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Highlights The review provides a comprehensive summary of performance limits of the single two-dimensional transition metal dichalcogenide (2D-TMD) transistor. The review details the two logical expressions of the single 2D-TMD logic transistor, including current and voltage. The review demonstrates the two calculating methods for dynamic energy consumption of 2D synaptic devices.

Abstract With field effect transistor (FET) sustained to downscale to sub‐10 nm nodes, performance degradation originates from short channel effects (SCEs) degradation and power consumption increment attributed to inhibition of supply voltage (VDD) scaling down proportionally caused by thermionic limit subthreshold swing (SS) (60 mV dec−1) pose substantial challenges for today's semiconductor industry. To further sustain the Moore's law life, incorporation of new device concepts or new materials are imperative. 2D materials are predicted to be able to combat SCEs by virtue of high carrier mobility maintainability regardless of thickness thinning down, dangling bonds free surface and atomic thickness, which contributes to super gate electrostatic controllability. To overcome increasing power dissipation problem, new device structures including negative capacitance FET (NCFET), tunnel FET (TFET), dirac source FET (DSFET) and the like, which show superiority in decreasing VDD by lowering SS below thermionic limit of 60 mV dec−1 have been brought out. The combination of 2D materials and ultralow steep slope device structures holds great promise for low power‐dissipation electronics, which encompass both suppressed SCEs and reduced VDD simultaneously, leading to improved device performance and lowered power dissipation.

Highlights This review introduces the potential of 2D electronics for post-Moore era and discusses their current progress in digital circuits, analog circuits, heterogeneous integration, sensing circuits, artificial intelligence chips, and quantum chips in sequence. A comprehensive analysis of the current trends and challenges encountered in the development of 2D materials is summarized. An in-depth roadmap outlining the future development of 2D electronics is presented, and the most accessible and promising avenues for 2D electronics are suggested.

Abstract The development of strain sensors with high stretchability and stability is an inevitable requirement for achieving full‐range and long‐term use of wearable electronic devices. Herein, a resistive micromesh reinforced strain sensor (MRSS) with high stretchability and stability is prepared, consisting of a laser‐scribed graphene (LSG) layer and two styrene‐block‐poly(ethylene‐ran‐butylene)‐block‐poly‐styrene micromesh layers embedded in Ecoflex. The micromesh reinforced structure endows the MRSS with combined characteristics of a high stretchability (120%), excellent stability (with a repetition error of 0.8% after 11 000 cycles), and outstanding sensitivity (gauge factor up to 2692 beyond 100%). Impressively, the MRSS can still be used continauously within the working range without damage, even if stretched to 300%. Furthermore, compared with different structure sensors, the mechanism of the MRSS with high stretchability and stability is elucidated. What's more, a multilayer finite element model, based on the layered structure of the LSG and the morphology of the cracks, is proposed to investigate the strain sensing behavior and failure mechanism of the MRSS. Finally, due to the outstanding performance, the MRSS not only performes well in monitoring full‐range human motions, but also achieves intelligent recognitions of various respiratory activities and gestures assisted by neural network algorithms (the accuracy up to 94.29% and 100%, respectively). This work provides a new approach for designing high‐performance resistive strain sensors and shows great potential in full‐range and long‐term intelligent health management and human–machine interactions applications.

Depression is currently a major contributor to unnatural deaths and the healthcare burden globally, and a patient’s battle with depression is often a long one. Because the causes, symptoms, and effects of medications are complex and highly individualized, early identification and personalized treatment of depression are key to improving treatment outcomes. The development of wearable electronics, machine learning, and other technologies in recent years has provided more possibilities for the realization of this goal. Conducting regular monitoring through biosensing technology allows for a more comprehensive and objective analysis than previous self-evaluations. This includes identifying depressive episodes, distinguishing somatization symptoms, analyzing etiology, and evaluating the effectiveness of treatment programs. This review summarizes recent research on biosensing technologies for depression. Special attention is given to technologies that can be portable or wearable, with the potential to enable patient use outside of the hospital, for long periods.

Research on the flexible hybrid epidermal electronic system (FHEES) has attracted considerable attention due to its potential applications in human–machine interaction and healthcare. Through material and structural innovations, FHEES combines the advantages of traditional stiff electronic devices and flexible electronic technology, enabling it to be worn conformally on the skin while retaining complex system functionality. FHEESs use multimodal sensing to enhance the identification accuracy of the wearer’s motion modes, intentions, or health status, thus realizing more comprehensive physiological signal acquisition. However, the heterogeneous integration of soft and stiff components makes balancing comfort and performance in designing and implementing multimodal FHEESs challenging. Herein, multimodal FHEESs are first introduced in 2 types based on their different system structure: all-in-one and assembled, reflecting totally different heterogeneous integration strategies. Characteristics and the key design issues (such as interconnect design, interface strategy, substrate selection, etc.) of the 2 multimodal FHEESs are emphasized. Besides, the applications and advantages of the 2 multimodal FHEESs in recent research have been presented, with a focus on the control and medical fields. Finally, the prospects and challenges of the multimodal FHEES are discussed.

