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Opportunities in Biotechnology for Future Army Applications (2001) / Chapter Skim
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Appendix C: Chemical Sensing Using MEMS Devices
Pages 92-95

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From page 92...
... Devices based on the selective Sacrificial area / FIGURE C-1 Cross-section of a vibrating-beam vapor sensor based on surface micromachining. The polymer film absorbs a specific vapor, changing the film mass and the vibration characteristics of the beam.
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From page 93...
... In operation, the beam is driven electrostatically across the 1 to 2,u air gap left by removing the sacrificial layer, and the beam vibration is sensed capacitively. As the mass of the polymer changes, the resonance frequency and vibration amplitude shift, providing a measure of the vapor concentration.
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From page 94...
... Temperature-programmed Resorption can also be very helpful in identifying different species. Although it is possible to "program" completed arrays of microhot-plates with different detecting films using chemical vapor deposition on selectively heated dielectric windows, achieving acceptable selectivity, stability, speed, and sensitivity with these devices remains a formidable challenge (Majoo et al., 1995~.
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From page 95...
... Thus,active-surface chemistries may greatly expand the utility of chip-based sensing platforms for both chemical and biological agents. Chromatography, the most common laboratory technique for analyzing gaseous mixtures, is based on the fact that different molecular species spend different amounts of time adsorbed to surfaces as a sample of the gas is passed through a long tube (column)
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Key Terms

  • devices based
  • frequency shift
  • mems devices
  • specific gases
  • detecting film

  • sacrificial layer
  • dynamic range
  • resonance frequency
  • miniature gcs
  • polymer changes

  • vibration amplitude
  • sensing approach
  • permeable membranes
  • tabletop gas
  • bulk films

  • column delays
  • calculations support
  • arrays coated
  • gas adsorbs
  • sensor based

  • time adsorbed
  • sufficient sensitivity
  • neural nets
  • devices remains
  • detector arrays

  • common laboratory
  • analyzing gaseous
  • shift tracking
  • vapor deposition
  • beam vibration


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