Effects of the material properties on piezoelectric PZT thick film micro cantilevers as sensors and self actuators

Abstract

In general, PZT thick films fabricated through screen printing show porosity ranging from 10% to 40%. Unfortunately, these high porosities of thick films greatly affect the electromechanical characteristics of PZT thick film cantilevers. In this paper, we report a systematic analysis on the effect of thick film porosity on the electromechanical characteristics of the PZT thick film cantilevers in order to make the PZT thick film cantilever a highly controllable micro mass sensor or micro self actuator. The theoretical calculations of mass sensitivity and actuating force of the optimal PZT thick film cantilevers are presented with respect to the material properties and geometry of PZT thick films, which are based on experimentally verified material properties and geometrical parameters. The 400 x 300 cantilever with 20% porosity of active material was evaluated to be reliable as an optimal mass sensor and self actuator. The thick film cantilever indicates both high mass sensitivity (similar to 48 pg/Hz), the same as sensitive thin film cantilever sensors, and high actuating force (similar to 1.7 N), similar to strong bulk cantilevers. From the results of the modeling, it was found that the harmonic oscillation response according to material properties including the porosity, and geometry of the fabricated thick film cantilever, is quite controllable and predictable, thus enhancing the actuating force and mass sensitivity. Also, it was confirmed that controlling the porosity of PZT thick films is more efficient than controlling the cantilever geometry to increase the cantilever resonating force. However, optimizing the geometric constituents is more effective than controlling the densification of PZT thick films to increase the mass sensitivity of the cantilevers.