Organic Electrochemical Transistor Device Research Articles

The Impact of Non‐Monolithic Semiconductor Capacitance on Organic Electrochemical Transistors Performance and Design

AbstractThe existing device models for organic electrochemical transistors (OECTs) fail to provide any device design guidelines for optimized performance parameters such as transconductance that are pivotal for the applications OECTs in sensing. Moreover, the current models are based on the questionable assumption of a homogenous organic semiconductor layer, and all predict a linear behavior of the resistance with the OECT channel length. Consequently, the experimentally observed nonlinear resistance behavior in OECTs has been overlooked thus far. Here, an OECT device model is developed that accurately describes the nonlinear behavior of the OECT channel resistance and offers the first guidelines for maximizing transconductance. The model is inherently nonlinear and the nonlinearity stem from the non‐monolithic capacitance of the organic semiconductor layer. Moreover, the model provides a consistent and reliable estimations for the contact resistance in OECTs. The success of the model in accurately describing and providing predictions of the OECT operation by relating the device's geometrical parameters with electrochemical parameters of the semiconductor layer paves the way toward unlocking OECT potentials in diverse applications, from biosensing to neuromorphic computing and flexible electronics.

Ultra‐Low Threshold Voltage in N‐Type Organic Electrochemical Transistors Enabled by Organic Mixed Ionic‐Electronic Conductors with Dual Electron‐Withdrawing Substitutions

AbstractAchieving low threshold voltage (Vth) in organic electrochemical transistors (OECTs) is essential for minimizing power consumption and enhancing sensitivity in bioelectronic devices. However, obtaining OECT materials with ultra‐low Vth, close to 0 V for n‐type conjugated polymers remains challenging. Here, a conjugated polymer FBDOPV‐CNTVT is introduced, which features a rigid backbone structure and high electron deficiency, leading to an exceptionally low lowest unoccupied molecular orbital (LUMO) energy level of −4.67 eV, achieved through dual electron‐withdrawing substitutions. With its ultra‐low LUMO energy level, FBDOPV‐CNTVT exhibits high susceptibility to electrochemical doping, even demonstrating efficient doping near 0 V. Consequently, the OECT device employing FBDOPV‐CNTVT as the active material shows an ultra‐low Vth of 7.5 mV, setting a new record for the Vth of n‐type OECT devices. Furthermore, FBDOPV‐CNTVT exhibits a µC* value of 6.13 F cm−1 V−1 s−1 and retains ≈85% of its current after 2000 s cycling. This study highlights the potential of conjugated polymers with dual electron‐withdrawing substitutions to achieve ultra‐low LUMO energy levels, effectively reducing the Vth of n‐type OECT devices and promising advancements in bioelectronics.

Correlation of Processing and Structure in an Ethylene-Glycol Side-Chain Modified Polythiophene via Combined X-Ray Scattering and 4D Scanning Transmission Electron Microscopy.

The results of a combined grazing incidence wide-angle X-ray scattering (GIWAXS) and 4D scanning transmission microscopy (4D-STEM) analysis of the effects of thermal processing on poly(3[2-(2-methoxyethoxy)ethoxy]-methylthiophene-2,5-diyl) are reported, a conjugated semiconducting polymer used as the active layer in organic electrochemical transistor devices. GIWAXS provides a measure of overall crystallinity in the film, while 4D-STEM produces real-space maps of the morphology and orientation of individual crystallites along with their spatial extent and distribution. The sensitivity of the 4D-STEM detector allows for collection of electron diffraction patterns at each position in an image scan while limiting the imparted electron dose to below the damage threshold. The effects of heat treatment on the distribution and type of crystallites present in the films isdetermined.

