Fake dog snouts upgrade bomb detectors

A 3-D printed labrador nose is 18 times better than standard devices at finding the faint odours that characterise explosives, contraband and even cancer.

In a report published in Scientific Reports, a team led by engineer and fluid dynamist Matthew Staymates from the US National Institute of Standards and Technology demonstrate that the artificial dog snout can be attached to current commercially produced bomb detectors, bringing about a massive – and potentially life-saving – increase in sensitivity.

Normally, explosive sampling machines use one of two methods: a passive approach, where samples are presented to the detector, or a suction approach, where the detector draws in nearby molecules – such as odorants – in a steady, continuous stream.

Dogs use a different mechanism. They actively sniff – sucking and expelling air repeatedly, at a rate of approximately five sniffs per second.

Staymates and colleagues began their work by confirming that their 3-D-printed dog nose sniffed like the real thing. They then compared its air-sampling performance against an existing suction based trace-detection device.

Amazingly, the dog-inspired sniffer’s sampling efficiency was 18 times better than the traditional device, when smelling from a distance of 20 centimetres. The efficiency boost came not only from the energy expended to pull air strongly into the prototype, but also from the specific anatomy of canine noses.

“During inspiration air near the nose, within a spatial extent of approximately one to two centimetres, is drawn into each nostril with a laminar, hemispherical profile,” the team wrote.

Exhaled air jets are forced downwards and to the side – the nose acting as a flow diverter – which in turn “mechanically disturb and volatilise latent odorant, thereby liberating vapour that may then be inspired”.

In other words, molecules of interest that might be hidden by other molecules are jostled until they’re freed.

Modelling shows this method extends the aerodynamic reach of their noses well beyond that achieved by simple suction. 

Physicist Paul Shaw from the University of Queensland in Australia, who was not involved in the study, said the ability of the artificial nose to detect samples from significant distances represented “a big jump up from the two to three centimetres” that current detectors reach.

“Vapour sampling works quite well over short ranges, but when you start getting a bit further [away], you don’t have the draw to bring the samples in,” he explained.  

Smelling success after demonstrating proof-of-concept, the researchers decided to attach a modified version of the 3-D sniffer to a commercially available trace vapour detector used to search for hidden explosives.

The lab nose improved its ability to find TNT molecules by a factor of 16 – a stunning increase in sensitivity.

Canine skill at spotting drugs, bombs and cancers is already well established. Soon it might be used even more widely – only without the actual animals.

Staymates’ team suggests that “bio-inspired design principles learned from the dog may be used to improve the performance of next-generation vapour detection technology”.

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