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Published February 1997 | Published
Book Section - Chapter Open

Array-based vapor sensing using chemically sensitive, polymer composite resistors


We describe herein the construction of simple, low-power, broadly responsive vapor sensors. Insulating polymer-conductor composites have been shown to swell reversibly upon exposure to vapors. Thin films of polymer composites have been deposited across two metallic leads, with swelling-induced resistance changes of the films signaling the presence of vapors. To identify and classify vapors, arrays of such vapor-sensing elements have been constructed, with each element containing either carbon black or poly(pyrrole) as the conducting phase mixed with one of several different organic polymers as the insulating phase. A convenient chemical polymerization of poly(pyrrole) which allows a high degree of processibility is also described. The differing gas-solid partition coefficients for the various polymers of the sensor array produce a pattern of resistance changes that can be used to classify vapors and vapor mixtures. This type of sensor array has been shown to resolve common organic solvents, including molecules of different classes (such as aromatics from alcohols) as well as those within a particular class (such as benzene from toluene and methanol from ethanol). The response of an individual composite to varying concentrations of solvent is shown to be consistent with the predictions of percolation theory. Accordingly, significant increases in the signals of array elements have been observed for carbon black-polymer composites that were operated near their percolation thresholds.

Additional Information

© 1997 IEEE. Date of Current Version: 06 August 2002. This work was supported in part by the Caltech Consortium in Chemistry and Chemical Engineering, the E.I. DuPont de Nemours and Company, Inc. and the Eastman Kodak Company, and by the National Aeronautics and Space Administration and the National Science Foundation, grant CHE-9202583. M.C.L. acknowledges Caltech for an Arthur Amos Noyes Fellowship and B.J.D. acknowledges the Natural Science and Engineering Research Council of Canada for a 1967 Centennial Fellowship and the O'Brien Foundation for financial support. We thank Profs. J.J. Hopfield and J.M. Bower, and the members of their research groups, for helpful discussions.

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