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My name is Katherine Mirica and my research
focuses on making gas sensors from carbon nanotubes.
These sensors might ultimately find applications
in the food industry, health care, and homeland security.
A carbon nanotube is a tube-shaped molecule
made up of carbon atoms.
It is one to 10 nanometers in diameter,
which is 50,000 times thinner than a human hair
and about a billion times thinner
than this model of a carbon nanotube.
Carbon nanotubes are chemically related
to the main component in the lead
of a pencil, which is graphite.
Graphite is composed of flat sheets of carbon atoms.
If you take one of these flat sheets
and roll it up into a cylinder you
get the structure of a carbon nanotube.
You can view the nanotube as a very conductive, hollow
molecular wire.
Because all the atoms of the nanotube
are on its surface, when something else,
like a molecule, interacts with that surface
it can have a very large effect on the flow of current
through the nanotube.
And this type of sensitivity is very useful for making sensors.
Are approach for overcoming the challenges
of working with carbon nanotubes relies on a solvent-free method
that is essentially similar to drawing with pencil on paper.
Instead of using a graphite-based lead,
like a regular pencil, we make our own lead that's
composed of carbon nanotubes.
To make our pencil lead we take a commercial powder of carbon
nanotubes and compress it into the shape
of a lead using a press.
To make the sensors we take a piece
of standard copy paper and deposit gold electrodes
onto its surface.
These electrodes help us measure the electrical current running
through the carbon nanotubes.
We then take our pencil lead and draw
our carbon nanotubes-based sensor between the electrodes.
And that's it.
We've just made a sensor that's capable of sensing
ammonia gas at low part per million concentrations.
Sensing ammonia is important because it's
a toxic gas that's sometimes used in refrigeration and food
processing applications.