Abstract Van der Waals (vdW) ferroelectric CuInP2S6 (CIPS) has great potential in post‐Moore's law electronics owing to their advantages of weak interlayer interaction, stable surface with free dangling bonds, and robust switchable spontaneous polarization. The flexoelectric effect is demonstrated as an alternative switching method for the design of ferroelectric domains in layered vdW CIPS. However, the investigation of the correlation between the polarization and elastic properties remains indistinct. Here, an elastic evolution is explored experimentally and theoretically in layered vdW CIPS with temperature, of which Young's modulus (EYoung) is determined by analyzing the force‐indentation responses of vdW ferroelectric CIPS. Interestingly, an anomalous leap in EYoung of CIPS from 35 to 65 GPa occurs when the temperature rises across the Curie temperature TC of ≈315 K. Deep potential molecular dynamic (DPMD) simulations identify that this abnormal behavior can be attributed to temperature‐dependent change of copper distribution and the local copper dynamic hopping, intertwined with the order‐disorder ferroelectric phase transition, which is quite different from the typical decrease of EYoung in the lattice constant due to temperature increasing. The exploration provides an important reference for the analysis of coupled mechanical properties and ferroelectricity in CIPS and its applications in flexible electronics.

Abstract Two‐dimensional material‐based field‐effect transistors (2DM‐FETs) are playing a revolutionary role in electronic devices. However, before electronic design automation (EDA) for 2DM‐FETs can be achieved, it remains necessary to determine how to incorporate contact transports into model. Reported methods compromise between physical intelligibility and model compactness due to the heterojunction nature. To address this, quasi‐Fermi‐level phase space theory (QFLPS) is generalized to incorporate contact transports using the Landauer formula. It turns out that the Landauer‐QFLPS model effectively overcomes the issue of concern. The proposed new formula can describe 2DM‐FETs with Schottky or Ohmic contacts with superior accuracy and efficiency over previous methods, especially when describing non‐monotonic drain conductance characteristics. A three‐bit threshold inverter quantizer (TIQ) circuit is fabricated using ambipolar black phosphorus and it is demonstrated that the model accurately predicts circuit performance. The model could be very effective and valuable in the development of 2DM‐FET‐based integrated circuits.

Abstract Memristor-based circuits offer low hardware costs and in-memory computing, but full-memristive circuit integration for different algorithm remains limited. Cellular automata (CA) has been noticed for its well-known parallel, bio-inspired, computational characteristics. Running CA on conventional chips suffers from low parallelism and high hardware costs. Establishing dedicated hardware for CA remains elusive. We propose a recirculated logic operation scheme (RLOS) using memristive hardware and 2D transistors for CA evolution, significantly reducing hardware complexity. RLOS’s versatility supports multiple CA algorithms on a single circuit, including elementary CA rules and more complex majority classification and edge detection algorithms. Results demonstrate up to a 79-fold reduction in hardware costs compared to FPGA-based approaches. RLOS-based reservoir computing is proposed for edge computing development, boasting the lowest hardware cost (6 components/per cell) among existing implementations. This work advances efficient, low-cost CA hardware and encourages edge computing hardware exploration.

Highlights This review introduces soft electronics for health monitoring assisted by machine learning, and discusses soft materials, physiological signals, and machine learning algorithms in sequence and their relationships. The principles of classic machine learning algorithms and neural network algorithms are summarized and explained by representative examples combining with soft electronics. The potential challenges of soft electronics assisted by machine learning especially in health monitoring field are outlined, and future research directions are outlooked.

Abstract High sensitivity and fast response are the figures of merit for benchmarking commercial sensors. Due to the advantages of intrinsic signal amplification, bionic ability, and mechanical flexibility, electrochemical transistors (ECTs) have recently gained increasing popularity in constructing various sensors. In the current work, we have proposed a pulse‐driven synaptic ECT for supersensitive and ultrafast biosensors. By pulsing the presynaptic input (drain bias, VD) and setting the modulation potential (gate bias) near transconductance intersection (VG,i), the synaptic ECT‐based pH sensor can achieve a record high sensitivity up to 124 mV pH−1 (almost twice the Nernstian limit, 59.2 mV pH−1) and an ultrafast response time as low as 8.75 ms (7169 times faster than the potentiostatic sensors, 62.73 s). The proposed synaptic sensing strategy can effectively eliminate the transconductance fluctuation issue during the calibration process of the pH sensor and significantly reduce power consumption. Besides, the most sensitive working point at VG,i has been elaborately figured out through a series of detailed mathematical derivations, which is of great significance to provide higher sensitivity with quasi‐nonfluctuating amplification capability. The proposed electrochemical synaptic transistor paired with an optimized operating gate offers a new paradigm for standardizing and commercializing high‐performance biosensors.

Abstract Lead halide perovskites have made remarkable progress in the field of radiation detection owing to the excellent and unique optoelectronic properties. However, the instability and the toxicity of lead‐based perovskites have greatly hindered its practical applications. Alternatively, lead‐free perovskites with high stability and environmental friendliness thus have fascinated significant research attention for direct X‐ray detection. In this review, the current research progress of X‐ray detectors based on lead‐free halide perovskites is focused. First, the synthesis methods of lead‐free perovskites including single crystals and films are discussed. In addition, the properties of these materials and the detectors, which can provide a better understanding and designing satisfactory devices are also presented. Finally, the challenge and outlook for developing high‐performance lead‐free perovskite X‐ray detectors are also provided.

