ELECTRODEPOSITED ELECTROSTATIC RIGID-ROTOR WOBBLE MOTORS ON SILICON

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