Silicon fabricated submicrometer stepper motor for microsurgical procedures

A linear stepper motor has been constructed with submicrometer step size and centimeter travel range. Silicon wafers with conventional dielectrics provide a basic electrostatic clamping mechanism, while a piezoelectric material serves as an electrical-to-mechanical power transducer. Movement is generated by using the inertial properties of an attached mass coupled with fast and slow expansions and contractions of the piezoelectric material. The fast transitions use the inertia of the mass to move the clamp, while the slow transitions move the mass while keeping the clamp fixed. Five prototype hand-held stepper motors have been successfully built and tested. The components of the motor fit within a pen-sized cylindrical stainless steel shell (15 cm × 1.2 cm) and delivery a displacement of 38 mm. For the given operating conditions, the tested handpieces had 1.2 mm/s advancement speeds against a 3 N load. The electrostatic clamp generates an attraction force of about 2 N using a clamp with an area of 3.75 cm² and 150 V across the faces. Maximum step sizes for the piezoelectric transducer (PZT) used here are slightly less than 10 μm, and steps less than 100 nm can be obtained with sufficiently low PZT voltages. Motor speed can be controlled by adjusting the operating frequency.