Researching new detectors for chemical, biological threats
Sandia scientists are thinking small, building on decades of sensor work to invent tiny detectors that can sniff out everything from explosives and biotoxins to smuggled humans.
The military needs to find low concentrations of chemicals, such as those used in roadside bombs or chemical warfare agents, before they hurt anyone, says Ron Manginell (1716). Soldiers often use detectors in less-than-ideal situations, looking for dangerous substances from among a rich miasma of diesel fumes, smoke, and dust. They also carry detectors into the field, where instruments must be portable, rugged, reliable, and easy to use. In addition, inspectors at checkpoints and border crossings that check large numbers of containers lack automated ways to find people or contraband.
In the late 1990s, Sandia developed a simple-to-use handheld chemical detector for the military, the MicroChemLab. Ever since, Sandia has improved such microfluidics- and microelectromechanical (MEMS) systems-based instruments that identify chemicals based on gas chromatography, or GC, and resonator-style instruments such as surface acoustic wave (SAW) detectors.
Detection world needs new instruments
Ron says SAW-based instruments will continue to be extremely important. But the world of detection also needs new instruments that can find compounds such as carbon dioxide, chemical signals unique to humans, or the volatile signatures of pathogens and diseases in livestock and humans.
Ron led a project to develop such a detector and couple it with a GC. Together, they identify vapors by “sniffing” volatile organic compounds (VOCs). The prototype of the new detector, a miniature pulsed-discharge ionization detector, or mini-PDID, is about 1 inch by 1 inch by 2 inches, can be coupled with micro-GCs, and can run for nine hours on a charge of helium.
Experiments have shown the mini-PDID can detect explosives-related compounds, pesticides, and toxic industrial compounds. “These are nasty things,” Ron says. The detector also homes in on signatures of human odors and bacteria, light gases such as carbon monoxide and carbon dioxide, and a broad range of organic compounds.
“We now have new detectors, like the PDID, with higher sensitivity and broader applicability that would integrate well with the SAW and micro-GCs to provide both sensitivity, the ability to detect a few molecules of a given compound, and selectivity, the ability to distinguish compounds from one another,” Ron says. A miniaturized vapor detection unit and subsidiary electronics could fit in a format no larger than a cell phone, he says.
A detector for human cargo
The universal detection capabilities of the mini-PDID are allowing researchers to look at vapor detection of bacteria, an approach aimed at bringing biological and chemical detection into a small, common platform, Ron says. He highlighted the work, funded by Sandia’s Laboratory Directed Research and Development program, in a presentation at last fall’s International Breath Analysis meeting in Sonoma, Calif. The Journal of Breath Research published a paper by the team in July.
Part of the project demonstrated the possibility of a VOC-based detector for humans.
“People are brought across the border for many reasons, sometimes for a better life, sometimes for malevolent reasons” that could involve drug, weapons, or explosives smuggling, Ron says.
Current commercial detectors to find human cargo are about the size of a large shoebox, minus the electronics to operate them. Thus, Ron’s team saw promise for a miniature vapor-based detector for what he calls “indications of human presence.”
In other words, sweat.
No other animal has one component of human sweat called hexenoic acid. The action of bacteria on sweat excreted by human glands results in that distinct eau de locker room smell — what’s really a byproduct of bacterial metabolism, or a bacterial VOC.
The project proved the miniature detector could find hexenoic acid at the parts-per-billion level.
So Sandia researchers, wondering whether the technique could detect other bacteria, tested it on the VOC signatures of Microbacteria bovis and Microbacteria tuberculosis. M.bovis causes TB in livestock and can cause TB in humans; M.tuberculosis causes TB in humans. The bacteria produce four unusual compounds not made by other bacteria that infect humans, and the mini-PDID approach can detect those markers at the same concentration or comparable to or better than current methods, Ron says.
Sandia, in collaboration with the University of California, Davis, has submitted a proposal to the US Department of Agriculture to use the approach on E.coli in soil and water to see whether it can differentiate between toxin-producing E.coli and more benign varieties, Ron says.
