Gesture recognition utilizing flexible strain sensors is a highly valuable technology widely applied in human–machine interfaces. However, achieving rapid detection of subtle motions and timely processing of dynamic signals remain a challenge for sensors. Here, highly resilient and durable ionogels are developed by introducing micro-scale incompatible phases in macroscopic homogeneous polymeric network. The compatible network disperses in conductive ionic liquid to form highly resilient and stretchable skeleton, while incompatible phase forms hydrogen bonds to dissipate energy thus strengthening the ionogels. The ionogels-derived strain sensors show highly sensitivity, fast response time (<10 ms), low detection limit (∼50 µm), and remarkable durability (>5000 cycles), allowing for precise monitoring of human motions. More importantly, a self-adaptive recognition program empowered by deep-learning algorithms is designed to compensate for sensors, creating a comprehensive system capable of dynamic gesture recognition. This system can comprehensively analyze both the temporal and spatial features of sensor data, enabling deeper understanding of the dynamic process underlying gestures. The system accurately classifies 10 hand gestures across five participants with impressive accuracy of 93.66%. Moreover, it maintains robust recognition performance without the need for further training even when different sensors or subjects are involved. This technological breakthrough paves the way for intuitive and seamless interaction between humans and machines, presenting significant opportunities in diverse applications, such as human–robot interaction, virtual reality control, and assistive devices for the disabled individuals.
Animal experiments traditionally identify sensitizers in cosmetic materials. However, with growing concerns over animal ethics and bans on such experiments globally, alternative methods like machine learning are gaining prominence for their efficiency and cost-effectiveness. In this study, to develop a robust sensitizer detector model, we first constructed benchmark data sets using data from previous studies and a public database, then 589 sensitizers and 831 nonsensitizers were collected. In addition, a graph-based autoencoder and Mondrian conformal prediction (MCP) were combined to build a robust sensitizer detector, iSKIN. In the independent test set, the Matthews correlation coefficient (MCC) and the area under the receiver operating characteristic curve (ROCAUC) values of the iSKIN model without MCP were 0.472 and 0.804, respectively, which are higher than those of the three baseline models. When setting the significance level in MCP at 0.7, the MCC and ROCAUC values of iSKIN could achieve 0.753 and 0.927, respectively. Regrouping experiments proved that the MCP method is robust in the improvement of model performance. Through key structure analysis, seven key substructures in sensitizers were identified to guide cosmetic material design. Notably, long chains with halogen atoms and phenyl groups with two chlorine atoms at ortho-positions were potential sensitizers. Finally, a user-friendly web tool (http://www.iskin.work/) of the iSKIN model was deployed to be used by other researchers. In summary, the proposed iSKIN model has achieved state-of-the-art performance so far, which can contribute to the safety evaluation of cosmetic raw materials and provide a reference for the chemical structure design of these materials.
In dealing with the increasing power dissipation of electronic systems with increasing integration density, a field-effect transistor (FET) with steep switching slope that overcomes the thermionic limit is vital to achieve low-power operations. Here, we report two types of threshold switching (TS) FETs based on 2D Van der Waals heterostructures by virtue of the abrupt resistive switching of the hexagonal boron nitride (hBN) TS device. The common hBN dielectric layer functions as the switching medium for the TS device and the gate dielectric for the 2D FET enabling seamless integration of the hBN TS device and baseline 2D FET. TS FET in source configuration by connecting the TS device to the source terminal of the 2D FET offers an ultralow average subthreshold swing (SS) of 1.6 mV/dec over six decades of drain current at room temperature and suppressed leakage current. TS FET in gate configuration by connecting the TS device to the gate terminal of the 2D FET also exhibits steep switching slope with ultralow SS of 10.6 mV/dec. The proposed compact device structures integrating 2D FET and TS device provide a potential approach of monolithic integration toward next-generation low-power electronics.
