Operating in open-loop mode, the Closed-Loop Picomotor actuator has a step size of < 30 nm, allowing for very small movements. In closed-loop mode, the encoder has a resolution of 63.5 nm, allowing for very small, controlled, and repeatable movements.

Picomotor actuators rely on the basic difference between dynamic and static friction. An example of this is the magician's "tablecloth trick," in which a quick pull (low dynamic friction) of the cloth leaves the dishes on the table, while a slow pull (high static friction) would pull the dishes off the table and cause a big mess! Our Picomotor actuator uses the same principle with a threaded jaw, similar to two halves of a split nut, clamped around a precision 80-pitch screw. One jaw is connected to one end of a piezoelectric transducer, and the other jaw is connected to the other end of the transducer. A slow electrical signal applied to the piezo slowly changes the length, causing the two jaws to slide in opposite directions. This slow sliding motion makes the screw turn (static friction). At the end of the transducer motion, a fast electrical signal quickly returns the jaws to their starting positions. Because of the screw’s inertia and low dynamic friction, it remains motionless, holding its position. Simply reversing the order of the fast and slow signals reverses the direction of rotation.