Nose, artificial

FIGURE 6-25 The flow of information in the array-based artificial nose. (Reproduced with permission from reference 94.)... 

Arrays, 131, 162, 185, 187, 194, 198 Artificial nose, 198 Atomic force microscopy, 47 Auger electron spectroscopy, 45... 

An important demonstrated application of this artificial nose system is the high-speed detection of low levels of explosives and explosive-like vapors. Several sensors, based on Nile Red attached to silica microspheres, show high sensitivity to nitroaromatic compounds (NAC) within a mixture12. Different fluorescence response profiles were observed for several NAC s, such as 1,3,5-trinitrotoluene (TNT) and 1,3-dinitrobenzene (DNB), despite their similar structures. These responses were monitored at low concentrations of the NAC vapors (ca. 5 ppb) and at short vapor exposure... 

High-speed detection is a necessity for many artificial nose applications. In one study123, it was shown that even at short exposure times (<1 sec), the nose could identify different vapors and the responses were reproducible. Figure 8 demonstrates this quality, when three high-speed exposures (0.38s exposure time) produced reproducible response profiles. 

Stitzel S. E., L. Cowen J., Albert K. J., Walt D. R., Array-to-array transfer of an artificial nose classifier, Anal. Chem. 2001 73 5266-71. 

Automatic baking control by introduction of intelligent multigas sensors (artificial noses). 

Microsystems are also expected to be introduced in the near future, including for example artificial noses, fingerprint sensing systems, bar code readers, rf-tag-ging systems, microfluidic pumps and dosing systems, gas flow control systems, new flexible and low cost displays or electronic paper. 

In Fig. 6.1, an attempt is made to show to what extent sensors have been penetrating the appliance market over the past years, a trend which is set to continue in the next decade. In the beginning, there were relatively simple sensors for temperature, pressure, flow, etc. Over the last years, non-contact measuring devices have attracted much attention, such as non-contact temperature monitoring for toasters or for hair blowers. The introduction of more complex sensor systems, such as water quality sensors or multi gas sensing artificial noses is imminent. 

Automatic baking control, e.g. by introduction of intelligent multi-gas sensors (artificial noses) in combination with non-contacting temperature distribution recognition... 

This can be realized with modem sensors such as infrared thermopiles, thermopile arrays, microspectrometers and color sensors, several types of humidity sensors, artificial noses and multi-gas sensors. 

Some of these functions could be monitored with improved sensors, instruments and microsystems, like microspectrometers and color sensors, thermopiles, artificial noses, etc. Also some dosing and mixing functions (e. g. of herbs and spices) could be controlled by microfluidic systems. 

Cross-reactive sensing arrays were developed to detect odors and vapors in an artificial nose manner. Solvatochromic dyes such as Nile Red are adsorbed on the surface or embedded into various polymeric or porous silica beads. The beads respond to analyte vapor by a change in fluorescence maxima or/and intensity due to changes of polarity inside the bead. A portable instrument and preliminary field test for the detection of petroleum products was recently described [106]. 

Dickinson TA, Michael KL, Kauer JS, Walt DR (1999) Convergent, self-encoded bead sensor arrays in the design of an artificial nose. Anal Chem 71 2192-2198... 

The above examples show that it is possible to envisage the application of PS in electronic artificial nose chips [Le26]. 

Although inventors are trying to develop electronic and artificial noses to detect odours, they have not yet been able to duplicate the sensitive nose of a skilled, trained, and talented perfumer. 

In parallel, during recent years, several applications of artificial noses and tongues were demonstrated to be suitable not only for a sensory-like evaluation but for a wider-ranging characterization of the samples. Nonspecific analytical responses, in fact, may provide information about the... 

Schafer and coworkers [23] developed a QCM-IL sensor for use as an artificial nose using the ubiquitous [C4Cilm][PFg]. The IL was spin coated onto the surface of a 10 MHz AT-cut quartz crystal with gold electrodes. The work specifically studied the response of the sensor to ethyl acetate. The deposition of the IL on the surface of the electrode decreased the resonance frequency of the QCM by 2017 Hz. Exposure to increasing amounts of ethyl acetate vapor produced a linear increase in frequency, which was attributed to a progressive decrease in viscosity of the IL upon adsorption of the analyte. The response time, given as the time to full saturation of the... 

Zannoni, M. (1995) Preliminary results of employ of an artificial nose for the evaluation of cheese. Sci. Tec. Lattiero Casearia 46 277-289. 

Keywords. Artificial nose, Chemical multisensor array, Artificial neural network, Bioprocess... 

Electrochemical nose — (electronic nose e-nose or artificial nose ) is an array of chemical and/or - electrochemical sensors mimicking the physiological olfac-... 

The creation of many effective combinations of artificial nose sensors with only a few functional monomers used in different relative amounts was proven here. The application of combinatorial technologies to the discovery of novel materials for more recent, miniamrized electronic nose systems based on small pol5mier beads (120), and to equally intriguing electronic tonguelike microsensors in solution to mimick the sense of taste for solution mixtures (121), should be highly beneficial and thus is to be expected in the near future. 

Dickinson, T. A. White, J. Kauer, J. S. Walt, D. R. Current Trends in artificial-Nose Technology. Trends Biotechnol. 1998, 16, 250-258... 

Lundstrom, I. Artificial Noses - Picture the Smell. Nature 2000, 406, 682-683... 

The development of instruments, an artificial nose or an electronic nose, that can evaluate the air quality as the human nose does is an ongoing activity. Many attempts have been made, some successful for the purpose they are designed for, others not. The reason is not only related to the still incomplete knowledge of the perception mechanism (information processes in the brain), but also to the fact that the nose is able to detect very low concentrations. 

Nature has devised some of the most refined and effective chemical sensors that are in existence. The olfactory system is an excellent example of what nature can do. Much work has been done in the field of sensors to create an artificial nose that can detect and differentiate virtually unlimited varieties of chemical mixtures at extremely low concentrations (often at parts per trillion levels Di Natale 1998). 

Human noses do need to tire imagine walking off the busy street into a chemist s shop. One would immediately detect the odour of the perfumes, fragranced toiletries and other goods, but the outside smells would be very much in the background. However, an instrument just inside the door would still be picking up the exhaust and diesel fumes of the passing cars and buses. In many applications of an ideal artificial nose, this needs to be catered for. Currently, the only answer is to ensure no extraneous odours or non-odorants enter the machine. 

FIGURE 1.15 Similarities between natural and artificial noses. 

There are also some potentially useful agent-sensing technologies that do not rely on biological sensors. These new devices may offer more rapid analysis and simpler, continuous measurement. One kind of new sensor is the electronic (or artificial) nose. An array of semiselective, cross-reactive sensors produces a response pattern characteristic of a chemical (Gardner and Bartlett, 1999 Albert and Walt, 2000). The patterns are preprogrammed mathematically so that upon exposure, the patterns are matched to the chemicals sensed. There are two main groups of electronic noses ... 

---