The rise of organic bioelectronics efficiently bridges the gap between semiconductor devices and biological systems, leading to flexible, lightweight, and lowcost organic bioelectronic devices suitable for health or body signal monitoring. The introduction of organic semiconductors in the devices can soften the boundaries between microelectronic systems and dynamically active cells and tissues. Therefore, organic bioelectronics has attracted much attention recently due to the unique properties and promising applications. Organic thin film transistors (OTFTs), owing to their inherent capability of amplifying received signals, have emerged as one of the state-of-the-art biosensing platforms. The advantages of organic semiconductors in terms of synthetic freedom, low temperature solution processing, biocompatibility, and mechanical flexibility render OTFTs ideal transducers for wearable electronics, e-skin, and implantable devices. How to realize highly sensitive, selective, rapid, and efficient signal capture and extraction of biological recognition events is the major challenge in the design of biosensors. OTFTs are prone to converting the presence or change of target analytes into specific electrical signals even in complex biological systems. More importantly, OTFT sensors can be conveniently functionalized with chemical or biological modifications and exhibit substantially improved device sensitivity and selectivity as well as other analytical figure of merits, including calibration range, linearity, and accuracy. However, the stability and reproducibility of the organic devices need to be further improved. In this Account, we first introduce the unique features of OTFTs for bioelectronic applications. Two typical OTFT configurations, including organic electrochemical transistor (OECT) and electrolyte gated organic field effect transistor (EGOFET), are highlighted in their sensing applications mainly due to the operation of the devices in electrolytes and the combination of ionic and electronic charge transports in the devices. These devices are potentiometric transducers with low working voltages (<1 V) and high sensitivity, and are thus suitable for wearable applications with low power consumption. Second, the functionalization strategies on channel materials, electrolytes, and gate electrodes based on various modification methods and sensing mechanisms are discussed in sequence. In an OECT-or EGOFET-based biosensor, the device performance is particularly sensitive to the physical properties of the two interfaces, including channel/electrolyte and gate/ electrolyte interfaces. Any change in the potential drop or capacitance of either interface can influence the channel current substantially. Therefore, the functionalization of the interfaces is critical to the sensing performance. In particular, when an electrochemically active material is modified on the interfaces, the reaction of the analyte catalyzed by the modified material can influence the interface potential and lead to a channel current response much...

Flexible fabric biosensors can find promising applications in wearable electronics. However, high-performance fabric biosensors have been rarely reported due to many special requirements in device fabrication. Here, the preparation of organic electrochemical transistors (OECTs) on Nylon fibers is reported. By introducing metal/conductive polymer multilayer electrodes on the fibers, the OECTs show very stable performance during bending tests. The devices with functionalized gates are successfully used as various biosensors with high sensitivity and selectivity. The fiber-based OECTs are woven together with cotton yarns successfully by using a conventional weaving machine, resulting in flexible and stretchable fabric biosensors with high performance. The fabric sensors show much more stable signals in the analysis of moving aqueous solutions than planar devices due to a capillary effect in fabrics. The fabric devices are integrated in a diaper and remotely operated by using a mobile phone, offering a unique platform for convenient wearable healthcare monitoring.

