cost-effectively processed at room temperature, and to volumetrically uptake large amounts of electrolytes, OEDs have recently garnered much interest for applications in bioelectronics. [1][2][3] These include biosensing, energy storage, neural recording, and stimulation, [4,5] drug delivery, [6] and electroceuticals [7] to name a few. Out of the many available architectures, a device of choice that has been heavily investigated in recent years is the organic electrochemical transistor (OECT). In a typical OECT device, the conductivity of a polymer channel, which is probed by a set of source and drain electrodes, is actively controlled by varying the voltage applied between the channel and a third gate electrode both of which reside in the same electrolyte solution. The choice for gate materials, channel materials, electrolyte solutions, and device dimensions can all be designed to obtain desired device characteristics. Thin photolithographically defined devices, for instance, are favored for high speed (>1 kHz) operation whereas large devices with thick polymer channels are more often chosen for their high transconductance. [8][9][10] In general, OECTs operate at relatively low voltages (<1 V) that are suitable for aqueous environments and biological tissues, and have been successfully used to monitor the integrity of barrier tissues, [11,12] in vitro glucose concentrations [13,14] and in vivo neural activities. [15] In OECTs, ions penetrate the whole polymer film, as facilitated by the swelling processes induced by the solvent. While such process is not strictly necessary, as ionic liquids have been shown to also induce transistor-like behavior in conjugated polymers, [16,17] compared to ionic liquid-gated devices, OECTs provide the opportunity to decouple ionic transport, through swelling caused by the electrolyte solvent, from the ability of the ions to generate mobile charges in the polymer.Despite recent advances in device fabrication and materials development, however, only a select few polymers have been found to stably operate as active OECT channels in aqueous environments. Current state-of-the-art OECTs are fabricated using the highly conductive mixture of poly(3,4ethylenedioythiophene) doped with poly(styrene sulphonate) (PEDOT:PSS). [8] While this materials blend exhibits high transconductance and good stability, the details of the chemical composition are often unknown due to the proprietary nature A general method and accompanying guidelines for fabricating both nonaqueous and aqueous based organic electrochemical devices (OECTs) using water-insoluble hydrophobic semiconducting polymers are presented. By taking advantage of the interactions of semiconducting polymers in certain organic solvents and the formation of a stable liquid-liquid interface between such solvents and water, OECTs with high transconductance, ON/OFF ratios of up to 10 6 , and enhancements in stability are successfully fabricated. Additionally, key fundamental properties are extracted of both the device and the active channel ma...

Organic electrochemical transistors (OECTs) have been successfully used as transducers in applications requiring the conversion of ion fluxes to electronic current. These applications range from regular biosensors to sophisticated devices for neuron recording and stimulation. For the rational optimization and understanding of the fundamentals of OECTs and OECT-based applications, however, it is essential to develop in-depth theoretical predictions of experimental data. Here, we review seminal works on modeling both the steady state and transient behavior of OECTs and discuss their strengths and weaknesses. Given that OECTs have been used and applied by a diverse community with very different backgrounds, our intention is to clarify and to extend most of the theoretical developments established so far. Special attention is given to the early models, while trying to make them accessible for everyone in the field of organic bioelectronics.

Cell membranes are fundamental for cellular function as they protect the cell and control passage in and out of the cell. Despite their clear significance, cell membranes are often difficult to study, due to their complexity and the lack of available technologies to interface with them and transduce their functions. Overcoming this complexity by developing simple, reductionist models can facilitate their study. Indeed, lipid layers represent a simplified yet representative model for a cell membrane. Lipid layers are highly insulating, a property that is directly affected by changes in lipid packing or membrane fluidity. Such physical changes in the membrane models can be characterized by coupling them with an electronic transducer. Herein, a lipid monolayer that is stabilized between two immiscible solvents is integrated with an organic electrochemical transistor, which is capable of operating in a biphasic solvent mixture. The platform is used to evaluate how lidocaine, a widely used anesthetic the working mechanism of which is still a matter of debate, interacts with the cell membrane. The present study provides evidence that the anesthetic directly interacts with the lipids in the membrane, affecting their packing and therefore the monolayer permeability. The proposed platform provides an elegant solution for studying compound–membrane interactions.