Summary: As one of the most potential ways to manipulate heat, thermal functional devices have achieved several breakthroughs in recent years, but are still limited to theoretical simulations. One of its theoretical bases is the existence of the negative differential thermal resistance (NDTR). However, most of the existing systems where the phenomenon of NDTR is found are atomic-level systems. In order to realize the macroscopic NDTR and provide effective theoretical guidance and support for the practical realization of thermal functional devices, we construct the overlapping graphene homojunction model, using the negative thermal expansion property of graphene to modify the overlapping area, and thus regulating the heat flow. The COMSOL-MATLAB co-simulation is used to perform calculations through negative feedback loops. It is found that the NDTR phenomenon exists under certain parameter conditions, which can provide new ideas and bring more opportunities for the experimental realization of nonlinear thermal functional devices.

A negative capacitance (NC) effect has been proposed as a critical pathway to overcome the ‘Boltzmann tyranny’ of electrons, achieve the steep slope operation of transistors and reduce the power dissipation of current semiconductor devices. In particular, the ferroic property in hafnium-based films with fluorite structure provides an opportunity for the application of the NC effect in electronic devices. However, to date, only a transient NC effect has been confirmed in hafnium-based ferroic materials, which is usually accompanied by hysteresis and is detrimental to low-power transistor operations. The stabilized NC effect enables hysteresis-free and low-power transistors but is difficult to observe and demonstrate in hafnium-based films. This difficulty is closely related to the polycrystalline and multi-phase structure of hafnium-based films fabricated by atomic layer deposition or chemical solution deposition. Here, we prepare epitaxial ferroelectric Hf _0.5 Zr _0.5 O _2 and antiferroelectric ZrO _2 films with single-phase structure and observe the capacitance enhancement effect of Hf _0.5 Zr _0.5 O _2 /Al _2 O _3 and ZrO _2 /Al _2 O _3 capacitors compared to that of the isolated Al _2 O _3 capacitor, verifying the stabilized NC effect. The capacitance of Hf _0.5 Zr _0.5 O _2 and ZrO _2 is evaluated as −17.41 and −27.64 pF, respectively. The observation of the stabilized NC effect in hafnium-based films sheds light on NC studies and paves the way for low-power transistors.

Abstract With the aging of society and the increase in people’s concern for personal health, long-term physiological signal monitoring in daily life is in demand. In recent years, electronic skin (e-skin) for daily health monitoring applications has achieved rapid development due to its advantages in high-quality physiological signals monitoring and suitability for system integrations. Among them, the breathable e-skin has developed rapidly in recent years because it adapts to the long-term and high-comfort wear requirements of monitoring physiological signals in daily life. In this review, the recent achievements of breathable e-skins for daily physiological monitoring are systematically introduced and discussed. By dividing them into breathable e-skin electrodes, breathable e-skin sensors, and breathable e-skin systems, we sort out their design ideas, manufacturing processes, performances, and applications and show their advantages in long-term physiological signal monitoring in daily life. In addition, the development directions and challenges of the breathable e-skin are discussed and prospected.

Perovskite-based X-ray detector, which is widely applied in fields of scientific research and medical diagnosis, has drawn much attention for its superior optoelectrical properties. To improve the detection performance, band engineering is becoming the hot topic for perovskite properties modulation. In this article, we review the recent progress of perovskite-based X-ray detectors with band engineering process from three aspects, which are background introduction, band theory of heterojunction devices, and optimized electrode contact devices. Lastly, research status and strategies are summarized and perspectives of future progress are analyzed. We hope this review can provide constructive instructions and suggestions for future development of band engineering for perovskite-based high-performance X-ray detector.

Abstract As a new generation of Zn-ion storage systems, Zn-ion hybrid supercapacitors (ZHSCs) garner tremendous interests recently from researchers due to the perfect integration of batteries and supercapacitors. ZHSCs have excellent integration of high energy density and power density, which seamlessly bridges the gap between batteries and supercapacitors, becoming one of the most viable future options for large-scale equipment and portable electronic devices. However, the currently reported two configurations of ZHSCs and corresponding energy storage mechanisms still lack systematic analyses. Herein, this review will be prudently organized from the perspectives of design strategies, electrode configurations, energy storage mechanisms, recent advances in electrode materials, electrolyte behaviors and further applications (micro or flexible devices) of ZHSCs. The synthesis processes and electrochemical properties of well-designed Zn anodes, capacitor-type electrodes and novel Zn-ion battery-type cathodes are comprehensively discussed. Finally, a brief summary and outlook for the further development of ZHSCs are presented as well. This review will provide timely access for researchers to the recent works regarding ZHSCs.

Abstract Glaucoma, a chronic optic neuropathy, is the leading cause of irreversible blindness in the world. Elevated intraocular pressure (IOP) has been considered to be the major contributor to glaucoma for a long time and is currently proved to be the only modifiable risk factor for the progression of optic neuropathy. IOP fluctuates throughout the day with a circadian rhythm change and is affected by body gesture changes. Moreover, the IOP spike usually occurs at night or in the early morning. Therefore, the current clinical practice of single and static measurements of IOP during office hours is not conducive to the early diagnosis and treatment of glaucoma. This review focuses on current advances in implantable and noninvasive IOP sensors for obtaining 24‐hour continuous IOP profiles. The content summarizes and classifies IOP sensors based on their working principles and provides representative examples of the sensors for IOP monitoring. Finally, the review further analyzes the challenges of current IOP sensors for clinical practice and puts forward the prospect of IOP sensors in the future.