Further development sought
The proof of concept works for biological detection, and Sandia is seeking funds to develop software and mathematics for pattern recognition for specific targets, he says. It will be several years before the technology could be ripe for tech transfer, he says.
The technology also needs engineering innovations, such as a tiny low-volume, high-flow-rate valve that can operate under high pressure, Ron says. In addition, researchers are looking for funds to further develop the mini-PDID and make it even smaller. Ron wants to reduce the housing to the size of a AAA battery, and ultimately to MEMS size — typically devices measuring between 20 micrometers to a millimeter. For comparison, a human hair averages 70 micrometers in diameter.
In general, Sandia’s chemical detection instruments work by collecting and concentrating a sample of air, separating the chemicals using a GC, and finding the targeted ones through selective detection.
Ron likens the GC to a racetrack for chemicals. Compounds in a mixture all enter the race at the same time, but various compounds get to the finish line at different times based on how they interact with the GC. The passage of time also helps indicate what a compound is since compounds separate at different rates, he says.
The microGC system can filter out common interfering agents such as water in the form of humidity, and detected compounds at sub-parts per billion concentrations in 6 seconds to 2 minutes in lab and field tests, Ron says.
Sandia’s microGC system approach is more compact and faster than commercial GC units and can be operated by non-experts. It also eliminates the need for a mass spectrometer, which detects chemicals by measuring the relative concentrations of atoms and molecules. Eliminating a mass spectrometer removes the need for vacuum pumps, which are too big and costly for broad field use.-- Sue Major Holmes
Capturing the moment of hydrogen ignition
by Patti Koning
Hydrogen fuel cell electric vehicles could be coming to a showroom near you in just a few years. Many automotive manufacturers are turning to hydrogen as an alternate transportation fuel, with initial commercialization expected soon.
For these zero-emission vehicles, a fuel cell converts hydrogen and ambient air into electricity to run an electric motor. Unlike conventional battery electric cars, however, hydrogen fuel cell vehicles can be rapidly fueled (~3-5 minutes) at existing gas stations once appropriate infrastructure upgrades are in place. The state of California is leading in the national deployment of commercial hydrogen refueling stations with a plan to have 68 public fueling stations in place by 2015.
A principal challenge to the widespread adoption of hydrogen infrastructure is the lack of quantifiable data on its safety envelope and worries about additional risk from hydrogen. Using advanced laser-based diagnostics and imaging capabilities in the Turbulent Combustion Lab (TCL), Isaac Ekoto (8367) and Adam Ruggles (8351) are working to provide that quantifiable data to accelerate the development of hydrogen fuel infrastructure.
“The use of hydrogen as a fuel presents some new challenges because of its unique storage requirements,” says Isaac. “To achieve sufficient energy density for relevant transportation uses, it needs to be stored at extremely low temperatures or under very high pressure, so an unintended release will behave differently than gasoline.”
Hydrogen does have certain added safety benefits. The high diffusion rate and buoyant nature means that leaks quickly dissipate into the atmosphere and move rapidly away from the source.
To assure regulatory officials, local fire marshals, fuel suppliers, and the public at large that hydrogen refueling is safe for consumer use, the risk to personnel and bystanders must be quantified and reduced to an acceptable level. Such a task requires validated methods to assess the potential harm from credible failure modes and a good understanding of effective mitigation measures to control any associated hazards.
Understanding ignition probability
Until recently, most methods used to analyze hydrogen infrastructure safety were adapted from those used for natural gas and industrial environments without much regard to the unique properties of hydrogen. This approach has often resulted in overly conservative rules and requirements that make infrastructure adoption prohibitive in densely populated areas.
To understand the thinking behind the specification of separation distances, one must consider the necessary sequence that results in a catastrophic event — essentially, a fire or explosion initiated by an unintended hydrogen release. First, the gas must be released from its containment system in sufficient quantities to create a hazard. A flammable mixture must then come into contact with an ignition source and ignite. Ignition, however, is not enough; the flame must be able to sustain itself long enough for a hazard to develop. Each process has its own specific probability that is dictated strongly by physical layout and system operation.
