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Electronic Noses

The Biomedical Sensors Laboratory has a considerable track record in electronic noses (or e-nose). Warwick developed the world's 1st commercial electronic nose was developed in collaboration with Bass plc and Neotronics plc in the early 1990's. Since these developments there is now around 20 different electronic nose companies selling around 200 machines a year, with many other research institutions throughout the world.

What is an 'Electronic Nose'

Artificial olfaction has been with us since the early 1980s, although the term “electronic nose”, or e-nose, was only defined as recently as 1994 . Such systems try not to identify specific chemicals within a complex odour, for example coffee is made up of over 1,000 headspace compounds, but more to classify the type of aroma. E-noses typically combine an array of chemical sensors with partially overlapping sensitivities. Hence each sensor responds to a class of chemical components within an odour, e.g. ketones. Identification is possible due to the differences between complex odours in the concentration and mixture of chemical components. Consequently the sensors produce a response profile, or chemical fingerprint, which can be matched to a specific odour. The identification process is usually performed with some form of statistically based multivariate method or non-parametric neural network. Such systems are used regularly in, for example, environmental testing and food quality.

Even with the success of many e-nose systems their performance, in terms of odour sensitivity and selectivity, still lags behind that of the human olfactory system. It is generally believed that this is due to the lower complexity of e-noses when compared to their biological counterparts. For example the human olfactory system contains some 100 million olfactory receptors with approximately 350 different types of receptor binding proteins, distributed along the olfactory epithelium (the lining of the nose and part of the olfactory mucosa). In contrast e-nose systems typically have 32 or less chemical sensors in a basic chamber. The figure below gives a comparison of the biological and artificial olfactory systems.

e-nose

Warwick Univesity has developed a number of different e-nose systems, both on their own and in collaboration with a number of industrial partners. The range of applications e-nose technology has been applied to is considerable, ranging from food quality, perfumes, environmental heath, security and medical diganostics.