ELECTRODEPOSITED ELECTROSTATIC RIGID-ROTOR WOBBLE MOTORS ON SILICON

A new design of a variable-capacitance (VC) vertically wobbling electrostatic micromotor fabricated on silicon is presented. The movement of the rotor is similar to that of a coin flipped on a table, as reported in our previous work on a first design, but here the rotor is completely rigid instead of being flexibly attached to a rotating ring. First, a theoretical model has been developed to describe the dynamics and relate the dimensions and driving voltage to the maximum mechanical output speed and power. Using this model, motors with rotors of 1-3 mm diameter have been designed to meet the typical power range of wristwatch motors (about 1 muW). They have been fabricated on silicon, utilizing in particular electroplating of nickel for the rotor parts, which where post-assembled. Successful operation of a motor having a rotor of 2 mm diameter has been achieved with driving voltages between 20 and 80 V. A maximum speed of 2.7 rpm has been measured.