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Recently, zinc and its alloys have been proposed as promising candidates for biodegradable metals (BMs), owning to their preferable corrosion behavior and acceptable biocompatibility in cardiovascular, bone and gastrointestinal environments, together with Mg-based and Fe-based BMs. However, there is the desire for surface treatment for Zn-based BMs to better control their biodegradation behavior. Firstly, the implantation of some Zn-based BMs in cardiovascular environment exhibited intimal activation with mild inflammation. Secondly, for orthopedic applications, the biodegradation rates of Zn-based BMs are relatively slow, resulting in a long-term retention after fulfilling their mission. Meanwhile, excessive Zn2+ release during degradation will cause in vitro cytotoxicity and in vivo delayed osseointegration. In this review, we firstly summarized the current surface modification methods of Zn-based alloys for the industrial applications. Then we comprehensively summarized the recent progress of biomedical bulk Zn-based BMs as well as the corresponding surface modification strategies. Last but not least, the future perspectives towards the design of surface bio-functionalized coatings on Zn-based BMs for orthopedic and cardiovascular applications were also briefly proposed., Graphical abstract Image 1, Highlights • The current surface modification methods of Zn-based alloys for industrial applications. • The recent progress of Zn-based biodegradable metals and the corresponding surface modification strategies. • Future perspectives on the surface design of Zn-based biodegradable metals for orthopedic and cardiovascular applications.

Summary As an emerging energy-harvesting technology, enhancing the output performance of triboelectric nanogenerators (TENGs) is crucial for its practical application. Here, a dielectric enhancement effect is firstly proposed to improve the output performance of TENGs. It is found that the dielectric enhancement layer greatly elevates the triboelectrification effect, and the enhanced performance is verified by all types of TENGs. Thus, the output power of alternative current TENG (AC-TENG) and direct current TENG (DC-TENG) realizes 8.5-fold and 2.6-fold enhancement of normal devices, respectively. Besides this, the dielectric enhancement layer with leakage performance is proven to be necessary for DC-TENG to produce a continuous output. Our work provides a simple and universal strategy for elevating the performance of all types of TENGs, which is beneficial to the promotion of large-scale energy harvesting by TENGs.

In this article, a 1×12 millimeter-wave (mmW) linearly tapered slot antenna (LTSA) array, fed by high-order waveguide modes, is introduced. Due to the antiphase characteristic between adjacent channels of a power divider based on the TE2n,0 mode waveguide, the cross-polarized E-field components can cancel each other out in an end-fire direction, even in the case of a relatively thick substrate. Moreover, the electric separations between the adjacent channels employed in a traditional substrate integrated waveguide (SIW) power divider can be removed without affecting the field distributions. This facilitates in improving robustness to avoid fabrication errors. Additionally, a general condition of generating a single high-order mode with symmetrical protection is outlined. By combining two antiphase TE30 mode waveguides, an equivalent TE60 mode waveguide with six identical output channels is realized. To feed a 12-element array, two equivalent TE60 mode waveguides are employed as an equivalent TE12,0 mode-feeding network. Instead of the complex 1-to-n-way power divider and relatively thin substrate featured in previous works, the high-order mode-fed LTSA array introduced in this study is able to operate over 26.5b–30 GHz with substrate height of 2 mm (0.19λ0), yielding a cross-polarization level of less than -15 dB.

In this study, a picosecond (ps) laser was employed to produce micro-textures on ductile iron in linearly processing leading to significantly higher processing efficiency. The fabrication efficiency was increased about 1331 times as compared to the more common spot-by-spot texturing method. The ps laser induced graphene (LIG) structures were simultaneously fabricated in dimples, which further enhanced the surface tribological properties. The surface micro-textures were produced by forming micro-dimples on the substrate via the laser ablation process. The dimple diameter and area density were regulated by varying the key laser processing parameters, and were experimentally correlated to the tribological properties of the ductile iron substrate. To understand deeper into the wear reduction mechanism of the micro-dimples, simulation models based on the Reynold equation were established, which analyze the flow field pressure distribution and demonstrate the hydrodynamic lubrication effect of the micro-textures. The ball-on disk friction test showed that the area density of the micro-textures had a significant influence on the friction and wear properties. The micro-texture with the area density of 20 % and the average dimple diameter of 36 μm showed the highest volume wear rate reduction of 70 % and the friction coefficient reduction of 20 % respectively. The results indicated that the simultaneous laser in-situ generation of graphene micro-textures is an effective way of enhancing tribological properties on the ductile iron surface. It enhances the hardness of textured surfaces, thermal diffusion, debris capture ability, and fluid dynamic lubrication effect.

Welding is a major manufacturing process that joins two or more pieces of materials together through heating/mixing them, with or without pressure, as they cool and solidify. The goal of welding manufacturing is to join materials together to meet service requirements at the lowest costs. Advanced welding manufacturing (AWM) is to use scientific methods to realize this goal. It involves three steps: (1) pre-design that selects process and joint design based on available processes (properties, capabilities, and costs); (2) design that uses models to predict the result from a given set of welding parameters and minimizes a cost function for optimizing the welding parameters; (3) real-time sensing and control that overcome the deviations of welding conditions from their nominal ones used in optimizing the welding parameters by adjusting the welding parameters based on such real-time sensing and feedback control. While step (1) and (2) are pre-manufacturing designs, step (3) is the step during manufacturing that must be addressed by manufacturers. This report reviews and analyzes the state-of-the-art in real-time sensing of the gas metal arc welding, that is the most widely used robotic welding process, including seam tracking, machine vision, weld pool monitoring, machine learning, etc.

