The ICx Nomadics detectors work by sensing minute amounts of vapor: a specially formulated film fluoresces under certain conditions. For peroxide detection, a film starts to glow when it comes in contact with the peroxide vapors. The film coats the inside of a glass tube, through which air is drawn. The glass walls of the tube guide light from the film to a light sensor, which registers changes in light intensity. (In the TNT sensor, TNT vapors encountering an already fluorescing film cause it to darken.)
The company is working with MIT professor of material sciences Yoel Fink to further improve the clarity of the detectors’ signal by making it easier to distinguish from background noise. Fink, who has created hollow fibers that can guide light much better than the glass tubes currently used, has also incorporated light detectors directly into fibers. A device that combines these features could “offer a huge simplification in instrumentation, making these almost ubiquitous,” Rose says. In the future, soldiers could carry fibers designed to detect a variety of substances. The company is also developing polymers for detecting a variety of toxic industrial chemicals. A bundle of fibers could be used to detect more than one substance at a time.
It remains unknown whether ICx Nomadics’s liquid-explosives-detection technology will ultimately result in the federal government lifting restrictions on taking bottled water and other liquids through airport security. “That’s up to the TSA,” Kelly says.