Chemical field-effect transistor

[3] A concentration gradient between the solution and the gate electrode arises due to a semi-permeable membrane on the FET surface containing receptor moieties that preferentially bind the target analyte.

[3] This concentration gradient of charged analyte ions creates a chemical potential between the source and gate, which is in turn measured by the FET.

[5] Anion-sensing is more complicated than cation-sensing in ChemFETs due to many factors, including the size, shape, geometry, polarity, and pH of the species of interest.

Dutch engineer Piet Bergveld studied the MOSFET and realized it could be adapted into a sensor for chemical and biological applications.

[10] In the ISFET structure, the metal gate of a standard MOSFET is replaced by an ion-sensitive membrane, electrolyte solution and reference electrode.

The schematic view of a ChemFET. Source, drain, and gate are the three electrodes used in a FET system. The electron flow takes place in a channel between the drain and source. The gate potential controls the current between the source and drain electrodes.