94

౪

4 Smell and Taste

Figure 4.11: QCM sensor data differentiating be-

tween three serotypes of the flu virus. The sensor

uses self-assembled N-Acetylglucosamine (GLcNAc)

monolayers, which are part of the natural ligand for

flu viruses as the sensor element [39].

detection of heavy metal ions [38]. The military is trying to use artificial noses to detect

explosives and chemical warfare agents [32]. The other large and growing area of their

application is in medical diagnostics [32]. These applications include the diagnostics of

diseases from the patient’s breath or the detection of different bacteria by looking at

how they bind to different receptors.

4.4 Summary and the Bigger Picture

Of all the human senses, smell and taste have so far been most successfully mimicked,

insofar as the terms of “artificial tongue” and “artificial nose” have been given to many

nanosized chemical sensors regardless of whether they actually mimic the human pro-

cesses or not. Chemical sensing methods are the furthest developed, often already com-

bining multiple sensing elements with a transducer and an analysis element (generally

a form of pattern recognition). Some of these sensors have already made it into indus-

trial use. Even so, they still face a common problem: competing binding from unrelated

chemical compounds reduces the specificity and reliability of analysis and compound

identification. A preceding separation step could alleviate this problem.

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