Reflective dust IDs substances

Researchers from the University of California at San Diego have found a way to coax microscopic silicon mirrors to orient so that the mirrors reveal information about their environment.

The tiny mirrored crystals -- dubbed smart dust -- are coated on one side with a molecule that is hydrophobic and oxidized on the other side to render it hydrophilic. When the crystals are added to a mixture of water and dichloromethane, a solvent used in paint remover, the particles align themselves along the boundary between the liquids, with the hydrophilic sides facing the water, and the hydrophobic sides facing dichloromethane. In addition, the dust absorbs some of the dichloromethane, which causes it to change color. Given enough dust, the color change is visible.

The researchers are currently working on attaching antibodies to one side of the crystals. This would enable them to recognize specific types of cells or bioorganisms.

Smart dust could eventually be used to target cancer cells in the body, or locate and identify pollutants or bacteria in drinking water, according to the researchers.

That method could be used in high throughput screening for drug discovery within three years, according to the researchers. The work appeared in the August 25, 2003 issue of Proceedings of the National Academy Of Sciences.