Smart dust gets magnetic

One of the main challenges in making labs-on-a-chip is finding ways to control and mix tiny amounts of liquids.

Researchers from the University of California at San Diego are using minuscule silicon particles to carry out these tasks.

The researchers' have modified their previously developed smart dust by trapping magnetic iron oxide nanoparticles within the silicon particles. The particles are chemically coated so that they adhere to water on one side, and repel water on the other side.

The chemical coating causes the silicon particles to surround water droplets, and the dust changes color depending on the chemicals it is in contact with. This allows the researchers to identify chemicals encased by the smart dust. The magnetic properties makes it possible to move the particles -- and the droplets they are surrounding -- using a magnetic field.

The silicon particles are 50 to 100 microns in diameter, which is one-tenth to one-twentieth of a millimeter.

The researchers demonstrated the system by filling and draining droplets and by combining two droplets to carry out a chemical reaction.

The system makes it possible to work with small amounts of chemicals, and can be automated, making it possible to carry out many reactions simultaneously, according to the researchers.

The method could be used practically in two to five years, according to the researchers. The work appeared in the November 7, 2004 issue of Nature Materials.