The Technology
There exist many mechanical designs of piezoelectric unimorph actuators that can generate various motions other than conventional in-plane motions. Such devices are used to generate deflections or bending, twisting or torsional motion, and parallel out-of-plane motion, for use in micro-electromechanical systems (MEMS). Tilting motion, which is crucial for micro-mirror actuation, has been achieved using the bending response of bimorph piezoelectric actuators. In such devices, bending deformation has to be converted into angular motion, because piezoelectric beams could not be directly driven in torsion mode. This makes those devices complex and requires a comparatively large area of the MEMS for implementation. There exists a need for simple, small area piezoelectric devices which overcomes at least some of the disadvantages of prior art systems and methods, and can provide at least one of torsional motion, bending motion and parallel out-of-plane motion, such as for use in micro-mirror actuators.
Single bulk unimorph piezoelectric elements, with interdigitated electrodes aligned obliquely relative to the direction perpendicular to the axis of the element, such that a torsional response is induced into the element. When such elements are used as a beam structure, with angularly oriented electrodes on both opposite surfaces of the beam, and with their orientations at mutually opposite angles, motion ranging from pure torsional rotation to pure bending can be obtained, depending on the comparative level and polarity of the voltages applied to each of the two electrode sets. If such elements are used as the spiral support arms of a central platform, a large displacement of the stage can be achieved. Due to the oblique orientation of the interdigitated electrodes, the piezoelectric transduction induces torsional deformation in the spirals, and this torsion is converted by the spiral arms to a parallel out-of-plane platform motion.
Advantages
- Simple, small area piezoelectric devices
- Torsional deformation for the provision of out-of-plane motion
Applications and opportunities
- Micro-electromechanical systems (MEMS), and particularly as micro-mirror actuators
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