Electronic Nose

Onboard the space station, astronauts are surrounded by ammonia. It flows through pipes, carrying heat generated inside the station (by people and electronics) outside to space. Ammonia helps keep the station habitable.

But it's also a poison. And if it leaks, the astronauts will need to know quickly. Ammonia becomes dangerous at a concentration of a few parts per million (ppm). Humans, though, can't sense it until it reaches about 50 ppm.

Ammonia is just one of about forty or fifty compounds necessary on the shuttle and space station, which cannot be allowed to accumulate in a closed environment.

And then there's fire. Before an electrical fire breaks out, increasing heat releases a variety of signature molecules. Humans can't sense them either until concentrations become high.

Astronauts need better noses!


That's why NASA is developing the Electronic Nose, or ENose for short. It's a device that can learn to recognize almost any compound or combination of compounds. It can even be trained to distinguish between Pepsi and Coke. Like a human nose, the ENose is amazingly versatile, yet it's much more sensitive.


Here's how it works: ENose uses a collection of 16 different polymer films. These films are specially designed to conduct electricity. When a substance -- such as the stray molecules from a glass of soda -- is absorbed into these films, the films expand slightly, and that changes how much electricity they conduct







 


Because each film is made of a different polymer, each one reacts to each substance, or analyte, in a slightly different way. And, while the changes in conductivity in a single polymer film wouldn't be enough to identify an analyte, the varied changes in 16 films produce a distinctive, identifiable pattern.

Electronic Noses are already being used on Earth. In the food industry, for example, they can be used to detect spoilage. There's even an Electronic Tongue, which identifies compounds in liquids. NASA's ENose needs to be able to detect lower concentrations than these devices.


As a safety device, the ENose has a lot to offer here on Earth, too. With some modifications, 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.