A planar variable reluctance magnetic micromotor with fully integrated stator and wrapped coils

A fully functional electrical excited planar variable reluctance magnetic micromotor has been demonstrated on a silicon wafer. The motor uses a micromachined nickel-iron rotor and a fully integrated stator, in which a toroidal-meander-type integrated inductive component is used for flux generation. To reduce the magnetic reluctance in the stator, a modified stator geometry that removes the yoke used in a conventional reluctance motor was adopted. Using polyimide as both an integral structural material and as an electroplating mold, a 40- mu m-thick nickel-iron rotor 500 mu m in diameter was microassembled onto a fully integrated nickel-iron stator 120- mu m thick. The speed and direction of the rotation can be adjusted by changing the frequency and phase firing order of the power supply, respectively. Continuous rotor rotation was observed at speeds up to 500 rpm; this limitation was solely due to the limitation of the maximum frequency of the controller used.<>