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Frontiers
An Electronic Nose For Business, NSF, NASA and Others
October 1996
In the future world of Nathan Lewis, bomb squads
won't need dogs, they'll have electronic sniffers to find explosives.
The portable noses also will uncover substandard food, and will sound
an alarm if a car's brake fluid smells deficient.
Lewis, a chemist at California Institute of Technology, is part of
an NSF-funded team that is building electronic noses.
It's a popular project. Besides the obvious commercial applications,
the National Aeronautics and Space Administration (NASA) and the Departments
of Defense and Agriculture have all shown interest. They're attracted
to the idea of an electronic gadget that will surf through the world's
smell-scape, much as dogs do.
Working with Caltech's Center for Neuromorphic Systems Engineering,
an NSF Engineering Research Center (ERC), Lewis and his colleague,
Robert Grubbs, say this is a new approach to artificial olfactory sensing.
Most other chemical sensors are keyed to specific chemicals. When those
chemicals are absent, the noses don't work.
The Caltech nose, however, will learn. Like a dog, it will memorize
scents and react to something it hasn't smelled before.
This versatility intrigues NASA, says Lewis. No one knows what new
gas may appear inside the space shuttle, but the Caltech nose could
learn what the spacecraft smells like under normal conditions, and
then ring a bell if the odors change.
So the nose--nicknamed Pinocchio--may someday fly to the moon. But
today, it's sniffing beer. Pinocchio is made up of small polymer sponges
lined up like toothbrush bristles. Each sponge holds a different electrical
conductor and is connected to a computer through a myriad of wires.
When beer is introduced to the sensor, the sponges swell and all of
the conductors react to the ethanol, yeast and other scents. But each
conductor reacts differently.
With the help of the computer, Lewis "fingerprints" the smell. The
next time he holds a beer near Pinocchio, the computer will show the
same pattern.
More importantly, the computer will learn to recognize the pattern.
Pinocchio can currently differentiate between beer and grain alcohol,
as well as recognizing many other scents.
Eventually, Lewis expects to create a more discerning nose, one that
can distinguish between light beer and stout ale, or tell a fine wine
from a $5-a-bottle variety.
Meanwhile, other researchers at Caltech's ERC are working on the nose's
computer design. The completed sniffer will be made up of 10,000 sensors
and will fit on a square-centimeter chip, says Rodney Goodman, Director
of the ERC. "We're about three years away from that."
The Center as a whole is working on integrating many types of neurosystems
and engineering, including noses, explains NSF's director of the
ERC programs, Lynn Preston. "How can we make an olfactory system
more like a nose? That's the challenge. When we succeed there are
a lot of applications."
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