Electronic Nose based on chemiresistive sensors for toxic gas detection
Keywords:electronic nose, metal oxide semiconductors, chemiresistive sensors, toxic gases, principal component analysis, cluster analysis
Development of gas sensors satisfying the ‘4-S sensor selection criterion’ is a daunting challenge. This criterion demands the accomplishment of performance satisfying the parameters namely sensitivity (sensor response), selectivity, stability and suitability. For chemiresistive sensors to achieve an optimum sensor configuration, optimization of parameters namely, sensing material, its thickness, amount and distribution, deposition method, pre and post deposition treatment, operating temperature and involved sensing mechanism is pre-requisite and a humongous task. Use of multiple sensors each having partial specificity towards a target gas is looked upon as a means to achieve a configuration satisfying the 4-S criterion. Besides, it offers advantages of cross verification and/or validation, removal of false or faulty sensor, overall reliability and simultaneous detection of multiple gases. These systems are often classified as an electronic nose or e-nose. Their important function is to mimic the mammalian olfactory system. However, its usage involves the complexity of data acquisition and analysis employing advanced date analytics such as machine learning and artificial neural networks. The present article reviews and summarizes the activity on electronic nose especially for toxic gas detection. Care has been taken to include some of the recent findings crucial for realizing a complete working and portable e-nose.