Multilayer piezoelectric actuator

The standard actuator element in piezo-MEMS devices is a piezoelectric laminated flexural structure that works on the basis of the transverse piezoelectric effect. Such actuators are optimal when a large displacement is required, as the deflection amplitude is indeed amplified by the length L of the structure. In the world of bulk or thick film materials, the longitudinal effect is greatly exploited, for instance as multilayers (ML) in actuators for injection valves. MLs allow driving voltages to be decreased. In the MEMS world, there are applications permitting only very small driving voltages, for instance for implants, for which ML bending structures would be needed. ­

A ML actuator is a stack of N ceramic layers, which are electrically connected in parallel. As the electrodes used for actuation are the same as those used for poling, the polarity of an applied electric field aligns with the polarization in each layer, and thus all piezoelectric thickness expansions have the same sign and additive.

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