Dunn says his technique uses some technologies that others are investigating, but does so in a different way.
"Rather than try to completely identify the contents of a random target or to create a detailed image, we are simply trying to see if the contents emit 'signatures' that are typical of explosives," he explains.
By looking at how the set of signatures differs from the "template" for an explosive, Dunn hopes to be able to distinguish between inert and explosive contents.
Dunn's process is swift. A yes/no result is displayed within 1 to 10 seconds - considerably faster than bomb dogs, long the standard of military and law enforcement. It takes bomb dogs about 5 minutes to work a vehicle, sniffing tires, doors, trunks and hoods.
So far, Dunn has been able to determine what signals come back when he interrogates an object containing an explosive substance. Currently, he's trying to find out the best way to analyze the data to make sure the analysis is correct - that there indeed are explosives on board.
Dunn says the problem becomes more complicated by the size of the container. Large cars make it easier to hide explosives, while it is easier to detect explosives in a briefcase or a knapsack.
"Even if you put other things in small containers, we think we're going to get a set of signals that indicate the presence of explosives if they are there," Dunn says. "With larger containers, it can become very complex, but we're still hopeful."
The research is past the proof of principle stage. Dunn is now trying to optimize the design of the system.
"Full field implementation will require that templates be constructed for various types of targets containing various explosive materials in various package geometries and with various other cargos," he says.
Nevertheless, with sufficient funding, he thinks he can have a working prototype within a year or two.
Beam me up, Scotty
To improve upon explosive screening at airports, the University of Arizona (UA) has designed a Star Trek-like device that may help TSA finally make the grade.
According to UA scientists, the "tricorder" technology can screen passengers for traces of explosives or illegal drugs as they walk through security portals, and handheld units scan the baggage.
The device would make it possible to screen 100 percent of passengers for explosives, instead of the random samples TSA screeners now obtain by current swabbing methods.
Rather than analyzing a swab from a person's briefcase, the UA technology could detect the traces of explosives left in the air that passes over a person who has handled explosives.
"The new device can be pocket sized," says principal investigator M. Bonner Denton, UA professor of chemistry, versus the analyzers currently used in airports that are about the size of a tabletop microwave oven.
Such a device also could be employed at border crossings to detect illicit drugs, as well as smuggled explosives.
"This is more sensitive than dogs' noses," says Denton. "And it tells you what material has been detected. Dogs just tell you something has been detected."
In yet another project in academia, scientists at Purdue University have come up with a fast, reliable means of detecting residues indicating the presence of trace quantities of several common explosives, as well as chemicals such as those found in biological and chemical warfare agents, within a few seconds. The technique works on just about any surface, including clothing, human skin and luggage. The new method uses a tool found in many chemistry and biology labs called a mass spectrometer, only the Purdue mass spectrometer has been modified to analyze samples directly from the environment rather than from samples that require lengthy pretreatment.
"Mass spectrometry is the gold standard in analytical chemistry," says lead investigator R. Graham Cooks, professor of analytical chemistry at Purdue. "However, mass spectrometers are traditionally slow since they require extensive preparation of the sample and the instruments."