A Linear Piezoelectric Stepper Motor with Submicrometer Step Size and Centimeter Travel Range

A linear stepper motor capable of submicrometer controlled movement has been constructed using the piezoelectric material lead zirconate titanate (PZT). This motor consists of a piezoelectric driving element measuring 25.4 mm × 12.7 mm × 1.6 mm connected between a glider base and an attached load. This device is inset in a trench to constrain motion to one dimension. An electrode on the bottom of the glider is used with an electrode on the top of the trench to implement an electrostatic clamp. This clamp enables the stepper motor to climb slopes of up to 12°, whereas without the clamp only slopes of 6° or less are tolerated. A linear inertial sliding motion can be achieved by expanding and contracting the piezoelectric bar but the addition of the electrostatic clamp enhances the movement capabilities of the glider by the periodic clamping and unclamping of the glider. Glider velocities of 5.7-476 μm/s were measured by timing the movement of the glider over a 1.0-mm portion of the track through an optical microscope. Displacement steps of 0.07-1.1 μm were calculated by dividing the measured glider velocity by the frequency of the applied voltage pulses. Displacement step size and glider velocity were controlled by the application of PZT extension voltages ranging from ±(60-340) V. The ability of the piezoelectric stepper motor to implement sub-micrometer motion with the large (centimeter) travel distances may have applications to electron microscopy, scanning tunneling microscopy, alignment of optical fibers, and magnetic recording.