Biomedical Engineering Reference
In-Depth Information
Finally, we note that we have not considered the possible metal semiconductor
property of the nanotube. For those nanotubes, the screening effect should be
considered, and the charges used here should be regarded as effective charges. It
is interesting to note that even for the metallic nanotube, the interaction between
a charge outside the single-walled nanotube and the charges inside the nanotube
is still quite strong. However, insulator nanochannels may be much better in the
application, which is expected to be fabricated in the future. Considering that
the external charges required for these manipulations are quite small, which are
still available after taking into account the screen effect of many nanotubes, our
designs may serve as lab-in-nanotube for the interactions and chemical reactions
of molecules especially biomolecules and hence may have wide applications in
nanotechnology and biotechnology.
1.1.3
Signal Transmission, Conversion, and Multiplication
with Polar Molecules Confined in Nanochannels
Another thing we are inspired from the one-dimensional hydrogen bonds chain
as shown in Fig.
1.2
is that the highly stable chain can be used in the signal
transmission, conversion, and multiplication at nanoscale and/or molecular scale.
Nanoscale structures or molecules have been utilized as the elements in electronic
devices [
73
-
76
], such as nanowires, switches, rectifiers, and logic circuits, and
the integration of these molecular-based devices and other nanoscale structures
has led to a number of demonstrations of new and useful applications [
77
,
78
].
Particularly, electrical transportation [
79
], electrical and partity switching [
73
-
76
], and chemical and biomolecular sensors [
80
,
81
] have been developed based
on nanowires or nanotubes. Biosensors for DNA diagnostics, gene analysis, fast
detection of warfare agents, and forensic applications have also been achieved by
electrochemical method
14
and microarrays
17
together with the particular behavior
of biomolecules in nanoscale [
82
].
In biology, signal representations are often related to electrical changes. For
example, in central nerve systems, the most common mechanism for signaling
between neurons is the neurotransmitter-releasing chemical synapse, but faster and
simpler signaling can be achieved with electrical synapses, specialized junctions
(gap junctions) that mediate electrical coupling between neurons [
83
-
86
]. Electrical
coupling mediated by electrical synapses is an important feature of local inhibitory
circuits and plays a fundamental role in the detection and promotion of synchronous
activity (firing pattern) within the neocortex [
87
-
89
]. In fact, weak coupling may
lead to antiphasic or asynchronous firing [
83
,
84
,
90
].
On the other hand, although it has been of great interest to study the mechanism
of signal transmission, conversion, and multiplication at molecular level, molecular
details in these systems remain largely unknown due to the intrinsic complexity in
these molecular systems and the significant noises arising from thermal fluctuations
