Ultrasonic micromotor control using selfactuated micro-structures

This paper presents control of a surface micromachined ultrasonic micromotor using self-actuated micro-structures placed at a micro-gap separation to the rotor. An ultrasonic micromotor fabricated using MUMPS process and driven by bulk piezoelectric PZT bonded to the motor, operates at a drive voltage of 1.3 - 10 Vpp in the frequency range of 100 kHz to 5 MHz. We have previously demonstrated that the rotor is suspended in air during operation. A non-contact method of controlling the motor rotation rate would enable the stability of air suspension improving rotor stability for applications in which smooth operation is important. We show the non-contact control of the motor rotation using two distinct micro-structures surrounding two motors, the control enabled by the control of micro-gaps that modulate acoustic streaming forces around the rotor.