Michael J. Vellekoop
Sensors that apply physical effects to determine chemical or biochemical measurands have generated significant interest in the past decade. In comparison to direct chemical sensors, where chemical-sensitive films are applied, physical chemosensors and biosensors have a simpler design and easier fabrication, a lower contamination sensitivity, and better aging properties. In this chapter, an introductory overview is given of the design and application of integrated physical chemosensors and biosensors.
Several definitions of chemical sensors and biosensors can be found in the literature. The definition given by Schultz and Taylor  reads: ‘measurement devices which utilize chemical or biological reactions to detect and quantify a specific analyte or event’. Goepel and Schierbaum  say ‘chemical sensors are (miniaturized) devices which convert a chemical state into an electrical signal’. In a study by the National Materials Advisory Board . chemical sensors are defined as ‘devices or instruments that determine the detectable presence, concentration, or quantity of a given analyte’. Others as well add the term ‘real-time measurement’.
Although these definitions seem similar, some distinct differences can be observed. The first one mentions the use of a chemical reaction, while the second definition talks about ‘a chemical state’. The third definition includes ‘instruments’, while the other two refer to ‘devices’. ...