In this work, we present a novel combination of solid-state ion-selective electrode and field effect transistor (FET) integrated on same platform. Thus, creating an extended gate field effect transistor (EGFET). We have built an electrochemical sensing unit comprised of all solid-state electrodes, an Ag/AgCl reference electrode and ionophore coated gold electrode. Unlike any of the earlier reports, all the electrodes are integrated with a FET in a single plane of the printed circuit board (PCB), hence mitigating the issues of separate wire bonding or external connection between the sensing element and the transducer by using PCB traces. In this work, we demonstrate for the first time, the use of ion sensitive electrode (ISE) in EGFET configuration without degrading the linearity and sensitivity due to the external voltage bias. Potentiometric measurement on our K + ISE shows near Nernstian limit sensitivity (49 mV/decade), low concentration for the limit of detection (10 −6 M), and linearity over a large range of detection(10 −4 M to 1 M).
A solid-state reference electrode based on bilayer coating with poly(p,p'-biphenol) and polyimide films for the gate of field effect transistor.
