Electronic Nose

Ultimately, Ryan believes, the ENose could serve as the sensory part of an intelligent safety system. "We'd have a lot of them, connected to a central computer." Any change in the atmosphere would set off a cascade of activity.

If the signal suggests a fire, says Ryan, "then the crew would immediately be notified." But if not, then the computer would try to determine exactly what was going on. Had it detected something toxic? Had it detected something that was approaching dangerous levels? Where is it coming from?

Depending on its answers, the system could choose from a range of responses - from notifying the crew, to turning on fans to change the direction of air flow, to turning on filters, to sealing off an area.

As a safety device, the ENose has a lot to offer here on Earth, too. With some modifications, says Ryan, an ENose could be used to check for gas buildups in offshore oil rigs. "The workers have to go down into the legs of the rigs, and they want to make sure it's not going to blow up while they're in there." Sanitation workers would benefit by knowing if any poisonous gases have collected down in the sewers. There are many other examples.

Ryan's team is working on an advanced version of the ENose that could expand its usefulness even more.

The Second Generation ENose. The volume of this design is ~760 cm3, about 35% of the original ENose. The computer (right) can be attached to the back of the sensor package (left).

"When we first started choosing polymers for the ENose," recalls Ryan, "we used what you might call an 'Edisonian' approach." (That's a scientist's way of saying trial and error. Edison tried thousands of filaments before he perfected the first light bulb.) "We tested between eighty and one hundred polymers against each analyte." That's a lot of testing.

But, points out Ryan, Edison's approach means that you can only use the ENose to identify substances whose patterns are already known. Ryan and her team are starting to go beyond that. They're trying to develop a computer model that can predict the responses of any polymer to any analyte - "without having to test a hundred polymers," she says. This would greatly accelerate the pace of ENose design. Ryan's team has already made enough progress to select some polymers using the model.

This is exciting, she says, because a successful computer model could also be used to help ENose identify unknown compounds.

"We want to be able to look at an unknown response, and then figure out what caused it," says Ryan. Such an ENose could identify unexpected vapors on Earth or in space habitats. It could even analyze strange gases encountered on interplanetary explorations.

Picture this: An astronaut lands on an alien world. Strange landforms beckon in all directions. Where to begin? Simple. "Hey, that crater smells interesting!" Follow your ENose.