Curtis D. Mowry

Micro-Flame Ionization Detection Using a Catalytic Micro-combuster

A microflame-based detector has been developed for sensing a broad range of chemical analytes. This detector combines calorimetry and flame ionization detection (FID) to produce unique analyte signatures. The microcombustor consists of a micromachined microhotplate with a catalyst on its surface, such as platinum/alumina, to rapidly initiate the ionization event. The low power microcombustor design permits quick, efficient heating of the deposited film. To perform calorimetric detection of analytes, the change in power required to maintain the resistive microhotplate heater at a constant temperature is measured. For FID, electrodes are placed around the microcombustor flame zone with an electrometer circuit measuring the production of ions. The calorimetric and FID modes respond generally to all hydrocarbons. Importantly these detection modes can be established on one convenient simultaneous microcombustor platform. The performance of the microFID mode is emphasized herein

Rapid detection of bacteria with miniaturized pyrolysis-gas chromatographic analysis

Rapid detection and identification of bacteria and other pathogens is important for many civilian and military applications. The profiles of biological markers such as fatty acids can be used to characterize biological samples or to distinguish bacteria at the gram-type, genera, and even species level. Common methods for whole cell bacterial analysis are neither portable nor rapid, requiring lengthy, labor intensive sample preparation and bench-scale instrumentation. These methods chemically derivatize fatty acids to produce more volatile fatty acid methyl esters (FAMEs) that can be separated and analyzed by a gas chromatograph (GC)/mass spectrometer. More recent publications demonstrate decreased sample preparation time with in situ derivatization of whole bacterial samples using pyrolysis/derivatization. Ongoing development of miniaturized pyrolysis/GC instrumentation by this department capitalizes on Sandia advances in the field of microfabricated chemical analysis systems ((mu) ChemLab). Microdevices include rapidly heated stages capable of pyrolysis or sample concentration, gas chromatography columns, and surface acoustic wave (SAW) sensor arrays. We will present results demonstrating the capabilities of these devices toward fulfilling the goal of portable, rapid detection and early warning of the presence of pathogens in air or water.

Micro-analytical systems for national security applications

Sandia National Laboratories has a long tradition of technology development for national security applications. In recent years, significant effort has been focused on micro-analytical systems - handheld, miniature, or portable instruments built around microfabricated components. Many of these systems include microsensor concepts and target detection and analysis of chemical and biological agents. The ultimate development goal for these instruments is to produce fully integrated sensored microsystems. Described here are a few new components and systems being explored: (1) A new microcalibrator chip, consisting of a thermally labile solid matrix on an array of suspended-membrane microhotplates, that when actuated delivers controlled quantities of chemical vapors. (2) New chemical vapor detectors, based on a suspended-membrane micro-hotplate design, which are amenable to array configurations. (3) Micron-scale cylindrical ion traps, fabricated using a molded tungsten process, which form the critical elements for a micro-mass analyzer. (4) Monolithically integrated micro-chemical analysis systems fabricated in silicon that incorporate chemical preconcentrators, gas chromatography columns, detector arrays, and MEMS valves.

Invited article: A materials investigation of a phase-change micro-valve for greenhouse gas collection and other potential applications.

The deleterious consequences of climate change are well documented. Future climate treaties might mandate greenhouse gas (GHG) emissions measurement from signatories in order to verify compliance. The acquisition of atmospheric chemistry would benefit from low cost, small size/weight/power of microsystems. In this paper, we investigated several key materials science aspects of a phase-change microvalve (PCμV) technology with low power/size/weight/cost for ubiquitous GHG sampling. The novel design, based on phase-change material low-melting-point eutectic metal alloys (indium-bismuth, InBi and tin-lead, SnPb), could be actuated at temperatures as low as 72 °C. Valve manufacturing was based on standard thick and thin-film processes and solder technologies that are commonly used in industry, enabling low-cost, high-volume fabrication. Aging studies showed that it was feasible to batch fabricate the PCμVs and store them for future use, especially in the case of SnPb alloys. Hermetic sealing of the valve prototypes was demonstrated through helium leak testing, and Mil spec leak rates less than 1 × 10(-9) atm cm(3)/s were achieved. This confirms that the sample capture and analysis interval can be greatly expanded, easing the logistical burdens of ubiquitous GHG monitoring. Highly conservative and hypothetical CO(2) bias due to valve actuation at altitude in 1 cm(3) microsamplers would be significantly below 1.0 and 2.2 ppmv for heat-treated InBi and SnPb solders, respectively. The CO(2) bias from the PCμV scales well, as a doubling of sampler volume halved the bias. We estimated the shelf life of the SnPb PCμVs to be at least 2.8 years. These efforts will enable the development of low cost, low dead volume, small size/weight microsystems for monitoring GHGs and volatile organic compounds.

