Current incarnations of the
magnetic snake are a few centimeters long, but the team envisions much
smaller versions as pumps to manipulate liquids on microscopic scales or
precursors for next-generation magnetic recording media in future
computers. The team's recent experiment shows that the speed of the water
flowing along the snake depends on how quickly the
magnetic field alternates.
To make a magnetic snake, the team put a water-filled beaker at the center
of a magnetic coil. In the water, they suspended magnetic nickel spheres a
little smaller than one tenth of a millimeter in diameter. These particles
reacted to an alternating magnetic field created by the coil. The nickel
spheres aligned themselves head-to-tail with nearby particles as though
they contained tiny bar magnets.
The movements of the particle chain made waves on the surface of the
water, encouraging the formation of parallel chains and causing a
segmented pattern. The self-assembly of the snakes can take anywhere from
a fraction of a second to several minutes.
Citation: M. Belkin et at., Physical Review Letters, forthcoming
article
Source: American Physical Society
Magnetic Snakes Create Water Current
Alternating magnetic fields create snake-like chains of
magnetic particles suspended in fluid. The snakes direct the
flow of the surrounding fluid along their lengths,
potentially leading to new methods to control fluids in
chip-based chemical analysis. Credit: M. Belkin, A. Snezhko,
I.S. Aranson, and W.-K. Kwok
