Micromachined Piezoelectric Generator
Both electromagnetic and piezoelectric generators utilise a cantilever/mass structure. The piezoelectric generator couples the motion of a silicon mass and cantilever beam to AlN or PZT piezoelectric thin films deposited on the top surface of the cantilever. Figure 1 shows a finite element plot of a typical device geometry.
Figure 1 - Finite element model of piezoelectric generator
This has been fabricated using a range of standard silicon micromachining techniques. Generators fabricated with sol-gel deposited PZT and sputtered AlN have been realised and different electrode configurations investigated. A scanning electron micrograph of a completed device with split electrodes is shown in figure 2.
PZT based devices with IDT electrodes have demonstrated 1.4 microwatt from 2g vibrations at 840 Hz. The overall device is 2 cubic millimeters in size.
Figure 2 - PZT generator with split electrodes