Design And Fabrication Of Piezoelectric Micro Generator Using Laser Micromachining And MEMS Technique

Abstract

An energy harvesting device based on PbPb(Zr0.52Ti0.48)O3-Pb(Zn1/3Nb2/3)O3 ceramics was fabricated by using laser micromachining technique. It was found that the laser machining process did not have a significant effect on electrical properties of piezoelectric material. The device was found to generate continuous power of 1.13 μW at. 870Hz across a 288.5 kΩ load with power density of 301.3 μW/cm3. The characterization was conducted in low frequency regime of 50-1000Hz at the constant force of 8g(where g=9.8m/s2) In order to fabricate a lead free MEMS device, BaTiO3 was selected as the piezoelectric material. BaTiO3 gel was synthesized by aqueous process using barium acetate and titanium bis (ammonium lacto) dihydroxide. This solution is very stable in air at room temperature over a long period of time, compared to other sols using non aqueous systems. By incorporating PVP (Polyvinylpyrrolidone) during the synthesis process, and increasing surface energy of the substrate by plasma treatment, a 600nm thick crack-free film with (111) preferred orientation was obtained. BaTiO3 has tetragonal symmetry at room temperature and by orienting the polarization along (111) direction high piezoelectric properties can be obtained. A Piezoelectric micro-generator based on lead free barium titanate thin film was fabricated by using MEMS approach. This device may be a promising candidate to supply power to implantable sensors in medical applications. BaTiO3 polycrystalline thin films on SOI (Silicon On Insulator) were used to fabricate the micro-generator. The etching rate of BaTiO3 thin film by using 2% HF solution was determined to be in from 86nm/min to 187nm/min. The fabricated device had interdigital electrode pattern which allowed accessing the longitudinal piezoelectric coefficients. Each cell of the micro-generator had six cantilevers connected in series to obtain high voltage.