Magnetic snakes create water current

Science Daily —
Physicists at Argonne National Laboratory have found that magnetic
particles suspended in water and subjected to an alternating magnetic
field will form snake-shaped structures that can control the flow of
the surrounding fluid.

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)

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.This research is to be published in a forthcoming
edition of Physical Review Letters. Authors are M. Belkin, A. Snezhko,
I.S. Aranson, and W.-K. Kwok.

Note: This story has been adapted from a news release issued by American Physical Society.

ScienceDaily: Magnetic Snakes Create Water Current

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