An American mechanical engineer has created a device based on a dog's nose that is able to improve detection of odours by almost 20 times.
“The dog is an active aerodynamic sampling system that literally reaches out and grabs odorants,” explained Matthew Staymates, a mechanical engineer and fluid dynamicist at the US National Institute of Standards and Technology (NIST).
“It uses fluid dynamics and entrainment to increase its aerodynamic reach to sample vapours at increasingly large distances. Applying this bio-inspired design principle could lead to significantly improved vapour samplers for detecting explosives, narcotics, pathogens, even cancer.”
Staymates said trace detection devices currently used at airports and other sensitive locations, typically employ passive sampling. Examples include equipment that requires swabbing hands or other surfaces and then running the sample through a chemical detector—typically an ion mobility spectrometer. Wand-like vapour detectors accommodate more sampling mobility, but unless the detector scans immediately above it, the chemical signature of a bomb-making ingredient will go unnoticed.
Reviewing previous studies, Staymates and his team discovered that when a dog sniffs, it exhales five times a second to reach out, then pull in a nose full of aromas.
Using a 3-D printer, they replicated the external features of a female Labrador retriever’s nose, including the shape, direction, and spacing of the nostrils. Moving air through the artificial nose at the same rate that a dog inhales and exhales allowed them to mimic the sniffing of dogs.
By using schlieren imaging, a technique widely used in aeronautical engineering to view the flow of air around objects, and high-speed video, they confirmed that their imitation nose could indeed sniff much like the real thing, a property documented in previous studies of live dogs.
With each sniff, air jets exit from both nostrils, moving downward and outward. The air jets then draw in vapour-laden air toward the nostrils.
Comparing the 'actively sniffing' artificial dog nose with trace-detection devices that rely on continuous suction, they found that sampling efficiency with the sniffing artificial dog nose was four times better at a distance of 10 cm from the vapour source and 18 times better at a distance of 20 cm. By then modifying a commercially available vapour detector with a bio-inspired 3D-printed inlet that would enable it to sniff like a dog, they found an improvement in odorant detection by a factor of 16 at a stand-off distance of 4 cm.
“Their incredible air-sampling efficiency is one reason why the dog is such an amazing chemical sampler,” Staymates said.
“It’s just a piece of the puzzle. There’s lots more to be learned and to emulate as we work to improve the sensitivity, accuracy and speed of trace-detection technology.”
[Matthew Staymates using a schlieren imaging system to visualise the flow of vapours into the artificial dog nose. Photo: Robert Rathe]