Bulk PZT Actuator for Parallel out-of-plane motion: The Superiority of Torsion Deformation over Bending Deformation

We present a new method for achieving a parallel out-of-plane (piston) motion, by using torsion actuation of a bulk, unimorph, piezoelectric actuator. Three piezoelectric spiral arms support a central stage, the arms are both poled and driven by interdigitated electrodes (IDEs) deposited directly on the top side of the structure. We show that when the IDEs are oriented at 90°relative to the spiral tangent, and thus only an internal moment is induced, the supported stage is only slightly displaced. In contrast, we show that when the IDEs are oriented at 45°relative to the spiral tangent, a torsional deformation is induced in the spiral arms, which results in a much larger (×20) displacement of the central stage. This demonstrates the superiority of torsion deformation in driving curved piezoelectric unimorph arms.