6. Generalization of the ISFET Concept

As long as the chemical reaction is governed by relatively simple equations like (5.30) or (5.31), the methods described in the previous chapter are quite efficient, but there are cases where one wants to detect large charged molecules or organic polymers. These so called macromolecules exhibit certain structures determining their activity and other properties. In this case, the structure of the molecule is important. Therefore, even if a simple reaction able to change the pH of the solution is available, it is not effective, because it does not provide a way to determine the actual structure of the molecule. However, there is a possibility to utilize an ISFET device to determine the structure of a molecule via the so-called long-range field-effect.

Figure 6.1: Sensing a macromolecule via the long-range field-effect.