Scientific endeavors rarely proceed without unforeseen complications. Before Erik Severin took his baby blue Mazda glc wagon down to Monterey Park, for example, he inquired about fish at his local Ralph’s supermarket. He was told that if his experiment required something that would rot with a pungency worthy of the cliché, he would do best with a saltwater fish, which Ralph’s did not have in stock. So Severin, a graduate student at Caltech, drove to Monterey Park, where he knew of a Chinese grocery by the unlikely, albeit appropriately Californian, name of Shun Fat. From bins of saltwater fish he chose a small kingfish, paid 69 cents, and brought it back to the Noyes Laboratory at Caltech.
Severin installed the kingfish in a glass jar with two glass tubes attached. He arranged for a stream of air to pass through one tube, circulate around the kingfish, absorb its aroma, and proceed out the other tube, over what is technically referred to as an array-based sensor apparatus, although Severin and his labmates call it the prototype electronic nose, or sometimes the noselet. I set the fish on a heating element and let it rot for days, says Severin. Fortunately, his sense of smell is not as keen as some. People would come in, their eyes would start tearing up, and they’d say, ‘My God, this is awful.’
The experiment’s denouement, according to Severin, was a qualified success: the electronic nose could easily distinguish between kingfish fresh and kingfish rancid, but not between, say, two-day rot and three-day rot. Still, Severin and his colleagues have high hopes for the nose. Since their noselet experiments, they’ve built a more sophisticated smelling device--the supernose. Using computerized switches, the supernose can automatically control details like the concentration of the aromas, how fast they flow by, and which odor follows which. I used to have to stick close to the noselet, changing the jars, adjusting valves, and so on, says Severin. I had trouble finding five minutes to run to the bathroom. Now, with the supernose, we set it up, press a button, and leave the nose running for days. Someday, the researchers expect, their supernose will be able to tell a merlot from a Beaujolais, a Heineken from a Budweiser, or anything that human noses, or even dog noses, can do effortlessly.
Until half a dozen years ago, such an olfactory accomplishment seemed safely beyond the reach of technology. With the Caltech achievement, though, the science of electronic noses appears to be in for a paradigm shift. The supernose points the way to an absurdly inexpensive nose on a chip--an electronic sniffer that will cost no more than the average kingfish. Such noses will serve as sensors and aromatic arbiters in uses so widespread that they may someday do for odors what the computer chip has done for pretty much everything else.
The Caltech nose is the change-of-life child of a chemist named Nate Lewis, who became famous in his field not just for the preternaturally early development of his chemical insight, but also for his ability to bring to bear on any single project a merger of disparate scientific talents, effecting a kind of cross-pollination of ideas and then publishing the final word on that particular research. His reputation attracted the brightest graduate students and postdocs in the country, whom he would unleash on problems of his choosing, further enhancing his reputation.
