Piezoelectric torsional actuators have been developed from single ceramic cylindrical bodies using PZT based high d constant piezoelectric ceramics. The actuator geometry is able to produce rotational motion directly by DC voltage control without conventional complex conversion from XY direction motions. The key feature of this actuator is the interdigital electrode on the outer surface of the cylinder at an angle of 45° from the length axis of the cylinder, and the design of this electrode is critical for adjusting torsional angle and driving voltage. When the cylinder wall thickness and the ratio between electrode width and pitch are kept constant, the rotational angle is approximately proportional to the electric field, i.e. the narrower electrode gap needs smaller driving voltage in order to obtain a certain rotational angle. Among the three different diameter samples tested, actual rotational displacements are the same under the same conditions. Therefore, the rotational angle is reversibly proportional to the diameter of the piezoelectric cylinder.
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Fuda et al. (1994) studied this question.