NDLI: Compact Model for the Static and Dynamic Behavior of a Piezoelectric Bimorph Actuator for Microfluidic MEMS

Content Provider	The American Society of Mechanical Engineers (ASME) Digital Collection
Author	Rumschoettel, Dominik Kagerer, Markus Irlinger, Franz Tim, C. Lueth
Copyright Year	2014
Abstract	Piezoelectric actuators are commonly used in Micro-Electro-Mechanical Systems (MEMS). They can deliver high forces, large accelerations, and high power densities. However, one of their weaknesses is the comparatively small actuator travel that can be readily achieved. The elongation attainable by a slab of piezoelectric material is only a few tenth of a percent. Therefore, it is often useful to employ mechanical structures which are capable of amplifying those minute deflections. A particularly often used configuration is a sandwich structure consisting of either two differently poled strips of piezoelectric material or a single strip of piezoelectric and a layer of passive material. Such a structure is called a bimorph. If one of the layers is mounted above a cavity, the structure forms a membrane actuator. Because of their capability to displace fluid volume, those actuators are suitable for a wide range of applications in the area of microfluidics, including, but not limited to, micropumps, microvalves, microdroplet generators, and high frequency acoustic transducers. The directed design of those actuators demands the determination of their mechanical and electrical properties in advance. In the present paper a compact model for the characterization of such a bimorphic membrane actuator is presented. The model is based on an analytical description of the bending line of the membrane by means of Euler-Bernoulli-Beam theory. Relationships for the dependency of the actuator deflection and the volume displaced by the membrane on the geometry and the material properties of the actuator are established. Other model parameters like the moving mass and the effective stiffness are also determined. The identified parameters are used to create a behavioral model of the full dynamic characteristics of the actuator. This allows the prediction of the dynamic response to an arbitrary input excitation signal. The model is validated by comparing the predicted static and dynamic behavior of the membrane actuator with empirically derived results. For this purpose a number of test specimen with different actuator geometries are fabricated. The quasi-static deflection of the actuator is monitored with a laser-vibrometer for different drive voltages. Furthermore the dynamic behavior of the actuator is determined by recording its step response function. Overall, a model for the prediction of the static and dynamic behavior of a piezoelectrically driven bimorph membrane actuator is presented. The model validation shows good agreement between the predicted and measured behavior for the quasi-static deflection of the actuator and reasonable agreement for its dynamic properties.
File Format	PDF
ISBN	9780791849590
DOI	10.1115/IMECE2014-36654
Volume Number	Volume 10: Micro- and Nano-Systems Engineering and Packaging
Conference Proceedings	ASME 2014 International Mechanical Engineering Congress and Exposition
Language	English
Publisher Date	2014-11-14
Publisher Place	Montreal, Quebec, Canada
Access Restriction	Subscribed
Subject Keyword	Actuators Strips Membranes Deflection Acoustics Design Cavities Fluids Laser doppler vibrometers Mechanical structures Materials properties Piezoelectric actuators Stiffness Excitation Signals Slabs Elongation Microelectromechanical systems Dynamic response Transducers Electrical properties Micropumps Generators Sandwich structures Geometry Piezoelectric materials Model validation Microfluidics
Content Type	Text
Resource Type	Article

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