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  • 1
    Electronic Resource
    Electronic Resource
    Miniaturization and integration of photoacoustic detection (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 92 (2002), S. 1555-1563 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Photoacoustic spectroscopy is an absorption spectroscopy technique that is currently used for low-level gas detection and catalyst characterization. It is a promising technique for chemical analysis in mesoscale analysis systems because the detection limit scales favorably with miniaturization. This work focuses on the scaling properties of photoacoustic spectroscopy, and on the miniaturization of gas-phase photoacoustic detection of propane in a nitrogen ambient. The detection system is modeled with a transmission line analogy, which is verified experimentally. The model includes the effects of acoustic leaks and absorption saturation. These two phenomena degrade the performance of the photoacoustic detector and must be controlled to realize the scaling advantages of photoacoustic systems. The miniature brass cells used to verify the model employ hearing aid microphones and optical excitation from a mechanically chopped, 3.39 μm He–Ne laser, transmitted into the cells with an optical fiber. These cells are able to detect 10 ppm of propane in nitrogen (a signal level of ∼1 Pa/W). We also describe the development of a miniaturized photoacoustic system formed by microfabrication. In this case, the pressure-driven deflection of the detection membrane is measured optically. These systems show that photoacoustic detection may be inappropriate for systems with large variations in gas concentration because of absorption saturation and changing gas acoustic properties. Nevertheless, photoacoustic spectroscopy is a promising technique for the analysis of dilute mixtures in miniature chemical systems. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1489493
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  • 2
    Electronic Resource
    Electronic Resource
    Noninvasive measurement of charging in plasmas using microelectromechanical charge sensing devices (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 69 (1996), S. 1471-1473 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The plasma induced charging of surfaces in a plasma during semiconductor processing has been measured noninvasively using microelectromechanical devices. We have designed, modeled, and fabricated microcantilevers to act as charge sensing probes. The devices exhibit a mechanical deformation when charged, which is probed in situ by optical techniques, or measured by optical inspection after removal from plasma. Charging voltage measurements in a parallel-plate reactive-ion-etching reactor show that more charging is evident at the electrode edge, and that the charging is a strong function of input rf power, chamber pressure, and flow rate of gases. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.116911
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  • 3
    Electronic Resource
    Electronic Resource
    Micromachined reactors for catalytic partial oxidation reactions (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 3059-3069 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Silicon-based microfabrication of a novel chemical reactor (microreactor) having submillimeter flow channels with integrated heaters, and flow and temperature sensors is described. The potential application of this reactor to partial-oxidation reactions is explored by using Pt-catalyzed NH3 oxidation as a model reaction. Investigation of reactor behavior as a function of operating conditions shows that conversion and selectivity behavior of conventional laboratory reactors can be reproduced and demonstrates the feasibility of conducting chemical reactions in microfabricated systems. Ignition-extinction behavior is explored, along with high-temperature microreactor materials degradation. Potential applications and scale-up of microreactors are also discussed.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690431117
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