A Piezoelectric Mems Sensor/Energy Harvester Based On Flexible Substrate

Flexible piezoelectric Micro-Electro-Mechanical System (MEMS) energy harvester has a wide range of application prospect and important application value in information communication, biomedicine and aerospace, due to the advantage of light quality, good flexibility and durability, integration and miniaturization. This subject designed a flexible and transparent piezoelectric MEMS sensor/energy harvester and then studied its working principle and power generation mechanism. Combining the hydrothermal synthesis process of single crystal Pb(Zr0.52Ti0.48)03nanowire (PZT NW) with MEMS micromachining process, flexible MEMS energy harvester had been fabricated. The electromechanical and optical properties of energy harvester have been tested.Single crystal PZT NW was successfully synthesized by hydrothermal synthesis process. The microstructure and the electrical properties of PZT NW were investigated. The maximum length of PZT NW is about75μm with the reaction temperature of200℃and reaction time of72h, the diameter of a NW is about700nm, and the aspect ratio is as high as about107. High resolution transmission electron microscopy images showed that the PZT NWs are single crystal. The individual PZT NW has the typical ferroelectric hysteresis loop, and the magnitude of current density is in the order of10-1A/cm2, which demonstrate that the individual PZT NW has good ferroelectric property.Polydimethylsiloxane (PDMS) flexible substrate was prepared by spin coating method and extrusion method. The flexible MEMS energy harvester had been fabricated using ultra-long single crystal PZT NW and PDMS. The transmittance spectra images showed that the average transmittance of PDMS film is about94%from400-1000nm, the MEMS sensor/energy harvester with20dots PZT NW has an average transmittance of60%, and the MEMS sensor/energy harvester with50dots PZT NW has the maximum transmittance of58%, and the average transmittance over above50%from400-1000nm, this indicated that energy harvesters has good optical transparency in the range of visible-near infrared. The electrical property of flexible MEMS energy harvester had been tested. The output voltage value of energy harvester is largest with the dynamic pressure frequency of100Hz. The open-circuit output voltage is increased with the increasing of dynamic pressure, when the dynamic pressure is75kPa, the open-circuit peak to peak voltage is about14.4V, the average open-circuit voltage is about7.2V, and the force sensitivity is about96mV/kPa. The root mean square output voltage is about1.15V, and the maximum output power is about0.19μW with the load resistance of7MQ and the dynamic pressure of75kPa. By connecting bridge rectifier circuit and the charge storage capacitance with energy harvester, the direct current voltage is about1.32V, the output power is about0.17μW, when the load resistance is7MΩ and the dynamic pressure is75kPa. These results show the higher output voltage and power density than those of the reported piezoelectric nano energy harvester and a comparable visible light transmission.