A superconducting actuator using the Meissner effect

Abstract

A new type of superconducting actuator of the order of 100 μm in size called a Meissnac is proposed. It utilizes magnetic levitation using the Meissner effect to remove the friction between the slider and the stator. The slider and the stator of the actuator consist of linear arrays of vertically magnetized permanent magnet strips and superconductor strips, respectively. The pitch of the stator and that of the slider are different and the driving force is obtained by providing this difference between them and controlling the state of the superconductors by applying a current having a value of more than a critical current density, Jc, to some of the superconductor strips. The lateral continuous movement of the slider is obtained by switching appropriate superconductors to the normal state. The magnetic field and the force in the actuator are analysed by a numerical method called the discrete surface current method. When the pitch size and and the levitation height are of the order of 100 μm, maximum values of the driving force and the levitating force are 0.26 and 1.7 N m ⁻² A⁻², respectively. The movement of the slider in a particular direction (right or left) is obtained by choosing a driving mode. A scale model (about ten times larger) or the micro Meissnac is fabricated using YBCO high-T_c bulk superconductors. The width of the superconductor strips and the pitch are of the order of 1 mm. The levitating force and the driving force of the scale model are experimentally measured and the levitating force is compared with that calculated numerically for the micro Meissnac.