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Proceedings Paper

Capillary sensors: a design concept for optrodes
Author(s): Bernhard H. Weigl; Otto S. Wolfbeis
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Paper Abstract

We describe the use of glass or plastic capillaries in optical chemical sensing. They possess several attractive features in that (a) they can act as a mechanical support for optically sensitive materials (coatings); (b), they represent an optical waveguide structure and enable various methods of optical interrogation; and (c) they can serve as a sample cavity of well-defined volume and are suitable for direct sampling, e.g. when drawing blood. The method of immobilization and the performance of such 'capillary sensors' is exemplified by a fast- responding carbon dioxide sensor chemistry. Its response times vary from 100 to 300 ms. Such capillary sensors have, in general, extremely short response times for three reasons, namely (a), because the two sensing layers passed by the light beam when penetrating the capillary can be made very thin; (b), equilibration of two thin layers is faster than that of a single layer of the same total thickness; and (c), the sample flow is laminar, resulting in a fast and homogeneous exchange of sample volume. We also give arrangements for optical readout devices and show that capillary sensors can overcome some of the problems of optrode membranes mounted in flow cells or on fiber tips.

Paper Details

Date Published: 21 October 1994
PDF: 10 pages
Proc. SPIE 2293, Chemical, Biochemical, and Environmental Fiber Sensors VI, (21 October 1994); doi: 10.1117/12.190976
Show Author Affiliations
Bernhard H. Weigl, Karl-Franzens-Univ. Graz (Austria) and Univ. of Southampton (United Kingdom)
Otto S. Wolfbeis, Karl-Franzens-Univ. Graz (Austria)


Published in SPIE Proceedings Vol. 2293:
Chemical, Biochemical, and Environmental Fiber Sensors VI
Robert A. Lieberman, Editor(s)

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