The development of a fluorescent ink has made it easier to sniff out even tiny amounts of explosives – no dogs required. Dr. William C. Trogler, professor of chemistry and biochemistry at the University of California, San Diego, in LaJolla, has developed a photoluminescent polymer that can be sprayed in a thin film over a “suspect surface” – and if there are even minute traces of explosives present, dark spots will show up under a UV light source. “For some explosives, as little as a few nanograms can be detected,” Trogler said.Trace explosive particles left on a surface after contact from a hand contaminated with TNT are visualized under a UV lamp with a thin sprayed-on film of silafluorene-spirofluorenyl blue-emitting polymer. The thin polymer film is invisible under normal lighting conditions. Courtesy of Jason Sanchez and William C. Trogler, University of California, San Diego.The technique has been licensed by RedXDefense LLC of Rockville, Md., for its XPAK device. “A wand similar to a lint roller is used to sample a surface, and then that is put in the instrument and sprayed with their proprietary fluorescent ink to provide a similar detection of explosive particles transferred to the wand,” Trogler said of the XPAK.It’s pretty user-friendly, which is part of the point. “Traditional methods use complex and sensitive electronic instruments,” he said. “The advantage of the fluorescent ink approach is it is intuitive and requires little training to use. It is also robust and portable.”Portability is another part of the point. “Because the instrument is portable and can sample surfaces of interest at any location – for example, lockers in a bus station – you could imagine using it in cases where an explosive-detection canine might be used,” Trogler said. “Unlike a dog, a small portable instrument can be left in a trunk of a car until needed.”