The potential of three-dimensional (3D) printing technology in the fabrication of advanced polymer composites is becoming increasingly evident. This review discusses the latest research developments and applications of 3D printing in polymer composites. First, it focuses on the optimization of 3D printing technology, that is, by upgrading the equipment or components or adjusting the printing parameters, to make them more adaptable to the processing characteristics of polymer composites and to improve the comprehensive performance of the products. Second, it focuses on the 3D printable novel consumables for polymer composites, which mainly include the new printing filaments, printing inks, photosensitive resins, and printing powders, introducing the unique properties of the new consumables and different ways to apply them to 3D printing. Finally, the applications of 3D printing technology in the preparation of functional polymer composites (such as thermal conductivity, electromagnetic interference shielding, biomedicine, self-healing, and environmental responsiveness) are explored, with a focus on the distribution of the functional fillers and the influence of the topological shapes on the properties and functional characteristics of the 3D printed products. The aim of this review is to deepen the understanding of the convergence between 3D printing technology and polymer composites and to anticipate future trends and applications.

Prussian blue analogs (PBAs) are potential contestants for aqueous Mg-ion batteries (AMIBs) on account of their high discharge voltage and three-dimensional open frameworks. However, the low capacity arising from single reaction site severely restricts PBAs' practical applications in high-energy-density AMIBs. Here, an organic acid co-coordination combined with etching method is reported to fabricate defect-rich potassium-free copper hexacyanoferrate with structural water on carbon nanotube fiber (D-CuHCF@CNTF). Benefiting from the high-valence-state reactive sites, arrayed structure and defect effect, the well-designed D-CuHCF@CNTF exhibits an extraordinary reversible capacity of 146.6 mAh g⁻¹ with two-electron reaction, nearly close to its theoretical capacity. It is interesting to unlock the reaction mechanism of the Fe²⁺/Fe³⁺ and Cu⁺/Cu²⁺ redox couples via x-ray photoelectron spectroscopy. Furthermore, density functional theory calculations reveal that Fe and Cu in potassium-free D-CuHCF participate in charge transfer during the Mg²⁺ insertion/extraction process. As a proof-of-concept demonstration, a rocking-chair fiber-shaped AMIBs was constructed via coupling with the NaTi₂(PO₄)₃/CNTF anode, achieving high energy density and impressive mechanical flexibility. This work provides new possibilities to develop potassium-free PBAs with dual-active sites as high-capacity cathodes for wearable AMIBs.

The fast booming of wearable electronics provides great opportunities for intelligent gas detection with improved healthcare of mining workers, and a variety of gas sensors have been simultaneously developed. However, these sensing systems are always limited to single gas detection and are highly susceptible to the inference of ubiquitous moisture, resulting in less accuracy in the analysis of gas compositions in real mining conditions. To address these challenges, we propose a synergistic strategy based on sensor integration and machine learning algorithms to realize precise NH₃ and NO₂ gas detections under real mining conditions. A wearable sensing array based on the graphene and polyaniline composite is developed to largely enhance the sensitivity and selectivity under mixed gas conditions. Further introduction of backpropagation neural network (BP-NN) and partial least squares (PLS) algorithms could improve the accuracy of gas identification and concentration prediction and settle the inference of moisture, realizing over 99% theoretical prediction level on NH₃ and NO₂ concentrations within a wide relative humidity range, showing great promise in real mining detection. As proof of concept, a wireless wearable bracelet, integrated with sensing arrays and machine-learning algorithms, is developed for wireless real-time warning of hazardous gases in mines under different humidity conditions.

Near-infrared (NIR) luminescent metal halide (LMH) materials have attracted great attention in various optoelectronic applications due to their low-temperature solution-processable synthesis, abundant crystallographic/electronic structures, and unique optoelectronic properties. However, some challenges still remain in their luminescence design, performance improvement, and application assignments. This review systematically summarizes the development of NIR LMHs through classifying NIR luminescent origins into four major categories: band-edge emission, self-trapped exciton (STE) emission, ion emission, and defect-related emission. The luminescence mechanisms of different types of NIR LMHs are discussed in detail by analyzing typical examples. Reasonable strategies for designing and optimizing luminescence/optoelectronic properties of NIR LMHs are summarized, including bandgap engineering, self-trapping state engineering, chemical composition modification, energy transfer, and other auxiliary strategies such as improvement of synthesis scheme and post-processing. Furthermore, application prospects based on the optoelectronic devices are revealed, including phosphor-converted light-emitting diodes (LEDs), electroluminescent LEDs, photodetectors, solar cells, and x-ray scintillators, as well as demonstrations of some related practical applications. Finally, the existing challenges and future perspectives on the development of NIR LMH materials are critically proposed. This review aims to provide general understanding and guidance for the design of high-performance NIR LMHs materials.