Abstract Human–robot interface (HRI) electronics are critical for realizing robotic intelligence. Here, we report graphene‐based dual‐function acoustic transducers for machine learning‐assisted human–robot interfaces (GHRI). The GHRI functions both an artificial ear through the triboelectric acoustic sensing mechanism and an artificial mouth through the thermoacoustic sound emission mechanism. The success of the integrated device is also attributed to the multifunctional laser‐induced graphene, as either triboelectric materials, electrodes, or thermoacoustic sources. By systematically optimizing the structure parameters, the GHRI achieves high sensitivity (4500 mV Pa–1) and operating durability (1 000 000 cycles and 60 days), capable of recognizing speech identities, emotions, content, and other information in the human speech. With the assistance of machine learning, 30 speech categories are trained by a convolutional neural network, and the accuracy reaches 99.66% and 96.63% in training datasets and test datasets. Furthermore, GHRI is used for artificial intelligence communication based on recognized speech features. Our work shows broad prospects for the development of robotic intelligence.

Graphene has extremely high electron mobility, good thermal conductivity, and excellent acoustic properties, making it an ideal acoustic material. Currently, there are three main types of graphene used in acoustic devices: graphene films prepared by chemical vapor deposition (CVD), vertical graphene (VGr) and laser-induced graphene (LIG). Among them, Graphene prepared by CVD is lighter, thinner and more sensitive; VGr is grown by the microwave plasma chemical vapor deposition (MPCVD) method, which has higher ductility and sound pressure level (SPL); LIG has the advantages of low cost, simple preparation and no biological toxicity. This paper introduces the applications of these three materials in the direction of acoustic devices. In addition to the simple acoustic-electrical conversion application, an artificial throat with the intelligent recognition function is introduced. These different types of graphene acoustic devices have greatly promoted the application of graphene in the field of acoustics.

This paper is a comprehensive review of the techniques for the detection of pancreatic enzymes, which are common biochemical indicators of pancreatitis, including amylase, trypsin, chymotrypsin, elastase, and lipase. Pancreatitis is a disease with self-digestion due to the abnormal activation of digestive enzymes in the pancreas. Hospitalization is often required due to the lack of convenient therapeutic agents. The main recent results are reported in this review, especially the techniques that enable portability and Point-of-Care testing (POCT). This is because timely diagnosis at the early stage and avoiding recurrence after recovery are the keys to treatment. It is also important to reduce the rate of misdiagnosis and to avoid overtreatment. Various detection methods are discussed, with particular attention given to the implementation of chemical sensing and probe design. The new sensing technology for digestive enzymes makes it possible to perform early screening for pancreatitis in remote areas or in one’s own home.

The observation of negative capacitance effect is focused on the ferroelectrics, while the antiferroelectrics based on Landau switches may have negative capacitance effect. Here, the authors report the static and transient negative capacitance effect in antiferroelectric PbZrO3 and reveal its origin.

Abstract Mixed‐dimensional (2D/3D) van der Waals (vdW) heterostructures made with complementary materials hold a lot of promise in the field of optoelectronic devices. Beyond simple mechanical stacking, directly growing the single‐crystal perovskite on 2D materials to construct a high‐quality vdW heterojunction can better promote carrier transport. In this work, a monolithic integrated graphene/perovskite heterojunction device is fabricated by directly growing a single‐crystal hybrid perovskite on monolayer graphene. Due to the strong interface coupling, the hybrid device achieves self‐powering behavior and exhibits prominent photoresponse properties with a fast response speed of up to 2.05 μs. Moreover, the responsivity and detectivity can be boosted to up to 10.41 A W−1 and 4.65 × 1012 Jones under the actuation of −3 V bias. This technique not only improves the device performance, but also provides an effective guideline for the development of next‐generation directly integrated vdW optoelectronic devices.

With its excellent electrical and mechanical properties and the rapid development of its device fabrication technologies, laser-induced graphene (LIG) has played an important role in the field of wearable technologies since its discovery in 2014. In recent years, with the relentless development of wearable devices, newly developed LIG-based wearable devices also possess multifunction and intelligence characteristics. This review is aimed toward two of the most important fields related to the development of LIG, namely, health care and human–computer interaction (HCI). We introduce multifunctional and intelligent LIG-based wearable systems for health care and HCI developed over the recent years, sorting out their design ideas, preparation process, performance, and application. Furthermore, we discuss the future development direction of LIG-based wearable systems for health care and HCI.

Continuous blood pressure (BP) monitoring is of great significance for the real-time monitoring and early prevention of cardiovascular diseases. Recently, wearable BP monitoring devices have made great progress in the development of daily BP monitoring because they adapt to long-term and high-comfort wear requirements. However, the research and development of wearable continuous BP monitoring devices still face great challenges such as obvious motion noise and slow dynamic response speeds. The pulse wave transit time method which is combined with photoplethysmography (PPG) waves and electrocardiogram (ECG) waves for continuous BP monitoring has received wide attention due to its advantages in terms of excellent dynamic response characteristics and high accuracy. Here, we review the recent state-of-art wearable continuous BP monitoring devices and related technology based on the pulse wave transit time; their measuring principles, design methods, preparation processes, and properties are analyzed in detail. In addition, the potential development directions and challenges of wearable continuous BP monitoring devices based on the pulse wave transit time method are discussed.

