在线英语听力室_免费在线英语听力学习网站

Old Yeller was a great smeller. Dogs in general have superior smelling abilities. They detect dead bodies, illegal drugs and explosives—even cancer. But dogs don't just have great olfactory¹ gear. Another reason they're amazing chemical detectors³? [sniffing⁵ sound] … is the sniff⁴. 

"And it turns out almost every breed of dog does this at 5 Hz. Five times a second." Matthew Staymates, a mechanical engineer and fluid dynamicist⁶ at the National Institute of Standards and Technology. Sniffing, he says, is really a two-part process. “Inspiration, expiration⁷, right? Inhale⁸, exhale⁹, inhale, exhale." That second part, the exhale, is key. 

"So when the dog is actively¹⁰ sampling or sniffing on the ground, there is a turbulent air jet that exits each nostril¹¹ during the exhale phase. Just like when you and I exhale there's an air jet that comes out of our nostrils¹². But the dog is down on the ground and those air jets are vectored down and toward its rear. And in the world of fluid dynamics¹³, if I pulse an air jet in one direction I basically pull air with it." So the dog is creating a pressure differential that effectively pulls new scents¹⁵ toward its nose.

Staymates and his colleagues discovered that effect using a 3-D–printed model of a Labrador retriever's nose, which they tested with fluid dynamics equipment. They then outfitted¹⁶ a commercial vapor¹⁷ detector² with sniffing nostrils, inspired by the dog nose. And they found that the actively sniffing detector was 16 times better at picking up the scent¹⁴ of explosives, compared to just continuously drawing in air—the usual method. The results are in the journal Scientific Reports. [Matthew E. Staymates et al., Biomimetic Sniffing Improves the Detection Performance of a 3-D Printed Nose of a Dog and a Commercial Trace Vapor Detector]

Staymates says he hopes next-generation sensors¹⁸ take sniffing seriously. "There's nanosensors out there that can detect very, very small amounts of materials. One of the things that's been overlooked: is how do you get the molecules¹⁹ of interest to the detector? So you can have the most sophisticated detector in the world, but unless you can get material to it, it's not very useful." Adding a sniffer though…could be just the thing to make those detectors more dogged.

—Christopher Intagliata