Surface-tension-directed gate functionalization in organic electrochemical transistor for wearable sweat lactate monitoring

Wearable sweat lactate detection holds significant potential for applications in healthcare and exercise performance evaluation. Organic electrochemical transistors (OECTs) is emerging as an efficient platform in wearable lactate sensing by integrating an electron transfer interface between the electrode and the bio-catalytic layer. In this study, we demonstrated a wearable OECT designed for dynamic lactate monitoring in sweat through a one-step deposition of gold nanoparticles (Au NPs) on the gate electrode. Utilizing the simple surface-tension-directed deposition strategy, this method ensures a uniform distribution of Au NPs with high catalytic activity, enabling rapid and sensitive lactate signal transition. Herein, the OECT device exhibits a linear detection range for sweat lactate from tens of micromolars to hundreds of millimolars (r² > 0.97), along with high selectivity and long-term stability in human sweat. Furthermore, we successfully employed this flexible OECT sensor for real-time lactate monitoring system during various physical activities, highlighting its potential for non-invasive evaluation of fatigue and exercise performance in athletes. This work provides an easy-to-use prototype for continuous physiological monitoring, enhancing personalized healthcare and training management.

Performance of Organic Electrochemical Transistors with Ionic Liquid Crystal Elastomers as Solid Electrolytes.

Organic electrochemical transistors (OECTs) have emerged as attractive devices for bioelectronics, wearable electronics, soft robotics, and energy storage devices. The electrolyte, being a fundamental component of OECTs, plays a crucial role in their performance. Recently, it has been demonstrated that ionic liquid crystal elastomers (iLCEs) can be used as a solid electrolyte for OECTs. Their capabilities, however, have only been shown for relatively large size substrate-free OECTs. Here, we study the influence of the different alignments of iLCEs on steady state and transient behavior of OECTs using a lateral geometry with source, drain, and gate in the same plane. We achieve excellent electrical response with an ON/OFF switching ratio of >105 and minimal leakage current. The normalized maximum transconductance gm/w of the most sensitive iLCE was found to be 33 S m-1, which is one of the highest among all solid-state-based OECTs reported so far. Additionally, iLCEs show high stability and can be removed and reattached multiple times to the same OECT device without decreasing performance.

High Performance Organic Mixed Ionic‐electronic Polymeric Conductor with Stability to Autoclave Sterilization

We present a series of newly developed donor‐acceptor (D‐A) polymers designed specifically for organic electrochemical transistors (OECTs) synthesized by a straightforward route. All polymers exhibited accumulation mode behavior in OECT devices, and tuning of the donor comonomer resulted in a three‐order‐of‐magnitude increase in transconductance. The best polymer gFBT‐g2T, exhibited normalized peak transconductance (gm,norm) of 298±10.4 S cm‐1 with a corresponding product of charge‐carrier mobility and volumetric capacitance, μC*, of 847 F V‐1 cm‐1 s‐1 and a μ of 5.76 cm2 V‐1 s‐1, amongst the highest reported to date. Furthermore, gFBT‐g2T exhibited exceptional temperature stability, maintaining the outstanding electrochemical performance even after undergoing a standard (autoclave) high pressure steam sterilization procedure. Steam treatment was also found to promote film porosity, with the formation of circular 200 – 400 nm voids. These results demonstrate the potential of gFBT‐g2T in p‐type accumulation mode OECTs, and pave the way for the use in implantable bioelectronics for medical applications.

High Performance Organic Mixed Ionic-Electronic Polymeric Conductor with Stability to Autoclave Sterilization.

We present a series of newly developed donor-acceptor (D-A) polymers designed specifically for organic electrochemical transistors (OECTs) synthesized by a straightforward route. All polymers exhibited accumulation mode behavior in OECT devices, and tuning of the donor comonomer resulted in a three-order-of-magnitude increase in transconductance. The best polymer gFBT-g2T, exhibited normalized peak transconductance (gm,norm) of 298±10.4 S cm-1 with a corresponding product of charge-carrier mobility and volumetric capacitance, μC*, of 847 F V-1 cm-1 s-1 and a μ of 5.76 cm2 V-1 s-1, amongst the highest reported to date. Furthermore, gFBT-g2T exhibited exceptional temperature stability, maintaining the outstanding electrochemical performance even after undergoing a standard (autoclave) high pressure steam sterilization procedure. Steam treatment was also found to promote film porosity, with the formation of circular 200-400 nm voids. These results demonstrate the potential of gFBT-g2T in p-type accumulation mode OECTs, and pave the way for the use in implantable bioelectronics for medical applications.

