This book deals with biomimetic sensors that can quantify taste and smell - the electronic tongue and nose. Of all sensor technologies, these have been widely considered as the most difficult to realise and the development of these sensors significantly contributes to the understanding of the reception mechanisms in gustatory and olfactory systems. The author begins by dealing with the basic principles of measurement and multivariate analysis. Reception mechanisms in biological systems are briefly reviewed. Several types of biosensor, including enzyme-immobilized membranes, SPR, the quartz resonance oscillator and IC technologies are explained in detail. This book is the first to focus on artificial taste and smell sensors and also reviews conventional biosensors, such as enzyme sensors, in detail.

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Gustatory and olfactory receptors receive multiple chemical substances of different types simultaneously, but they can barely discriminate one chemical species from others. In this article, we describe a device used to measure taste, i.e. , taste sensors. Toko and colleagues developed a taste sensor equipped with multiarray electrodes using a lipid/polymer membrane as the transducer in 1989. This sensor has a concept of global selectivity to decompose the characteristics of a chemical substance into taste qualities and to quantify them. The use of taste sensors has spread around the world. More than 600 examples of taste-sensing system have been used, while providing the first “taste scale” in the world. This article explains the principle of taste sensors and their application to foods and medicines, and also a novel type of taste sensor using allostery. Taste-sensor technology, the underlying principle of which is different from that of conventional analytical instruments, markedly affects many aspects including social economy as well as the food industry.

Diffusion characteristics of volatile organic compounds (VOCs) were investigated indoors using tin oxide gas sensors. The chemicals cause various kinds of symptoms in humans, for example, the sick house syndrome. In this study, eight sensors were installed in a vertical direction and on a plane surface. These sensors were of the same type. The VOC is placed in a generation source, and the sensor output increases as the chemical diffuses. The sensor output becomes higher as the concentration increases.The following chemicals were tried as air pollutants: formaldehyde, toluene, and xylene. The sensor output changes in short, quick steps by slight fluctuations of the wind velocity. Therefore, the differential characteristic of the sensor output was adopted and the noise component was removed as far as possible. A threshold time t th to the characteristic was set up. It is assumed that the examining chemical reaches the installed sensor point in a time greater than this time. The new speed of arrival is proposed using the threshold time. The speed s [cm/min] is indicated using the distance d and the reaching time t th , namely, s = d/t th . Here, d means the distance between the sensor position and the polluting source. As a result, the speed for the sensor that is installed near the ceiling (at a height of 260 cm from the floor) is the highest. And, it became obvious that s was larger for the chemical with a smaller molecule. The speed of formaldehyde for the sensor installed near the ceiling was 700 cm/min and that for the sensor installed at the height of 100 cm from the floor was 370 cm/min. There is almost a two times difference in the speed. 

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