The attenuation of CO2 injectivity has become the biggest technical barrier for the application of CO2 enhanced coalbed methane recovery (CO2-ECBM). Commonly, the intermittent CO2 injection, N2 displacing CO2 and pre-fracturing are the potential CO2 enhanced injectivity methods for coal reservoirs, but their mechanism and effectiveness remain to be clarified. This paper thus conducted small-scale experiments to simulate the working process of these engineering measures by an independently developed experimental device. Results show that the CO2 injectivity of coal is remarkably improved by the intermittent injection mode since the CO2 injection time is increased by folds and the loss of reservoir pressure can be complemented in time. The N2 displacing CO2 method promotes the desorption of CO2 and reduces the swelling strain, with the result that the permeability of coal is improved by 74.82% and 64.95% compared with the methods of the primary subcritical CO2 (SubCO2) and supercritical CO2 (ScCO2) injection. However, the permeability reduces again with the secondary CO2 injection. The permeability of the coal sample after pre-fracturing is averagely improved by 1–2 orders of magnitude, the irreversible permeability loss rate, average stress sensitivity coefficient and the permeability loss rate due to adsorption are averagely reduced by 95.885%, 61.538% and 96.297%, respectively. This indicates that the permeability of coal after pre-fracturing is no longer sensitive to both the effective stress and ScCO2 adsorption, the injectivity is thus improved and stable. The CO2 enhanced injectivity effects of the intermittent CO2 injection, the N2 displacing CO2 and the pre-fracturing are various, which thus can be selected individually or jointly to improve the CO2 injectivity according to the reservoir physical properties and geological conditions. This research deepens the understanding of the functional mechanism of CO2 enhanced injectivity methods and provides some guidance for their selection and application in engineering practices.

Dy2−xCo17Lax (x = 0.0, 0.1, 0.2, 0.3 and 0.4) alloy powders were prepared by vacuum smelting, homogeneous heat treatment and high-energy ball milling. The structure, morphology, magnetic properties and electromagnetic parameters of the powders were characterized by x-ray diffraction, scanning electron microscopy, vibration sample magnetometry and vector network analysis. On this basis, the microwave absorption properties of alloy powders were studied. With increasing amounts of La doping, the peak position of the reflection loss of the alloy moved to a low frequency, and the saturation magnetization decreased accordingly. When the doping amount was x = 0.4 and the matching thickness was 1.4 mm, the minimum reflection loss (RLmin) value was −27.4 dB at 8.56 GHz, and its effective absorption bandwidth (EAB) could reach 1.6 GHz (7.68–9.36 GHz). At the same time, the influence of the matching thickness on the value of reflection loss and peak frequency was also investigated.

The tungsten (W) material as the divertor of fusion reactors is exposed to low-energy and high-flux He/H isotope irradiation, leading to the growth of fuzz layers. The W fuzz growth does not show any dependence on the plasma irradiation devices used; however, it is strongly dependent on He+ fluence and energy, irradiation temperature, and impurity level. When the incident He ions collide inside the dense fuzz layers with the extremely high specific area, their mean free path can be up to 690 nm. Up to now, the He bubble-driven W fuzz growth process is not entirely understood; however, it can be closely related to the surface bursting of He bubbles in the W surface layer and W surface erosion by He+ implantation. The formation of He bubbles can be attributed to the solute He diffusion into defects or bubbles, which is strongly affected by the temperature and He+ fluence. The W fuzz grows over the W surface, where the micro-stress caused by He bubbles in the W surface layer acts as the driving force. The W fuzz layer inhibits He+ implantation into W bulk, and provides an entire protection against the He+ erosion into W bulk beneath the fuzz layer. In this review article, the current status of experiment and theory are presented, and some of the remaining issues are discussed.

Perforated structure is the mechanical weak link of polymer-bonded explosive (PBX). Improving its mechanical property may promote the reliability and effectiveness of weapon system. In this study, strengthening of the perforated PBX plate is conducted by employing surface coating. Digital image correlation (DIC) analysis results suggest that the regional applied epoxy coating layer is able to improve the mechanical properties of the plate. By confining the deformation and releasing the stress concentration around the perforation, the coating layer enhances the load carrying ability and energy dissipation capacity of the plate significantly. This investigation may provide a convenient and effective structure modification method for energetic material, and at the same time, lay foundation to the performance optimization of weapon system.

Wearable on-skin electrodes or conductors should be vapor permeable, strain-insensitive, isotropically stretchable and stable under cyclic stretching. Various strategies have been proposed to prepare the required conductors up to now; however, it is a challenge to fabricate them with above properties in a simple manner. In this paper, a highly permeable and stretchable conductor based on electrospun fluorine rubber fiber mat is reported. The fibers are pre-stretched in electric field during electrospinning, and they shrink isotropically by ~ 35–40% in area after being detached from the substrate. The obtained fiber mat conductor demonstrates high stretchability up to ~ 170%, and the resistance changes only 0.8 under 60% strain, which is superior to many other strain-insensitive conductors. The conductor possesses high stability, no cracks or structure damage are observed after washing and cyclic stretching. Moreover, the conductor is vapor permeable with a water vapor transmission rate of ~ 850 g m−2 day−1, which is comparable to the normal water evaporation in ambient conditions, indicating that it would not disturb the sweat evaporation when being used on skin. The conductor is successfully used as stretchable yarns and electromyography (EMG) electrodes, showing high reliability in E-textiles and on-skin applications.

The flourishing development in flexible electronics has provoked intensive research in flexible strain sensors to realize accurate perception acquisition under different external stimuli. However, building hydrogel-based strain sensors with high stretchability and sensitivity remains a great challenge. Herein, MXene nanosheets were composited into polyacrylamide-sodium alginate matrix to construct mechanical robust and sensitive double networked hydrogel strain sensor. The hydrophilic MXene nanosheets formed strong interactions with the polymer matrix and endowed the hydrogel with excellent tensile properties (3150%), compliant mechanical strength (2.03 kPa−1 in Young’s Module) and long-lasting stability and fatigue resistance (1000 dynamic cycles under 1,600% strain). Due to the highly oriented MXene-based three dimensional conductive networks, the hydrogel sensor achieved extremely high tensile sensitivity (18.15 in gauge factor) and compression sensitivity (0.38 kPa−1 below 3 kPa). MXene hydrogel-based strain sensors also displayed negligible hysteresis in electromechanical performance, typical frequent-independent feature and rapid response time to external stimuli. Moreover, the sensor exhibited accurate response to different scales of human movements, providing potential application in speech recognition, expression recognition and handwriting verification.