Isaac and Adam have examined well-characterized hydrogen jets in the TCL to address the need for suitable analysis tools for large-scale hydrogen storage safety and to better understand potential hazards from unintended releases.
They are able to recreate representative hydrogen leaks using custom burners and a laser spark apparatus to pinpoint ignition at various locations within the release plume. These capabilities enable statistical characterization of the release plume and insight into phenomenological processes during ignition and transition to sustained flame light-up.
To ensure the controlled laboratory experiments preserve relevant flow physics expected from releases from compressed storage, Adam recently designed a high source pressure hydrogen jet and integrated it into the lab. The ability to study realistic release scenarios using state-of-the-art measurement tools distinguishes the TCL from similar labs around the world.
“It’s very easy to study an atmospheric hydrogen jet to understand the fundamentals, but in any real-world release scenario, the stored hydrogen is going to be under extreme pressure or at a very low temperature,” says Isaac. “The next step in this lab is to add the capability to test hydrogen at those low temperatures.”
In a recent experiment, they attempted to spark ignite a hydrogen jet at numerous locations. “We can record whether the mixture ignites and whether ignition leads to a sustained flame or is simply extinguished,” says Adam.
The diagnostics enable the researchers to freeze a moment in time and visualize the distribution of the flammable range. From their results, Adam and Isaac have been able to identify the ignition probability for all locations of a given unintended hydrogen release. Their methods represent a tremendous technical advance over the current method used to establish separation distances for hydrogen, the lower flammable limit (LFL) determined from mean concentration boundaries. For hydrogen, the LFL is about 4 percent.
Grossly excessive safety distances
“Basing hydrogen separation on the LFL leads to safety distances that are grossly excessive. Yes, the flammable limit of hydrogen is much wider, but at what point is there a true hazard? Right now, we can predict the probability of ignition with much more specificity over the old methods based on LFL,” says Adam.
In establishing safety distances for a hydrogen fueling station, the probability of a sustained flame developing is the key metric, not ignition probability. “The hazards of a leak only occur when ignition has transitioned to a sustained flame,” he adds. “If you only consider ignition probability, you end up with distances that are quite large and can inhibit the development of stations in crowded areas. But if you consider the lower probability of sustained flame development, the distances shrink even further. This provides a technical case for building stations with a smaller footprint without compromising safety.”
Isaac and Adam are working to develop validated methods for predicting flame light-up transition.
Hydrogen fueling stations for light-duty vehicles are just one application for this research. Another growing area of hydrogen utilization is in the materials handling sector through the use of hydrogen fuel cell-powered forklifts. In a separate project, Isaac and recently retired
Sandian Bill Houf (8365) examined the risks and potential impact of an accidental release inside a warehouse.
“The codes and standards for how much refueling you could do indoors were based on floor layout, overall volume, and the ventilation system. Essentially, if you had a certain level of active ventilation, you could refuel as much as you wanted,” Isaac says.
Some surprising results
After testing different scenarios they came up with some surprising results. “We found a critical period after a release of about five seconds up to a minute in which the hydrogen was above the LFL before it diffused out,” says Isaac. “If the released gas came into contact with an ignition source within that window, things went bad quickly no matter what kind of ventilation system was in place.” This work has already had an impact on the codes governing hydrogen fuel cell use in warehouses.
The researchers are working with several different codes and standards communities, including the International Organization for Standardization (ISO), International Fire Code (IFC), and National Fire Protection Association (NFPA). Adam and Isaac have performed targeted experiments to answer specific questions, from which they ultimately plan to develop a toolkit that couples release/ignition behavior and hazard modeling with quantitative risk analysis tools that determine failure frequencies.
“The idea is to develop a toolkit that the operator can use to minimize risk as they design a system or facility like a hydrogen fueling station or a pipeline,” says Isaac. “Each setup is unique, so rather than give specific parameters, the toolkit will enable operators to optimize their design using risk reduction strategies.” With sufficient funding, they hope to have a beta version ready within two years.
