Fabrication And Performance Study Of The Miniature Vibration Energy Harvester

For a long time,the development of battery technologies has not caught up with the pace of the extreme pursuit for batteries' miniaturization.Due to the shortcomings of the chemical batteries,researchers began to harvest power from the environment or the human body for portable electronic devices and wireless sensor network.The vibrational energy is the most common energy in industrial production and daily life.In this paper,the miniature low-frequency vibration energy harvester is studied.Usually the cantilever beam energy harvester is composed of piezoelectric ceramic pieces with unimorph and bimorph structure.As the thickness of the piezoelectric ceramic piece is almost identical to that of the cantilever beam,the harvester has comparatively high frequency.In this paper,the vibration energy harvesters are fabricated from double-layer lead zirconate titanate(PZT)thick films via a dip-coating process.Since the thickness of films is much smaller than that of the beam,harvesters with unimorph and bimorph structure operate at the same resonant frequency.The perforance of the harvester with Ti as substrate material was firstly studied in this paper.The cantilever beam energy harvester was fabricated by PZT thick films with the thickness of 1.71 ?m and Ti substrate via a dip-coating process,and only one side of the PZT piezoelectric layer was polarized.When the harvester was tested under the circumstance of 3m/s2 vibration acceleration and the optimum load resistor of 47.5k?,the measured resonant frequency was only 24.2Hz,the optimal output power was up to 50.9?W and the normalized power density was 44.15 kg.s.m-3.In comparison with literature,the Ti-based energy harvester has a lower resonant frequency,which is more conducive to practical application,and the output power density has great improvement.Then,the tandem bimorph-architecture cantilever beam energy harvester with 726 nm-thick PZT films was fabricated.At 0.8m/s2 vibration acceleration,25 k? load resistor and 12 Hz vibration frequency,the output power was up to 9.248?W.A corrugated piezoelectric energy harvester,similar to a mechanical spring,was also fabricated.The elastic vibration of the harvester was tested in the vertical direction.Under 1.5m/s2 vibration acceleration and the attached mass of 4.2g,the resonant frequency was only 11.3Hz,and the measured DC open circuit output voltage was 880 mV.Therefore,the harvester can output power directly without the need for rectification circuit.Finally,the author makes a summary of the whole paper,and puts forward some improvements in the experiment.There is still room for improvement of this research.With possible enhanced experimental conditions and methods,vibrational energy harvesters with more outstanding performance could be obtained.