Organic electrochemical transistors monitoring micelle formation

Organic electrochemical transistors (OECTs) exploit electrolyte gating to achieve the transduction of ionic currents. Therefore, they are ideally suitable to sense different chemo/bio species dissolved in the electrolyte. Current modulation in OECTs relies on doping or dedoping of the OECT channel by electrolyte ions. Nevertheless the role played by the specific physicochemical properties of an electrolyte on OECT operation is largely unknown. Here we investigate OECTs, making use of aqueous solutions of the micelle-forming cationic surfactant cetyltrimethylammonium bromide (CTAB) as the electrolyte. Micelle-forming salts are remarkable model systems to study the doping and dedoping mechanism of OECTs, because the aggregation of dissociated ions into micelles at the critical micelle concentration permits to modify the size and the type of the species that dope or dedope the OECT channel in situ. The current modulation of OECTs using a CTAB electrolyte shows a marked increase close to the critical micellar concentration. The measurement of the transistor's drain current as a function of CTAB concentration provides a simple, fast method to detect the formation of micelles from dissociated ions.