They also have begun conducting experiments on other fuels like liquid natural gas to refine the understanding of the flammable envelope. “When we started this research 10 years ago, the understanding of hydrogen was way behind other gases. But now, despite its limited use, our understanding of hydrogen has advanced far beyond what we know about other gases because of this targeted effort,” says Isaac. “Everything we do here in the Turbulent Combustion Lab with hydrogen can be done with other gases.”
He and Adam feel as if they’ve just scratched the surface in studying hydrogen releases. Right now the TCL has a simple setup, with an unimpeded vertical jet. “We’d like to do different orientations and with barriers. It’s not likely a release will come from a perfectly concentric circle — most cracks are elongated and we don’t know how that changes the release,” says Adam. “We want to keep taking this one step closer to what could happen in the real world, outside of a lab.”
As Adam and Isaac push toward a better understanding of the true hazards of hydrogen leaks, they are adding to Sandia’s vast body of knowledge and experience when it comes to high-pressure hydrogen systems.
“This effort demonstrates how Sandia’s expertise in combustion science, laser diagnostics, risk assessments, and high-pressure hydrogen science and engineering, is uniquely leveraged to remove barriers to a clean and secure transportation energy future” says Daniel Dedrick (8367), Sandia’s hydrogen and fuel cells program manager.
-- Patti Koning
Sandia showcase shines a light on research and tech transfer
by Nancy Salem
Sandia will again take its cutting-edge research and technology to the community at a daylong event that will also spotlight intellectual property and how to do business with the Labs through licensing, partnership agreements, procurement, and economic development programs.
The second annual Sandia Research & Technology Showcase is Sept. 10 from 8 a.m.-4 p.m. at the Embassy Suites in Albuquerque. The event is free and open to the public.
“This is Sandia’s opportunity to highlight our great work in front of a large, interested audience, “says Jackie Kerby Moore, manager of Technology and Economic Development Dept. 7933. “It allows us to share with the community some of the work we do behind the fences.”
The showcase will include presentations, panel discussions, posters, and booths. Posters will focus on four broad themes: bioscience, computing and information science, energy and climate, and nanodevices and microsystems. Within each theme, a collection of research projects, technologies, and facilities will be featured, illustrating the range of Sandia’s work from early stage research through technology deployment.
The showcase is targeted to local and regional industry and academic partners. The agenda includes an overview of Sandia research and partnerships by Labs Vice President and Chief Technology Officer Julia Phillips. Pete Atherton, senior manager of Industry Partnerships Dept. 7930, will discuss technology transfer. Researchers and licensing executives will talk about available intellectual property (IP) at a panel moderated by Mary Monson, manager of Business Development and IP Management Dept. 7932.
Companies that have partnered with Sandia will talk about achieving business success on a panel moderated by Technology Ventures Corp.’s John Freisinger. Ben Cook (7910), a manager in the CTO Programs Office, will lead a panel on university partnerships and strategies for engagement.
And Jackie will moderate a panel of local leaders who have used Sandia’s economic development programs, including the Sandia Science & Technology Park and the New Mexico Small Business Assistance Program.
Researchers and business development specialists will be on hand to discuss the showcased technology. And careers and recruiting staff will be available to answer hiring questions.
The inaugural 2012 showcase had about 400 attendees, including businesspeople from New Mexico, Arizona, California, Colorado, Illinois, Maryland, Massachusetts, Nevada, New York, Texas, and Utah. Representatives came from the University of New Mexico, New Mexico State University, New Mexico Tech, Central New Mexico Community College, and the University of Texas El Paso. The New Mexico congressional delegation also was fully represented.
Jackie says connections were established between Sandians and potential suppliers and partners.
“The planning for this year’s event is going well. We are thrilled with the enthusiasm shown by Sandia’s principal investigators who are participating and pleased to be highlighting their work,” Jackie says. “We hope to increase partnerships as a result.”
In addition to Sandia, sponsors include the New Mexico Manufacturing Extension Partnership, Sandia Laboratory Federal Credit Union, the City of Albuquerque, Bernalillo County, Technology Ventures Corp., and the Sandia Science & Technology Park. Online registration is required. For the agenda, more information, and to register, visit www.sstp.org/showcase.
-- Nancy Salem