Biomedical Engineering Reference
In-Depth Information
in the SWNT decays as the number of water molecules in this water chain
increases [ 128 ]. How to achieve long correlation in the dipole orientation in
practice is a huge challenge.
(2). Is there an energy transfer, and how does the energy transfer process work
during such a dipole signal transmission, conduction, and multiplication?
These questions are still unclear.
(3). Water molecules are very small. The devices and sensors based on water can
be very small. However, the very small size of the water molecules can at the
same time make the experimental realization and applications very difficult.
The exploration of other larger polar molecules, such as urea, ethanol, and
glycerol, to be used as media in the nanotubes is highly needed and desired.
(4). What other methods can ignite the initial dipole orientation of the monitored-
water or some other molecules? Examples might be external electric fields
and/or other polar molecules connected to this monitored-water. Finally, we
should note that most of the progresses discussed in this short feature chapter
are based on MD simulations so far. Experimental validations are therefore
much needed.
1.2
Conclusion Remarks
Inspired by the biological channels called aquporins, the behavior of water inside
the nanochannels has been extensively investigated. Particularly, the water channel
with single-filed water is gated by external mechanical and electric signals; the
water flow inside the nanochannel with single-filed water can be driven with biased
direction by the static asymmetric electric field based on the ratchet effect; the water
molecules inside the nanochannel with single-filed structure can even be used for
signal transmission, conversion, and multiplication at the molecular level. When the
radius of the nanochannel is larger, the channel can even serve as the lab-in-tube to
controllably manipulate biomolecules for various applications, including chemical
reaction.
Finally, we noted that most of the studies for the water inside nanochannels
are experimental and numerical. Analytical study may better exploit the physics
underlying, and we think this is an important direction.
References
1. Whitesides, G.M.: The origins and the future of microfluidics. Nature 442 (7101), 368-373
(2006)
2. Whitby, M., Quirke, N.: Fluid flow in carbon nanotubes and nanopipes. Nat. Nanotech. 2 (2),
87-94 (2007)
3. Squires, T.M., Quake, S.R.: Microfluidics: fluid physics at the nanoliter scale. Rev. Mod.
Phys. 77 , 977 (2005)
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