The regulation of carrier generation and transport by Schottky junctions enables effective optoelectronic conversion in optoelectronic devices. A simple and general strategy to spontaneously generate photocurrent is of great significance for self-powered photodetectors but is still being pursued. Here, we propose that a photocurrent can be induced at zero bias by the transmittance contrast of MXene electrodes in MXene/semiconductor Schottky junctions. Two MXene electrodes with a large transmittance contrast (84%) between the thin and thick zones were deposited on the surface of a semiconductor wafer using a simple and robust solution route. Kelvin probe force microscopy tests indicated that the photocurrent at zero bias could be attributed to asymmetric carrier generation and transport between the two Schottky junctions under illumination. As a demonstration, the MXene/GaN ultraviolet (UV) photodetector exhibits excellent performance superior to its counterpart without transmittance contrast, including high responsivity (81 mA W^–1), fast response speed (less than 31 and 29 ms) and ultrahigh on/off ratio (1.33 × 10⁶), and good UV imaging capability. Furthermore, this strategy has proven to be universal for first- to third-generation semiconductors such as Si and GaAs. These results provide a facile and cost-effective route for high-performance self-powered photodetectors and demonstrate the versatile and promising applications of MXene electrodes in optoelectronics.

Layered two-dimensional (2D) materials have garnered marvelous attention in diverse fields, including sensors, capacitors, nanocomposites and transistors, owing to their distinctive structural morphologies and superior physicochemical properties. Recently, layered quasi-2D materials, especially layered bismuth oxyselenide (Bi₂O₂Se), are of particular interest, because of their different interlayer interactions from other layered 2D materials. On this basis, this material offers richer and more intriguing physics, including high electron mobility, sizeable bandgap, and remarkable thermal and chemical durability, rendering it an utterly prospective contender for use in advanced electronic and optoelectronic applications. Herein, this article reviews the recent advances related with Bi₂O₂Se. Initially, its structural characterization, band structure, and basic properties are briefly introduced. Further, the synthetic strategies for the preparation of Bi₂O₂Se are presented. Furthermore, the diverse applications of Bi₂O₂Se in the field of electronics and optoelectronics, photocatalytic, solar cells and sensing were summarized in detail. Ultimately, the challenges and future perspectives of Bi₂O₂Se are included.

Due to their unique photoelectric properties, nontoxic tin-based perovskites are emerging candidates for efficient near-infrared LEDs. However, the facile oxidation of Sn²⁺ and the rapid crystallization rate of tin-based perovskites result in suboptimal film quality, leading to inferior efficiencies of tin-based perovskite light-emitting diodes (Pero-LEDs). In this study, we investigate the influence of commonly used solvents on the quality of the CsSnI₃ films. Remarkably, DMSO exhibits a stronger interaction with SnI₂, forming a stable intermediate phase of SnI₂·3DMSO. This intermediate effectively inhibits the oxidation of Sn²⁺ and slows down the crystallization rate, bringing in lower defect state density and higher photoluminescence quantum yield of the prepared perovskite films. Consequently, the corresponding Pero-LEDs achieve a maximum external quantum efficiency (EQE) of 5.6%, among the most efficient near-infrared Pero-LEDs. In addition, the device processes ultra-low efficiency roll-off and high reproducibility. Our research underscores the crucial role of solvent-perovskite coordination in determining film quality. These findings offer valuable guidance for screening solvents to prepare highly efficient and stable tin-based perovskites.