Summary Water-wave energy, as one of the important renewable energies, is greatly difficult to efficiently harvest due to its characteristics of low frequency and randomly moving direction. Herein, we report an active resonance triboelectric nanogenerator (AR-TENG) system fabricated by using simple pendulum, tumbler, and flexible ring TENG, which can harvest omnidirectional and frequency varying water-wave energy through excellent structural design and resonance effect. Besides, thanks to the high-frequency damped motion of simple pendulum and tumbler, the high-frequency output generated by the AR-TENG system under the driving condition of low-frequency water wave can greatly improve the efficiency of wave energy harvesting. More importantly, based on the low damping coefficient, resonance effect, and elimination of water screening effect, the output performance of AR-TENG system in the water wave is closest to the simulated test. This work not only can realize the omnidirectional water-wave energy harvesting by TENG but also provide a method for large-scale blue energy harvesting.

Leaky-wave antenna (LWA) is known as a type of traveling antenna with dispersive frequency responses, which has found important applications in modern communication, imaging, and radar systems. The beam scanning rate is a key consideration in some applications since it can minimize the bandwidth requirement of the system, during the scanning in broad angular regions. However, the sweeping linearity, namely the scanning angular range per unit frequency, is seldom considered at the same time in the published literature. In this article, we propose a waveguide-type LWA working from 11.1 to 12 GHz. By loading periodical pins with glide symmetry in the waveguide, it is possible to manipulate the dispersion properties of the fast wave mode, hereby giving rise to a good balance between the scanning rate and the sweeping linearity. This scenario has been validated by numerical simulation and experiment with excellent agreement. The measurement results reveal that the scanning angles have been increased to a range from 16.7°~67.5° varying the frequency from 11.1 to 12.1 GHz. The relative average scanning rate is enhanced up to 589.3°, with high sweeping linearity.

Strain localization, usually manifesting as shear bands, is frequently observed in geomaterials and is of the essential reason inducing the failure of geostructures. Anisotropic characteristics of soils has an important effect on the shear band behavior. This paper is devoted to study the effect of the fabric anisotropy on the initiation and evolution of the shear bands. In particular, the anisotropy is introduced to the strength parameter of the yield criterion by incorporating the material principal direction and the joint invariant of the stress tensor and the microstructure tensor. Furtherly, an elasto-plastic constitutive model considering the fabric anisotropy is established in the micropolar theory framework, and is then applied to simulate the shear bands in transversely geomaterials via three numerical examples, including the plane strain compression test, slope stability and the shallow foundation problems. Moreover, the mesh independency of the proposed model is discussed. Results show that the bifurcation, the shear bands pattern, and the bearing capacity highly depend on the material principal orientation and the anisotropic degree. Comparison with existing study indicates that the proposed model has a good performance in simulating the typical pre and post strain localization behaviors of transversely isotropic geomaterials.

Picosecond fiber laser was subjected on surface of ductile cast iron to induce graphene-like micro-texture array and enhance the tribological properties. The size of the dimples was regulated in the range of 5 μm–110 μm. The in-situ fabrication process was carried out on the workpiece surface in parallel manner and the scanning speed can be up to 3 m/s. The formation mechanism of graphene-like structure was analyzed. The tribological properties of the textured samples were investigated using a ball-on-disk tribometer. The results showed that the laser textured samples exhibit low coefficient of friction and the anti-wear properties were improved significantly. The textured sample showed no distinct wear pit, while the non-textured sample showed typical wear pit with depth up to 15 μm. Volume wear rate was reduced by 69.6 ± 6.9%. The graphene-like micro-texture array conducted by picosecond fiber laser scanning will not change the material isotropic, and the improved tribological properties are attributed to the combined effects of the increased surface hardness, improved heat dispersion property and entrapment of wear debris.

The progress of flexible/wearable electronic devices with multi-functionality has stimulated the rapid development of the matching power supply devices. Flexible supercapacitors with high electrochemical performance and mechanical flexibility are considered as attractive technologies to power flexible electronics and have been studied intensively. Carbon nanomaterials, such as carbon nanotube, graphene, and their composites, possess unprecedented physical/chemical properties and exhibit great potential for use in flexible supercapacitors. In this review, the recent progress of state-of-the-art flexible supercapacitors using advanced carbon nanomaterials is expounded comprehensively and systematically, the topic covered the micro/nano-structure control, macroscopic morphologies design, property optimization and application of carbon nanomaterials. Based on the current advances, the challenges and prospects of carbon nanomaterials applied in flexible supercapacitors are outlined and highlighted. As last, the matching between the characters of carbon nanomaterials, construction of flexible supercapacitors and fabrication technologies are put forward.

This paper is concerned with the active control of thermo-mechanical buckling of composite laminated plates using piezoelectric facesheets as actuators. The four-variable trigonometric shear deformation theory and Hamilton’s principle are applied to formulate the governing equation of structural system. The temperature feedback control strategy is proposed to conduct the active control of thermal-mechanical buckling. The simulation results show that the thermo-mechanical buckling of composite laminated plates can be effectively controlled by the presented control method. With a specific control gain, the critical mechanical buckling load can remain constant at different temperatures. The effects of geometric parameters, fiber angle, stacking sequence, position of piezoelectric layer and boundary conditions on the active control of thermo-mechanical buckling are also investigated.