Rapid identification of bacteria with miniaturized pyrolysis/GC analysis

Identification of bacteria and other biological moieties finds a broad range of applications in the environmental, biomedical, agricultural, industrial, and military arenas. Linking these applications are biological markers such as fatty acids, whose mass spectral profiles can be used to characterize biological samples and to distinguish bacteria at the gram-type, genera, and even species level. Common methods of sample analysis require sample preparation that is both lengthy and labor intensive, especially for whole cell bacteria. The background technique relied on here utilizes chemical derivatization of fatty acids to the more volatile fatty acid methyl esters (FAMEs), which can be separated on a gas chromatograph column or input directly into a mass spectrometer. More recent publications demonstrate improved sample preparation time with in situ derivatization of whole bacterial samples using pyrolysis at the inlet; although much faster than traditional techniques, these systems still rely on bench-top analytical equipment and individual sample preparation. Development of a miniaturized pyrolysis/GC instrument by this group is intended to realize the benefits of FAME identification of bacteria and other biological samples while further facilitating sample handling and instrument portability. The technologies being fabricated and tested have the potential of achieving pyrolysis and FAME separation on a very small scale, with rapid detection time (1-10 min from introduction to result), and with a modular sample inlet. Performance results and sensor characterization will be presented for the first phase of instrument development, encompassing the microfabricated pyrolysis and gas chromatograph elements.

Development of a Mesoscale Pulsed Discharge Helium Ionization Detector for Portable Gas Chromatography

Miniaturization of gas chromatography (GC) instrumentation enables field detection of volatile organic compounds (VOCs) for chembio-applications such as clandestine human transport and disease diagnostics. We fabricated a mesoscale pulsed discharge helium ionization detector (micro-PDHID) for integrating with our previously described mini-GC hardware. Stainless steel electrodes fabricated by photochemical etching and electroforming facilitated rapid prototyping and enabled nesting of inter-electrode insulators for self-alignment of the detector core during assembly. The prototype was ∼10 cm(3) relative to >400 cm(3) of a commercial PDHID, but with a comparable time to sweep a VOC peak from the detector cell (170 ms and 127 ms, respectively). Electron trajectory modeling, gas flow rate, voltage bias, and GC outlet location were optimized for improving sensitivity. Despite 40-fold miniaturization, the micro-PDHID detected 18 ng of the human emanation, 3-methyl-2-hexenoic acid with <3-fold decrease in sensitivity relative to the commercial detector. The micro-PDHID was rugged and operated for 9 months without failure.

Pulsed Discharge Helium Ionization Detector for Highly Sensitive Aquametry

Trace moisture quantitation is crucial in medical, civilian and military applications. Current aquametry technologies are limited by the sample volume, reactivity, or interferences, and/or instrument size, weight, power, cost, and complexity. We report for the first time on the use of a pulsed discharge helium ionization detector (PDHID-D2) (∼196 cm(3)) for the sensitive (limit of detection, 0.047 ng; 26 ppm), linear (r(2) >0.99), and rapid (< 2 min) quantitation of water using a small (0.2 - 5.0 μL) volume of liquid or gas. The relative humidity sensitivity was 0.22% (61.4 ppmv) with a limit of detection of less than 1 ng moisture with gaseous samples. The sensitivity was 10 to 100 to fold superior to competing technologies without the disadvantages inherent to these technologies. The PDHID-D2, due to its small footprint and low power requirement, has good size, weight, and power-portability (SWAPP) factors. The relatively low cost (∼

An Economic Analysis of Mobile Pyrolysis for Northern New Mexico Forests

5000) and commercial availability of the PDHID-D2 makes our technique applicable to highly sensitive aquametry.

Real-time discriminatory sensors for water contamination events :LDRD 52595 final report.

In the interest of providing an economically sensible use for the copious small-diameter wood in Northern New Mexico, an economic study is performed focused on mobile pyrolysis. Mobile pyrolysis was selected for the study because transportation costs limit the viability of a dedicated pyrolysis plant, and the relative simplicity of pyrolysis compared to other technology solutions lends itself to mobile reactor design. A bench-scale pyrolysis system was used to study the wood pyrolysis process and to obtain performance data that was otherwise unavailable under conditions theorized to be optimal given the regional problem. Pyrolysis can convert wood to three main products: fixed gases, liquid pyrolysis oil and char. The fixed gases are useful as low-quality fuel, and may have sufficient chemical energy to power a mobile system, eliminating the need for an external power source. The majority of the energy content of the pyrolysis gas is associated with carbon monoxide, followed by light hydrocarbons. The liquids are well characterized in the historical literature, and have slightly lower heating values comparable to the feedstock. They consist of water and a mix of hundreds of hydrocarbons, and are acidic. They are also unstable, increasing in viscosity with time stored. Up to 60% of the biomass in bench-scale testing was converted to liquids. Lower ({approx}550 C) furnace temperatures are preferred because of the decreased propensity for deposits and the high liquid yields. A mobile pyrolysis system would be designed with low maintenance requirements, should be able to access wilderness areas, and should not require more than one or two people to operate the system. The techno-economic analysis assesses fixed and variable costs. It suggests that the economy of scale is an important factor, as higher throughput directly leads to improved system economic viability. Labor and capital equipment are the driving factors in the viability of the system. The break-even selling price for the baseline assumption is about

Monitoring of CoS2 reactions using high-temperature XRD coupled with gas chromatography (GC)

11/GJ, however it may be possible to reduce this value by 20-30% depending on other factors evaluated in the non-baseline scenarios. Assuming a value for the char co-product improves the analysis. Significantly lower break-even costs are possible in an international setting, as labor is the dominant production cost.