Sensors enable the detection of physiological indicators and pathological markers to assist in the diagnosis, treatment, and long-term monitoring of diseases, in addition to playing an essential role in the observation and evaluation of physiological activities. The development of modern medical activities cannot be separated from the precise detection, reliable acquisition, and intelligent analysis of human body information. Therefore, sensors have become the core of new-generation health technologies along with the Internet of Things (IoTs) and artificial intelligence (AI). Previous research on the sensing of human information has conferred many superior properties on sensors, of which biocompatibility is one of the most important. Recently, biocompatible biosensors have developed rapidly to provide the possibility for the long-term and in-situ monitoring of physiological information. In this review, we summarize the ideal features and engineering realization strategies of three different types of biocompatible biosensors, including wearable, ingestible, and implantable sensors from the level of sensor designing and application. Additionally, the detection targets of the biosensors are further divided into vital life parameters (e.g., body temperature, heart rate, blood pressure, and respiratory rate), biochemical indicators, as well as physical and physiological parameters based on the clinical needs. In this review, starting from the emerging concept of next-generation diagnostics and healthcare technologies, we discuss how biocompatible sensors revolutionize the state-of-art healthcare system unprecedentedly, as well as the challenges and opportunities faced in the future development of biocompatible health sensors.

Sleep is an essential physiological activity, accounting for about one-third of our lives, which significantly impacts our memory, mood, health, and children’s growth. Especially after the COVID-19 epidemic, sleep health issues have attracted more attention. In recent years, with the development of wearable electronic devices, there have been more and more studies, products, or solutions related to sleep monitoring. Many mature technologies, such as polysomnography, have been applied to clinical practice. However, it is urgent to develop wearable or non-contacting electronic devices suitable for household continuous sleep monitoring. This paper first introduces the basic knowledge of sleep and the significance of sleep monitoring. Then, according to the types of physiological signals monitored, this paper describes the research progress of bioelectrical signals, biomechanical signals, and biochemical signals used for sleep monitoring. However, it is not ideal to monitor the sleep quality for the whole night based on only one signal. Therefore, this paper reviews the research on multi-signal monitoring and introduces systematic sleep monitoring schemes. Finally, a conclusion and discussion of sleep monitoring are presented to propose potential future directions and prospects for sleep monitoring.

The discovery of ferroelectricity in hafnium zirconium oxide (HZO) thin films has attracted wide attention from academia to industry due to the application in ferroelectric non-volatile random access memories (FeRAM) with prominent performance in scalability and CMOS process compatibility. Dielectric behavior of ferroelectric HZO thin films is a key factor affecting the dynamic effect, piezoelectric and electrostrictive effect. Interface between HZO and capping electrodes plays an important role in regulating the dielectric properties. In this paper, the impedance frequency response and dielectric spectrum of ferroelectric HZO thin films were analyzed. Parameters of the interface were extracted to analyze the regulating effect on the dielectric properties based on an impedance model with constant phase element (CPE). Besides, dielectric spectrums at elevated temperatures were identified to verify this analysis.

Electrocardiogram (ECG), as a product that can most directly reflect the electrical activity of the heart, has become the most common clinical technique used for the analysis of cardiac abnormalities. However, it is a heavy and tedious burden for doctors to analyze a large amount of ECG data from the long-term monitoring system. The realization of automatic ECG analysis is of great significance. This work proposes a beat-level interpretation method based on the automatic annotation algorithm and object detector, which abandons the previous mode of separate R peak detection and heartbeat classification. The ground truth of the QRS complex is automatically annotated and also regarded as the object the model can learn like category information. The object detector unifies the localization and classification tasks, achieving an end-to-end optimization as well as decoupling the high dependence on the R peak. Compared with most advanced methods, this work shows superior performance. For the interpretation of 12 heartbeat types in the MIT-BIH dataset, the average accuracy is 99.60%, the average sensitivity is 97.56%, and the average specificity is 99.78%. This method can be used as a clinical auxiliary tool to help doctors diagnose arrhythmia after receiving large-scale database training.

In this paper, an N-type silicon line tunneling TFET (LT-TFET) with an ultra-shallow N+ pocket was proposed. The pocket was formed by using the germanium preamorphization implantation (Ge PAI), arsenic ultra-low energy implantation and spike annealing. Due to the Ge PAI, the tunneling probability was improved significantly. As a result, a high on-state current of 40 μA/μm, a minimum subthreshold swing (SS) of 69 mV/decade and an average SS of 80 mV/decade over 5 decades of drain current were achieved with VDS = VGS = 1 V at room temperature. It is shown that once the trap assisted tunneling is suppressed at the low temperature, the band-to-band tunneling becomes dominant. When the temperature decreases from 300 K to 4.9 K, the on-state current only reduces 20% and a minimumpoint SS of 10 mV/decade was obtained. The LT-TFET exhibits improved transconductance efficiency at deep cryogenic temperature range. The proposed structure in this work shows attractive merits in the cryogenic digital and analog application.

Human–Machine Interface (HMI) plays a key role in the interaction between people and machines, which allows people to easily and intuitively control the machine and immersively experience the virtual world of the meta-universe by virtual reality/augmented reality (VR/AR) technology. Currently, wearable skin-integrated tactile and force sensors are widely used in immersive human–machine interactions due to their ultra-thin, ultra-soft, conformal characteristics. In this paper, the recent progress of tactile and force sensors used in HMI are reviewed, including piezoresistive, capacitive, piezoelectric, triboelectric, and other sensors. Then, this paper discusses how to improve the performance of tactile and force sensors for HMI. Next, this paper summarizes the HMI for dexterous robotic manipulation and VR/AR applications. Finally, this paper summarizes and proposes the future development trend of HMI.

