Polymer-Based Chemicapacitor Sensor for 1-Octanol and Relative Humidity Detections at Different Temperatures and Frequencies

In this paper, the temperature dependency of conventional polymer-based gas sensors is addressed and a novel polymer-based chemicapacitor sensor is presented for application in early detection of deterioration of grain in storage facilities. 3-D heat transfer simulations are used to investigate several heated platforms with the sensing area in millimeter range dimensions to enhance spoilage-induced analyte detection. A resistive heater is employed to heat and maintain the sensor at the desired operating temperature. The platform is optimized to achieve a uniform heat distribution throughout the sensing area with a temperature variation of ΔT ≤ 1^°C. Capacitive measurements are performed as a more sophisticated technique for analyte detection, where mechanisms other than swelling are involved. In this method, the need for conductive filler is eliminated, resulting in an improvement in sensor reproducibility and repeatability. 1-octanol and relative humidity measurements are performed, as they are the two key volatiles due to grain deterioration. The results verify functionality of the fabricated sensors at different temperatures, in ppm range for 1-octanol, and up to 75% RH. Responses at the elevated temperature of 40 °C, above the grain bins ambient temperature, are insensitive to ambient temperature fluctuations. Sensitivity measurements demonstrate that an array of detectors, each held at different temperatures and operating at different frequencies, can be utilized to further enhance the sensor sensitivity and selectivity to a desired analyte.