In the process of photocatalytic synthesis of ammonia, the kinetics of carrier separation and transport, adsorption of nitrogen, and activation of the N≡N triple bond are key factors that directly affect the efficiency of converting nitrogen to ammonia. Here, we report a new strategy for anchoring MXene quantum dots (MXene QDs) onto the surface of ZnIn₂S₄ by forming Ti—S bonds, which provide a channel for the rapid separation and transport of charge carriers and effectively extend the lifespan of photogenerated carriers. The unique charge distribution caused by the sulfurization of the MXene QDs further enhances the performance of the photocatalysts for the adsorption and activation of nitrogen. The photocatalytic ammonia synthesis efficiency of MXene QDs–ZnIn₂S₄ can reach up to 360.5 μmol g⁻¹ h⁻¹. Density functional theory calculations, various in situ techniques, and ultrafast spectroscopy are used to characterize the successful construction of Ti—S bonds and the dynamic nature of excited state charge carriers in MXene QDs–ZnIn₂S₄, as well as their impact on nitrogen adsorption activation and photocatalytic ammonia synthesis efficiency. This study provides a new example of how to improve nitrogen adsorption and activation in photocatalytic material systems and enhance charge carrier dynamics to achieve efficient photocatalytic nitrogen conversion.

The inherent unpredictability of the maritime environment leads to low rates of survival during accidents. Life jackets serve as a crucial safety measure in underwater environments. Nonetheless, most conventional life jackets lack the capability to monitor the wearer's underwater body movements, impeding their effectiveness in rescue operations. Here, we present an intelligent self-powered life jacket system (SPLJ) composed of a wireless body area sensing network, a set of deep learning analytics, and a human condition detection platform. Six coaxial core-shell structure triboelectric fiber sensors with high sensitivity, stretchability, and flexibility are integrated into this system. Additionally, a portable integrated circuit module is incorporated into the SPLJ to facilitate real-time monitoring of the wearer's movement. Moreover, by leveraging the deep-learning-assisted data analytics and establishing a robust correlation between the wearer's movements and condition, we have developed a comprehensive system for monitoring drowning individuals, achieving an outstanding recognition accuracy of 100%. This groundbreaking work introduces a fresh approach to underwater intelligent survival devices, offering promising prospects for advancing underwater smart wearable devices in rescue operations and the development of ocean industry.

Optoelectronic logic gates have emerged as one of the key candidates for the creation of next generation logic devices. However, current optoelectronic logic gates can provide only one or two logic gates, severely limiting their applications. Here we report a self-powered and mechanically flexible device based on a BaTiO₃ ferroelectric film to produce multi-modal logic gates. By exploiting the photo-induced photovoltaic and pyroelectric effects of a Schottky junction which is created between BaTiO₃ and LaNiO₃, the device is able to provide five different optoelectronic logic gates, which can be operated using input lasers of different wavelength (405 or 785 nm). The mode of operation of the logic gate can be switched by controlling the wavelength and intensity of the input laser, where the switching process is both lossless and reversible. A logic gate array was designed to conduct the five logic operations, with 100% accuracy, thereby providing application potential for the Internet of Things, big data, and secure solutions for data processing and transmission.

Organic solar cells (OSCs) have emerged as a promising solution for sustainable energy production, offering advantages such as a low carbon footprint, short energy payback period, and compatibility with eco-solvents. However, the use of hazardous solvents continues to dominate the best-performing OSCs, mainly because of the challenges of controlling phase separation and domain crystallinity in eco-solvents. In this study, we combined the solvent vapor treatment of CS₂ and thermal annealing to precisely control the phase separation and domain crystallinity in PM6:M-Cl and PM6:O-Cl systems processed with the eco-solvent o-xylene. This method resulted in a maximum power conversion efficiency (PCE) of 18.4%, which is among the highest values reported for sustainable binary OSCs. Furthermore, the fabrication techniques were transferred from spin coating in a nitrogen environment to blade printing in ambient air, retaining a PCE of 16.0%, showing its potential for high-throughput and scalable production. In addition, a comparative analysis of OSCs processed with hazardous and green solvents was conducted to reveal the differences in phase aggregation. This work not only underscores the significance of sustainability in OSCs but also lays the groundwork for unlocking the full potential of open-air-printable sustainable OSCs for commercialization.

