Single mask 3-phase electrostatic rotary stepper micromotor

In a hard disk drive, the angular alignment of the read/write head relative to a data track varies with the radial position of the track, increasing a risk of data track misregistration. We present a frictionless rotary micromotor which can be used as a secondary stage actuator to maintain a constant angle between the head and the tracks during disk operation. The monolithic device is fabricated in single-crystal silicon using a single mask process based on standard silicon-on-insulator micromachining. The motor employs a flexural suspension of the rotor to avoid any mechanical contact during operation, enabling precise, repeatable and reliable stepping motion without feedback control. The preliminary experimental characterization of a prototype with a diameter of 1.15 mm has demonstrated a rotational range of 4.2deg (+/-2.1deg) at 45 V and a resolution of 0.14deg in a coarse stepping mode.