Peri-implant infection is one of the major causes for implant failure. The transmucosal/transcutaneous surface of implant abutment is directly connected to the external environment and constantly exposed to a large number of bacteria. Establishing a robust anti-biofilm barrier at the abutment surface to minimize the risk of peri-implant infection is highly desirable in the field of dental implantology but remains challenging. Herein, a new class of therapeutic abutments featuring excellent anti-biofilm performance is developed, which is achieved by admirably integrating the outstanding self-cleaning property of polyethylene glycol and the long-lasting renewable antibacterial property of N-halamine. Through a comprehensive series of in vitro and in vivo experiments closely mimicking clinical conditions, therapeutic abutments have been successfully demonstrated to possess the ability of inhibiting biofilm accumulation to prevent peri-implant infection, as well as to achieve persistent and accurate administration to reverse early-stage peri-implant infection. Furthermore, the therapeutic abutment could be repeatedly used, representing the characteristic of sustainable medical devices. These findings indicate a new paradigm for the prevention and treatment of peri-implant infection.
Bioinspired neuromorphic machine vision system (NMVS) that integrates retinomorphic sensing and neuromorphic computing into one monolithic system is regarded as the most promising architecture for visual perception. However, the large intensity range of natural lights and complex illumination conditions in actual scenarios always require the NMVS to dynamically adjust its sensitivity according to the environmental conditions, just like the visual adaptation function of the human retina. Although some opto-sensors with scotopic or photopic adaption have been developed, NMVSs, especially fully flexible NMVSs, with both scotopic and photopic adaptation functions are rarely reported. Here we propose an ion-modulation strategy to dynamically adjust the photosensitivity and time-varying activation/inhibition characteristics depending on the illumination conditions, and develop a flexible ion-modulated phototransistor array based on MoS2/graphdiyne heterostructure, which can execute both retinomorphic sensing and neuromorphic computing. By controlling the intercalated Li+ ions in graphdiyne, both scotopic and photopic adaptation functions are demonstrated successfully. A fully flexible NMVS consisting of front-end retinomorphic vision sensors and a back-end convolutional neural network is constructed based on the as-fabricated 28 × 28 device array, demonstrating quite high recognition accuracies for both dim and bright images and robust flexibility. This effort for fully flexible and monolithic NMVS paves the way for its applications in wearable scenarios.
Flexible, wearable electronics are the future of electronics. Although organic photovoltaic devices have the advantages of high efficiency, low cost, and flexibility, they face the problem of failure due to the effects of water vapor in the environment. Therefore, the development of encapsulation films with outstanding mechanical and encapsulation properties is the key to realizing wearable devices. This review provides an overview of the development of thin-film encapsulation (TFE), the application of TFE in the field of optoelectronics, recent advances in the field of flexible encapsulation with TFE using atomic layer deposition technology, and an outlook on future trends in the field of flexible encapsulation with TFE using atomic layer deposition technology.
Soft robots have drawn a lot of interest in the field of human–robot interfaces because they can mimic the propulsion of soft bodies and archive complex tasks that cannot be made by rigid robots such as performing the complex motion, avoiding collisions by absorbing impacts, and shape adaptation by elastic deformation. Herein, drawing inspiration from creatures in the Cambrian period, such as Hallucigenia, we develop a centimeter-sized soft robot with multiple magnetic legs (referred to as a soft centirobot). This robot is equipped with graphitic carbon nitride (g-C3N4) nanosheets to kill biological threats by photogenerated reactive oxygen species under black light illumination. The motion of g-C3N4 soft centirobot is controlled by magnetic actuation even in complex wastewater samples (with a relative speed of 0.12 body lengths per second). The magnetic multilegs work as a propeller to walk across and cover large regions, and water disinfection is more efficient than what could be achieved by nano/micrometer scale sheets of g-C3N4. Finally, factors affecting the accelerated propulsion of g-C3N4 soft centirobot such as design principle, structure geometry, body mass, driving mechanism, and magnetic sensitivity, have been investigated. We envision that such a photoactive 2D material-based integrated centimeter-sized robot shall find application in many areas where pathogen removal is required.
