The compact linear-motion piezoelectric actuator developed has relatively large displacement capabilities. It is composed of a number of parallel bars of lead zirconium titanate (PZT) connected together in a meander-line configuration so that they are mechanically in series and electrically in parallel. The polarity of the adjacent bars is arranged so that if a given bar expands under the applied voltage, the adjacent bars contract. An electromechanical model of the actuator predicted and measurements verified that stiffeners added to the basic meander line geometry significantly increased the force output without affecting the displacement versus applied voltage relationship.

Three types of microactuator for linear displacement are presented which use piezoelectric thin films for the electrical-to-mechanical energy conversion process. One actuator uses a folded-path or meander-line geometry to produce horizontal tethered linear displacements. The second geometry uses a number of unimorph bars arranged in a planar format and mechanically connected in series to produce a tethered displacement perpendicular to the plane containing the unimorphs. The third actuator uses an inertial recoil mechanism in conjunction with an electrostatic clamp to produce incremental stepping motion. Sufficient repetition of the stepping sequence produces virtually unlimited travel range, being limited by practical considerations such as electrical connections. Electromechanical models for all three actuators are developed and are used to quantitatively estimate the performance of microactuators designed to a particular set of dimensions. Fabrication procedures for the microactuators have been developed and the status of the fabrication efforts is presented.

Thermally induced interactions between materials in complex microactuator structures were investigated. The device structure contained a combination of a piezoelectric layer (lead zirconate titanate - PZT) an electrode with adhesion layer (Pt/Ti), buffer layer (SiO2 or TiO2), structural material (polysilicon and/or silicon nitride), and sacrificial oxide (SiO2). The presence of a SiO2 sacrificial layer did not affect either the bottom electrode or PZT layer. XRD results showed significant platinum and titanium silicide formation in the Pt/Ti electrode at 700 °C (PZT crystallization temperature) on both polysilicon and silicon nitride structural materials when no buffer layer was used. Auger analysis shows that the Ti adhesion layer oxidizes, that measured levels of silicon increase in the electrode zone, and that electrode elements diffuse into the structural material. Buffer layers of SiO2 (0, 0.1, 0.73, 1.3, 1.5 μm) and amorphous TiO2 (0.065 μm) were inserted between the electrode and the structural material. XRD and sheet resistance measurements demonstrated that SiO2 thicknesses greater than 0.73 μm reduced pyrochlore formation in the PZT and reduced the degradation of the electrode. However, this thickness was incompatible with overall surface micromachining processes. The TiO2 layer effectively prevented pyrochlore formation and electrode degradation, while being compatible with overall actuator processing.

A novel actuator has been developed which, in a macroscale version, is composed of a number of parallel bars of lead zirconate titanate ( E T ) which are connected together in a meander line configuration so that they are nicchanically in series and electrically in parallel. The polarity of the adjacent bars is arranged so that if a given bar expands under the applied voltage, the adjacent bars contract. Both ends of the meander line are clamped and the center of the meander line is the output where external loads are connected and where displacement relative to the clamped ends occurs. The absolute displacement of the output end of the meander line is the same as that of a single straight bar of the piezoelectric whose length is one half of that of the unwrapped meander line, assuming that the same voltage is applied to each structure. Experimental measurements are in agreement with the predictions of an electromechanical model of the actuator which we have developed. The design and fabrication of a micromechanical version of the actuator is also described. The micromechanical version of the actuator is capable of either linear motion in the plane parallel to the substrate or normal to the substrate depending on how the voltage is applied to the structure.

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