Biomedical Engineering Reference
In-Depth Information
13.4
Artificial B-Noses Using OR/CPNT Platform
13.4.1
Chemiresistive B-Nose to Detect Odorant Gases
13.4.1.1
Construction of the Chemiresistive B-Nose
The olfactory system is a highly, precise biological process. The human nose can de-
tect gaseous odorants at low concentrations (sub-part per trillion [ppt] level: 10
−9
).
Thus, it is challenging to mimic the human olfactory system, which can discriminate
thousands of odorant molecules [
74
-
79
]. Recently, progress in nanotechnology the
development of the nanotechnology, B-noses were designed using carbon nanotube
(CNT) [
35
]. However, the B-noses using the CNT platform exhibited limitations
such as unstable interaction between receptors and transducers in liquid state and
antagonism study. To overcome the critical disadvantages, we attempted to con-
struct a chemiresistive B-nose, based on 1D CP nanomaterials. Chemiresistor-based
sensors exhibit several attractive characteristics, such as facile process, label-free
detection, and low power consumption. Chemiresistive sensors can be applied to
simple resistance change in response to various small molecules, including volatile
organic compounds (VOCs) and nerve agents. From their strong points, the B-nose
based on a chemiresistive system was created for the APS-treated IMA
via
the im-
mobilization of the human olfactory (hOR3A1) on the CPNT, as shown Fig.
13.3
.
To assess the chemiresistive sensing platform, a standard gas generation system
with a mass flow controller (MFC) was also introduced (Fig.
13.4
). The gas genera-
tion system consisted of MFCs and measurements sections. The odorant gases that
moved through the carrier gas (N
2
) were controlled by MFC system, resulting that
the odorant gases were reached into the gas chamber.
13.4.1.2
Characterization and Real-Time Responses of the Chemiresistive
B-Nose
To confirm the electrical properties of the B-nose, current-voltage (
I
-
V
) charac-
terizations were carried out. Generally, chemiresistive sensors measure the poten-
tial difference across two points, leading to accurate detection
via
simple based on
changes in resistance values. Figure
13.5a
displays the linear
I
-
V
values of B-nose
based on OR-conjugated CPNTs. The
I
-
V
values were maintained with continuous
linearity after the introduction of the OR on the CPNT. Moreover, a significant
change in the
I
-
V
values was observed, due to the attachment of the ORs. This
indicates that excellent electrical contact between the CPNTs and IMAs can be
achieved using the immobilization process, which provides reliable electrical re-
sistance properties.
Significant resistance changes from the chemiresistive B-nose can be observed
by the introduction of target odorant gas. Figure
13.5b
presents the sensing capa-
bility of the chemiresistive B-nose upon periodic exposure to helional gas. Rapid
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