Pole Piece Effect on Improvement of Magnetic Controllability for Noncontact Micromanipulation

A single electromagnet can be used for one-dimensional (vertical) magnetic levitation, but cannot control the distribution of the magnetic field on a horizontal plane. For three-dimensional (3-D) levitated movement of objects, an arrangement of multiple electromagnets is required. A pole piece can connect the individual poles of the electromagnets in order to eliminate the appearance of multiple poles and produce a focal point of maximum magnetic field in the horizontal plane. This paper presents the results of an investigation of the effect on different pole pieces on the regulation and control of a large gap magnetic field for 3-D micromanipulation. In a large and wide magnetic gap, a levitated object tends to stay at the maximum point of magnetic field, B_max, in order to minimize the system energy. By producing a unique B_max point and controlling its position, 3-D levitated movement of a small permanent magnet (single magnetic dipole moment) can be realized. If the B_max point is converted into an area with a uniform field that is stronger than any nearby point (B_max area), complex objects, such as microrobots affixed with several permanent magnets, can be levitated and moved. By selecting a proper pole piece and tuning the electric currents in the electromagnets, the required field distribution will be obtained. The paper proposes a number of pole pieces and discusses their effect on magnetic field distribution. Through simulation results and experimental measurements, it shows that a number of proposed pole piece profiles can generate a magnetic field for 3-D levitated motion. Finally, it reports a demonstration of 3-D levitated motion of a single magnet (using the B _max point) and a microrobot (using the B_max area) to show the feasibility of the proposed method for micromanipulation