4.3 Biomimetic Chemical Sensors

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are incorporated into all biomimetic sensors, but there are a large variety of different

approaches for “artificial noses” and “artificial tongues” that have been reported. In this

chapter, only a small selection will be described.

A common setup is shown in Figure 4.8 [23]. Some sensing molecule binds a specific

compound or a specific type of compound with different strengths. The binding results

in a changed signal. The signal is compared to a calibration and, in the case of multiple

compounds, the binding molecule is identified through pattern recognition.

Figure 4.8: Common set-up for “artificial noses” and “artificial tongues” (adapted from [23]).

In the case of human smell and taste, the sample air or water is actively transported

past the gas sensors in the nose (by breathing in air) and the aqueous sensors in the

tongue (by swallowing the sample). Only a few of the reported sensors have tried to

mimic this active obtainment of the molecule. In a microbead chemical sensor, capillary

forces actively pull the sample into the microfluidic sensor [24]. In another example,

channels were created that included the binding molecules in their inside wall [25, 26].

This method additionally results in size control—particles larger than the pore size were

excluded from the sensor.

Mucin has also been used to recreate the active “catching” of the molecule [27].

An “E-tongue” was developed to identify bitter and astringent tastes only. It consists of

and elastic hydrogel from a copolymer of acrylamide and acrylate mixed with chitosan.

Mucin strongly binds the model substances for bitter taste (quinine sulfate) and astrin-

gent taste (tannic acid), but only weakly the model substances for sour taste (tartaric

acid), and not at all the model substance for sweet taste (sucrose), salty taste (NaCl),

and umami taste (monosodium glutamate). When measuring the voltammograms in