Our piezomotor actuators are compact and provide extremely high-resolution incremental movement, as low as 20nm.  The motion of these actuators relies on the structured, high-speed "vibration" of a piezo stack along with the force difference between the friction of a moving object (dynamic) vs. friction of a non-moving object (static). Recall that that friction on a non-moving object is higher than that of moving friction.   In the motion process, the piezo is expanded slowly, enabling higher static friction, and this makes the screw rotate in a direction.  Then, the piezo is retracted very quickly, for lower static friction such that the screw does not rotate.  Applying this process repeatedly at a high rate causes the actuator screw to rotate continuously in a particular direction. Simply reversing the order of the fast and slow piezo expansion/retraction changes the direction of rotation, allowing the screw to move in the opposite direction.  One of the key benefits of piezomotor actuation is that the static friction, which is in effect when the piezomotor is not operating, also acts like a locking mechanism which ensures excellent stability.  Our PDM piezo actuators are available in two travel ranges, 13- and 6.5-mm and have industry-standard 9.5-mm and 6-mm diameter mounting interfaces allowing them to be drop-in replacements for standard micrometers.  They also have ball-tip or flat-tip options.  Another convenient feature of these actuators is that the electrical cable is conveniently removable.  Please note that these actuators do not have internal feedback and therefore are open-loop.  Vacuum compatible versions are also available.  If your application needs different specifications we can customize our piezomotor actuators to your unique requirements.