Miniaturization of chemical preconcentrators brings better bomb-detecting and drug-sniffing devices

You might call it an "electronic dog."

Researchers in Contraband Detection Dept. 5848 are working this summer on a hand-carried gadget that, like a trained police dog, could sniff out the vanishingly faint odors of drugs and bombs at airports, border crossings, military installations, and schools.

The device is based on chemical preconcentrator technology used in an explosives-detection walk-through portal Sandia developed for the Federal Aviation Administration (FAA). The portal might soon be seen at hundreds of US airports as a screening tool for airline passengers. (See "Coming soon to an airport near you" on page 4.)

Kevin Linker (5848), project leader for the FAA airport portal’s development, says recent Sandia improvements in preconcentrator technology are allowing development of ever-smaller sniffing tools.

"Miniaturization of the underlying preconcentrator is allowing us to develop better detection tools that are portable, cheap, sensitive, and fast," he says.

The preconcentrator works by drawing in a large volume of air, collecting heavy organic vapors from the air stream onto a filter, then concentrating these organics in a smaller parcel of air that is delivered to a detector. By drawing larger volumes of air past the filter using a clever design trick, the researchers have been able to shrink the preconcentrator’s largest feature — its air intake and valves — from a nine-inch diameter to a one-inch diameter, enabling increasingly smaller sniffing tools.

Portable crime scene sniffers

Already Dave Hannum (5848) has delivered to the FBI Academy and Research Lab (Quantico, Va.) a chemical preconcentrator unit that is fit onto the front of a hand-carried, battery-powered ion mobility spectrometer (IMS) made by Ion Track Instruments.

Now, rather than take swipes of chemical particulates back to a crime lab for analysis, forensics investigators can place the two-inch-square metal felts they use as swipes into the device for analysis without leaving the crime scene. The preconcentrator — about the size of a peanut butter and jelly sandwich — heats up the swipe and draws the heavy organic compounds that are vaporized from the felt into the IMS for detection.

The device expands crime-scene investigators’ capabilities to detect residues of both explosives and narcotics, says Dave. With the Sandia preconcentrator, the portable IMS is much more sensitive, capable of detecting less than a nanogram of explosives residue on the swipe. For comparison, the fingerprint of a person who had handled a bomb or a suitcase with explosives in it would likely contain 100,000 times more residue, says Kevin.

With the new swipe-analysis device, many more chemical analyses can be performed by forensics teams on the spot, which should improve the quality of evidence collected from a crime scene. "They could spend all night taking samples at a crime scene," says Dave.

Some airports already use desktop swipe-analyzers for randomly screening airline passengers for explosives residues, he adds, but they are larger and require AC power.

"There are a lot of good detectors out there," he says. "The trick is to deliver a concentrated sample to the detector. A hand-carried, battery-powered detector with one of these preconcentrators would greatly expand their capabilities."

Air sniffer for lockers, border crossings

This summer, Nathan Varley, Chad Custer (both 5848), Dave, and Kevin also are continuing work on a preconcentrator that turns a portable IMS into a highly sensitive air sampling sniffer. When finished, their "electronic dog" should be able to detect nanograms of explosives from several cubic feet of air drawn from outside a car, for instance, or from the seams of a school locker.

Unlike a dog, the sniffer never gets tired, you don’t have to feed it, and you can switch it off when you don’t need it, says Kevin.

Although a dog’s nose is somewhat more sensitive than the sniffing device, dog experts say a trained dog can’t work reliably for more than 30 or 40 minutes without a rest. In addition, each drug dog with a handler typically costs $40,000 to $60,000 a year, whereas an electronic sniffer with a preconcentrator would cost $20,000 to $40,000 total.

"Dogs are very good at smelling things, so electronic sniffers may never be as good as a dog’s nose," Kevin says. "But with a preconcentrator you can detect incredibly small traces of chemicals well enough without the logistics problems associated with dogs."

Sandia is funding a New Mexico State University team to research whether the same IMS/preconcentrator system can detect narcotics, so far with promising results, he says.

Sandia has applied for patents on both portable sniffers.

Meanwhile, even as the first airport portal makes its way to US airports, the Sandia contraband-detection team continues to improve on its walk-through portal designs. The FAA has funded the group to design a second-generation portal that uses only one detector and one air exhaust unit (half the equipment used in the first portal prototype). The team is improving on the portal’s air flow, adopting concave rather than planar interior walls. A prototype is scheduled for delivery in April.

"Since the first portal we’ve learned some things about how to make the technology smaller, cheaper, and faster," says Kevin.

The team also is researching whether using a mass spectrometer, rather than an ion mobility spectrometer, as the portal’s detector would enable the portal to reliably detect explosives, narcotics, and chemical and biological warfare agents with only one "sniff."

"A fast mass spec would mean we could look at everything at once," he says. "It would give us the mass number of anything it detected so you’d know exactly what you’re seeing right away."

In addition, DOE’s Office of Safeguards and Security is funding development of an explosives-detecting Mardix-type security booth for checkpoints outside of areas where Special Nuclear Materials are stored. The booth would incorporate much of the technology used in the FAA’s airport portal. The goal is to further prevent insiders from smuggling such material out of protected facilities, says Chuck Rhykerd (5848). A prototyype is expected to be completed by October.

As a result of the FAA airport portal development effort, team member Frank Bouchier (5848) has made improvements in the IMS software that is benefiting the IMS user community as a whole. Frank’s copyrighted version of LabView, which Sandia is distributing free of charge to universities and national labs, allows equipment control, data acquisition, and data analysis to be accomplished using one interface.

"Frank has set a new standard for IMS data acquisition and analysis," says Kevin. "It’s putting some users of older IMS software ahead 10 to 15 years."