Flexible Organic Electrochemical Transistor Based on Conjugated Conducting Polymers

— The use of organic electrochemical transistors (OECTs) based on conjugated polymers has gained significant recognition owing to their impressive performance, flexibility, ease of fabrication, and suitability for specific applications where solid-state transistors may not be efficiently employed. Key advantages of OECT technology, such as simple device architecture, robustness in ambient or aqueous environments, straightforward additive manufacturing processes, low operational voltage, and compatibility with flexible, rough, stretchable, and large-area substrates, underscore its significance in various applications. These applications span the sensing of glucose [1], bacteria [2], dopamine [3], DNA [4], lactate [5], cell activities [6], and electrophysiological signals [7]. Notably, the absence of the necessity for a reference electrode, a crucial feature for wearable and textile sensors compared to three electrode-based electrochemical sensors, stands out. In this context, we have fabricated a side-gated OECT on a flexible polyethylene terephthalate (PET) substrate through a scalable screen-printing process where the source, drain, and gate terminals are screen-printed using silver (Ag) conductive ink. The semiconducting channel material employed is polyethylene dioxythiophene: polystyrene sulfonate (PEDOT: PSS), which is spin-coated. Additionally, poly methyl methacrylate (PMMA) has been spin-coated to serve as the dielectric. The OECT operates by volumetric gating of the channel through a gel electrolyte containing poly sodium 4-styrene sulfonate (PSSna), enabling polarization of the gate and channel to induce charge accumulation or depletion, driven by the application of a gate-source voltage. The OECT device structure demonstrated switching from the "ON" to "OFF” state with the application of a positive gate voltage, indicating its functionality as a p-type depletion mode transistor. Additionally, the OECT displayed a transconductance (gm) of 6.25×10-4 A/V, mobility (µ) of 1.242×1010 cm2 /Vs, and a threshold voltage (Vth) of -0.39 V, with the on/off ratio being relatively low at 7.22. The repeatability was confirmed through the fabrication of three devices that exhibited nearly identical behavior. Furthermore, in pursuit of faster response time, lower operating voltage, and miniaturization, additional work involves downscaling the active area length to 100µm from the reported 4mm active area length. The fabrication method not only holds the capability for large-scale production with a high yield in a cost-effective manner but also opens up possibilities for applications requiring swift design changes and digitally enabled direct-write techniques. Future work emphasizes functionalizing the electrolyte used in OECT to detect biomolecules such as glucose, pH, and ion species. Thus, this research underscores the potential usability of fabricated OECTs in various high-performance chemical and biological sensing applications. REFERENCES Tang, H.; Yan, F.; Lin, P.; Xu, J.; Chan, H.L.W. Highly Sensitive Glucose Biosensors Based on OrganicElectrochemical Transistors Using Platinum Gate Electrodes Modified with Enzyme and Nanomaterials.Adv. Funct. Mater. 2011, 21, 2264–2272. [CrossRef]He, R.-X.; Zhang, M.; Tan, F.; Leung, P.H.M.; Zhao, X.-Z.; Chan, H.L.W.; Yang, M.; Yan, F. Detection of bacteria with organic electrochemical transistors. J. Mater. Chem. 2012, 22, 22072–22076. [CrossRef]Gualandi, I.; Tonelli, D.; Mariani, F.; Scavetta, E.; Marzocchi, M.; Fraboni, B. Selective detection of dopamine with an all PEDOT:PSS Organic Electrochemical Transistor. Sci. Rep. 2016, 6, 35419. [CrossRef]Tao, W.; Lin, P.; Hu, J.; Ke, S.; Song, J.; Zeng, X. A sensitive DNA sensor based on an organic electrochemical transistor using a peptide nucleic acid-modified nanoporous gold gate electrode. RSC Adv. 2017, 7, 52118–52124. [CrossRef]Braendlein, M.; Pappa, A.-M.; Ferro, M.; Lopresti, A.; Acquaviva, C.; Mamessier, E.; Malliaras, G.G. Owens, R.M. Lactate Detection in Tumor Cell Cultures Using Organic Transistor Circuits. Adv. Mater. 2017, 1605744.Lin, P.; Yan, F.; Yu, J.; Chan, H.L.W.; Yang, M. The Application of Organic Electrochemical Transistors in Cell-Based Biosensors. Adv. Mater. 2010, 22, 3655–3660Liang, Y.; Ernst, M.; Brings, F.; Kireev, D.; Maybeck, V.; Offenhäusser, A.; Mayer, D. High Performance Flexible Organic Electrochemical Transistors for Monitoring Cardiac Action Potential. Adv. Healthc. Mater. 2018, 1800304. [CrossRef] Figure 1

