The aim of this thesis is to investigate the electrical behaviour of the Electrolyte-Gated-Organic Field-Effect Transistors (EGOFETs) when working with poly[3-(5-carboxypentyl)-thiophene-2,5-diyl] (P3CPenT) as organic semiconductor with polarizable or non-polarizable gate electrodes and provided with an electrolytic solution of deionized water (DI H_2 O) and sodium chloride (NaCl) at different concentrations. These devices are developed with equivalent technological process and are subjected to a complete electrical characterization according to three variables: the gate electrode, the ionic strength of the electrolyte and the scan rate of the measurements. The experiments are performed in a semi-automatized environment which includes a proper microfluidic system. The electrical characterizations are followed by the analysis of some of their main figures of merit to offer a comparison when changing one or more parameters..