Dr. Nate Lewis patiently adds a chemical to a machine in his laboratory. The chemical smells a little bit like rotten (变质的) fish. We know that because we have our noses to smell and know it. Dr. Lewis, however, wonders if his machine can smell the chemical, too. The machine is actually an electronic nose.
You might wonder why anyone would want to build an electronic nose. After all, if you want to smell something, you can just breathe in through your own nose. For example, it's common for someone to smell a bottle of milk to check if it has gone bad. But imagine if a person had to smell the thousands of bottles of milk that farms produce every day-all that milk would go bad long before the testing was done! The food industry uses electronic noses every day to test the foods for freshness.
There are millions of different smells in the world. How can our nose tell the difference between all these smells? Scientists know there are cells in our noses that act as smell detectors (探测器). They think that a certain pattern of cells respond (回应) to every smell. Our nose creates a fingerprint for each smell using this pattern. Our brain understands all the odor (气味) fingerprints, Dr. Lewis's electronic nose works like the human nose to detect odor fingerprints.
The biggest difference, however, between human noses and the electronic noses that have been built so far is the brain. We need our brains to explain each smell we meet. But the electronic nose can only identify the chemical makeup of a smell while our brain can decide whether something your nose smells is good or bad. "It doesn't know which smells it likes and which is terrible because it can't think." explains Dr. Lewis.
Dr. Lewis is working on how to make the electronic nose get smarter. Maybe someday fridges with electronic noses will tell you when food has gone bad, or your locker room will use them to remind you to wash your sports clothes. There are many possible uses for a machine to take the place of the human nose. Every day scientists are getting closer to building a more perfect electronic nose.
