Actively controlled magneticlevitation of a ferrofluid droplet in mid-airusing a bar-shaped electromagnet

Abstract

　Ferrofluid is a magnetic functional fluid that flows in the direction of strong magnetic field. The authors tried non-contact levitation of a ferrofluid droplet in mid-air by controlling external magnetic field from a bar-shaped electromagnet. This paper describes the magnetic levitation system which consists of the electromagnet with a tapered tip, displacement sensor, and z-positioning stage with an oil-repellent film. This paper also reports on the procedure to establish non-contact levitation of the droplet. We evaluated the deformation and levitating behavior of the 15 mg droplet before and after the levitation start by using a high-speed camera. Finally, from the viewpoint of magnetic levitation technology, we experimentally derived the relationship between control current, mass of a droplet, and levitation gap.