A non-contact Laser-EMAT integrated system (LEIS) that uses a pulse laser as a generator and an Electromagnetic acoustic transducer (EMAT) as a detector is proposed. To explain the LEIS could simultaneously measure the width and the depth of metal plate, the finite element model (FEM) of the LEIS, which can describe the entire process from laser generates ultrasound to EMAT receives ultrasound, is established. In detail, the intensity ratios of Rayleigh wave, Shear wave and Longitudinal wave excited by laser under the consideration of three components, the particle displacement, the particle vibration velocity in out-plane direction and particle vibration velocity in in-plane direction, are focused. Combining the characteristics of the ratio and the EMAT as a velocity sensor, the Rayleigh wave and Longitudinal wave in the case of the particle vibration velocity in out-plane direction are chosen as the using waveforms, and the changes of directivity of various waveforms with laser parameters are studied. Furthermore, after the coil structure parameters and magnetic field direction of EMAT were reanalyzed and reconsidered, it is decided to use the coil with the wire spacing of 0.1 mm and a number of turns of 8 to combine with the transverse magnetic field to simultaneously detect the Rayleigh wave and Longitudinal wave generated by the laser. Finally, the signal-to-noise ratio of the two waveforms reach a balanced value, and can be clearly distinguished and extracted to achieve the purpose of measuring the depth and width of the metal plate at the same time.

A PLGA/Ti3C2 hybrid coating was successfully deposited on the surface of magnesium-strontium (Mg-Sr) alloys. Compared with the corrosion current density (icorr) of the Mg-Sr alloy (7.13 × 10−5 A/cm2), the modified samples (Mg/PLGA/Ti3C2) was lower by approximately four orders of magnitude (7.65 × 10−9 A/cm2). After near infrared 808 nm laser irradiation, the icorr of the modified samples increased to 3.48 × 10−7 A/cm2. The mechanism is that the local hyperthermia induced the free volume expansion of PLGA, and the increase in intermolecular gap enhanced the penetration of electrolytes. Meanwhile, the cytotoxicity study showed that the hybrid coating endowed the Mg-Sr alloy with enhanced biocompatibility.

MXene-based hydrogels, a flourishing family of soft materials, have recently emerged as promising candidates for stretchable electronics. Despite recent progress, most works use MXenes as conductive nanofillers. Herein, by tuning the molecular interactions between MXene nanosheets and other constituents within the hydrogels, we demonstrate Ti3C3Tx MXene can act as a versatile cross-linker to activate the fast gelation of a wide range of hydrogels, starting from various monomer- and polymer-based precursors. The gelation behavior varies significantly across hydrogels. In general, the fast gelation mechanism is attributed to the easier generation of free radicals with the help of Ti3C2Tx MXene and the presence of multiscale molecular interactions between MXene and polymers. The use of MXene as a dynamic cross-linker leads to superior mechanical properties, adhesion, and self-healing ability. Owing to the inherent photothermal behavior of Ti3C3Tx and the heterogeneous phase-transforming features of polymers, a polymer-MXene hydrogel is demonstrated to exhibit distinctive thermosensation-based actuation upon near-infrared illumination, accompanied by rapid shape transformation.

An unprecedented A2MIMIIIX6-type double perovskite adopting a fully hexagonal BaNiO3-type structure, (piperidinium)2[KBiCl6], undergoes a 2/mF ferroelastic phase transition at 285 K with a spontaneous strain of 0.0615, arising from the order–disorder transition of organic cations together with the synchronous displacement of inorganic chains.

Self-reporting polymers, which can indicate damage with perceptible optical signals in a tailored force range, are useful as stress-sensitive sensors. We demonstrate a simple approach to realize this function by embedding two distinct mechanophores — rhodamine (Rh) and bis(adamantyl)-1,2-dioxetane (Ad), in polyurethane/polylactic acid blends. The deformed blends generate red coloration and red chemiluminescence. Such a unique dual-responsive behavior was evaluated by solid-state UV-vis spectroscopy, macroscopic tensile tests with in situ RGB and light intensity analyses, which supported a stress-correlated occurrence of the ring-opening of Rh, the scission of Ad and the fluorescence resonance energy transfer process between the respective mechanochemical species. Complementarity stemming from the difference in properties and manifestations of the two mechanophores is essential. That is, the more labile Rh allows shifting the appreciable optical changes to a much lower force threshold; the transient nature and high dynamic range of mechanochemiluminescence from Ad map in real time where and when many of the covalently incorporated dioxetane bonds break; besides, the disrupted yet non-scissile structure of Rh acts as a fluorescent acceptor to effectively harvest chemiluminescence from ruptured Ad. The current strategy is thus empowering multi-functional mechano-responsive polymers with greatly improved sensitivity and resolution for multimodal stress reporting., Probing bond scission process in a broader force range was realized by embedding mechanochromic rhodamine and mechanochemiluminescent 1,2-dioxetane in polymer blends.

Lateral flow immunoassays (LFIAs) provide a powerful tool for rapid real-time assay of cancer biomarkers, which is vital for cancer detection and treatment follow-up. Lanthanide-based LFIAs is one of the most widely used methods, especially Eu (III) chelates, which possess distinctive and attractive characteristics, such as time-resolved fluorescence and large Stokes shift. Herein, we adopted a new one-step mini-emulsion polymerization method to synthesize carboxyl-modified fluorescent microsphere (OS-EuCM), which shows good stability, resistance to non-specific adhesion and uniform particle size distribution compared with traditional microspheres synthesized through the swelling method. Benefiting from the above advantages, OS-EuCM was successfully used in LFIAs to detect tumor marker Alpha-fetoprotein with high sensitivity and selectivity in concentration as high as 320 ng/mL, as well as a detection limit of 0.683 ng/mL. This lanthanide-based microsphere holds great potential for rapid point-of-care screening and clinical application.

