Fabrication and characterization of MEMS-based PZT/PZT bimorph thick film vibration energy harvesters

Abstract

We describe the fabrication and characterization of a significantly improved version of a microelectromechanical system-based PZT/PZT thick film bimorph vibration energy harvester with an integrated silicon proof mass; the harvester is fabricated in a fully monolithic process. The main advantage of bimorph vibration energy harvesters is that strain energy is not lost in mechanical support materials since only Pb(Zr x Ti 1−x)O 3 (PZT) is strained; as a result, the effective system coupling coefficient is increased, and thus a potential for significantly higher output power is released. In addition, when the two layers are connected in series, the output voltage is increased, and as a result the relative power loss in the necessary rectifying circuit is reduced. We describe an improved process scheme for the energy harvester, which resulted in a robust fabrication process with a record high fabrication yield of 98%. The robust fabrication process allowed a high pressure treatment of the screen printed PZT thick films prior to sintering. The high pressure treatment improved the PZT thick film performance and increased the harvester power output to 37.1 μW at 1 g root mean square acceleration. We also characterize the harvester performance when only one of the PZT layers is used while the other is left open or short circuit.

MEMS Technologies for Energy Harvesting

“…A MEMS vibration energy harvester based on a PZT/PZT thick film bimorph with an integrated silicon tip mass is described in [91], Figure 33. bimorph PZT/PZT thick film harvester was present in [6], where it was shown that by using PZT thi film, it is possible to realize a self supporting devi without the need of a passive mechanical structu However, the fabrication yield was low due to process sequence with an early (DRIE) step, which turned most of the structure into fragile membrane.…”

On the dynamics of a capacitive electret-based micro-cantilever for energy harvesting

“…solar, wind and vibration) and convert it into electrical energy for self-powered wireless electronic applications ranging from structural health monitoring to medical implants [1][2][3]. Vibration energy harvesting devices are developed based on three basic energy conversion mechanisms including, electromagnetic [4,5], piezoelectric [6][7][8] and electrostatic (capacitive) [9][10][11][12] transductions. Since the technology for manufacturing electrostatic transducers such as capacitive-based sensors and actuators (e.g., accelerometers, gyroscopes, comb drives) is well established, it is beneficial to utilize the same technology (standard MEMS technology) for manufacturing capacitive energy harvesting devices.…”

A vibration energy harvester using AlN piezoelectric cantilever array

“…But the design and fabrication of the d 33 mode harvester are much complex. Xu et al [23] have fabricated a PZT/PZT thick film bimorph harvester. The two layers are connected in series to increase the output voltage, and the relative power loss in the necessary rectifying circuit is reduced.…”