Although much research has been done on ISFETs during last decades, several problems still remain unsolved.
Among these, the most important is the extension of ISFETs for measuring species other than hydrogen ions.
A simple solution which has been previously proposed is to chemically modify the surface sites of the insulator
surface by grafting 2 . By this technique, the w x insulatorrelectrolyte interface remains simple and totally
blocking, its potential is determined by surface complexation reaction which can be modeled by the site-binding
model as pH sensitivity 3 . This principle insures a low w x response time and a long lifetime for this simple ISFET
structure, and moreover, there is no indefinite interfacial potential as it is the case for polymeric membranerinsulator
interface 4 . The drawback of the grafting process is that the chemical species are not commercially available,
and a heavy work of chemical synthesis has to be done.
The responses of the grafted ISFETs are sub-nernstian, due
to the low density of grafted sites 5,6 . w x