Magnetic levitation is old hat these days, with maglev
in China and planned systems taking shape in other countries. But they run
by manipulating the train, which is "floating" on a magnetic field, with electricity. Now a team of researchers in Japan have found a way to manipulate magnetically levitating objects using light. The technique could lead to new forms of powered maglev transportation systems and could make solar-powered
generators more efficient.
To make the levitating graphite device, Masayuki Kobayashi and professor Jiro Abe of Aoyama Gakuin
University in Kanagawa arranged a set of magnets made of neodymium, iron and boron
in a grid. They then put a piece of graphite on top of the grid. When exposed to an
external magnetic field, graphite — specifically an artificial type called
pyrolitic graphite — generates its own field that repels the external one, a
property called diamagnetism. That makes graphite levitate when it's placed on
top of permanent magnets.
The researchers then hit the graphite with a laser. The
laser heated up part of the graphite and changed its susceptibility to the
surrounding magnetic field. Hitting the graphite in the center made it sink, as
the heating was more even. Aiming
the laser at the edge made it move in the direction of the beam.
Next, they put the graphite on top of a tower of
cylindrical magnets and hit the edge of it with the laser beam. The result
was a little graphite disc spinning at up to 200 rpm when it was exposed to the
laser — or sunlight.
The researchers published the results of their study in the Journal of the
American Chemical Society.
Being able to generate useful mechanical motion this way could
change the way solar power setups are made. A spinning disk could run a
generator directly rather than extracting the energy in several steps such as
converting the DC current from a photovoltaic cell or using solar power to make
Credit: Masayuki Kobayashi and Jiro Abe