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Array-based vapor sensing using conductive carbon black-polymer composite thin film detectors


Severin, Erik J. (1999) Array-based vapor sensing using conductive carbon black-polymer composite thin film detectors. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/HHS2-DJ06.


A simple, broadly responsive detector array, based on polymer-carbon black composites that can detect, classify, and quantify various vapors and vapor mixtures is described. The individual detector elements of the array are constructed from films consisting of carbon black particles dispersed into insulating organic polymers. The carbon black provides an electrically conductive network in the films, whereas the different organic polymers are the source of chemical diversity between elements in the detector array. Swelling of the polymer upon exposure to a vapor increases the electrical resistance of the film by disrupting the conductive network of carbon black particles, thereby providing a simple means for monitoring the presence of a vapor. The dc electrical resistance change of an individual composite is shown to be consistent with the predictions of percolation theory. The differing gas-solid partition coefficients between vapor analytes for the various polymers of the detector array produce a characteristic pattern of resistance changes for each analyte. The response of these detectors is linear with variations in analyte concentration, allowing quantification as well as identification of a test analyte. This type of detector array can be used to discriminate different classes of analyte molecules (such as aromatics from alcohols) as well as those within a particular class (such as benzene from toluene and methanol from ethanol). Additionally, by using polymers with chiral subunits, enantiomerically different vapors can be discriminated. Principle component data analysis is used to identify and quantify airborne analytes and the relative compositions of simple gas mixtures. Integration of the electrical resistance signals with data analysis software has made sensing and analysis functions possible in a compact, low-power, simple vapor sensor device.

Item Type:Thesis (Dissertation (Ph.D.))
Degree Grantor:California Institute of Technology
Division:Chemistry and Chemical Engineering
Major Option:Chemistry
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Lewis, Nathan Saul
Thesis Committee:
  • Unknown, Unknown
Defense Date:28 May 1999
Record Number:CaltechETD:etd-12272004-162841
Persistent URL:
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:5142
Deposited By: Imported from ETD-db
Deposited On:28 Dec 2004
Last Modified:21 Dec 2019 01:30

Thesis Files

PDF (Severin_ej_1999.pdf) - Final Version
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