(Invited) Designing Materials for Organic Electrochemical Transistors

Organic electrochemical transistors (OECTs) have gained a renewed interest in the field or bioelectronics and biosensors. OECTs act as amplifiers and therefore provide high signal/noise ratio for detecting a wide range of biomolecules or physiological signals. A critical component of the OECTs is the channel material, which is an organic mixed ionic-electronic conductor (OMIEC). In simpler terms, OMIECs are (semi)conducting polymers that can transport electronic charges (electrons or holes), transport ionic charges, and display a capacitive behavior (reversible doping/dedoping process). Amongst OMIECs, the polyelectrolyte complex PEDOT:PSS has been the most widely used, likely due to its commercial availability and ease of use as a water dispersion. PEDOT:PSS, however, is a black box with a proprietary composition and does not have particularly reactive handles for functionalization. As such, it is difficult to modify its properties for specific applications in biosensing. In this talk, I will describe my team’s work in understanding PEDOT:PSS and methods for modifying it using covalent organic chemistry. Our principal approach is to control the synthesis of the PSS polymer and/or modify it with functional units by using random or block copolymerization. This approach was successfully used to achieve high performance OECT devices and new conductive materials with temperature or light-response.

Tailoring the Density of State of n-Type Conjugated Polymers through Solvent Engineering for Organic Electrochemical Transistors.

Conjugated polymers with ethylene glycol-type side chains are commonly used as channel materials in organic electrochemical transistors (OECTs). To improve the performance of these materials, new chemical structures are often created through synthetic routines. Herein, we demonstrate that the OECT performance of these polymers can also be improved by changing their density-of-state (DOS) profile through solvent engineering. Depending on the solvent polarity, it solvates the backbone and side chains of the conjugated polymer differently, leading to differences in molecule orientation, π-stacking paracrystallinity, and film defects, such as grain boundaries and pinholes. This then results in a change in the DOS profile of the polymer. A more intense and narrow-width DOS distribution is usually observed in organic films with an "edge on" orientation and fewer film defects, while films with a "face on" orientation and apparent defects show a broadened DOS profile. The OECT devices that use the polymer film with a more intense and narrow-width DOS profile exhibit a better-normalized transconductance and figure-of-merit μC* than those with a broadened DOS profile (0.74 to 4.29 S cm-1 and 3.5 to 14.3 F cm-1 V-1 s-1). This study provides useful insights into how the DOS profile affects the mixed ionic-electronic conduction performance and presents a new avenue for improving n-type OECT materials.

A universal pre-charging method for enhancing transient speed in Organic Electrochemical Transistors

Organic electrochemical transistors (OECT) have shown great potential in diverse applications; however, in many OECTs, their slow transient response has thus far limited their practical use. One reason for the slow response is the complex interplay between lateral and vertical ion transport that has so far been poorly understood. In this work, we study the impact of lateral ion transport on OECT transient response, introduce a robust pre-charging method to manipulate the slow lateral ion transport. This approach leads to quicker ion redistribution and improved switching speeds. We show the general utility of pre-charging method in enhancing the switching speeds across various material systems, characterized by both low and high ion mobilities, and across different device architectures, achieving nearly symmetric speeds for both on-switching and off-switching. Moreover, we showcase the efficacy of the pre-charging method in enabling slow OECTs to capture rapid signals in real-world applications. Our findings present a groundbreaking strategy for enhancing the response times of OECT devices and deepening our understanding of the transient mechanisms in OECT device.

