Experimental study on the dynamic behaviour of magnetic levitating magnet-magnetic fluid element in the external alternating magnetic field is described. Two types of element motions occur according to the magnetic field strength and frequency of the external alternating magnetic field. Seesaw motions of the element and harmonic motions of magnetic fluid surface are observed using high-speed video camera system. Transient phenomena in element response and the change of spikes pattern on the magnetic fluid surface are revealed.

����� �Masato NAKANISHI (Stu. Mem.), Michihiro SHINOZAKI, Seiichi SUDO (Mem.), Hideya NISHIYAMA (Mem.)This paper is concerned with the development of micro magnetic fluid diaphragm driven by alternating magnetic field. The micro magnetic fluid diaphragm is composed of a ring-shaped permanent magnet and kerosene-based magnetic fluid. The response characteristics on the relations between input and output signals were examined by using a photodiode detector system and a digital high-speed video camera system. Sinusoidal, triangle, square, and saw tooth waves as input signals were examined. The magnetic fluid device showed good responses even at the frequency f 0 =1000 Hz in alternating field.

Response characteristics in the opening and closing operations of the micro magnetic fluid diaphragm mechanism by the alternating magnetic field are described. The micro magnetic fluid diaphragm mechanism was composed of a ring shaped permanent magnet and kerosene-based magnetic fluid. The driving principle of micro magnetic fluid device was based on the surface phenomena of magnetic fluid adsorbed on a permanent magnet. The opening and shutting time of diaphragm mechanism in the alternating magnetic field was measured by high-speed video camera system. The details of magnetic fluid surface response in the opening and closing operations of magnetic fluid hole were revealed experimentally.

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