration.And the maximum average output power is 3.837?W,and the maximum power output density is 319.7?W/cm3.