ARTIFICIAL OLFACTORY IMAGES FROM A CHEMICAL SENSOR USING A LIGHT-PULSE TECHNIQUE

THERE is much interest in the use of chemical sensor arrays, in conjunction with pattern-recognition routines, for developing artificial olfactory devices-'electronic noses'-which can characterize the chemical composition of gas mixtures 1-5. Here we describe a technique that uses a continuous sensing surface and a detection method involving a scanning pulsed light source, to generate images that represent a fingerprint of the gases detected. The detector is a large-area field-effect device with a number of different catalytic metals constituting the detecting surface (the device's active gate) 6,7. A pulsed light beam scanned across this surface generates a photocapacitive current that varies with the value of the surface potential 8,9. A continuous sensing surface of this type provides information that would require an array of hundreds of discrete sensors. The technique also provides a new means of studying the coupling between the electronic properties of catalytic metals and chemical reactions taking place on their surfaces.