Vibration response and band gap characteristics of the functionally graded frame structures are investigated based on the first-order shear deformation theory. The material properties of functionally graded material rods vary continuously in thickness direction according to a power law. Spectral stiffness matrix of the periodic functionally graded material frame structure in the global coordinate system is derived in detail. Consequently, the vibration band gap properties of the functionally graded material frame structure can be calculated and analyzed by using the spectral element method. The calculation accuracy for dynamic responses of the functionally graded material frame structure is validated by the finite element method. The results demonstrate that the wider band gaps in the low and medium frequency ranges can be achieved for the functionally graded frame structures comparing with the homogeneous ones. Moreover, the frequency windows and ranges for the band gaps of the functionally graded material frame structure can be effectively adjusted through designing the gradient indexes for the functionally graded material rods, which provide a novel idea for vibration suppression of frame structures.

Due to the impressive flexibility and stitchability, one-dimensional (1D) power storage devices are promising in facilitating devices assembly and provide highly efficient power sources for textile...

A novel biomaterial ink consisting of regenerated silk fibroin (SF) and 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-oxidized bacterial cellulose (OBC) nanofibrils was developed for 3D printing lung tissue scaffold. Silk fibroin backbones were cross-linked using horseradish peroxide/H2O2 to form printed hydrogel scaffolds. OBC with a concentration of 7wt% increased the viscosity of inks during the printing process and further improved the shape fidelity of the scaffolds. Rheological measurements and image analyses were performed to evaluate inks printability and print shape fidelity. Three-dimensional construct with ten layers could be printed with ink of 1SF-2OBC (SF/OBC = 1/2, w/w). The composite hydrogel of 1SF-1OBC (SF/OBC = 1/1, w/w) printed at 25 °C exhibited a significantly improved compressive strength of 267 ± 13 kPa and a compressive stiffness of 325 ± 14 kPa at 30% strain, respectively. The optimized printing parameters for 1SF-1OBC were 0.3 bar of printing pressure, 45 mm/s of printing speed and 410 μm of nozzle diameter. Furthermore, OBC nanofibrils could be induced to align along the print lines over 60% degree of orientation, which were analyzed by SEM and X-ray diffraction. The orientation of OBC nanofibrils along print lines provided physical cues for guiding the orientation of lung epithelial stem cells, which maintained the ability to proliferate and kept epithelial phenotype after 7 days’ culture. The 3D printed SF-OBC scaffolds are promising for applications in lung tissue engineering. Electronic supplementary material The online version of this article (10.1007/s10570-020-03526-7) contains supplementary material, which is available to authorized users.

LiNi0.5Mn1.5O4 materials with different crystal surface proportions are synthesized by graphite-assisted calcination method. Scanning electron microscopy (SEM) reveals homogeneous microsized polyhedral morphology with different proportions of exposed {100} and {111} surfaces. The most highlighted result is that LiNi0.5Mn1.5O4 with appropriate proportion exposed {100} and {111} surfaces can achieve both high power and long lifetime simultaneously. The LiNi0.5Mn1.5O4 with appropriate proportion exposed {100} and {111} surfaces can provide a large capacity of 74.8 mAh g−1 even at a discharge rate as high as 20 C. Besides, the capacity retentions of the LiNi0.5Mn1.5O4 with appropriate proportion exposed {100} and {111} surfaces are found to be 93.33% at 1 C after 100 cycles. These results represent the experimental evidence for lattice-plane anisotropy in LiNi0.5Mn1.5O4 crystals. Moreover, the LiNi0.5Mn1.5O4 with appropriate proportion exposed {100} and {111} surface structure is beneficial for obtaining high volumetric energy density and excellent processability in practical applications.

Miniaturized and flexible power resources such as supercapacitors with resistance of high voltage play a critical role as potential energy storage devices for implantable and portable electronics because of their convenience, high power density, and long-term stability. Herein, we propose a novel strategy for the fabrication of high voltage microsupercapacitors (HVMSCs) employing porous laser-induced graphene (from polyimide films with alkalization treatment) followed by laser carving of the polyvinyl alcohol/H3PO4 gel electrolyte to realize a series assembly of supercapacitors and significantly increase the voltage resistance. The results elucidated that HVMSCs (3 mm × 21.15 mm) exhibited excellent capacitive performance including exceptional potential window (10 V), high areal capacitance (244 μF/cm2), acceptable power density (274 μW/cm2) and energy density (3.22 μW h/cm2), good electrochemical stability and flexibility at different bending status (0, 45, 90, 135, and 180°), as well as impressive voltage durability more than 5 V in smaller scale (0.5 mm × 5.5 mm). As such, the HVMSCs have great potential to be integrated with microcircuit modules for the next-generation self-powered systems and storage electronic devices in high voltage applications.

The medium-voltage direct current (MVDC) distribution grids have been given significant attention because of their wide applications in the grid integration of the renewable energy sources and in the improvement of the stability and quality of the grid. However, due to the absence of the natural zero current crossings and the high rate of the short-circuit current, the fault current interruption in the MVDC systems is more problematic than that in the ac systems. Several types of interruption schemes have been proposed, and the vacuum interrupter-based dc circuit breaker (DCCB) is a promising solution for the MVDC interruption. Because of its high arcing current, the dielectric strength of the vacuum interrupter after the current crossing point stays low, which makes the dielectric recovery strength a critical factor for the reliability of the interruption. To estimate the reliability of the MVDC interruption, an experimental circuit is designed to measure the dielectric recovery strength of the vacuum interrupter, and the main influence factors are investigated with the experiments conducted under different arcing currents, contacts, $di/{\Delta t}$ before the current zero, and arcing times. The analysis and comparison of the dielectric recovery strength under different conditions are presented. The safe recovery time under different interruption conditions is proposed.

