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Science Forum Index » Nanotechnology Forum » microfluidics to nanofluidics: when is small too small?
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| Leanna Levine |
 Posted: Thu Aug 21, 2003 7:20 am |
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The push seems to be to ultra-small, single molecule detection on the
nanoscale.
If we approach the development of micro-and nano- fluidics as an
excercise in applied science, toward the end of developing analytical
tools that provide useful information, what will a nanofluidic device
offer that a microfluidic device can't?
As a bioanalytical chemist who grew up beleiving that measuring
average properties provides useful information about the behavior of
the natural world, why do we want to meaure a single molecule?
Given the issues of surface area to volume that are substantially
greater at the nanoscale, what benefit is gained, other than using
less sample (which creates statisitcal problems of the existence of
the analyte of interest in such small samples), by creating fluidic
networks on the nanoscale? |
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| J. Damon Hoff |
| Posted: Fri Aug 22, 2003 7:07 pm |
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llevine@alineinc.com (Leanna Levine) wrote in message
news:<bi2gv001kgq@enews4.newsguy.com>...
Quote: The push seems to be to ultra-small, single molecule detection on the
nanoscale.
If we approach the development of micro-and nano- fluidics as an
excercise in applied science, toward the end of developing analytical
tools that provide useful information, what will a nanofluidic device
offer that a microfluidic device can't?
As a bioanalytical chemist who grew up beleiving that measuring
average properties provides useful information about the behavior of
the natural world, why do we want to meaure a single molecule?
Single-molecule studies provide insights into the mechanism of
activity for biomolecules (proteins) that ensemble studies can not.
For example, the step sizes and processivity of motor proteins such as
kinesin or myosin were elucidated only through the use of
single-molecule studies; mechanisms of interactions between finite
enzymes, or measurement of the mechanical properties of individual
molecules are similarly often best treated with single molecule
studies.
It is clear that there is a great deal of information about the
mechanisms of biomolecular activity that can only be uncovered by
studying individual molecules. Of course, the next question must be,
"Why is this information important -- how can it be applied?"
As with any form of basic research, the hope is that understanding the
underlying mechanisms of biomolecules will reveal new thrusts of
applied research. For example, understanding the basic underlying
cause of a disease -- where in the molecular machinery a defect has
occured, and what direct effect that defect is causing -- may allow a
direct targeting of the mechanism/process at fault.
I would say that more direct applications of nano-fluidics are
integrated biosensors -- lab-on-a-chip devices. For many operations,
all you really gain from reducing to the nano-scale is a decrease in
reagent/analyte required. Under most circumstances, this is probably
not a great selling point, since micro-devices already require such
small volumes. Certain operations, though, can be performed
considerably "better" (depending on what your metric is) with
nano-fluidics. For example, single molecule DNA sequencing in
nanofluidic channels appears to have the potential to greatly simplify
sequence reconstruction due to a longer "read-length."
Quote: Given the issues of surface area to volume that are substantially
greater at the nanoscale, what benefit is gained, other than using
less sample (which creates statisitcal problems of the existence of
the analyte of interest in such small samples), by creating fluidic
networks on the nanoscale?
Yes, the scaling issues are likely a big hurdle to overcome.
Obviously, you want to apply nano-fluidics only where the nano-
provides advantages over the micro- or macro-. There are applications
where nano- outshines micro-. One that comes to mind is pumping. A
very attractive mechanism for generating flow in microdevices is
electromotive flow, where a charged substrate draws the electric
double layer at the solid-fluid interface along. This flow is most
efficient at small scales, where the double layer represents a larger
portion of the total volume of the channel. This technique, when
applied in nanochannels, allows the buildup of pressures unattainable
by other means; quite possibly providing the pressure to drive flow in
the entire lab-on-a-chip device, whether the other components are
micro- or nano-.
There does seem to be an attitude floating around that smaller is
better, which as you point out is not always true. There are
important applications for nano-scale systems; but there are probably
many more applications for which micro-scale systems will perform as
well or better.
Just my 2 cents,
--Damon |
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