Microfabricated preconcentrator-focuser for a microscale gas chromatograph

Wei Cheng Tian, Stella W. Pang, Chia Jung Lu, Edward T. Zellers

Research output: Contribution to journalArticle

108 Citations (Scopus)

Abstract

The design, fabrication, and testing of a precon- centrator-focuser (PCF), consisting of a thick micromachined Si heater packed with a small quantity of a granular adsorbent material are described. The PCF is developed to capture and concentrate vapors for subsequent focused thermal desorption and analysis in a micro gas chromatograph. The microheater contains an array of high-aspect-ratio, etched-Si heating elements, 520 μm (h) × 50 μm (w) × 3000 μm (l), bounded by an annulus of Si and thermally isolated from the remaining substrate by an air gap. This structure is sandwiched between Pyrex glass plates with inlet/outlet ports that accept capillary tubes for sample flow and is sealed by anodic bonding (bottom) and rapidly annealed glass/metal/Si solder bonding (top). The large microheater surface area allows for high adsorption capacity and efficient, uniform thermal desorption of vapors captured on the adsorbent within the structure. The adsorbent consists of roughly spherical granules, ∼200-μm in diameter, of a high-surface-area, graphitized carbon. Key design considerations, fabrication technologies, and results of performance tests are presented with an emphasis on the thermal desorption characteristics of several representative volatile organic compounds as a function of volumetric flow rates and heating rates. Preconcentration factors as high as 5600 and desorbed peak widths as narrow as 0.8 s are achieved from 0.25-L samples of benzene at modest heating rates. The effects of operating variables on sensitivity, chromatographic resolution, and detection limits are assessed. Testing of this PCF with a micromachined separation column and integrated sensor array is discussed briefly.

Original languageEnglish
Pages (from-to)264-272
Number of pages9
JournalJournal of Microelectromechanical Systems
Volume12
Issue number3
DOIs
Publication statusPublished - 2003 Jun 1

Fingerprint

Thermal desorption
Adsorbents
Heating rate
Gases
Vapors
Electric heating elements
Fabrication
Glass
Capillary tubes
Sensor arrays
Testing
Volatile organic compounds
Soldering alloys
Thermoanalysis
Aspect ratio
Benzene
Flow rate
Adsorption
Carbon
Substrates

Keywords

  • Adsorbent
  • Gas detection
  • Micro gas chromatograph (μGC)
  • Microelectromechanical systems (MEMS)
  • Microheater
  • Preconcentrator-focuser (PCF)

ASJC Scopus subject areas

  • Mechanical Engineering
  • Electrical and Electronic Engineering

Cite this

Microfabricated preconcentrator-focuser for a microscale gas chromatograph. / Tian, Wei Cheng; Pang, Stella W.; Lu, Chia Jung; Zellers, Edward T.

In: Journal of Microelectromechanical Systems, Vol. 12, No. 3, 01.06.2003, p. 264-272.

Research output: Contribution to journalArticle

Tian, Wei Cheng ; Pang, Stella W. ; Lu, Chia Jung ; Zellers, Edward T. / Microfabricated preconcentrator-focuser for a microscale gas chromatograph. In: Journal of Microelectromechanical Systems. 2003 ; Vol. 12, No. 3. pp. 264-272.
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