ABSTRACT
It is more than fifteen years ago since the first integrated solid state electrochemical sensors have been described [1,2]. These were ion-sensitive field effect transistors (ISFET) which belong to the group of electrochemical sensors, specifically potentiometric sensors. Since then, other solid state electrochemical and non-electrochemical sensors have appeared and the ISFETs themselves have reached the state of maturity which now brings some of them close to commercialization. This is quite remarkable if we realize that only a relatively few researchers have been working in this area, certainly as compared to the related ion selective electrodes. The obstacles which had to be overcome have been both of the conceptual and practical nature originating from the fact that these devices are the product of integration of two seemingly diverse technologies: solid state device physics and electrochemistry. Soon after the initial explorations of the ISFETs, transistors utilizing enzymatic selectivity [3] and potentiometric solid state sensors based on 18chemical modulation of electron work function [4] have appeared. The purpose of this paper is to review the present state of development of these devices both from a theoretical and practical point of view.
