MicroHound ‘sniffer’ goes to federal emergency response teams for evaluation

A Sandia team has developed a more capable "electronic nose" for sniffing out vanishingly faint concentrations of explosives. The latest sniffer, called the MicroHound(tm), is the size of a totable toolbox and weighs just 12 pounds. It draws in a bathtubfull of air with each breath, collecting explosives vapors and particles on a metal filter. The filter is heated, re-launching the trapped explosives into a much smaller puff of air, about a tablespoon’s worth. This air is sampled using an on-board sensor called an ion mobility spectrometer (IMS), which detects and identifies the explosives. This "preconcentration" technique can be likened to netting thousands of fish from waters as vast as an ocean, releasing the catch into a pond, and then fishing the pond — with much increased odds. The approach, pioneered and patented by Sandia in the mid ’90s, has enabled the development of highly sensitive sniffers, ranging from a drive-through vehicle checkpoint to a walk-through portal for screening airline passengers at airports, that catch the faintest whiffs of bomb-making chemicals. By early 2000, the Sandia team had miniaturized the preconcentration equipment enough to create "luggable" devices for identifying trace concentrations of explosives at special events and crime scenes.

Installable, luggable, portable

The MicroHound (a.k.a. µHound) — a collaboration of Security Systems and Technology Center 5800 and Microsystems Science, Technologies, and Components Center 1700 — is the latest evolution in smaller and cheaper explosives-detection devices, says project leader Kevin Linker (5848). It is the first hand-carried sniffer that integrates in a single device Sandia technologies for the preconcentration, sampling, and detection of explosives, he says. (The previous Sandia device, a preconcentration module called the Hound II, weighed about 28 pounds including the commercial hand-held sensor it attaches to.) The 12-pound sniffer can detect explosives in parts-per-trillion concentrations, depending on the type of explosive. That’s sensitive enough to identify explosives in a fingerprint left by a person who had recently been working with bomb-making ingredients, he says. The MicroHound could be used to sniff out hidden explosives in courtrooms, schools, or other high-risk facilities, or at entry points to screen people or parcels. Demand for such sensitive and portable explosives-detection capabilities have increased significantly since 9/11, accelerating Sandia’s development work, says Kevin. For now the customers are members of federal emergency response teams involved in homeland security. Sandia has fabricated, assembled, and delivered several prototype MicroHounds for field-testing and evaluation. Although the MicroHound is not yet available commercially, Sandia might consider licensing the technology in the future, he says.

Miniaturizing security sensors

Meanwhile the Sandia team continues to improve the MicroHound’s capabilities and reduce its size and cost. The next MicroHound might include a second preconcentration cycle that would improve its sensitivity even further. In addition, says Kevin, the ability to fashion more of the MicroHound’s components from silicon using microelectronics fabrication techniques, one goal of the ongoing project, could significantly reduce the size and cost of future hand-held sniffers. Future versions of the sniffer will include not only a micro-sized IMS detector, but also a Sandia-developed surface acoustic wave (SAW) sensor. The two devices will work in tandem to validate explosives-detections and reduce false alarm rates. (See "MicroHound meets MicroChemLab" at right.) Inexpensive manufacture of the micro-sized IMS is being made possible through a new fabrication process that employs a low-temperature, co-fired ceramic material, developed jointly with Manufacturing Systems, Science, and Technology Div. 14000 and Center 1700. An associated micro-valve is being developed that uses a Sandia-patented semiconductor fabrication process. And a micro Faraday detector for improved ion detection, also under development in Dept. 2552 and building on previous work at the University of Arizona (a collaborator on the project), could enhance the detection of explosives by orders of magnitude, as well, says Kevin. "This is one of several projects involving the application of microtechnology to security problems within Center 5800," says Rebecca Horton, Dept. 5848 manager. Beyond explosives, adds Kevin, the MicroHound concept might be the beginning of a single integrated portable platform with multiple detectors to find a variety of contraband, including radiation sources, narcotics, hazardous chemicals, and more. "Kind of like a tricorder," he says. Other Sandians involved in the project include Doug Adkins (1764), Ivan Alderete (14171), Lester Arakaki (5848), Johnny Baca (1738), Charles Brusseau (5848), Todd Christenson (1743), James Gonzales (14171), Chris Gresham (2552), C.J. Hartwigsen (5832), James Kuthakun (14171), Tom Lemp (1743), Mary-Anne Mitchell (5848), Ken Peterson (14171), Kent Pfeifer (1744), Scott Rawlinson (6218), Chuck Rhykerd (5848), Mike Rightley (1745), Steve Rohde (1738), Diane Ross (5848), Art Rumpf (1744), Robert Sanchez (2554), Gary Shannon (5848), Robert Stokes (14171), Rose Torres (14171), Dan Trudell (1764), Timothy Turner (14171), Eric Varley (5848), and Jimmie Wolf (1738).