Levitational and Vacuum-Compatible Micro Conveyer Utilizing the Meissner Effect of Ceramic Superconductor

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The purpose of this research is develop a micro miniature device to levitate and carry a small object in vacuum environment. The stable levitation without active control was achieved by using the repulsive force between a superconductor and a permanent magnet. One possible application of the device is the wafer conveyer in a clustered vacuum apparatus for semiconductor IC fabrication. Contamination by particles generated in sliding surfaces can be avoided by the non-contact movement with levitation. Furthermore friction force which is dominant in micromachines can also be eliminated by levitation. Miniaturization of the devices was achieved by using micromaching processes. Following results are obtained:(1) We designed the levitational actuator which was composed of a slider with permanent magnets, a superconductor for repulsive force, and line electrodes on the superconductor for carrying current to drive the slider. Therefore the device was the combination of both the magnetic repuls … More ive suspension and the linear synchronous stepping-motor. Through the optimal arrangement of permanent magnets and driving electrodes, we obtained the maximum levitation force and driving force while having enough accuracy in positioning. The repulsive force and the drag force acting between different kinds of superconductors and the magnet were determined experimentally; the result suggested a Y-based ceramic superconductor was most suitable to this device.(2) In order to achieve X-Y two directional movement, we have two sets of line electrodes on insulation films and placed them orthogonally on the superconductor. The pitch of the lines was 0.18 mm. The slider had four magnets of 1 mm cub. The superconductor was cooled by closed loop cooling set-up for vacuum environment. Driving experiments were successfully carried out in the vacuum. With currents over 500 mA, the slider moved step by step; one step was 0.18 mm. Two-degree-of -freedom movement was confirmed. Instantaneous speed of the slider was 33 m/s and the settling time for a step was 20 ms.(3) From the above experiment it was concluded that the device cleared basic requirements for a conveyer in vacuum apparatus. Less