Indacenodithiophene‐based single‐component ambipolar polymer for high‐performance vertical organic electrochemical transistors and inverters

AbstractSingle‐component ambipolar polymers are highly desirable for organic electrochemical transistors (OECTs) and integration into complementary logic circuits with reduced process complexity. However, they often suffer from imbalanced p‐type and n‐type characteristics and/or stability issues. Herein, a novel single‐component ambipolar polymer, namely, gIDT–BBT is reported based on indacenodithiophene (IDT) as the electron donor, benzobisthiadiazole (BBT) as the electron acceptor and oligo ethylene glycol (OEG) as the side chain. Benefitting from the extended backbone planarity and rigidity of IDT, pronounced electron‐withdrawing capability of BBT, favored ionic transport from OEG together with vertical OECT device structure, a nearly balanced ambipolar OECT performance is achieved for gIDT–BBT, revealing a high transconductance of 155.05 ± 1.58/27.28 ± 0.92 mS, a high current on/off ratio >106 and an excellent operational stability under both p‐type and n‐type operation conditions. With gIDT–BBT in hand, furthermore, vertically stacked complementary inverters are successfully fabricated to show a maximum voltage gain of 28 V V−1 (VIN = 0.9 V) and stable operation over 1000 switching cycles, and then used for efficient electrooculogram recording. This work provides a new approach for the development of ambipolar single‐component organic mixed ionic–electronic conductors and establishes a foundation for the manufacture of high‐performance ambipolar OECTs and associated complementary circuits.

Influence of reaction cell electrodes on organic electrochemical transistors

Organic electrochemical transistors (OECTs) hold great potential in various applications, including biosensing and neural network computation. Traditional “all-in-one” OECT device architecture faces the problems of unclear amplification mechanisms and complex side reactions, to name a few. The reaction cell OECT (RC-OECT) device architecture, proposed by Ting et al. [Adv. Funct. Mater. 31(19), 2010868 (2021)], effectively resolves these problems. Furthermore, in many applications of OECTs, such as high throughput (bio)sensing, an OECT device array instead of a single OECT is needed. Therefore, the size (area) of the OECT device, which represents the amount of occupied chip real estate and the integration of the device, matters. In this paper, we developed a hydrogen peroxide sensor based on the RC-OECT. We utilized an RC cathode modified by the poly(3,4-ethylenedioxythiophene) polystyrene sulfonate film and a Ag/AgCl OECT gate electrode for facilitating device integration, varied RC anode area, and achieved optimization of at least one of the two parameters, sensitivity and lower limit of detection (LLoD), in conjunction with the level of integration of the device. Multiple quantitative sensitivity metrics have been adopted in this work. We also evaluated the correlation between RC anode area and LLoD. In addition, a mechanistic analysis of the RC-OECT device structure, in terms of faradic and non-faradaic currents, was carried out to illustrate the interplay between sensing performance and the electrode area of the reaction cell. This mechanistic analysis provides insights for miniaturizing OECT devices with the RC-OECT architecture.

The unexpected fast polymerization during the synthesis of a glycolated polythiophene.

Conjugated polymers with ethylene glycol side chains are emerging as ideal materials for bioelectronics, particularly for application in organic electrochemical transistors (OECTs). To improve the OECT device performance, it is important to develop an efficient synthetic strategy that will provide access to novel high-performing materials besides focusing on molecular design. While a lot of efforts are being devoted to designing of new polymers by modifying the glycol side chains, understanding how their nature affects the polymerization kinetics and eventually the polymer structure and properties is not known. In this work, we have studied the influence of the content of the ethylene glycol side chain and its linkage on the formation of the active Grignard monomer species upon Grignard metathesis in three thiophene derivatives. A strong dependence of the monomer's concentration on polymerization was noted in our study indicating that for synthesizing P3MEEMT, a high-performing OECT material, by Kumada catalyst transfer polymerization (KCTP) a minimum of 0.15 M monomer is needed. Furthermore, kinetic studies by GPC show uncontrolled polymerization behavior contrary to the controlled chain growth characteristics of the KCTP.

