A breakthrough in gas diagnosis with a temperature-modulated generic metal oxide gas sensor

Sharp operating temperature fluctuations in an analyte-exposed gas sensor result in temporal responses containing considerable amounts of extractable analyte-related information. Due to their high thermal capacity, applying step heating voltages fails to provide step temperature variations in generic metal oxide gas sensors. On the other hand, the custom-made low thermal capacity sensors are vulnerable to thermal noise and environmental agitations in field applications. A novel technique is reported here for inducing the sharp pallet temperature rises required for obtaining selective responses in commonly used bulk tin oxide gas sensors, affording the gas discrimination capacity sought after since the advent of these typically non-selective, though user friendly, devices. In this technique, a voltage spike surpassing the nominal heating voltage of the device is applied prior to a voltage step. The thermal impact of the spike is adjusted to obtain step-like temperature profiles with rise times less than 1/10 of the sensor thermal time-constant. The temporal responses recorded for 12 different airborne analytes, each in a wide concentration range, appear different enough to identify contaminants with minimal computational cost. Analyte examination and recognition take only 4s. In addition to analyte discrimination, the fabricated prototype also classifies the analytes in terms of their molecular structures of, for example, alcohols and ketones. This single-sensor gas diagnosis device is presented as a potential replacement for array-based electronic nose systems in a number of applications. (C) 2012 Elsevier B.V. All rights reserved.