The emerging memories are great candidates to establish neuromorphic computing challenging non-Von Neumann architecture. Emerging non-volatile resistive random-access memory (RRAM) attracted abundant attention recently for its low power consumption and high storage density. Up to now, research regarding the tunability of the On/Off ratio and the switching window of RRAM devices remains scarce. In this work, the underlying mechanisms related to gate tunable RRAMs are investigated. The principle of such a device consists of controlling the filament evolution in the resistive layer using graphene and an electric field. A physics-based stochastic simulation was employed to reveal the mechanisms that link the filament size and the growth speed to the back-gate bias. The simulations demonstrate the influence of the negative gate voltage on the device current which in turn leads to better characteristics for neuromorphic computing applications. Moreover, a high accuracy (94.7%) neural network for handwritten character digit classification has been realized using the 1-transistor 1-memristor (1T1R) crossbar cell structure and our stochastic simulation method, which demonstrate the optimization of gate tunable synaptic device.

Electronic skin (e-skin) has attracted tremendous interest due to its diverse potential applications, including in physiological signal detection, health monitoring, and artificial throats. However, the major drawbacks of traditional e-skin are the weak adhesion of substrates, incompatibility between sensitivity and stretchability, and its single function. These shortcomings limit the application of e-skin and increase the complexity of its multifunctional integration. Herein, the synergistic network of crosslinked SWCNTs within and between multilayered graphene layers was directly drip coated onto the PU thin film with self-adhesion to fabricate versatile e-skin. The excellent mechanical properties of prepared e-skin arise from the sufficient conductive paths guaranteed by SWCNTs in small and large deformation under various strains. The prepared e-skin exhibits a low detection limit, as small as 0.5% strain, and compatibility between sensitivity and stretchability with a gauge factor (GF) of 964 at a strain of 0–30%, and 2743 at a strain of 30–60%. In physiological signals detection application, the e-skin demonstrates the detection of subtle motions, such as artery pulse and blinking, as well as large body motions, such as knee joint bending, elbow movement, and neck movement. In artificial throat application, the e-skin integrates sound recognition and sound emitting and shows clear and distinct responses between different throat muscle movements and different words for sound signal acquisition and recognition, in conjunction with superior sound emission performance with a sound spectrum response of 71 dB (f = 12.5 kHz). Overall, the presented comprehensive study of novel materials, structures, properties, and mechanisms offers promising potential in physiological signals detection and artificial throat applications.

With the development of integrated circuits according to Moore’s law, traditional silicon-based devices have gradually reached their performance limitation. Nanoelectronics based on carbon nanomaterials provides a broad prospect for the continuation of Moore’s law. In particular, in the field of optoelectronic devices, it is necessary to further develop new types of nano-optoelectronic devices. Carbon nanotubes (CNTs) are one of the representative materials of nanoelectronics with excellent electrical and optical properties, e.g., high mobility, suitable band structure, and good infrared absorption. The application of CNTs in optoelectronic devices is a very attractive research topic, which has been developed rapidly in recent years. Until now, various prototypes of CNT-based optoelectronic devices have been developed. In this Review, we briefly introduce the structure and photoelectric properties of CNTs. Then, according to different photo-electron coupling mechanisms, four types of CNTs based on optoelectronic devices are introduced in detail, namely, solar cells, photodetectors, light-emitting diodes, and lasers. Intrinsic and composite CNT-based optoelectronic devices are presented in order to describe the development of CNT-based optoelectronic devices. Finally, different material preparation, separation, and mixing methods of CNTs are discussed, which are the methods for basic material preparation for the fabrication of high performance CNT-based optoelectronic devices. An in-depth study of the development trend of CNT-based optoelectronic devices will contribute to the future development of novel high-performance nanoelectronic devices.

In this paper, a synaptic transistor based on the indium zinc oxide (IZO)-hafnium oxide (HfO2) thin film structure was demonstrated. Blue light pulses (470 nm) were used as the presynaptic stimulus, the IZO channel was used as the postsynaptic membrane, and the HfO2 electrolyte film was regarded as the synaptic cleft. The synaptic transistor exhibited the behavior of paired-pulse facilitation. With different light power densities, the channel current of the transistor can be regulated to different levels, corresponding to different synaptic weights. In addition, the transistor showed the brain's memory behaviors including the short-term memory and the transition from the short to the long term memory. The synaptic behaviors of the transistor can be explained by the trapping and releasing processes of the photo-generated carriers.

Synaptic transistors mimicking the biological synapse's short term plasticity and short-term memory property were demonstrated using the amorphous indium-gallium-zinc oxide channel in combination with the nanogranular SiO2 as the gate oxide. The lowest energy consumption was ~1.08 pJ per pulse activity and the operating voltage was within 100 mV. The device's plasticity and memory characteristics can be explained by the movement of protons in the insulating layer. The proton relaxation was revealed by two ways of dual sweeping: continuous and discontinuous sweepings. We observed that the excitatory postsynaptic current (EPSC) rose as the voltage decreased anomaly during the backward sweeping process. In the electrical stimulus, both the short-term potentiation and depression were observed for this proposed device. The amplitude of the EPSC changed with the pulse number following a saturating exponential function. For the electrical stimulus under constant illumination, the UV light wavelength, intensity and duration time were found to have little effect on the paired pulse facilitation. While in the light stimulus, the light frequency promoted the paired pulse facilitation and had more effect on the synapse's plasticity than the other light pulse parameters including intensity, numbers and width.

