A Whiff of the Future

The human nose is a wonderful thing. A whiff of a special smell can bring back fond memories of a great holiday or a budding romance. The pleasing odor of a favorite meal cooking, or cookies in the oven, can have us salivating with hunger. But its ability to smell foul odors is what makes the nose truly valuable. Our capability to detect foods that have gone off simply by giving them a sniff can prevent us from eating things that could make us sick. The smell of smoke has saved many people from fires. Now, a team of researchers at the British universities of Warwick, Leicester and Edinburgh are close to creating an electronic nose that will replicate our ability to sniff out danger. Once completed, it will be the world's smallest nose — a micronose that will fit on a square-centimeter silicon chip.

Artificial noses are not entirely new. Some have been in use for a few years in the cosmetics and food industries. But they're large machines that aren't too precise. Moreover, they're expensive, costing between ?25,000 and ?40,000 a unit. But the handheld nose that the British researchers are devising would retail for around ?100, says Julian Gardner, an engineering professor at Warwick.

Gardner envisions all sorts of applications for the nose-on-a-chip, but primarily in the medical field, where it can be used to screen for pathogens. "It will not only sniff out bacteria, but recognize the species and strain," he explains. In the food industry, it could be used to find bacteria that cause spoilage. Environmentally, it could monitor air in water supplies in buildings for bacteria that cause "sick building syndrome." And it could also keep tabs on the air circulating in cars and airplanes. One other potential use would be to incorporate the electronic nose in refrigerators to pinpoint foods that have gone bad.

To get such a sensitive device, the scientists are taking a "neuromorphic" approach, which means they're trying as much as possible to mimic the human nose. "We want to adopt the features of the human olfactory system," Gardner says. To do that, the nose will be fitted with arrays of electrically conductive polymers, which act as sensors. Signal processing systems will process and interpret the signals from the sensors the way a human nose would. When odor molecules hit the olfactory receptor neuron in a real nose, they ignite a spike of voltage along a nerve fiber for processing by the brain. The micronose is being similarly designed, so that when odor molecules bombard the sensors, they trigger spikes of voltage to the processor.

Gardner says the first working prototype should be ready later this year, and a much more sophisticated prototype will be finished in 2003. Already there is industry interest. Osmetech, a British manufacturer of electronic noses is supporting the research, he says. If the research team eventually creates the world's smallest nose, the first thing it's likely to detect is the sweet smell of success.