Silver nanowire (AgNW) networks hold great promises as next-generation flexible transparent electrodes (FTEs) for high-performance flexible optoelectronic devices. However, achieving large-area flexible AgNW network electrodes with low sheet resistance, high optical transmittance, and a smooth surface remains a grand challenge. Here, we report a straightforward and cost-effective roll-to-roll method that includes interface assembly/wetting-induced climbing transfer, nanowelding, and washing processess to fabricate flexible ordered layered AgNW electrodes with high network uniformity. By manipulating the stacking number of the interfacially assembled AgNW monolayer, we can precisely tailor and balance the transparency and the conductivity of the electrodes, achieving an exceptional Figure of Merit (FoM) value of 862. Moreover, the ordered layered structure enhances surface smoothness, compared with randomly arranged structures. To highlight the potential of these ordered layered AgNW network electrodes in flexible optoelectronic devices, we successfully employ them as highly sensitive strain sensors, large-area flexible touch screens, and flexible smart windows. Overall, this work represents a substantial advance toward high-performance FTEs over large areas, opening up exciting opportunities for the development of advanced optoelectronic devices.

Due to its non-invasive nature, ultrasound has been widely used for neuromodulation in biological systems, where its application influences the synaptic weights and the process of neurotransmitter delivery. However, such modulation has not been emulated in physical devices. Memristors are ideal electrical components for artificial synapses, but up till now they are hardly reported to respond to ultrasound signals. Here we design and fabricate a HfO_x-based memristor on 64°Y-X LiNbO₃ single crystal substrate, and successfully realize artificial synapses modulation by shear-horizontal surface acoustic wave (SH-SAW). It is a prominent short-term resistance modulation, where ultrasound has been shown to cause resistance drop for various resistance states, which could fully recover after the ultrasound is shut off. The physical mechanism illustrates that ultrasound induced polarization potential in the HfO_x dielectric layer acts on the Schottky barrier, leading to the resistance drop. The emulation of neuron firing frequency modulation through ultrasound signals is demonstrated. Moreover, the joint application of ultrasound and electric voltage yields fruitful functionalities, such as the enhancement of resistance window and synaptic plasticity through ultrasound application. All these promising results provide a new strategy for artificial synapses modulation, and also further advance neuromorphic devices toward system applications.

A wearable sensing system that can reconstruct dynamic 3D human body models for virtual cloth fitting is highly important in the era of information and metaverse. However, few research has been conducted regarding conformal sensors for accurately measuring the human body circumferences for dynamic 3D human body reshaping. Here, we develop a stretchable spring-sheathed yarn sensor (SSYS) as a smart ruler, for precisely measuring the circumference of human bodies and long-term tracking the movement for the dynamic 3D body reconstruction. The SSYS has a robust property, high resilience, high stability (>18 000), and ultrafast response (12 ms) to external deformation. It is also washable, wearable, tailorable, and durable for long-time wearing. Moreover, geometric, and mechanical behaviors of the SSYS are systematically investigated both theoretically and experimentally. In addition, a transfer learning algorithm that bridges the discrepancy of real and virtual sensing performance is developed, enabling a small body circumference measurement error of 1.79%, noticeably lower than that of traditional learning algorithm. Furtherly, 3D human bodies that are numerically consistent with the actual bodies are reconstructed. The 3D dynamic human body reconstruction based on the wearing sensing system and transfer learning algorithm enables excellent virtual fitting and shirt customization in a smart and highly efficient manner. This wearable sensing technology shows great potential in human-computer interaction, intelligent fitting, specialized protection, sports activities, and human physiological health tracking.

The anomalous Hall effect (AHE) that associated with the Berry curvature of occupied electronic states in momentum-space is one of the intriguing aspects in condensed matter physics, and provides an alternative for potential applications in topological electronics. Previous experiments reported the tunable Berry curvature and the resulting magnetization switching process in the AHE based on strain engineering or chemical doping. However, the AHE modulation by these strategies are usually irreversible, making it difficult to realize switchable control of the AHE and the resultant spintronic applications. Here, we demonstrated the switchable control of the Berry-curvature-related AHE by electrical gating in itinerant ferromagnetic Cr₇Te₈ with excellent ambient stability. The gate-tunable sign reversal of the AHE can be attributed to the redistribution of the Berry curvature in the band structure of Cr₇Te₈ due to the intercalation-induced change in the Fermi level. Our work facilitates the applications of magnetic switchable devices based on gate-tunable Berry curvature.