Field-effect transistors fabricated from semiconducting conjugated polymers are candidates for flexible and low-cost electronic applications. Here, we demonstrate that the mobility of high molecular weight (300 kDa) regioregular, poly[4-(4,4-dihexadecyl-4H-cyclopenta[1,2-b:5,4-b']dithiophen-2-yl)-alt-[1,2,5]thiadiazolo[3,4-c]pyridine] can be significantly improved by introducing long-range orientation of the polymer chains. By annealing for short periods, hole mobilities of 6.7 cm(2)/(V s) have been demonstrated. The transport is anisotropic, with a higher mobility (approximately 6:1) parallel to the polymer backbone than that perpendicular to the polymer backbone.

Early detection of malign patterns in patients’ biological signals can save millions of lives. Despite the steady improvement of artificial intelligence–based techniques, the practical clinical application of these methods is mostly constrained to an offline evaluation of the patients’ data. Previous studies have identified organic electrochemical devices as ideal candidates for biosignal monitoring. However, their use for pattern recognition in real time was never demonstrated. Here, we produce and characterize brain-inspired networks composed of organic electrochemical transistors and use them for time-series predictions and classification tasks using the reservoir computing approach. To show their potential use for biofluid monitoring and biosignal analysis, we classify four classes of arrhythmic heartbeats with an accuracy of 88%. The results of this study introduce a previously unexplored paradigm for biocompatible computational platforms and may enable development of ultralow–power consumption hardware-based artificial neural networks capable of interacting with body fluids and biological tissues.

Organic electrochemical transistors (OECTs) are an emerging class of devices which operate in electrolytic solution and show controllable memory effects. For these reasons, OECT hold great potential for applications in bioelectronics and neuromorphic computing. Among the methods proposed to fabricate OECT channels, electropolymerization stands out because it allows to produce electrical connections on the substrates on‐demand and further modify them to adjust their electrical properties to meet circuit requirements. However, the practical application of this method is hampered by the difficulty in controlling the growth direction as well as the morphology of the film, resulting in a large device‐to‐device variability and limiting the down‐scaling of the devices. In this study, AC‐electropolymerization is proposed to produce directionally controlled channels. The method allows to adjust physical properties such as resistance and capacitance by varying the polymerization parameters, such as voltage, frequency, and salt concentration. The growth mechanism, material morphology, and network topology is investigated, and the advantages of this approach by showing tunable neuromorphic features and the possibility to scale down the channels to the micrometer scale is demonstrated.

Entirely photopatternable solid organic electrochemical transistors were fabricated and their excellent performance and pronounced hysteretic behavior studied in detail.

Precise monitoring of changes in ion concentration in electrolytic environments is of growing interest in multiple fields, such as bioelectronics, food packaging, agricultural sensing, and control of industrial chemical processes. However, combining sensitivity, ion-selectivity, and cost reduction has been proven to be a difficult task. In this work, we use an organic mixed ionic–electronic conductor [poly­(3,4-ethlyenedioxythiophene) doped with poly­(styrene sulfonate), PEDOT:PSS] to realize a sensor showing good selectivity and sensitivity to alkali ions without employing ion-selective membranes. We achieve this by combining a straightforward impedance analysis and static current–voltage measurement of an organic electrochemical transistor. We show that, after a calibration stage, the composition of unknown solutions can be determined. The ease of fabrication of this system, combined with the proposed measurement method and the potential biocompatibility of the organic semiconductor, makes such a sensor suitable for applications in biological environments, such as within the body or soil.