10:00 〜 10:15
▲ [5a-C24-5] Light-assisted non-contact manipulation of phosphorescent object levitating in magnetic field
キーワード：non-contact manipulation, Magnetic levitation, Magneto-Archimedes effect
This study demonstrates non-contact manipulation of objects whose magnetic susceptibility can be controlled by irradiation of light. In order to realize such an interesting experiment, we chose a photo luminescent material, which is also called luminous paint. The electrons in the material can be activated by light and its relaxation time is very long; the material keeps emitting light for a long time even after the irradiation light is turned off.Firstly, we prepared a small piece of photoreactive polymer (~1 mm) including the photo luminescent materials. Secondly, the piece was made levitate in an aqueous solution of gadolinium chloride by Magneto-Archimedes method in the bore of a helium-free superconducting magnet with the maximum magnetic field of 13 T, and it was kept in dark at room temperature for one night so that it becomes mostly deactivated in terms of emission of light and equilibrated in terms of the diffusion of gadolinium ions from solvent, water, to polymer matrix. After that, the piece was irradiated by UV light and its positon was recorded using a CCD camera. It should be noted that red LEDs were always turned ON to shine the sample, and, on the other hand, UV LEDs were turned ON only when we needed to activate and move the sample. The experiments clearly showed that the levitating object responded very sensitively to the UV light with the wavelength of 375 nm and moved straight upwards, towards the non-magnetic field, at about 1 mm/sec. Once the light was turned OFF, the sample started going down, towards high magnetic field, however, the speed of motion in OFF state is much slower than in ON state. This is because activated electron has a very long life time in the decay process and it kept shining. The process was reversible and controllable by the intensity or duration of the irradiation of light, wave length, etc. The detail of the experiments will be discussed in the presentation.