Orientation and morphology control in acid-catalyzed covalent organic framework thin films.

As thin films of semiconducting covalent organic frameworks (COFs) are demonstrating utility for ambipolar electronics, channel materials in organic electrochemical transistors (OECTs), and broadband photodetectors, control and modulation of their thin film properties is paramount. In this work, an interfacial growth technique is utilized to synthesize imine TAPB-PDA COF films at both the liquid-liquid interface as well as at the liquid-solid interface on a Si/SiO2 substrate. The concentration of acetic acid catalyst in the aqueous phase is shown to significantly influence the thin film morphology of the liquid-solid growth, with concentrations below 1 M resulting in no film nucleation, concentrations of 1-4 M enabling smooth film formation, and concentrations greater than 4 M resulting in films with a higher density of particulates on the surface. Importantly, while the films grown at the liquid-liquid interface are mixed-orientation, those grown directly at the liquid-solid interface on the Si/SiO2 surface have highly oriented COF layers aligned parallel to the substrate surface. Moreover, this liquid-solid growth process affords TAPB-PDA COF thin films with p-type charge transport having a transconductance of 10 μS at a gate voltage of -0.9 V in an OECT device structure.

High-Performance Organic Electrochemical Transistors Achieved by Optimizing Structural and Energetic Ordering of Diketopyrrolopyrrole-Based Polymers.

For optimizing steady-state performance in organic electrochemical transistors (OECTs), both molecular design and structural alignment approaches must work in tandem to minimize energetic and microstructural disorders in polymeric mixed ionic-electronic conductor films. Herein, a series of poly(diketopyrrolopyrrole)s bearing various lengths of aliphatic-glycol hybrid side chains (PDPP-mEG; m = 2-5) is developed to achieve high-performance p-type OECTs. PDPP-4EG polymer with the optimized length of side chains exhibits excellent crystallinity owing to enhanced lamellar and backbone interactions. Furthermore, the improved structural ordering in PDPP-4EG films significantly decreases trap state density and energetic disorder. Consequently, PDPP-4EG-based OECT devices produce a mobility-volumetric capacitance product ([µC*]) of 702 F V-1 cm-1 s-1 and a hole mobility of 6.49 ± 0.60 cm2 V-1 s-1 . Finally, for achieving the optimal structural ordering along the OECT channel direction, a floating film transfer method is employed to reinforce the unidirectional orientation of polymer chains, leading to a substantially increased figure-of-merit [µC*] to over 800 F V-1 cm-1 s-1 . The research demonstrates the importance of side chain engineering of polymeric mixed ionic-electronic conductors in conjunction with their anisotropic microstructural optimization to maximize OECT characteristics.

High-Performance n-Type Polymeric Mixed Ionic-Electronic Conductors: The Impacts of Halogen Functionalization.

Developing high-performance n-type polymer mixed ionic-electronic conductors (PMIECs) is a grand challenge, which largely determines their applications in vaious organic electronic devices, such as organic electrochemical transistors (OECTs) and organic thermoelectrics (OTEs). Herein, two halogen-functionalized PMIECs f-BTI2g-TVTF and f-BTI2g-TVTCl built from fused bithiophene imide dimer (f-BTI2) as the acceptor unit and halogenated thienylene-vinylene-thienylene (TVT) as the donor co-unit are reported. Compared to the control polymer f-BTI2g-TVT, the fluorinated f-BTI2g-TVTF shows lower-positioned lowest unoccupied molecular orbital (LUMO), improved charge transport property, and greater ion uptake capacity. Consequently, f-BTI2g-TVTF delivers a state-of-the-artµC* of 90.2 F cm-1 V-1 s-1 with a remarkable electron mobility of 0.41 cm2 V-1 s-1 in OECTs and an excellent power factor of 64.2 µW m-1 K-2 in OTEs. An OECT-based inverter amplifier is further demonstrated with voltage gain up to 148V V-1 , which is among the highest values for OECT inverters. Such results shed light on the impacts of halogen atoms on developing high-performing n-type PMIECs.

