Array-based sensing technology

Array-based sensing technology (e. g. , electronic nose) may in principle provide olfactory responses to different odorants. "Electronic noses" have been around for almost 40 years, but they have had limited influence in either industry or university academia. There are four little secrets about electronic noses that are responsible for this failure: (1) When exposed to any chemical environment, sensor obsolescence and response change are inevitable, and this is a big problem for recognizing the library pattern because the library quickly becomes obsolete. (2) Water vapor is also a potential analyte, and the humidity changes by thousands of ppm daily. If one wants to distinguish concentrations below the ppm range from VOCs, it is very difficult to respond to changes in humidity. (3) Sensitivity is often limited to 100 ppm because the initial analyte-sensor interaction is physical absorption. (4) The chemometric data from these conventional electronic noses are actually very small, regardless of the number of sensors, and are not sufficient to accurately distinguish between similar analytes. In addition, for any pattern-based approach, changes in odors require the retrieval of analytical libraries. To overcome these limitations, it is important to pay special attention to the design and underlying nature of sensor interactions with analytes. The sensors must first be disconnected from the electronic components so that disposable sensors can be used. In this case, the pattern recognition library no longer needs to match with the sensors' aging. Second, sensors can be built into the hydrophobic environment to minimize the response to moisture. Third, a range of chemical properties and reactivity must be considered, interactions of which are much stronger and much more diverse than physical adsorption.