Scientists Use Lasers, Sunlight, to Move Levitating Graphite Discs
December 28, 2012 4:21 PM
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Technique could be applied to transportation or solar power harvesting via micro-turbines
Dr. Masayuki Kobayashi (
Aoyama Gakuin University
in Kanagawa, Japan) and Professor Jiro Abe (Aoyama Gaukin Univ.; CREST, Japan Science and Technology Agency in Tokyo) have published a study showcasing an intriguing phenomenon -- the ability to move magnetically levitate objects by controlling their material properties via laser light.
I. No Sharks, But Lots of Lasers
The premise is entertaining -- the researchers essentially got to play with lasers.
Magnetic attraction is governed by ferromagnetic and paramagnetic properties; magnetic repulsion is occurs due to diamagnetism. When diamagnetism overwhelms ferro/paramagnetism and the force of gravity, magnetic levitation occurs -- causing the object to "float" in the air.
Where the lasers come in is that two things can control the levitating object's height and/or induce it into motion -- changes in its magnetic properties, or changes in the magnetic field. The latter is a well-proven technique;
current maglev trains, like the L0 prototype
being tested Japan Railway Comp. (JR Tokai) (
), operate by controlling strong electromagnets.
The latter technique -- controlling the actual properties to achieve motion -- is where the lasers come in. By exploiting the photothermal effect, in which intense light heats a material, allowing electrons to flow more freely, weakening the paramagnetic effect and causing the exposed disk area to decrease in height.
The changes to the disc's properties via the photothermal effect cause it to follow the laser light-beam. [Image Source: JACS]
Graphite -- a
form of carbon
with strong paramagnetism -- was used in the study. A graphite disk was magnetically levitated above strong permanent magnets. When one side was exposed to laser light, that side would dip. Further, the disc would follow the laser, when it was moved, due to differential levitation height. When locked in place with a different kind of permanent magnetic (cylinders), the disc will instead rotate when exposed to a steady laser light on one edge.
While this may seem a scientifically intriguing parlor trick, the authors are convinced that the research could one day be applied to novel propulsion systems, including mag-lev trains driven by concentrated solar power or other intense light sources.
II. Novel Solar Power Generation
What's more the technique could be applied directly to power generation. Concentrated sunlight alone was enough to get the spinning graphene disc up to 200 rpm, raising the promise of mechanical mag-lev based
novel solar power harvesting devices
The effect can also achieve rotation; a trick the researchers hope to leverage for solar power generation. [Image Source: JACS]
Professor Abe, "At this moment, we are planning to develop a maglev turbine blade suitable for this system. In this case, it is predicted that friction disrupts the rotation of the maglev turbine. Therefore, we would like to develop a light energy conversion system with a high energy conversion efficiency with reference to the so-called MEMS (Microelectromechanical Systems) technique."
"As for the actuator, the maglev graphite can convey anything that has almost the same weight as the levitating graphite disk. So, if the scale expansion of the photo-actuator system is achieved, it is not a dream that a human on the maglev graphite can drive himself."
The study has been
[abstract] with peer-review in the Journal of the American Chemical Society (JACS).
This article is over a month old, voting and posting comments is disabled
12/29/2012 4:18:56 PM
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