‘electronic nose’ for preventing development of unpleasant foot odour

The first step for preventing the development of unpleasant foot odour is to get to the root of the problem, the cause of smelly feet. Using an objective, sensor-driven system for assessing perspiration odour, scientists at the Hohenstein Institute, the Test and Research Institute Pirmasens (PFI) and the Department of Measurement Technology at the University of the Saarland have made a major stride towards achieving this aim. The structural characteristics of shoes (for example, materials used for the uppers and soles) and stockings (e.g. fibres) play a special role in the development of odours, adding to the contribution the wearer of the shoe makes to the development of smells due to the bacterial decomposition of perspiration. Until now, product development with respect to sensory properties, such as smell, could be done only through a process of trial and error by means of costly tests using human probands. A system of sensors for the objective assessment of foot perspiration odour developed under the auspices of the research programme AiF (German Federation of Industrial Research Associations) - No. 201 ZN now provides a future means of avoiding customer returns and the subsequent re-designing and restructuring of shoes. During the research project, human test subjects, or probands, wore different combinations of shoes and stockings under realistic conditions in order to generate genuine foot perspiration odour. Throughout the duration of the experiment, in parallel research, the odours generated were objectively assessed with the aid of an “electronic nose” and subjectively evaluated by a “sensory panel” (a group of human test sniffers). In what is known as the “electronic nose”, diverse semiconductor gas sensors reacted to volatile substances, such as those generated during the process of bacterial decomposition of perspiration. The substances' adsorption on or reaction with the surfaces of the semiconductors changes their conductivity, and a measurement signal is generated. The human sniffers augmented the data gathered by the sensors with a very fine and welldifferentiated sense of smell. The aim of the research project was to correlate the measurement data gathered by the sensors with the subjective odour evaluations given by the “sensory panel” of human sniffers, by placing them in reference to one another. This goes some way towards sparing subjective odour evaluations in future, because perspiration odour can be quantitatively assessed using measurements taken by the “electronic nose” alone. Through this innovation, major savings in time and money can be achieved during the development of shoes, stockings and socks. The research project has shown that in principle, it is possible to correlate these two data sets using complex mathematical and statistical processes (e.g. linear discriminant analysis). Yet the accuracy that has been achieved through correlation of the amount of data that has been gathered to date is still not great enough to do without the odour evaluations of the “sniffer panel” entirely. This aim can be achieved through further measurements with the “electronic nose” and by optimising the evaluation of data gathered by the sensors. Applying the measurement principles that have been developed in this project to other garments and their materials (e.g. T-shirts, underwear, shirts, blouses) is possible. Further studies are scheduled subsequent to this one.

Hohenstein Institute