A key component of organic bioelectronics is electrolyte-gated organic field-effect transistors (EG-OFETs), which have recently been used as sensors to demonstrate label-free, single-molecule detection. However, these devices exhibit limited stability when operated in direct contact with aqueous electrolytes. Ultrahigh stability is demonstrated to be achievable through the utilization of a systematic multifactorial approach in this study. EG-OFETs with operational stability and lifetime several orders of magnitude higher than the state of the art have been fabricated by carefully controlling a set of intricate stability-limiting factors, including contamination and corrosion. The indacenodithiophene-co-benzothiadiazole (IDTBT) EG-OFETs exhibit operational stability that exceeds 900 min in a variety of widely used electrolytes, with an overall lifetime exceeding 2 months in ultrapure water and 1 month in various electrolytes. The devices were not affected by electrical stress-induced trap states and can remain stable even in voltage ranges where electrochemical doping occurs. To validate the applicability of our stabilized device for biosensing applications, the reliable detection of the protein lysozyme in ultrapure water and in a physiological sodium phosphate buffer solution for 1500 min was demonstrated. The results show that polymer-based EG-OFETs are a viable architecture not only for short-term but also for long-term biosensing applications.
Low-temperature energy harvest, delivery, and utilization pose significant challenges for thermal management in extreme environments owing to heat loss during transport and difficulty in temperature control. Herein, we propose a light-driven photo-energy delivery device with a series of photo-responsive alkoxy-grafted azobenzene-based phase-change materials (a-g-Azo PCMs). These a-g-Azo PCMs store and release crystallization and isomerization enthalpies, reaching a high energy density of 380.76 J/g even at a low temperature of –63.92 °C. On this basis, we fabricate a novel three-branch light-driven microfluidic control device for distributed energy recycling that achieves light absorption, energy storage, controlled movement, and selective release cyclically over a wide range of temperatures. The a-g-Azo PCMs move remote-controllably in the microfluidic device at an average velocity of 0.11–0.53 cm/s owing to the asymmetric thermal expansion effect controlled by the temperature difference. During movement, the optically triggered heat release of a-g-Azo PCMs achieves a temperature difference of 6.6 °C even at a low temperature of –40 °C. These results provide a new technology for energy harvest, delivery, and utilization in low-temperature environments via a remote manipulator.
Surface-enhanced Raman scattering (SERS) has been applied in many fields due to its advantages of fast and nondestructive detection. For semiconductors, the large-scale electron-hole pair separation of heterojunction is conducive to efficient charge transfer, which is a promising SERS substrate. Here, we designed a Fe2O3@CeO2 heterojunction substrate by hydrothermal method and explored its enhancement mechanism in detail. α-Fe2O3 is a promising semiconductor with a narrow bandgap, and CeO2 has adequate oxygen vacancies on the surface. Combing α-Fe2O3 and CeO2 into a shell-core structure, Fe2O3@CeO2 heterojunction presents higher SERS performance than pure Fe2O3 and CeO2 for methyl orange (MO) molecule with a limit of detection (LOD) of 5 × 10–8 mol/L. Under the excitation of 514 nm, Fe2O3 can produce an effective exciton resonance due to its narrow bandgap (2.01 eV). The oxygen vacancy in CeO2 acts as the active site to promote the adsorption of molecules and facilitate the photo-induced charge transfer (PICT) between the substrate and MO molecules. Therefore, the high SERS performance of Fe2O3@CeO2 heterojunction is achieved due to the coupling effect of excitons resonance, molecular resonance, and PICT resonance. It is found that Fe2O3@CeO2 has good SERS performance and stability to organic pesticides, especially metamitron (LOD = 5 × 10–9 mol/L). This work combines the advantages of Fe2O3 being prone to producing photoelectrons and abundant oxygen vacancies of CeO2, providing a reference for designing semiconductor SERS.
