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Organic electrochemical transistors (OECTs) based complementary inverters have been considered as promising candidates in electrophysiological amplification, owing to their low power consumption, and high gain. To create complementary inverters, it is important to use highly stable p‐type and n‐type polymers with well‐balanced current. In this study, the electrochemical stability of p‐type ladder‐conjugated polymer‐based OECT is improved through an annealing process that maintains its doped‐state drain current from 76% to 105% after 4,500 cycles in ambient environment. Next an OECT‐based complementary inverter made from p‐type and n‐type ladder‐conjugated polymers (PBBTL and BBL) that possess ultra‐low power consumption (≈170 nW), high gain (67 V/V), and high noise margin (92%) with full rail‐to‐rail swing, is presented. Furthermore, its potential for amplifying the envelope of surface electromyography (EMG) for robotic hand control is demonstrated. The high variation in the output (0.35 V) allows the amplified EMG signals to be directly captured by a commercial analog‐to‐digital converter, which in turn controls the robot hand to grasp different objects with low delay and low noise. These results demonstrate the capability of OECT inverter‐based amplifier in future signal processing‐free human‐machine interface, particularly useful for prosthetic control and gesture control applications. [ABSTRACT FROM AUTHOR]

The development of organic electrochemical transistors (OECTs) capable of maintaining their high amplification, fast transient speed, and operational stability in harsh environments will advance the growth of next‐generation wearable and biological electronics. In this study, a high‐performance solid‐state OECT (SSOECT) is successfully demonstrated, showing a recorded high transconductance of 220 ± 59 S cm−1, ultrafast device speed of ≈10 kHz with excellent operational stability over 10 000 switching cycles, and thermally stable under a wide temperature range from −50 to 110 °C. The developed SSOECTs are successfully used to detect low‐amplitude physiological signals, showing a high signal‐to‐noise‐ratio of 32.5 ± 2.1 dB. For the first time, the amplifying power of these SSOECTs is also retained and reliably shown to collect high‐quality electrophysiological signals even under harsh temperatures (−50 and 110 °C). The demonstration of high‐performing SSOECTs and its application in harsh environment are core steps toward their implementation in next‐generation wearable electronics and bioelectronics. [ABSTRACT FROM AUTHOR]

Recently emerged on‐skin electronics with applications in human–machine interfaces and on‐body healthy monitoring call for the development of high‐performance skin‐like electrodes and semiconducting polymers. The development of waterproof and breathable membranes that can provide a high level of protection for human skins and a comfortable contact between electronics and skin are the pressing demands for on‐skin electronics. However, major challenges remain, such as the limited mechanical durability and permeability of gas and liquid, hindering long‐term stability and reusability. Herein, a fibrous electrolyte containing polymer matrix and ionic liquid, which is highly robust, breathable, waterproof, and conformal with human skin is reported. Serving as fibrous substrate and electrolyte of organic electrochemical transistors (OECTs), a high transconductance of ≈0.8 mS, stability over pulsing and time (≈1000 cycles and 30 days) are achieved. The softness of fibrous OECTs enables a comfortable contact after attaching to human skin, which can reduce the interfacial impedance to achieve a high‐quality local amplification of the electrocardiography signals (signal‐to‐noise ratio of 21.7 dB) even in skin squeezed state or after one week. These results indicated that our fibrous OECTs have huge potential for versatile on‐skin electronics such as non‐invasive medical monitoring, soft sensors, and textile electronics. [ABSTRACT FROM AUTHOR]

The ability to operate in aqueous environments makes poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate), PEDOT:PSS, based organic electrochemical transistors (OECTs) excellent candidates for a variety of biological applications. Current research in PEDOT:PSS based OECTs is primarily focused on improving the conductivity of PEDOT:PSS film to achieve high transconductance (gm). The improved conductivity and electronic transport are attributed to the formation of enlarged PEDOT‐rich domains and shorter PEDOT stacking, but such a change in morphology sacrifices the ionic transport and, therefore, the doping/de‐doping process. Additionally, little is known about the effect of such morphology changes on the gate bias that makes the maximum gm (VGPeak), threshold voltage (VT), and transient behavior of PEDOT:PSS based OECTs. Here, the molecular packing and nanostructure of PEDOT:PSS films are tuned using ionic liquids as additives, namely, 1‐Ethyl‐3‐methylimidazolium (EMIM) as cation and anions of chloride (Cl), trifluoromethanesulfonate (OTF), bis(trifluoromethylsulfonyl)imide (TFSI), and tricyanomethanide (TCM). It is demonstrated that an optimal morphology is realized using EMIM OTF ionic liquids that generate smaller fibril‐like PEDOT‐rich domains with relatively loose structures. Such optimal morphology improves ion accessibility, lowering the gate bias required to completely de‐dope the channel, and thus enabling to achieve high transconductance, fast transient response, and at lower gate bias window simultaneously. [ABSTRACT FROM AUTHOR]