Juiced liquid jolts metal into shapes

One strategy for constructing microscopic devices is finding ways to make materials assemble themselves.

Researchers from Argonne National Laboratory and the Russian Academy of Sciences have found a way to use electricity to drive metal microparticles into patterns.

The self-assembly process could be used to construct micromachines and materials, including materials useful in space.

The researchers immersed 120-micron bronze spheres in a mix of toluene and ethanol, which does not conduct electricity well, and trapped them between glass plates coated with conducting material. A micron is one-thousandth of a millimeter. The researchers used an electric field to shake the tiny spheres into shapes: the field caused spheres in contact with the lower plate to be repelled back and forth between the plates.

The process caused the particles to form patterns like rings and honeycombs. The shape depends on how the flow of the poorly-conducting liquid affects the charged spheres.

The method could be used to make nanoscale structures in three to four years, and it could be used to form materials that improve heat transfer in space applications in 10 years, according to the researchers. The work appeared in the March 21, 2003 issue of Physical Review Letters.