Scientists have fabricated micrometer-size silicon mirrors, or "smart dust," that can swarm and stick to a target–conceivably, contaminants in drinking water or a cancer cell–and then relay information about that target to the outside world.
To make the mirrors, researchers at the University of California, San Diego etched each side of a silicon chip so that one side appeared green and the other red. They also coated the red side with a hydrophilic (water seeking) chemical and oxidized the green side, making it water avoiding, or hydrophobic. Applying ultrasound shattered the silicon chip into micrometer-size particles.
In an upcoming Proceedings of the National Academy of Sciences, the researchers report adding the particles to a vial of wat