Surface effect sensors

A form of surface effect sensor that exploits altered surface resistance, or chemiresistors, forms the surface from a mixture of tailored polymers and a finely divided conductive material, such as carbon black, as a thin film on a substrate. They use a number of polymers, 32 in one implementation, with different properties to form an array of chemiresistors. When a vapor is passed over the array,... 

Chapter 12, Explosive Vapor Detection Using Microcantilever Sensors, is representative of a general class of sensors Surface Effect Microsensors that use the change in some mechanical or electrical property of an ultra-small structure to sense and identify a wide variety of molecules. 

The detection principle of field-effect sensors with catalytic metal contacts is based on tbe change of the electric charge at the insulator surface caused by dissociation of the gas molecules by the catalytic material. Adsorbed gas molecules and reaction products form a polarized layer at the metal-insulator interface (Figure 2.1). This gives rise to an electric field in the insulator, which causes the concentration of mobile carriers in the semiconductor underneath the insulator to change. 

The sensitivity and selectivity of the polymeric porphyrin depends not only on the potential of NO to oxidize but also on the fast process of electrochemical NO oxidation, which generates the high current. In addition, surface effects, axial ligation to the central metal in the porphyrin, nature of the central metal (iron > nickel > cobalt zinc, copper), gas permeability through sensor layer(s), and fast removal of NO" " by Nafion are all important in promoting fast and selective oxidation... 

R. Gruden, O. Kanoun, and U. Troltzsch, Influence of surface effects on the characteristic curves of detergent sensors, in 9th International Multi-Conference on Signals, Sensors and Devices, 20.-23. Mdrz 2012, Chemnitz, 2012. 

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