Chemical Sensors and Chemical Sensor Systems: Fundamentals Limitations and New Trends

Chemical sensors are becoming more and more important in any area where the measurement of concentrations of volatile compounds is relevant for both control and analytical purposes. They have also found many applications in sensor systems called electronic noses and tongues. This chapter will first consider fundamentals of sensor science including a brief discussion on the main terms encountered in practical applications, such as: sensor, transducer, response curve, differential sensitivity, noise, resolution and drift. Basic electronic circuits employed in the sensor area will be discussed with a particular emphasis on the noise aspects, which are important for achieving high resolution values in those contexts where measurement of the lowest concentration values of chemicals is the main objective. All the most relevant transducers such as: MOSFET, CMOS, Surface Plasmon Resonance device, Optical Fibre, ISFET, will be covered in some detail including their intrinsic operating mechanisms and showing their limitation and performance. Shrinking effects of these transducers will also be commented on. The electronic nose and electronic tongue will be described as systems able to give olfactory and chemical images, respectively, in a variety of applications fields, including medicine, environment, food and agriculture. Finally some future trends will be outlined in order to predict possible applications derived from today’s micro and nanotechnology developments.