New sensor upgrades artificial bomb sniffers

November 08, 2001

Researchers have developed a disposable plastic sensor to enhance efficiency of the artificial nose, a high-tech sniffing device they hope will improve detection of bombs and landmines.

Although experts predict that a practical device is at least five years away from actual use at airports, on battlefields and elsewhere, the researchers say their new sensor will improve the sensitivity and reliability of current prototypes. Their findings are reported in the November 1 issue of Analytical Chemistry, a peer-reviewed journal of the American Chemical Society, the world's largest scientific society.

Trained dogs -- and people armed with dirt-clearing probes or metal detectors -- are the current methods of choice for landmine detection. But dogs get fatigued easily, while human minesweepers are at risk of serious injury and death. The new sensor could ultimately help save lives and reduce injuries, says David R. Walt, Ph.D., a professor of chemistry at Tufts University in Medford, Mass., and lead investigator in the study.

But first, he says, the sensors must be made more user-friendly. And they must be able to solve a wider array of odor recognition problems, says Walt, who holds several patents on the new sensor technology.

His and other sensors in development tend to degrade over time, Walt says, just as the human nose looses its ability to sense and remember certain odors as people age. So the sensors need to be retrained or resensitized frequently to recognize target odors, he says.

In a process akin to replacing a dead battery with a fresh one, the new sensor is made with specially designed disposable fluorescent polymer beads. Because the beads are conditioned not to need odor-recognition training, degradation and retraining problems could be eliminated, Walt and his associates say.

Billions of the sensor beads can be made at once, as needed, whether daily, weekly or yearly, providing a continuous replacement stock, according to the researchers.

To test their sensor, the researchers developed a stock of polymer beads that is sensitive to nitroaromatic compounds similar to those used in explosives. The sensor containing the initial bead-array detected the compounds with 98 percent accuracy. When beads from the same batch were installed in a different array and tested six months later, they detected the compounds with similar accuracy (94 percent), demonstrating successful odor memory transfer from one bead array to another, they say.

Walt estimates that at least a dozen labs are working to develop a practical artificial nose technology, but acceptable accuracy still remains an elusive goal. Now about the size of a desktop computer, today's prototypes could also be miniaturized -- to fit wands carried by soldiers or robots, the researcher says.

Eventually, sensors also may be able to detect diabetes and cancer on the basis of breath odors, similar to breath-analyzer tests for alcohol, he says.

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This research was funded by grants from the Air Force Office of Scientific Research / Defense Advanced Research Projects Agency, the Department of Energy, and the Office of Naval Research.

The online version of the research paper cited above was initially scheduled to be published September 28 on the journal's Web site. Journalists can arrange access to this site by sending an e-mail to newsroom.org or calling the contact person for this release.

David R. Walt, Ph.D., is a professor of chemistry at Tufts University in Medford, Mass.

American Chemical Society

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