Malodor Detection Based on Electronic Nose

Abstract

Recent decades have observed significantly increasing interest in the applications of electronic nose (E-nose) for qualitative analysis of odors. The first E-nose experiments were conducted in the early 1990s. (Shurmer et al., 1990; Shurmer & Gardner, 1992) Since then, Enose has become a powerful tool to complement or even replace traditional chemical analysis in many applications ranging from quality control of foods (Barie et al., 2006; Panigrahi et al., 2006; Santonico et al., 2008; Tikk et al., 2008) and beverages (RagazzoSanchez et al., 2008; Yu & Wang, 2007; Wongchoosuk et al., 2009b, 2010b), environment protection (Negri & Reich, 2001; Kuske et al., 2005), medical applications (Chan et al.,2009) to public safety (Scorsone et al., 2006; Zhang et al., 2007). Electronic nose employs an array of chemical gas sensors, numbering from 2 up to a few hundred sensors. Research on chemical gas sensors is mainly focused on improving two properties: selectivity (specificity to a molecule or a class of molecules) and sensitivity (strength of signal upon exposure to low concentration of molecules). Both selectivity and sensitivity leads to performance enhancement of an e-nose for specific applications such as bomb detection (Lubczyk et al., 2010), determination of food freshness based on amine detection (Lorwongtragool et al., 2011; Liao et al., 2010), quality control of alcoholic beverages (Wongchoosuk et al., 2009b, 2010b) and hydrogen gas sensing (Wongchoosuk et al., 2010a). Chemical sensors can be classified into 4 types (James et al., 2005) based on their transduction, a mechanism that converts chemical interaction into a sensor signal: (1) Optical, (2) Thermal, (3) Electrochemical and (4) Gravimetric. Electrochemical transduction has so far dominated research activities on gas sensors, because its interface setup is more straightforward than other transduction methods. (Choopun et al., 2007; Lorwongtragool et al., 2011) Nevertheless, many research groups including us have been working on many transduction principles, i.e., optical (Uttiya et al, 2008) and gravimetric (Tuantranont et al, 2008), in parallel in order to take advantage of hybrid methodology that could dramatically enhance the performance of electronic nose. Due to the simplicity of the electronics involved, most commercial chemical gas sensors adopt electrical transduction technology in which the metal oxide semiconductors assume the most used sensor architecture according to their low-cost, high sensitivity and simplicity in function. (Korotcenkov, 2007) Thus, one