Development of a polymer-based gas sensor - humidity and CO2 sensitivity

A low cost polymer-based gas sensor array for volatile odor detection and identification is being investigated for grain storage application. These sensors are found sensitive to changes in humidity, a common factor in any environment, and a variable parameter in grain storage facilities. The humidity caused resistance variations are investigated for twelve composite polymer films as the sensing materials of odor detectors. Significant variation in humidity sensitivity is found amongst the investigated polymers. Understanding of polymer-based odor sensor response due to humidity is needed to enable compensation for humidity induced variability in sensor measurements. In addition to humidity, the polymer-based sensors are shown sensitive to CO2, a released component due to the grain deterioration. The sensitivity of odor detectors are examined at different CO2 concentration levels, showing remarkable sensor responses. The performed measurements are indicating that polymer-based sensors suffer from ambient temperature dependency. To overcome this drawback, a new sensor structure is being proposed. This device utilizes a thin SiO2 platform to be fabricated on silicon wafer. A thin layer of titanium is used to effectively heat and maintain a constant temperature throughout the detector reactive area. Therefore this structure may eliminate sensor response shifts caused by ambient temperature variations.