According to the U.S. "Science Daily" website on February 15th, for many years humans have relied on the miracle of biological evolution -sniffer police dogs- to detect explosives and drugs in airports. On the surface, dog's nose can sniff out a variety of odors, be it a single odor or mixed odors, with an accuracy up to one part in a trillion. But dogs are expensive, training dogs takes a lot of time, and some environments are very dangerous for dogs. So recently researchers have developed various chemical sensing technologies, or artificial dog noses.