It doesn’t take much anthrax to make a person sick?perhaps just one bad molecule among trillions of good molecules. But a group of electrical engineers at Purdue University hope that their research could lead to ultrasensitive sensors capable of detecting a single molecule of a biological agent or chemical pollutant.

Known as nanoantennae, these tiny sensors would use the light reflected off a substance to determine its molecular makeup. "Molecules irradiate light in a certain way that bears information about their structure," says Vladimir Shalaev, a professor at Purdue’s School of Electrical and Computer Engineering in West Lafayette, Ind. "By learning about molecules, we can get lots of important information. We can diagnose how much and what kind of molecules you have in the atmosphere, in water, in blood?everywhere."

Although Shalaev and his group are far from creating specific devices, they have done mathematical simulations proving that tiny metallic nanoantennae about 10 nanometers thick could look at individual molecules. They have already created the nanoantennae and have begun experiments. In the next one to three years, they plan to further advance the technology for real use.

The research could lead to detectors millions of times more sensitive than current technology. "Right now, devices aren’t that sensitive. There are no commercial devices that can detect single molecules," Shalaev says, noting that even a dog’s nose is more sensitive than current man-made technology.

The nanoantennae could be used to detect pollution in its very early stages, dangerous chemical or biological warfare agents in very small amounts, or certain proteins in blood indicating the early stage of a disease. Medical professionals could also use the technology for diagnostic imaging that would be less invasive than current devices such as X-rays.