Transduction capacitor

As discussed above the key to any biosensor is in the transduction mechanism. The mechanism of the capacitive affinity sensor is shown in Figure 2. The sensor consists of a planar capacitor composed of interdigi-tated metal fingers on an insulating substrate. This structure is then coated with a thin layer of a passivation material. The role of the passivation material is to protect the metal structure from deterioration from contact with the solution. A sample of the analyte or an analog retaining the ability to bind an antibody to the analyte is covalently bound to the... 

Chemical modulation of work function (WF) is one mode of transduction on which a whole new class of chemical sensors can be based [49]. The measurement of WF requires that the chemically sensitive layer is capaci-tively coupled to the rest of the sensor at one interface. This requirement is satisfied in the vibrating capacitor (Kelvin probe) and in all solid-state devices utilizing the insulated gate. Typical examples are so-called chemically sensitive diodes and chemically sensitive field-effect transistors. 

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