Amy Ryan, Principal Investigator, Electronic Nose Project, Jet Propulsion
Amy Ryan is the Principal Investigator on the NASA Life Sciences Electronic
Nose Technology Development Task and Flight Experiment at NASA's Jet Propulsion
Laboratory (JPL), Pasadena, Ca.
NASA TECH BRIEFS:
(For readers who might not be familiar with electronic-nose technology):
What is an "electronic nose" and how long has this type of device
been in existence?
MARGARET AMY RYAN:
An electronic nose is an array of weakly specific chemical sensors, controlled
and analyzed electronically, which mimics the action of the mammalian
nose by recognizing patterns of response to vapors. Unlike most existing
chemical sensors, which are designed to detect specific chemical compounds,
the sensors in an electronic nose are not specific to any one vapor; by
using an array of different sensors which respond to several compounds,
gases and gas mixtures can be identified by the pattern of response of
the array. A baseline of clean air is established, and deviations from
that baseline are recorded as changes in resistance of the sensors. The
pattern of distributed response of the sb ensors may be deconvoluted,
and contaminants identified and quantified by using a software analysis
program such as pattern recognition and/or neural network.
The concept of an "Electronic Nose" has been discussed since
the mid-1980's. Electronic Noses have been discussed by several authors,
and there are several such devices which have been built and tested; there
are several different kinds of chemical sensors which can be used in an
array. There are commercially available electronic noses which have been
applied to environmental monitoring and quality control in such wide fields
as food processing, and industrial environmental monitoring.
NTB: Why is this
technology important to NASA space missions?
to monitor the constituents of the breathing air in a closed chamber in
which air is recycled is important to NASA for use in closed environments
such as the space shuttle, the space station, and planned human habitats
on Mars or the Moon. The best real time, broad band air quality monitor
now available in space habitats is the human nose. It is limited by human
factors such as fatigue, exposure to toxins, and inability to detect some
compounds. At present, air quality from the space shuttle is determined
on the ground after a flight by collecting samples and analyzing them
in laboratory analytical instruments such as a gas chromatograph-mass
spectrometer (GC-MS). The availability of a miniature, portable instrument
capable of identifying contaminants in the breathing environment at levels
which have the potential to be harmful to crew health would greatly enhance
the capability for monitoring the quality of recycled air as well as providing
notification of the presence of potentially dangerous substances from
spills and leaks. Such an instrument is the Electronic Nose (ENose) which
has been developed at JPL in collaboration with Caltech.
It is important to remember that the ENose is not an analytical instrument.
The ENose cannot be used to walk in to a room or spacecraft and determine
all the constituents of the air. It is used to monitor for changes in
the air, such as from spills, leaks, air filters which need to be changed,
or incipient fires. If an event such as a leak is sufficient to require
the crew to use breathing apparatus, the ENose can be used to determine
when it is safe to breathe the air again.
NTB: What sets NASA's
E-Nose apart from earlier versions of the electronic nose?
two primary differences between the JPL ENose and versions built elsewhere.
1. The sensing films are made from insulating polymers which have been
loaded with fine particles of carbon to make them electrically conducting.
Each sensor is made of a thin (< 1mm) film deposited over a pair of
electrodes. The resistance of the film is measured, and changes in resistance
are recorded. Those changes result in a pattern across the array of sensor;
the pattern and magnitude of the pattern are used to identify and quantify
the compound responsible for the change.
2. The ENose built at JPL was designed to quantify certain compounds at
the "Spacecraft Maximum Allowable Concentration" level. For
most compounds, this level is ~ 10 - 100 parts per million (10 ppm = .001%).
Analysis of a response includes both identification and quantification;
if the response is correct on identity but not quantity, it is not a correct
response; people responsible for astronaut health need to know both in
order to judge whether there is a danger in the breathing air.
NTB: How does the
device work? (in particular, how do the polymeric thin film sensors work?)
used here are conductometric chemical sensors which change resistance
when exposed to vapors. Each sensor is made up of a polymer film which
has been loaded with carbon, and the film deposited over a pair of electrodes.
When the film is exposed to a change in atmosphere, it swells or shrinks
and the resistance measured between the electrodes changes.
(You can take a look at the PowerPoint File I have attached. Run it in
slide view mode in PPT 97; it is an animated version of what happens to
the thin films.)
NTB: Will a similar
device be used aboard the International Space Station?
goal of the program at JPL is the development of a miniature sensor which
may be used to monitor the breathing air in the international space station,
and which may be coordinated with the environmental control system to
solve air quality problems without crew intervention. The experiment on
STS-95 showed that the ENose is microgravity insensitive, and that it
does not respond to every person passing nearby (which would make analyzing
responses very difficult)
The ultimate goal is to have several miniature ENoses distributed around
ISS, coordinated with the environmental controls. In the case of a leak,
the location of the leak can be determined by the ENose unit nearby, and
the control system program can be used to decide whether the problem can
be solved automatically, for example by turning on fans and filters, or
whether a crew member should be notified.
NTB: What additional
compounds will future versions of the E-Nose be able to detect?
list of compounds has not yet been set. In the phase we are now working
on "Second generation ENose"), we will include hydrazine and
compounds which are evolved from wiring as it heats up but before an electrical
fire starts. Other compounds will be determined in cooperation with the
Toxicology Branch at Johnson Space Center.
NTB: This sounds
like a technology with tremendous commercial potential. What are some
applications that we might see in the near future?
several applications for such a technology. Electronic Noses have already
been used in the food industry to monitor the production of coffee, beer,
wine and bread, to determine whether the product and/or the ingredients
are ok. In addition to monitoring space shuttle air, an electronic nose
can be used to monitor the air in any enclosed space, such as a submarine,
an aircraft, or closed working spaces such as tunnels. Industrial uses
include checking the identity of a tank full of liquid (is it alcohol
or is it acetone?) and monitoring for leaks from large pressure vessels.
There are also medical applications: compounds distinctive of particular
diseases can be detected, and bacteria can be differentiated.
Ms. Ryan can be reached
Here for More News...
| [an error occurred while processing this directive]