With their similarity to the organs of the most advanced creatures that inhabit the Earth, sensors are regarded as being the "senses of electronics" arti?cial eyes and ears that are capable of seeing and hearing beyond the range of - man perception; electronic noses and tongues that can recognise odours and ?avours without a lifetime training; touch that is able not only to feel the texture and temperature of the materials but even to discern their chemical compo- tion. Among the world of chemical sensors, optical devices (sometimes termed "optodes," from the Greek "the optical way") have...