Effects of the material properties on piezoelectric PZT thick film micro cantilevers as sensors and self actuators
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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 × 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 (~48 pg/Hz), the same as sensitive thin film cantilever sensors, and high actuating force (~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.
KeywordsCantilever Sensor Actuator Piezoelectric Thick film Porosity Mass sensitivity Actuating force
The authors are grateful for the financial support from the Intelligent Microsystem Center sponsored by the Korea Ministry of Science and Technology as a part of the 21st Century’s Frontier R&D Projects (Grant MS-01-133-01) and National Core Research Center for Nanomedical Technology sponsored by KOSEF (Grant R15-2004-024-00000-0). Also, this work was supported by the Korea Research Foundation Grant funded by the Korean Government (MOEHRD), (Grant Number: KRF-2006-351-D00002).
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