Functional chiral suprastructures are common in biology, including in biomineralization, and they are frequently found in many hardened structures of both marine and terrestrial invertebrates, and even in pathologic human otoconia of the inner ear. However, the biological processes by which they form remain unclear. Here, we show that chiral hierarchical suprastructures of calcium sulfate dihydrate (gypsum) can be induced by the chiral Aspartic acid (Asp). Left-handed (clockwise) morphology of gypsum is induced by the D-enantiomer of Asp, while right-handed (counterclockwise) morphology is induced by the L-enantiomer. A layer-by-layer, oriented inclination mineral growth model controlled by continuous self-assembly of chiral Asp enantiomers on an amorphous calcium sulfate mineral surface of gypsum platelet layers is postulated to produce these chiral architectures. This hybrid amorphous-crystallized chiral and hierarchical suprastructure of gypsum displays outstanding mechanical properties, including high-performance strength and toughness. Furthermore, the induction of chiral gypsum suprastructures can be more generally extended from specific acidic amino acids to other (nonamino acid) molecules. These findings contribute to our understanding of the molecular mechanisms by which biomineral-associated enantiomers exert structural control over chiral architectures commonly seen in biominerals and in biomimetically synthesized functional materials.
Liquid-solid tubular triboelectric nanogenerators (LST-TENGs) hold significant promise for environmental mechanical energy harvesting due to advantages such as low wear, long service life and simple fabrication. However, the lack of unified standards and norms of design leads the output performance still being lower than that of traditional solid-solid TENGs. In this study, we first report a comprehensive set of standards for designing high-performance LST-TENGs based on several of the most critical factors, including the selection of triboelectric materials, the choice of motion modes, and the determination of structural parameters. Guided by the designing standards, the charge generation capability of LST-TENGs is optimized and enhanced by over 100-fold. The transferred charge can reach up to 3.4 µC, which is a new record for all kinds of LST-TENGs. Notably, the practical application potential of design standards has been demonstrated in the actual harvesting of wave energy. This study establishes a fundamental design standard for designing high-performance LST-TENGs and holds excellent potential to accelerate the industrialization of TENGs.
Surface-enhanced Raman scattering (SERS) has been visualized as a promising analytical technique in marked-molecule detection for disease diagnosis, environmental pollution, and so on. Noble metal nanoparticles, especially gold nanoparticles (AuNPs), are commonly used to fabricate SERS substrates. Herein, we facilely fabricated a special platform to improve the dispersity and homogeneity of AuNPs. Practically, based on nano-graphene oxide (GO), a special platform (s-GO-PEG-R’hB) was prepared through GO functionalization with biocompatible poly(ethylene glycol) (PEG), acid-activated fluorescence molecule (Rhodamine B lactam derivative, R’hB) and thiol sites with cysteamine. AuNPs were then in situ grown on s-GO-PEG-R’hB sheets to provide GO/AuNPs nanocomposite (Au@s-GO-PEG-R’hB) for use as an efficient SERS substrate, which can exert unique electromagnetic characteristics of AuNPs and improve its dispersity. With systematic morphology and composition characterizations, it was confirmed that uniform AuNPs were located on multi-functionalized GO sheets in Au@s-GO-PEG-R’hB as we designed. Au@s-GO-PEG-R’hB performed well in SERS detection towards 4-aminothiophenol (4-ATP) and p-phenylenediamine (PD), with preferable sensibility, stability and effectiveness. With well-knit SERS results, it is indicated that Au@s-GO-PEG-R’hB could take the advantages of inherent electrochemical properties of AuNPs and functionalized GO to be a potential substrate in SERS detection. Thus, it is foreseen that Au@s-GO-PEG-R’hB can meet diverse SERS sensing demands in real life.
P2-type layered Ni–Mn-based oxides are vital cathode materials for sodium-ion batteries (SIBs) due to their high discharge capacity and working voltage. However, they suffer from the detrimental P2 → O2 phase transition induced by the O2––O2– electrostatic repulsion upon high-voltage charge, which leads to rapid capacity fade. Herein, we construct a P2-type Ni–Mn-based layered oxide cathode with a core-shell structure (labeled as NM–Mg–CS). The P2-Na0.67[Ni0.25Mn0.75]O2 (NM) core is enclosed by the robust P2-Na0.67[Ni0.21Mn0.71Mg0.08]O2 (NM–Mg) shell. The NM–Mg–CS exhibits the phase-transition-free character with mitigated volume change because the confinement effect of shell is conductive to inhibit the irreversible phase transition of the core material. As a result, it drives a high capacity retention of 81% after 1000 cycles at 5 C with an initial capacity of 78 mA h/g. And the full cell with the NM–Mg–CS cathode and hard carbon anode delivers stable capacities over 250 cycles. The successful construction of the core-shell structure in P2-type layered oxides sheds light on the development of high-capacity and long-life cathode materials for SIBs.