Manganese dioxide (MnO2) nanostructures have aroused great interest among analytical and biological medicine researchers as a unique type of tumor microenvironment (TME)-responsive nanomaterial. However, reliable approaches for synthesizing yolk-shell nanostructures (YSNs) with mesoporous MnO2 shell still remain exciting challenges. Herein, a YSN (size, ∼75 nm) containing a mesoporous MnO2 shell and Er3+-doped upconversion/downconversion nanoparticle (UCNP) core with a large cavity is demonstrated for the first time. This nanostructure not only integrates diverse functional components including MnO2, UCNPs, and YSNs into one system but also endows a size-controllable hollow cavity and thickness-tunable MnO2 layers, which can load various guest molecules like photosensitizers, methylene blue (MB), and the anticancer drugs doxorubicin (DOX). NIR-II fluorescence and photoacoustic (PA) imaging from UCNP and MB, respectively, can monitor the enrichment of the nanomaterials in the tumors for guiding chemo-photodynamic therapy (PDT) in vivo. In the TME, degradation of the mMnO2 shell by H2O2 and GSH not only generates Mn2+ for tumor-specific T1-MR imaging but also releases O2 and drugs for tumor-specific treatment. The result confirmed that imaging-guided enhanced chemo-PDT combination therapy that benefited from the unique structural features of YSNs could substantially improve the therapeutic effectiveness toward malignant tumors compared to monotherapy.

In industrial production, the standoff distance of magnetic pulse welding (MPW) is a critical parameter as it directly affects welding quality. However, the effects of standoff distance on the physical properties of MPW joints have not been investigated. Therefore, in this study, aluminum alloy (AA5182) sheets and high-strength low-alloy steel (HC340LA) sheets were welded through MPW at a discharge energy of 20 kJ, under various standoff distances. Thereafter, mechanical tests were performed on the MPW joints, and the results indicate that there is a significant change in the shear strength of the AA5182/HC340LA-welded joints with respect to the standoff distance. When the standoff distance ranges from 0.8 to 1.4 mm, the strength of the joint is higher than that of the base AA5182 sheet. Microscopic observations were conducted to analyze the interfacial morphology, element diffusion behavior, and microdefects on the welding interface of the AA5182/HC340LA joints. The AA5182/HC340LA joint with a standoff distance of 1.4 mm possesses the longest welded region and the largest interfacial wave. This interfacial wave pattern is suitable for achieving MPW joints with high shear strengths.

The structure of current collectors has significant effects on the performance of a lithium-ion battery (LIB). In this study, we use copper fiber felts made by multi-tooth cutting and high-temperature solid-phase sintering as the current collector for LIBs. An integrated porous electrode based on CuO nanoflowers/copper fiber felt is developed for the anode. Results suggest that the reversible capacity and cycle stability of this new anode are significantly improved, compared with the pristine bare-surface copper plate under the same condition of rate cycles. The new anode structure based on the copper-fiber felt with a porosity of 60% exhibits a higher performance with an initial specific capacity of 609.5 mAh g−1 and retains 486.1 mAh g−1 after 200 cycles at a current density of 0.5 C. The improved electrochemical performance of this electrode is attributed to its large surface area of CuO nanoflowers and porous structure of the copper fiber felt, due to enhanced contact between the active material of CuO nanoflowers and electrolyte. This pore-rich structure makes the electrolyte easy to permeate into the electrode, shortens the diffusion path of Li+, reduces the internal resistance and alleviates the volume expansion of the active material during the insertion and desertion processes of Li+.

As one of the most environmentally friendly photovoltaic (PV) conversion equipments, aqueous-processed CdTe nanocrystal solar cells (NC SCs) have attracted great interest in recent years because of their excellent properties such as high charge-carrier mobility and broad absorption. However, two issues including interfacial recombination and leakage current seriously restrict their performance. In this paper, insulating polymer poly(vinyl pyrrolidone) (PVP) is introduced into CdTe NC SCs to solve the problems. The experimental results of transmission electron microscopy (TEM), atomic force microscopy (AFM) and dark current measurements, etc., demonstrate the leakage current is effectively suppressed by introducing PVP. Through further designing device structure, the reduction of interfacial recombination after introducing PVP is confirmed. By strategically taking the advantages of PVP properties (e.g., water solubility and thermostability), the power conversion efficiency of the devices with PVP is enhanced by almost 37% compared to pure CdTe devices. This work demonstrates an effective and low-cost method to fabricate NC SCs via aqueous route. Moreover, it also proves that appropriate content of insulating polymer is of beneficial in promoting the PV performance.

The patterning of silver nanowires (AgNWs) is subject to critical challenges, which have seriously limited their practical applications. This work describes a simple and efficient method combining screen printing with vacuum filtration for patterning AgNW networks. The screen-printed poly(dimethylsiloxane) (PDMS) mask layer was shown to be strongly adhered to the filtration membrane, which resulted in well-defined sharp edges of the deposited AgNW patterns, and a 50 μm patterning resolution was achieved. The patterned films with low densities of AgNWs (≤15 μg/cm2) were transferred to the surface of PDMS to make patterned stretchable transparent conductive films (TCFs). The low sheet resistance of 7.3 Ω/sq was achieved at an optical transmittance of 79.6% (at 550 nm wavelength) with a AgNW deposition density of only 12.5 μg/cm2. As an application example, the patterned TCFs were used as the top electrodes to fabricate stretchable alternating current electroluminescent (ACEL) displays with stretchability up to 70% of their original dimension, which were applied to a smart system for simulating heart beats together with a digitally operated flexible circuit. The ACEL device exhibited a bright and uniform emission with a clear and smooth edge even with a pattern width as narrow as 100 μm, as well as exceptional elasticity and durability in spite of bending, stretching, and twisting. The present work provides a new way of patterning AgNWs and can be extended to a variety of applications.

