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Explosives detector works 16 times better when it can ‘sniff’ like a dog

Building an explosives detector so that it can “sniff” like a dog made it 16 times more likely to detect chemicals such as TNT.

Dogs know how to follow their noses — and scientists are now taking the hint, too. Researchers who 3-D printed a model of a dog's snout have found that high-speed sniffing seriously upgrades the ability of detectors to pick up explosive chemicals like TNT.

The discovery, described in the journal Scientific Reports, could lead to better chemical sensors for explosives, narcotics and even cancer.

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Scientists have long looked to the dog's nose as an olfactory marvel, thought to be on the order of 10,000 to 100,000 times better than our own. Much of that is attributed to the roughly 300 million olfactory receptors in a dog's nose, and the generous proportion of brain space devoted to decoding odors.

But while that's a big part of what makes dogs' sense of smell so spectacular, it's not the only factor, said study lead author Matthew Staymates, a fluid dynamicist at the National Institute of standards and Technology.

"The dog is generally known as the gold standard for trace chemical detection. And so we were really interested in understanding, what is it about the dog that makes it this amazing chemical detector?" Staymates said. "There's been a lot of work in the past that focuses on what happens inside the olfactory region of the dog [nose] ... but there's been a limited amount of work on what's happening outside of the dog's nose."

Searching for clues, the scientists 3-D-printed a dog snout modeled from a female Labrador retriever and put it in a schlieren imaging system, a device that uses the way that light moves through fluids of different temperatures and densities to actually watch what was happening to the air flow. They made the nose 'sniff' the way a dog would – rapidly inhaling and exhaling about 5 times per second – and watched what happened.

The faux nose appeared to draw in air the way a real dog did — and it seemed to be working remarkably well. The nostrils were positioned so that each time the nose exhaled, air shot down and out from the nostrils, which actually helped pull in more "fresh" vapor from a can of acetone in front of the snout.

The scientists then tested this sniffing nose out on a mass spectrometer. Compared with devices that use continuously inhaled air, the "sniffing" method was about four times better for a source at 10 centimeters and 18 times better for a source at 20 centimeters.

Finally, they plugged the sniffing dog nostrils onto the end of a commercially available vapor detector. Usually, this device would inhale continuously in 10-second intervals, but the scientists found that the sniffing nose was 16 times as good at detecting odors from 4 centimeters away as the device's normal mode.

"You can collect vapor from extended distances much better if you are mimicking what the dog does," Staymates said. "That's kind of the whole point of this — this concept of biomimicry.  It's taking what nature already does and applying or integrating it into the technology that we're trying to improve."

The findings demonstrated the need to think beyond just chemical detection in the next wave of sensor technology, he said.

"The dog is a smart sampling system," Staymates said, "so I guess we're just proposing that the next generation hopefully considers different ways of sampling the environment around them."

In the meantime, he and his colleagues will probably continue to learn from the dog's nose —including its ability to smell in stereo.

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