Covalent organic frameworks (COFs) are new porous organic materials made of organic building blocks precisely constructed by strong covalent bonds. These new materials feature tunable structure, permanent porosity, high crystallinity, high specific surface area, and excellent stability, which enable COFs to be used in many applications. Linkage chemistry is a key factor in the synthesis of COFs and the control of their physicochemical properties. The boroxine, boronate-ester, imine, hydrazone, imide, and C=C linkages have been widely used in the construction of COFs. Among the various linkages, imine has become the most important linkage for the COFs due to the easy formation of imine linkage with structural and functional diversity. Over the past decade, imine-linked COFs have made significant progress and become an indispensable part of various applications of COFs. Here, we aim to provide a comprehensive review of the research progress in the field of imine-linked COFs, especially the advances in topology design and COF powder and film preparation, and their important advances in gas adsorption, catalysis, and optoelectronic devices. Finally, we discuss the challenges in the design, synthesis, and application of imine-linked COFs, and present our views on the further development of imine-linked COFs.
Charge manipulation is crucial in optoelectronic devices. The unoptimized interfacial charge injection/extraction in solution-processed bulk-heterojunction (BHJ) organic photodetectors (OPDs) presents significant challenges in achieving high detectivity and fast response speed. Here, we first develop an approach for intrinsic charge manipulation induced by molecularly engineered donors to block electron injection and facilitate hole extraction between the indium tin oxide (ITO) transparent anode and the photoactive layer. By utilizing a polymer donor with 3,4-ethylenedioxythiophene (EDOT) as the conjugated side chain, a polymer-rich layer forms spontaneously on the ITO substrate due to the increased oxygen interactions between ITO and EDOT. This results in electron-blocking-layer (EBL)-free devices with lower dark current and noise without a reduction in responsivity compared to control devices. As a result, the EBL-free devices exhibit a peak specific detectivity of 2.36 × 1013 Jones at 950 nm and achieve a –3 dB bandwidth of 30 MHz under –1 V. Enhanced stability is also observed compared to the devices with poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS). This work demonstrates a new method to intrinsically manipulate charge injection in BHJ photoactive layers, enabling the fabrication of solution-processed EBL-free OPDs with high sensitivity, rapid response, and good stability.
Proton chemistry is becoming a focal point in the development of zinc-ion energy storage devices due to its swift H+ insertion/extraction kinetics. This characteristic feature confers to electrodes a remarkable power density, rate capability, and prolonged cycling durability. However, the storage mechanism of H+ in electrodes based on covalent-organic frameworks (COFs) has not been thoroughly investigated. In this work, we introduce an unprecedented concept involving a supramolecular approach based on the design of a benzotrithiophene-sulfonate COF (COF-BTT-SO3H) with remarkable storage capacity for simultaneous insertion and extraction of H+ and Zn2+. The ad hoc positioning of the -SO3H groups within the COF-BTT-SO3H structure facilitates the formation of a robust H-bonded network. Through density functional theory calculations and employing in situ and ex situ analyses, we demonstrate that this network functions as a spontaneous proton ion pump leading to enhanced ion-diffusion kinetics and exceptional rate performance in zinc-ion energy storage devices. COF-BTT-SO3H reveals a high capacity of 294.7 mA h/g (0.1 A/g), a remarkable maximum energy density of 182.5 W h/kg, and power density of 14.8 kW/kg, which are superior to most of the reported COF-based electrodes or other organic and inorganic electrode materials in Zn2+ energy storage devices.