non-wetting surface can enable the growth of perovskite films with large grain size and high crystallinity, which impressively suppresses the nonradiative recombination and improves the photovoltaic performance of PSCs. [23] Snaith and co-workers have used a self-assembled fullerene monolayer to grow high-quality perovskite films and passivate the defects on TiO 2 layers, leading to hysteresis-free PSCs with good photovoltaic performance. [25] Therefore, proper surface modification of substrates can decrease the density of nucleation sites and enlarge the grains of perovskite films. However, the orientation of the solution processed perovskite films cannot be conveniently controlled.Van der Waals (vdW) epitaxy is a prevalent technique for preparing high-quality semiconductor films with preferential orientations on 2D substrates with smooth and dangling-bond-free surfaces. [26][27][28] The weak vdW interactions between the crystals and the substrates can enable epitaxial growth of the films with high crystallographic orientation and low defect states even in the presence of large lattice mismatch and symmetry misfit between them. [29,30] Recently, Duan and co-workers realized scalable solution-phase vdW epitaxial growth of cubic PbSe layer on 2D rhombohedral Bi 2 Se 3 nanoplates. [31] Liu and co-workers also employed solution-phase vdW epitaxy strategy to fabricate ultrathin graphdiyne film with high quality by using 2D graphene as a growing template. [32] Inspired by the intriguing effects, we consider that dangling-bond-free 2D materials with proper lattice parameters can be utilized as growth templates for preparing high-quality perovskite films with a controllable orientation.Molybdenum disulfide (MoS 2 ) is a promising 2D material with high carrier mobilities and a suitable energy band structure for many optoelectronic applications. [33][34][35] Due to its dangling-bondfree and clean surface, MoS 2 has been used as growth templates for preparing vdW epitaxial 2D materials. [36] In this paper, solution processed large few-layer MoS 2 flakes have been employed as a growth template for perovskite films. We find for the first time the vdW epitaxial growth of MAPbI 3 perovskite on MoS 2 flakes, leading to highly oriented perovskite films with large grain sizes and low defect densities. Transmission electron micro scopy (TEM) images demonstrate that the (008) plane of MAPbI 3 and the (110) plane of MoS 2 can match perfectly, which facilities the out-of-plane growth of perovskite films with preferential orientation along (110). Then, MoS 2 flakes are modified on The quality of perovskite films is critical to the performance of perovskite solar cells. However, it is challenging to control the crystallinity and orientation of solution-processed perovskite films. Here, solution-phase van der Waals epitaxy growth of MAPbI 3 perovskite films on MoS 2 flakes is reported. Under transmission electron microscopy, in-plane coupling between the perovskite and the MoS 2 crystal lattices is observed, leading to perovskite films ...

The outbreak of COVID-19 and its continued spread have seriously threatened public health. Antibody testing is essential for infection diagnosis, seroepidemiological analysis, and vaccine evaluation. However, convenient, fast, and accurate antibody detection remains a challenge in this protracted battle. Here, we report an ultrafast, lowcost, label-free, and portable SARS-CoV-2 immunoglobulin G (IgG) detection platform based on organic electrochemical transistors (OECTs), which can be remotely controlled by a mobile phone. To enable faster detection, voltage pulses are applied on the gate electrode of the OECT to accelerate binding between the antibody and antigen. By optimizing ion concentrations and pH values of test solutions, we realize specific detection of SARS-CoV-2 IgG in several minutes with a detectable region from 10 fM to 100 nM, which encompasses the range of serum SARS-CoV-2 IgG levels in humans. These portable sensors show promise for use in diagnosis and prognosis of COVID-19.

The analysis of protein biomarkers is of great importance in the diagnosis of diseases. Although many convenient and low-cost electrochemical approaches have been extensively investigated, they are not sensitive enough in the detection of protein biomarkers with low concentrations in physiological environments. Here, this study reports a novel organic-electrochemical-transistor-based biosensor that can successfully detect cancer protein biomarkers with ultrahigh sensitivity. The devices are operated by detecting electrochemical activity on gate electrodes, which is dependent on the concentrations of proteins labeled with catalytic nanoprobes. The protein sensors can specifically detect a cancer biomarker, human epidermal growth factor receptor 2, down to the concentration of 10 g mL , which is several orders of magnitude lower than the detection limits of previously reported electrochemical approaches. Moreover, the devices can successfully differentiate breast cancer cells from normal cells at various concentrations. The ultrahigh sensitivity of the protein sensors is attributed to the inherent amplification function of the organic electrochemical transistors. This work paves a way for developing highly sensitive and low-cost biosensors for the detection of various protein biomarkers in clinical analysis in the future.