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The organic electrochemical transistor (OECT) is one of the most versatile building blocks within the bioelectronics device toolbox. While p‐type organic semiconductors have progressed as OECT channel materials, only a few n‐type semiconductors have been reported, precluding the development of advanced sensor‐integrated OECT‐based complementary circuits. Herein, green aldol polymerization is uses to synthesize lactone‐based n‐type conjugated polymers. Fluorination of the lactone‐based acceptor endows a fully locked backbone with a low‐lying lowest unoccupied molecular orbital, facilitating efficient ionic‐to‐electronic charge coupling. The resulting polymer has a record‐high n‐type OECT performance with a high product of mobility and capacitance (µC* = 108 F cm−1 V−1 s−1), excellent mobility (0.912 cm2 V−1 s−1), low threshold voltage (0.02 V), and fast switching speed (τON, τOFF = 336 µs,108 µs). This work demonstrates two types of device architectures and applications enabled by the high performance of this n‐type OECT, i.e., an artificial synapse and a complementary amplifier for detecting α‐synuclein, a potential biomarker of Parkinson's disease. This study shows that materials that enable high gain and fast speed n‐type OECTs can be developed via a green polymerization route, and the diverse form factors that these devices take promise for exploration of other application areas. [ABSTRACT FROM AUTHOR]

The organic photodiode (OPD) is a promising building block for solution‐processable, flexible, lightweight, and miniaturized photodetectors, ideal for wearable applications. Despite the advances in materials used in OPDs, their photocurrent and light responsivity are limited, and alternative methods are required to boost the signal response. Herein, a miniaturized organic electrochemical transistor (OECT) is integrated with an OPD module to unlock the potential of OPDs to acquire physiological signals. In this integrated photodetector (IPD) system, the light intensity regulates the OPD voltage output that modulates the OECT channel current. The high transconductance of the OECT provides efficient voltage‐to‐current conversion, enhancing the signal‐to‐noise ratio on the sensing site. A microscale, p‐type enhancement‐mode OECT with high gm and fast switching speed performs better in this application than depletion‐mode OECT of the same geometry. The IPD achieves a photocurrent and responsivity 318 and 140 times higher than the standalone OPD, respectively. It is shown that with the IPD, the amplitude of the photoplethysmogram signals detected by the OPD is enhanced by a factor of 2.9 × 103, highlighting its potential as a wearable biosensor and to detect weak, often uncaptured, light‐based signals from living systems. [ABSTRACT FROM AUTHOR]

The integration of n‐type (electron‐transporting) polymers with oxidase enzymes has allowed building high‐performance organic electrochemical transistor (OECT) based metabolite sensors. Yet, the operation mechanism of these devices is poorly understood. Here, the process is investigated for the conversion of metabolite oxidation to electrical current in an n‐type organic electrochemical transistor (n‐OECT). By monitoring oxygen (O2), hydrogen peroxide, and pH changes in the electrolyte as well as the potential of each electrical contact of the n‐OECT during glucose detection, light is shed on the physical phenomena occurring at the polymer‐enzyme interface. It is shown that the n‐type film performs O2 reduction reaction in its doped state and that the n‐OECT characteristics are sensitive to O2. A correlation is found between the consumption of electrolyte‐dissolved O2 and the generation of n‐OECT current during the metabolite oxidation. The results demonstrate how the sensitivity of a polymer to O2, species known to deteriorate the performance of many semiconductor devices, becomes a feature to exploit in sensor applications. The importance of in operando analysis of the electrolyte composition and the terminal potentials is highlighted for understanding the operation mechanism of bioelectronic devices and for sensor design and materials development. [ABSTRACT FROM AUTHOR]

• An organic electrochemical transistor (OECT) based on an n-type polymer is developed. • The channel and gate are functionalized with the enzyme, glucose oxidase. • The OECT is integrated with a microfluidic system for real-time glucose monitoring. • Microfluidic integrated OECT sensor shows excellent signal-to-noise ratios and a detection limit of 1 nM. • Transistor configuration allows high signal-to-noise-ratios for metabolite sensing. The organic electrochemical transistor (OECT) can translate biochemical binding events between a recognition unit and its analyte into an electrical signal. We present an OECT comprising an n-type (electron transporting) conjugated polymer-based channel and lateral gate electrode functionalized with the enzyme, glucose oxidase. The device is integrated with a microfluidic system for real-time glucose monitoring in a flow-through manner. The n-type polymer has direct electrical communication with glucose oxidase, allowing glucose detection while surpassing hydrogen peroxide production. The microfluidic-integrated OECT shows superior features compared to its microfluidic-free counterpart, including higher current and transconductance values as well as improved signal-to-noise (SNR) ratios, which enhances the sensor sensitivity and its detection limit. Thanks to the low noise endowed by the integrated microfluidics, the gate current changes upon metabolite recognition could be resolved, revealing that while the relative changes in gate and drain currents are similar, the drain current output has a higher SNR. This is the first demonstration of the integration of a microfluidic system with an n-type accumulation mode OECT for real-time enzymatic metabolite detection. The microfluidic-integrated design provides new insights into the mechanisms leading to high sensor sensitivities, crucial for the development of portable and autonomous lab-on-a-chip technologies. [ABSTRACT FROM AUTHOR]