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Journal of Sensors
Volume 2016, Article ID 2435945, 22 pages
Research Article

Organic Membranes for Selectivity Enhancement of Metal Oxide Gas Sensors

1Laboratory for Gas Sensors, Department of Microsystems Engineering-IMTEK, University of Freiburg, Georges-Koehler-Allee 102, 79110 Freiburg, Germany
2ams Sensor Solutions Germany GmbH, Gerhard-Kindler-Strasse 8, 72770 Reutlingen, Germany
3Fraunhofer-Institute for Physical Measurement Techniques IPM, Heidenhofstraße 8, 79110 Freiburg, Germany

Received 1 September 2015; Accepted 19 October 2015

Academic Editor: Sheikh Akbar

Copyright © 2016 Thorsten Graunke et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


We present the characterization of organic polyolefin and thermoplastic membranes for the enhancement of the selectivity of metal oxide (MOX) gas sensors. The experimental study is done based on theoretical considerations of the membrane characteristics. Through a broad screening of dense symmetric homo- and copolymers with different functional groups, the intrinsic properties such as the mobility or the transport of gases through the matrix were examined in detail. A subset of application-relevant gases was chosen for the experimental part of the study: H2, CH4, CO, CO2, NO2, ethanol, acetone, acetaldehyde, and water vapor. The gases have similar kinetic diameters and are therefore difficult to separate but have different functional groups and polarity. The concentration of the gases was based on the international indicative limit values (TWA, STEL). From the results, a simple relationship was to be found to estimate the permeability of various polar and nonpolar gases through gas permeation (GP) membranes. We used a broadband metal oxide gas sensor with a sensitive layer made of tin oxide with palladium catalyst (SnO2:Pd). Our aim was to develop a low-cost symmetrical dense polymer membrane to selectively detect gases with a MOX sensor.