Artificial electronic tongue in comparison to the electronic nose. State of the art and trends

Many researchers aim for the development of sensors or sensor systems which are similar or comparable to the human sensory system. Of all the human sensory systems, olfaction is the least understood in terms of the primary receptor mechanism and biological transduction. It is difficult to describe a set of reference odours that describe the olfactory input. A high degree of signal processing takes place in the olfactory system so that compounds of similar chemical structure can give completely different olfactory responses. That is the reason why the understanding of the olfactory system is relatively poor. The situation is comparable in the case of gustation. Nevertheless, there are many practical applications that require a quantitative or qualitative objective recording of odours or taste. In the following the development in the field of electronic tongue is described. It is a relatively new field. The state-of-the-art in understanding of electronic noses and tongues is discussed. They are illustrated describing their working principles, the types of sensors, circuit architectures and features. The applied sensor types are considered more in detail. Future perspectives of electronic tongue systems and their applications are illustrated. Problems which had to be solved yet are discussed.