In order to study the effect of brine environment on the performance of oil well cement fluid loss additive (FLA) sodium p-styrene sulfonate/N-methylol acrylamide/itaconic acid (SSS/HAM/IA), the water loss of three different cement slurry systems added with different FLA additions (fresh water cement slurry, semi-saturated brine cement slurry and saturated brine cement slurry) were tested at 90°C and 150°C. The results show that SSS/HAM/IA has good salt tolerance. The water loss of three cement slurry systems was controlled within 100mL with FLA addition adjusted in the range of 1%~3% below 150 °C. The salt tolerance mechanism of SSS/HAM/IA was analyzed based on the microstructure of the three system terpolymer solutions characterized under environmental scanning electron microscopy (ESEM).

Fluorescence sensing has the advantages of being real time, noninvasive, and convenient and having a low impact on the original environment for in vivo detection. Here, a reversible time-gated ratiometric in vivo detection method that could eliminate the interferences from probe amount, photon scattering, and absorption is proposed. Correspondingly, the composite probe must be able to reversibly respond to changes in the microenvironment and emit two luminescence signals at the same working wavelength but different lifetimes. Benefitting from the reversible detection mechanism, the probes could be used to monitor a dynamic biological process and the ratio signal value could be determined only by the concentration of analytes, independent of the probe concentration. Furthermore, benefitting from the same working wavelength, the read-out errors from photon absorption and scattering could be minimized. This method is very suitable for in vivo detection in which the probe distribution and depth are unknown and variable. As a typical model, different pH values in the gastrointestinal area and pH changes caused by drugs and fasting are successfully monitored.

Due to the demands of thermal performance enhancement of heat pipe solar collector, the fabrication of large-area flat heat pipes with the advantages of low cost and outstanding thermal performance has become more urgent. In this paper, a large-area ultra-thin flat heat pipe (LUFHP) with multiple parallel microchannels was fabricated by the aluminum extrusion process. Its total thickness is only 1.5 mm while the effective width is 170 mm. The effect of different filling ratios on the thermal performance was investigated under natural air convection and forced water cooling, respectively, including heat transport capability and thermal resistance. The experimental results indicate that the maximum heat transport capabilities for natural air convection and forced water cooling are 40 W with an optimal filling ratio of 25% and 25 W with an optimal filling ratio of 30%, respectively. The minimum total thermal resistances of the LUFHP are about 0.22 °C/W (natural air convection) and 0.73 °C/W (forced water cooling), which decrease by 74% and 57% compared with these of aluminum plate, respectively. That is, the proposed LUFHP shows better thermal performance under NAC for the replacement of aluminum plate in a wider range of heat load.

Zn–2Al alloy is used as a filler metal for brazing of aluminium 6063 alloys by ultrasonic-assisted resistance brazing (RB) technology. The evolution of the microstructure and phase composition unde...

Zinc and its alloys have emerged as a new research direction of biodegradable metals (BMs) due to the significant physiological functions of Zn2+ ions in human body. However, low inhibitory concentration threshold value to cause cytotoxicity by Zn2+ ions during in vitro study and delayed osseointegration in vivo are two key flaws for the bulk Zn-based BMs. To combat these issues, we constructed a barrier layer of ZrO2 nanofilm on the surface of Zn-0.1(wt.%) Li alloy via atomic layer deposition (ALD). A decreased release of Zn2+ ions accompanied with accelerated release of Li+ ions was observed on account of galvanic coupling between the coating compositions and Zn-0.1Li alloy substrate. Cytocompatibility assay reflected that ZrO2 nanofilm coated Zn-0.1Li alloy exhibited improved cell adhesion and viability. Histological analysis also demonstrated better in vivo osseointegration for the ZrO2 nanofilm coated Zn-0.1Li alloy. Hence, the present study elucidated that the ALD of ZrO2 nanofilm on Zn-based BMs can effectively promote osseointegration and control their biodegradation behavior. Statement of Significance Zn-Li binary alloy was reported recently to be the promising biodegradable metals with ultimate tensile strength over 500 MPa, yet the low inhibitory concentration threshold value to cause cytotoxicity by Zn2+ ions is the obstacle needed to be overcome. As a pilot study, a systematic investigation on the ZrO2 nanofilm coated Zn-Li alloy, prepared by atomic layer deposition (ALD) technique, was conducted in the present study, which involved in the formation process, in vitro and in vivo degradation behavior as well as biocompatibility evaluation. We found a controllable corrosion rate and better in vivo osseointegration can be achieved by ZrO2 nanofilm coating on Zn-Li alloy, which provides new insight into the surface modification on biodegradable Zn alloys for usage within bone.

It is an important precondition and basis for the design of tailings reservoir and its safety facilities by reasonably judging and estimating the mud-sand flow hazard due to dam-break. In this paper, the mud-sand flow hazard scope, extent and spatial state after dam-broken of heightened Mawuqing tailing dam were simulated and analyzed through a flood and debris flow numerical simulation approach, and the hazard risk grade of different spatial locations of downstream Xiaoqingkou(XQK) village was obtained from the simulation. Then the spatial simulation of sand flow hazard under different preventive measures was carried out, and the variation of hazard risk grade at different spatial locations in XQK was obtained. The result of spatial simulation and analysis has shown that if the retaining wall or detention dam is set at the edge of the village, the risk hazard of the village due to dam-break can be reduced after the tailing dam is heightened. At the same time, it can be concluded that to reduce dam break hazard the above local engineering measures are more effective than an overall engineering measures to control the mud-sand flow. The spatial simulation and analysis have provided the basis to make more reasonable engineering decision and protection measures for XQK after the reconstruction of the tailing dam, and also provided the technical support for tailing dam-break accident prevention, the safety management of tailing dam and the mine production safety.

Uniformly dispersed 5 wt % ruthenium catalysts supported on AlxSBA-15 (x = Si/Al ratio) were prepared by chemical fluid deposition employing supercritical CO2 as the solvent for hydrogenating dimet...