An ultraviolet (UV) photodetector based on hydrothermally processed ZnO nanorods (ZnO NRs) decorated by gold nanoparticles (Au NPs) was demonstrated to exhibit extraordinary optoelectronic properties. Due the implementation of Au NPs, the UV responsivity and specific detectivity reached 70 A/W and 3.41 $\times$ 1012 cm Hz1/2 W−1, respectively, which were enhanced by approximately four times at an excitation wavelength of 365 nm compared with those of pristine ZnO NRs. Moreover, such photodetector shows good flexibility as well due to the mica substrate, which maintains almost constant performances under different bending radii of curvature and repeatable bending test more than 200 cycles. The photodetector also exhibits good transparency, giving it the potential of integration with other light photodetectors. In addition, a schematic band-diagram and the accompanying finite-difference time-domain analysis were performed to reveal the electron transfer and electric field distribution of ZnO NRs decorated with Au NPs. Our results revealed that the noble metal modified plasmon-enhanced ZnO NRs photodetector with high responsivity, low cost has a great potential for application in manufacturing flexible and transparent integrated optoelectronics.

With the rapidly aging society and increased concern for personal cardiovascular health, novel, flexible electrodes suitable for electrocardiogram (ECG) signal monitoring are in demand. Based on the excellent electrical and mechanical properties of graphene and the rapid development of graphene device fabrication technologies, graphene-based ECG electrodes have recently attracted much attention, and many flexible graphene electrodes with excellent performance have been developed. To understand the current research progress of graphene-based ECG electrodes and help researchers clarify current development conditions and directions, we systematically review the recent advances in graphene-based flexible ECG electrodes. Graphene electrodes are classified as bionic, fabric-based, biodegradable, laser-induced/scribed, modified-graphene, sponge-like, invasive, etc., based on their design concept, structural characteristics, preparation methods, and material properties. Moreover, some categories are further divided into dry or wet electrodes. Then, their performance, including electrode–skin impedance, signal-to-noise ratio, skin compatibility, and stability, is analyzed. Finally, we discuss possible development directions of graphene ECG electrodes and share our views.

Abstract Ferroelectric memories with ultralow‐power‐consumption are attracting a great deal of interest with the ever‐increasing demand for information storage in wearable electronics. However, sufficient scalability, semiconducting compatibility, and robust flexibility of the ferroelectric memories remain great challenges, e.g., owing to Pb‐containing materials, oxide electrode, and limited thermal stability. Here, high‐performance flexible nonvolatile memories based on ferroelectric Hf0.5Zr0.5O2 (HZO) via quasi‐van der Waals heteroepitaxy are reported. The flexible ferroelectric HZO exhibits not only high remanent polarization up to 32.6 µC cm−2 without a wake‐up effect during cycling, but also remarkably robust mechanical properties, degradation‐free retention, and endurance performance under a series of bent deformations and cycling tests. Intriguingly, using HZO as a gate, flexible ferroelectric thin‐film transistors with a low operating voltage of ±3 V, high on/off ratio of 6.5 × 105, and a small subthreshold slope of about 100 mV dec−1, which outperform reported flexible ferroelectric transistors, are demonstrated. The results make ferroelectric HZO a promising candidate for the next‐generation of wearable, low‐power, and nonvolatile memories with manufacturability and scalability.

Despite the need to develop resistive random access memory (RRAM) devices for machine learning, RRAM array-based hardware methods for algorithm require external electronics. Here, the authors realize a Markov chain algorithm in a single 2D multilayer SnSe device without external electronics.

Summary: Organometal trihalide perovskites (OTPs) are promising optoelectronic materials for high-performance photodetectors. However, up to now, traditional polycrystal OTP-based photodetectors have demonstrated limited effective photo-sensing range. Recently, bulk perovskite single crystals have been seen to have the potential for position-sensitive photodetection. Herein, for the first time, we demonstrate a position-dependent photodetector based on perovskite single crystals by scanning a focused laser beam over the device perpendicular to the channel. The photodetector shows the best-ever effective photo-sensing distance up to the millimeter range. The photoresponsivity and photocurrent decrease by nearly an order of magnitude when the beam position varies from 0 to 950 μm and the tunability of carrier diffusion length in CH3NH2PbBr3 with the variation of the exciting laser intensity is demonstrated. Furthermore, a numerical model based on transport of photoexcited carriers is proposed to explain the position dependence. This photodetector shows excellent potential for application in future nanoelectronics and optoelectronics systems. : Physics; Photonics; Optical Materials Subject Areas: Physics, Photonics, Optical Materials

COVID-19 is a highly contagious human infectious disease caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), and the war with the virus is still underway. Since no specific drugs have been made available yet and there is an imbalance between supply and demand for vaccines, early diagnosis and isolation are essential to control the outbreak. Current nucleic acid testing methods require high sample quality and laboratory conditions, which cannot meet flexible applications. Here, we report a laser-induced graphene field-effect transistor (LIG-FET) for detecting SARS-CoV-2. The FET was manufactured by different reduction degree LIG, with an oyster reef-like porous graphene channel to enrich the binding point between the virus protein and sensing area. After immobilizing specific antibodies in the channel, the FET can detect the SARS-CoV-2 spike protein in 15 min at a concentration of 1 pg/mL in phosphate-buffered saline (PBS) and 1 ng/mL in human serum. In addition, the sensor shows great specificity to the spike protein of SARS-CoV-2. Our sensors can realize fast production for COVID-19 rapid testing, as each LIG-FET can be fabricated by a laser platform in seconds. It is the first time that LIG has realized a virus sensing FET without any sample pretreatment or labeling, which paves the way for low-cost and rapid detection of COVID-19.

