Washington, Aug 26: Tiny silicon crystals that can line themselves up according to order may be a first step to making "smart dust" that could detect biological or chemical agents or disease-causing microbes, U.S. researchers said. A team at the University of California, San Diego said they had created microscopic grains of sand that can orient themselves.
"This is a key development in what we hope will one day make possible the development of robots the size of a grain of sand," said Michael Sailor, a professor at UCSD's department of chemistry and biochemistry who led the study.
"The vision is to build miniature devices that can move with ease through a tiny environment, such as a vein or an artery, to specific targets, then locate and detect chemical or biological compounds and report this information to the outside world," Sailor added in a statement.
"Such devices could be used to monitor the purity of drinking or sea water, to detect hazardous chemical or biological agents in the air or even to locate and destroy tumor cells in the body."

Writing in the Proceedings of the National Academy of Sciences, Sailor and graduate student Jamie Link said their little grains of smart dust consist of two colored mirrors, green on one side and red on the other.

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One side was designed to find and stick to water, the other to oil. When lined up correctly, the mirrors shone either red or green.

Link and Sailor first used chemicals to etch one side of a silicon chip, making it mirror-like and green. They made it repel water by attaching a water-repellent chemical.

They etched the other side of the chip to create a porous red mirror, then exposed it to air so that it became attractive to water.

Using vibrations, they broke the chip into tiny pieces, each about the size of the diameter of a human hair.
Each piece became, in essence, a tiny sensor with a red surface attracted to water and a green surface attracted to oil. Each one is too small to see individually but when they clump up they are clearly visible.

Attaching the correct "recognition elements" could make the little chip particles into tools for biodetection or medical uses, the researchers said.
Bureau Report