Nanopores
Holes have always found use for a variety of reasons. You can grow things in them (like plants),
pour things in them (like concrete), and use them to store things (like garbage
or treasure). So, is it any surprise
that nanometer-sized holes have found some interesting uses in
nanotechnology? By definition, a nanoporous
material has many deep pores with diameters in the nanometer scale.
Nanopores can be fabricated by either a top-down or
bottom-up approach. As usual, the
top-down approach is steadier but ultimately limited in density by the
diffraction limits of lithography. The
bottom up approach is quickly become the more important one as researchers have
recently developed a very reliable technique.
The key to making the bottom-up approach feasible was in finding a way
to control the diameter of the pores. Since
a bottom up approach required self-assembly of nanotubes, there wasn't as much
control over distribution of diameters.
Recently, researchers at Sandia National Laboratories found that they
could use UV light to tune the diameter of the self-assembled nanopores. This discovery could lead to a number of
exciting applications that we will now discuss.
For one thing, a nanoporous material would be an ideal
storage source for fuels or batteries.
Nanopores represent the ultimate in matter storage density while at the same
time demonstrating high strength and durability. Many exciting new ideas are focused on using nanoporous materials
for hydrogen fuel cell storage.
In the medical sciences, a single nanopore could be tuned to
the diameter of a DNA strand. This
would act as a filter for DNA and would also allow researchers to analyze the entire
length of the DNA strand in sequence.
Speaking of filters, nanoporous materials could finally
unlock the most sought after filter of all time: the oxygen-nitrogen
separator. For many years, industry
experts in the field of air filtration have spent millions of dollars trying to
pull oxygen directly out of our ambient atmosphere. This would save so much money compared to chemical oxygen
synthesis that it's not even funny.
With the new spate of highly controllable self-assembled
nanopores, researchers are promising the kind of precision that would make this
kind of filter happen. To give you an
idea of the precision required, consider that the difference in diameter
between oxygen and nitrogen is only 0.2 angstroms!
In a final note, nanoporous silicon has been recently made
to emit light. This was a huge
discovery because silicon is an indirect bandgap material that normally doesn't
radiate light. If we could ever build a
laser from silicon (instead of GaAs) electronics-photonics applications would
be a lot more efficient.
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