Abstract Single-walled carbon nanotubes (SWCNTs) offer great potential for field-effect transistors and integrated circuit applications due to their extraordinary electrical properties. To date, as-made SWCNT transistors are usually p-type in air, and it still remains challenging for realizing n-type devices. Herein, we present efficient and reversible electron doping of semiconductor-enriched single-walled carbon nanotubes (s-SWCNTs) by firstly utilizing decamethylcobaltocene (DMC) deposited by a simple spin-coating process at room temperature as an electron donor. A n-type transistor behavior with high on current, large I on /I off ratio and excellent uniformity is obtained by surface charge transfer from the electron donor DMC to acceptor s-SWCNTs, which is further corroborated by the Raman spectra and the ab initio simulation results. The DMC dopant molecules could be reversibly removed by immersion in N, N-Dimethylformamide solvent, indicating its reversibility and providing another way to control the carrier concentration effectively as well as selective removal of surface dopants on demand. Furthermore, the n-type behaviors including threshold voltage, on current, field-effect mobility, contact resistances, etc. are well controllable by adjusting the surface doping concentration. This work paves the way to explore and obtain high-performance n-type nanotubes for future complementary CMOS circuit and system applications.

The functional integration of sound generation and detection on a single device is required to assist mute people. Here, the authors demonstrate a graphene-based artificial throat capable of detecting and converting diverse throat vibrations into meaningful sound within a single device.

A ferroelectric thin film transistor (Fe-TFT) based on annealing-free hafnium zirconium oxide (HfZrO) is demonstrated in this paper. Indium zinc oxide was used as channel semiconductor. The as-deposited 30-nm HfZrO film implemented as gate dielectric was proved to be crystallized with a mixture of monoclinic, tetragonal, and orthorhombic phases and showed ferroelectricity naturally. Thus, high temperature annealing process was avoided. The transfer characteristic of this Fe-TFT was demonstrated with operating voltage that was smaller than 3 V, memory window about 1 V, and small subthreshold slope (SS) about 82 mV/dec. The charge trapping phenomenon in this device was explored by characterizing the transfer curves with different ranges of gate voltages. This HfZrO-based device with low processing thermal budget and small SS has high potential for Fe-TFT memory which can be used in oxide semiconductor-based systems and applications.

Graphene is an excellent thermoacoustic material due to its small heat capacity per unit area. However, there is obvious thermal leakage from the substrate which lower the sound emission efficiency. Here, in order to improve the efficiency, vertical graphene has been used as thermoacoustic device. In this paper, the high-quality vertical graphene was prepared by the MPCVD method, and the height of the vertical graphene was about 3.4 μm. Then a thermoacoustic device was fabricated based on vertical graphene. Compared to graphene, the unique structure of vertical graphene makes the device less area to substrate with less thermal leakage and can produce a higher sound pressure level (SPL) per unit area under the same height, the SPL value can reach as high as 60 dB at a measure distance of 0.3 cm with input power of 1.2W. This sound device based on vertical graphene is potential to be used in a wide range of applications.

Alignment and patterning of neurons have great importance in some research fields, especially for regenerative medicine and for the formation of artificial neural networks. Alignment of neurons on quartz grooves and parylene cues on quartz substrate was evaluated in this work. The neurons’ alignment on quartz grooves is considered to be topographical alignment, while the neurons’ alignment on parylene cues on quartz substrate is considered to be chemical alignment. Both quartz grooves’ and parylene cues’ widths were fabricated in a range from 2 µm to 8 µm; quartz grooves’ heights were in a range from 0.25 µm to 4 µm, while parylene cues’ heights were only 0.25 µm. Neurons were dissociated hippocampal neurons from rat E18. Neurons were cultivated on test substrates for 7 days before alignment evaluation. As expected, neurons aligned according to the direction of grooves and cues; however, transversal growth direction was also observed with much smaller tendency. Chemical alignment was found to be more effective than topographical alignment. If parylene cues are thin and distanced enough, then neurons have a tendency to follow the direction of individual parylene cues; however, neurons on quartz grooves have a tendency just to follow a preferable direction than individual quartz grooves.

Heart rate measurement is a basic and important issue for either medical diagnosis or daily health monitoring. In this work great efforts have been focused on realizing a portable, comfortable and low cost solution for long-term domestic heart rate monitoring. A tiny but efficient measurement system composed of a polymer-based flexible pressure sensor and an analog anti-interference readout circuit is proposed; manufactured and tested. The proposed polymer-based pressure sensor has a linear response and high sensitivity of 13.4 kPa−1. With the circuit’s outstanding capability in removing interference caused by body movement and the highly sensitive flexible sensor device, comfortable long-term heart rate monitoring becomes more realistic. Comparative tests prove that the proposed system has equivalent capability (accuracy:

This paper proposes a novel flexible piezoelectric micro-machined ultrasound transducer, which is based on PZT and a polyimide substrate. The transducer is made on the polyimide substrate and packaged with medical polydimethylsiloxane. Instead of etching the PZT ceramic, this paper proposes a method of putting diced PZT blocks into holes on the polyimide which are pre-etched. The device works in d31 mode and the electromechanical coupling factor is 22.25%. Its flexibility, good conformal contacting with skin surfaces and proper resonant frequency make the device suitable for heart imaging. The flexible packaging ultrasound transducer also has a good waterproof performance after hundreds of ultrasonic electric tests in water. It is a promising ultrasound transducer and will be an effective supplementary ultrasound imaging method in the practical applications.