Outer rotor surface-micromachined wobble micromotor

The design and fabrication of a surface micromachined electrostatic wobble micromotor are reported. The rotor is located outside the stator, and the design aims to generate torque on the order of 10^-4-10^-5 Nm. This design has the significant advantage of driving passive structures which are coupled to the rotor directly, magnetically, or by a lubricant. Since the generated torque is proportional to the cube of the radius of the stator, the dimensions of the motor must be on order of millimeters in diameter and 10 μm in thickness. Electroplated copper was used as the structural material because of its low residual stress. A five-mask fabrication sequence was used to make the stators. A rotor was manually assembled to the stators after stator fabrication in this study, but the fabrication sequence can enhanced to use preassembly techniques. When 20 V is applied to the stators, a wobble motion of the rotor is observed