Chemical "Nose" Could Sniff Out Landmines

November 13, 1998

Newly designed polymers may soon rival dogs as the most advanced landmine detection device. Mimicking dogs' acute biochemical mechanisms of smell, the polymers are engineered to notice trace vapors of TNT and its derivatives, which are commonly used in landmines.

The latest generation of these polymers is described in the November 10 Web edition of the Journal of the American Chemical Society, published by the American Chemical Society, the world's largest scientific society. It is scheduled to appear in the print version of the peer-reviewed journal on November 25.

Currently man's best friend is also the best tool for finding the estimated 120 million unexploded landmines hidden around the world. The chemicals that may relieve dogs of this dangerous duty are being developed by a team of scientists at the Massachusetts Institute of Technology, in Cambridge.

"We've come up with a very specific, sophisticated polymeric material," says team leader Timothy M. Swager, Ph.D.

The new sensors are fluorescent polymers, activated by light to have high energy electrons. The polymers look like 3-dimensional X's, attached through their center to parallel rows of chemical backbones. This structure keeps individual sensor polymers separated. When TNT floats in between the spaces it momentarily steals an electron, decreasing the fluorescence and sending a signal to the detector's "brain."

The system is expected to be very sensitive because "one TNT molecule can deactivate many of these electrons," according to Swager.

Swager says this chemistry could enable development of a simple, low cost, rugged and portable instrument to complement existing technologies for finding unexploded land mines. Current methods have drawbacks ranging from frequent false alarms to fragility to complex operation. A device based on Swager's polymers is currently being tested.

The invention might have other applications as well. For example, Swager envisions a system that would replace security spot checks: "Everyone walks through a little air shower and it would look at you" for substances ranging from drugs to explosives.
A nonprofit organization with a membership of more than 155,000 chemists and chemical engineers, the American Chemical Society publishes scientific journals and databases, convenes major research conferences, and provides educational, science policy and career programs in chemistry. Its main offices are in Washington, D.C., and Columbus, Ohio.

American Chemical Society

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