Organic electrochemical transistors for monitoring complex fluids microstructure and biomolecular sensing

Organic electrochemical transistors (OECTs) are amplifying transducers of chemical and biological signals. In an OECT, a conducting polymer channel connects two electrodes (Source and Drain) and is in contact with an electrolytic medium. The device is completed by a third electrode (Gate) which is directly immersed in the electrolyte solution. When a voltage (VGS) is applied between the Gate and Source, the ionic species contained in the electrolyte are pushed away from the gate electrode and, penetrating in the active channel, interact with the electronic charges modifying the polymer conductivity. Hence, these devices allow to convert and amplify small variations of the ionic currents flowing through the electrolyte into changes of the electronic IDS current. Here, first of all, we show that the response of OECTs based on poly (3,4-hylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) active channels is sensitive to the microstructure features of surfactant-based complex fluids. In the worm-like regime, indeed, the devices behave distinctively from that exhibited when pure surfactant solutions, containing only spherical micelles, are analyzed. Moreover, when immersed in oil/water solutions obtained at different stages of a nano-emulsification process, the OECTs response is clearly correlated with the emulsion microstructures. More recent experiments have been focused on the application of OECTs in the sensing of biomolecules such as Lhomocysteine and L-homocystine. In particular, L-homocysteine is a non-proteinogenic ?-amino acid, whose high blood levels (hyper-homocysteinemia) are a strong and independent cardiovascular risk factor, connected to vascular endothelial injury and inflammation. Here, we discuss preliminary results dealing with the response of OECT in solutions with different concentrations of L-homocystine and L-homocysteine. response of OECT in L-homocystine/L-homocysteine solutions.