Olfactory System Cybernetics: Artificial Noses

Abstract

The remarkable capabilities of biological chemosensory systems in detecting, recognizing, and discriminating complex mixtures of chemicals, together with rapid advances in understanding how these systems operate, has stimulated the imagination and interest of many researchers and commercial organizations. Such stimulation has led to the development of electronic analogues. An artificial sensing system that emulates the human sense of smell is of upmost need in a number of fields, including the food, flavor, beverage, and cosmetic industries, as well as environmental protection industries and governmental agencies. Although the human sense of smell has been used for centuries in applied industrial settings in quality control and other processes, it is liable to variation from illness and other factors, including subject age, gender, and training. Moreover, there are linguistic limitations in communicating odor experiences among individuals. While, as noted in other chapters of this volume, the human sense of smell is exquisitively sensitive and can provide reliable estimates of odorant intensity and quality, there can be considerable variability of response among untrained individuals to different odors and odor concentrations. An instrument that could perform simple odor discrimination and provide an accurate indication of odor intensity with less variation than that observed in human responses would be very useful in modern industry. Cybernetics was defined by Norbert Wiener (1948) as “the theory of control in engineering, whether human or animal or mechanical”, including “not only the study of language but the study of messages as a means of controlling machinery and society, the development of computing machines and other such automata, certain reflections upon psychology and the nervous system, and a tentative new theory of scientific method.” The developments in “electronic nose” technology now herald the birth of “olfactory system cybernetics.” The motives arise from (1) the perceived limitations of traditional analytical chemistry and instrumentation in classification of gas mixtures or odors; (2) applications where the gestalt of a defined mixture of chemical species may be important in perception, applications where it is important to separate subjective and objective assessments; and (3) the commercial drive to achieve devices capable of operating rapid, on-line process measurement and control in areas of foods, beverages, chemical industries, and waste management. Another motive driving research is the attempt to create biomimetic devices that emulate aspects of biological sensory systems. The developments described in this chapter were based on the coalescence of several evolving scientific disciplines where key developments and concepts were evolving and converging in the last four decades, leading to a veritable explosion in the last decade. Today, electronic noses abound in various configurations and are used in specific applications, but “artificial noses” do not yet exist.