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Using organic electrochemical transistors as sensors, the sample-receptor reaction often induces moderate changes only in the drain current dynamics as the gate voltage level is switched. Here, we report an electrochemical sensor circuit including electrochemical transistors based on poly(3,4-ethylenedioxythiophene) doped with polystyrenesulfonate that puts out a static sensor response signal. The circuit includes a sample and a reference transistor that are both driven in the resistive mode at 0.1 V. Measurements were performed on aqueous salt electrolytes ranging from 100 to 500 mM concentrations. The signal-ON sensor circuit provides a tenfold increase in the sensitivity as compared to single transistor sensors. [ABSTRACT FROM AUTHOR]

An all-organic printed electrochemical rectifier is reported. The device is based on a patterned layer of poly(3,4-ethylenedioxythiophene) poly(styrene sulfonate) (PEDOT:PSS) that interfaces a patterned electrolyte top layer. Overlap between the electrolyte layer and the conducting polymer pattern results in the formation of two electrochemically active areas within the conducting polymer pattern. When bias voltage is applied across the conducting polymer pattern, the PEDOT in the negatively biased areas is reduced electrochemically, while the PEDOT in the positively biased area is further oxidized. Reducing PEDOT from its p-doped, pristine state to the neutral state results in a marked loss of electrical conductivity. Due to the unsymmetrical device geometry, the current through the device may be shut off for one polarity of applied bias voltage with an electrical current rectification ratio of 100 compared to the opposite polarity. The output characteristics of a corresponding half wave rectifier as well as those from a full wave bridge rectifier show stable performance at frequencies below 15 Hz. [ABSTRACT FROM AUTHOR]