Promoting Personal Safety
& National Security
of radar stations along its south and east coasts to provide advanced warning of potential
attacks from both sea and land. For the first time in history, a nation could use machine-enabled remote sensing to prepare its defenses in advance of an imminent attack. Undoubtedly, the invention of radar saved countless lives, both soldier and civilian.
Today, researchers such as Dr. Claire Hartmann-Thompson, of the Michigan Molecular
Institute, are developing what might be called chemical radar. Instead of using radio waves
to see distant bombers and battleships, these new technologies use laser beams to detect
atmospheric chemical weapons.
“It’s nice to detect something dangerous at a distance, and obviously it’s safer for
humans.… The main challenge is getting high-quality information from a distance, and
you find there’s a trade-off between the number of things you can detect and the sensi-
tivity. So you normally find a sensing technique that can easily detect one thing down
to very, very low levels, and an example of that would
be land mines. Some techniques can detect parts per
trillion of a nitroaromatic vapor above ground, above
a buried land mine or buried ordinance, and then at
the other end of the spectrum one has a system where
you don’t know what to expect — you could expect any
one of a number of different chemical warfare agents
and you may want to be able to distinguish those, but
you normally find that the more things you can distin-
guish, the higher the levels have to be before you can
detect them, so you’re always working with that trade-
off and trying to strike a balance for the application
you’re working on.”
Dr. Hartmann-Thompson’s research involves that
trade-off between versatility and sensitivity. In the ACS
journal Chemistry of Materials, she and her colleagues
provided details on a system that uses a collection of
laser-sensitive nanoparticles to detect at a distance chemical warfare agents such as the nerve gas VX.
The nanoparticles in the collection carry different fluorescent dyes, each of which emits light of a unique color
when struck by a laser beam. But more importantly, those
colors change when the nanoparticles come in contact
with various chemicals, in this case nerve agents. The exact manner in which the array of
particles change colors depends on which chemicals are interacting with the nanoparticles.
The set of colors associated with a particular chemical is like a fingerprint for that chemical.
In its current form, this technology would be useful for detecting nerve agents drifting
into an area in a suspicious-looking cloud and distinguishing them from chemically similar
but less harmful pesticides that might have been sprayed on a farm field.
“In a real-world setting I can imaging some kind of military or homeland security application where you could launch a mixture of these particles into a cloud and then monitor what comes back from the cloud. All these techniques exist — the military is good
at launching projectiles to defined locations. A lot of technologies are good at detecting
various wavelengths of radiation coming back from the remote location, from the IR to
the visible to the UV. So it’s a matter of putting together existing technologies to apply
this in the real world. “
But Dr. Hartmann-Thompson is already thinking beyond this current system to one that
could be set up to create a permanent monitor for airborne chemical weapons.
“We’re working on that right now. We’ve managed to create analogous sensors in the
