Virtual Gas Sensor Array Formed by Thermal Shock Induction of a Generic Chemoresistor

Professor Faramarz Hossein-Babaei
Electrical Engineering Department
K. N. Toosi University of Technology
Tehran, Iran

Gas sensor arrays used as the sensing heads in artificial olfaction systems suffer from the unpredictable drifts of the individual responses of the array components often necessitating expensive array replacements. The virtual gas sensor array made by modulating the operating temperature of a single chemoresistive sensor is much better off as: (a) the drift of a single sensor is easy to compensate and (b) the replacement and recalibration costs are minor. However, the response patterns generated by these virtual arrays contain insufficient information for gas identification. Sharp operating temperature fluctuations in an analyte-exposed gas sensor result in temporal responses containing considerable amounts of extractable analyte-related information, but applying step heating voltages fails to provide step temperature variations in generic metal oxide gas sensors due to their large thermal capacity. On the other hand, the custom-made low thermal capacity sensors are vulnerable to thermal noise and environmental agitations in the field applications. A technique is reported [1, 2] for inducing sharp pallet temperature rises 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. The single-sensor gas diagnosis device fabricated based on this technique differentiates mint from peppermint in a 4 s test.  In addition to the analyte discrimination, the fabricated prototype is able to classify the analytes in terms of their molecular structures, e.g. alcohols and ketones. The method is resilient to the aging-caused sensitivity drift of the sensor used.

[1] F Hossein-Babaei, A Amine, A breakthrough in gas diagnosis with a temperature-modulated generic metal oxide gas sensor, Sensors and Actuators B: Chemical 166, 419-425
[2] F Hossein-Babaei, A Amine, Recognition of complex odors with a single generic tin oxide gas sensor, Sensors and Actuators B: Chemical 194, 156-163