Study and development of an "electronic nose" and comparison with mammalian olfaction
<p>Arrays of broadly responsive vapor detectors (i.e., electronic noses) are receiving an increasing amount of scientific attention for their potential as analytical devices, as models for studying mammalian olfaction, and perhaps for someday ultimately duplicating or surpassing the mammali...
| Summary: | <p>Arrays of broadly responsive vapor detectors (i.e., electronic noses) are receiving
an increasing amount of scientific attention for their potential as analytical devices, as
models for studying mammalian olfaction, and perhaps for someday ultimately duplicating
or surpassing the mammalian olfactory sense. Herein, research was primarily focused on
an electronic nose composed of an array of carbon black-polymer composite detectors
while arrays of tin oxide detectors and organic conducting polymer detectors were used
only in a comparison study. The research determined the odorant resolving power of
electronic nose sensor arrays, explored the dependence of the electronic nose array
response intensity on odorant vapor pressure, compared the odorant detection thresholds
and odorant classification properties of the electronic nose to the mammalian olfactory
sense, and attempted to predict human odor quality judgements using electronic nose
detector responses.</p>
<p>The Fisher linear discriminant statistical metric was utilized to quantify the
performance of arrays composed of carbon black-insulating polymer composite detectors,
tin oxide detectors and bulk conducting organic polymer detectors in resolving nineteen
odorant vapors. The odorant resolving power of the sensor arrays as a function of the
chemical composition of the detectors and the number of detectors they contained was
studied. The results provided insights into optimizing the chemical diversity and size of a
chemical vapor sensor array for various tasks.</p>
<p>Response data were collected for a carbon black-polymer composite electronic nose
array during exposure to homologous series of 1-alcohol and n-alkane odorants. The mean
response intensity of the electronic nose detectors, and the response intensity of the most
strongly-driven set of electronic nose detectors, was essentially constant for members of a
chemically homologous odorant series when the concentration of each odorant in the gas
phase was maintained at a constant fraction of the odorant's vapor pressure. A similar
trend is observed in human odor detection threshold values for these same odorants. The
data imply that the trends in detector responses and human detection thresholds can be
understood based on the thermodynamic tendency to establish a relatively constant
concentration of sorbed odorant into each of the polymeric films of the electronic nose and
into the olfactory epithelium of humans at a constant fraction of the odorant's vapor
pressure.</p>
<p>Experiments were performed to compare the detection thresholds and trends in
discrimination abilities of the electronic nose to those of the mammalian olfactory sense,
and to develop models predicting human odor quality judgements from electronic nose
detector responses. The detection thresholds for the electronic nose and the human nose
were compared for series of n-alkanes and 1-alcohols. Trends in the odorant-discriminating
abilities of an electronic nose and mammalian noses were compared for
series of esters, alcohols and carboxylic acids. Electronic nose response data were
collected for a diverse set of odorants which had previously been quantitatively
characterized by human panelists according to many categories of odor quality. The
responses of the electronic nose detectors were then used in attempts at predicting the
human odor quality judgements.</p> |
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