One-step wet-spinning of conducting polymer and cellulose nanofiber composites for fiber-type organic electrochemical transistors

Considering that textile-based sensors are suitable for monitoring/communicating human vital health information, organic electrochemical transistors (OECTs) are considered as an efficient device platform for augmenting the capabilities and effectiveness of smart textile applications in diverse areas. Herein, we investigated the fabrication process and properties of poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS)-TEMPO-oxidized cellulose nanofiber (CNF) composites as active channel materials for fiber-type OECTs. Utilizing highly crystalline, mechanically rigid, and chemically robust CNFs directly extracted from biomass-derived tunicate, we fabricated PEDOT:PSS-CNF composite fibers with varying CNF portions (0, 5, 10, 20, and 30 %) through a simple one-step wet-spinning process using sulfuric acid-based coagulation media. The addition of CNFs significantly improved the mechanical strength of the composite fibers with Young's modulus up to 13.4 ± 2.1 GPa. Moreover, the fiber-type OECT devices based on the PEDOT:PSS(80 %)-CNF(20 %) composite showed highest carrier mobility (4.0 ± 0.2 cm2 V−1 s−1) with the marginal trade-off in volumetric capacitance (57.1 ± 3.7 F/cm3), resulting in the decent benchmark performance parameter (μ·C*) of 229 F cm−1 V−1 s−1. Our findings suggest that the synergistic interaction between PEDOT:PSS and CNFs leads to a significant improvement in fiber properties, and the resulting composite fibers hold great potentials for use in eco-friendly wearable/textile electronics.

Highly sensitive detection of malaria biomarker through matching channel and gate capacitance of integrated organic electrochemical transistors

Organic electrochemical transistors (OECTs) possess versatile advantages for biochemical and electrophysiological applications due to electrochemical gating and ion-to-electron conversion capability. Although OECTs have been successfully applied for biochemical sensing, the effect of relative capacitance for specific sensing events is still unclear. In the present work, we design integrated interdigitated OECTs (iOECTs) with on-plane gold gate and different channel geometries for point-of-care diagnosis of malaria using aptamer as receptor. The transconductance of the iOECTs gated with micro-size gold electrodes decreased with increasing the channel thicknesses, especially for devices with large channel areas, which is inconsistent with devices gated by typical Ag/AgCl electrodes, attributing to the limited gating efficiency of the micro-size gate electrode. The capacitance of gate electrode was heavily suppressed by receptors but increased with the incubation of targets. In addition, the integrated iOECTs with thin channels exhibited superior sensitivity for malaria detection with the detection limit as low as 3.2 aM, much lower than their thick channel counterpart and other state-of-the-art biosensors. These deviations could be caused by the high relative capacitances, with respect to the gate and channel capacitance (Cg/Cch), resulting in a high gate potential drop over the organic channel and thus entirely gating on the thin channel device. These findings provide guidance to optimize the geometry of OECT devices with on-chip integrated gates and the fabrication of miniaturized OECTs for biosensing applications.

Organic Electrochemical Transistors functionalized with Protein Minibinders for Sensitive and Specific Detection of SARS‐CoV‐2

AbstractThere is a need for rapid, sensitive, specific, and low‐cost virus sensors. Recent work has demonstrated that organic electrochemical transistors (OECTs) can detect the severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) spike protein. Here, a simple and low‐cost approach to the fabrication of OECT devices with excellent stability and unprecedented sensitivity and specificity for the detection of SARS‐CoV‐2 virus is demonstrated. The devices rely on the engineered protein minibinder LCB1, which binds strongly to SARS‐CoV‐2. The resulting devices exhibit excellent sensitivity for the detection of SARS‐CoV‐2 virus and SARS‐CoV‐2 spike protein receptor binding domain (RBD). These results demonstrate a simple, effective, and low‐cost biomolecular sensor applicable to the real‐time detection of SARS‐CoV‐2 virus and a general strategy for OECT device design that can be applied for the detection of other pathogenic viruses.