Li-rich 3d-transition metal layered oxides xLi2MnO3·(1 − x)LiMO2, one of the increasingly prospective cathode materials for high energy–density lithium-ion batteries, have attracted intensive attention by the research community. Nevertheless, their practical commercial applications are hindered by problems like the drop in the capacity and discharge voltage during cycling. Here, Li-rich Li1.2Mn0.54Ni0.13Co0.13O2 is synthesized by sol–gel process. The outstanding electrochemical performance of which is benefited from its layered-spinel heterostructure which composited by amounts of spinel LiNi0.5Mn1.5O4. The results indicate that spinel LiNi0.5Mn1.5O4 can inhibit phase transformation as well as facilitate fast lithium-ion transportation.

A wave equation of rock under axial static stress is established using the equivalent medium method by modifying the Kelvin-Voigt model. The analytical formulas of longitudinal velocity, space and time attenuation coefficients and response frequency are obtained by solving the equation using the harmonic method. A series of experiments on stress wave propagation through rock under different axial static stresses have been conducted. The proposed models of stress wave propagation are then verified by comparing experimental results with theoretical solutions. Based on the verified theoretical models, the influences of axial static stress on longitudinal velocity, space and time attenuation coefficients and response frequency are investigated by detailed parametric studies. The results show that the proposed theoretical models can be used to effectively investigate the effects of axial static stress on the stress wave propagation in rock. The axial static stress influences stress wave propagation characteristics of porous rock by varying the level of rock porosity and damage. Moreover, the initial porosity, initial elastic modulus of the rock voids and skeleton, viscous coefficient and vibration frequency have significant effects on the P-wave velocity, attenuation characteristics and response frequency of the stress wave in porous rock under axial static stress.

5,6,12,13-Tetraazaperopyrenes with different number of tert-butyl groups (c-TAPP-T, c-TAPP-H) were synthesized, via four-fold Bischler-Napieralski cyclization as the key step. As deduced from the single-crystal structures and optical properties, N-doping and substitution type allow for a precise control of intermolecular interactions. Compared to the reported 1,3,8,10-tetraazaperopyrenes, significantly different packing modes were found in 5,6,12,13-tetraazaperopyrenes. Going from c-TAPP-T to c-TAPP-H, two additional tert-butyl groups lead to different preferential growth directions, affording 1D and 2D microcrystals, respectively. Most importantly, both microcrystals exhibit excellent optical waveguide properties with extraordinarily low loss coefficients and unique polarization features. Although c-TAPP-H possesses a rigid and planar core, its crystals display an exceptional mechanochromic fluorescence, which, again, depends on the mode of molecular packing.

The lithium-ion battery (LIB) is an efficient electrochemical energy storage device with high voltage, long life, good safety, etc. Silicon has a high theoretical specific capacity (4200 mA h g−1), due to which it is considered a promising anode material for next-generation LIBs. However, the huge volume change (400%) of the Si material during the lithiation/delithiation processes destroys its structure, which greatly reduces the initial coulombic efficiency, cycle stability and rate performance of the battery. Accordingly, constructing nanostructured Si, particularly silicon nanowires (SiNWs), can help to address the above issues. Additionally, it is important to further improve the electrochemical performance by incorporating some additives in SiNW-based electrodes. Therefore, this review focuses primarily on SiNW-based materials as anodes for LIBs from a material-based perspective. Various materials incorporated into SiNW-based anodes through doping or compositing are reported. The electrochemical effects of diverse additives, including carbon materials, metals, metal oxides, polymers, Si-based materials and other special substances, are comprehensively reviewed.

Probes functioning in the second near-infrared window (1000-1700 nm, NIR-II) exhibit higher resolution and diminished auto-fluorescence compared to those in the traditional NIR region (700-950 nm). Here, we designed and synthesized rare earth ion doped probes with core/shell/shell structures and bright luminescence in the NIR-II region excited at 808 nm. With the doping of Ce3+ ions, the emission intensity of Er3+ at 1530 nm increased 10 times, while the upconversion luminescence decreased to less than 1%. After being modified with polyacrylic acid and polyethylene glycol, the as-obtained water-soluble probe exhibits continuous high-resolution for distinguishing 0.25 mm blood vessels even 10 h after injection. Noteworthily, the imaging of tumors was achieved by injecting the probe, indicating that the designed NIR-II probe has sufficient brightness and the ability to passively target tumor tissue.

Broadening the temperature range of lithium-ion batteries can be achieved by optimizing the composition of lithium salts in the electrolyte, which is currently one of the most popular methods. In this study, we report an extra-high temperature electrolyte by optimizing the proportion of mixed lithium salts (LiBOB and LiBF4) with ethylene carbonate (EC), diethyl carbonate (DEC) and ethyl methyl (EMC) as an equal volume mixture. An extra-high temperature of 75 °C is applied in a half cell with lithium iron phosphate (LFP) as the cathode and a lithium foil as the anode. The cycle stability and rate performance of the cell with various electrolytes based on mixed lithium salts are systematically investigated and a comparison of the polarization and impedance characteristics is conducted as well. The most outstanding electrolyte composition is electrolyte B (0.6 M LiBOB + 0.1 M LiBF4-EC/DEC/EMC). The optimized electrolyte not only maintains good cycle stability (the capacity retention rate is 98% after 80 cycles) and excellent rate performance at the extra-high temperature, but also minimizes the polarization during cycling, which is mainly due to the formation of a dense and smooth cathode electrolyte interface (CEI) film, as observed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The CEI film that contains B–O bonds and organic components is systematically analyzed by energy-dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS), which shows that the components aid the extra-high temperature cycling stability of the cell. Our data indicate that the composition of lithium salts in the electrolyte is pivotal to the properties of the CEI film, which largely determines the performance of the cell at extra-high temperatures. The conclusions of this work can contribute significantly to the application of extra-high temperature electrolytes.

Stretchable electrodes have attracted great attention for developing next generation wearable and flexible electronics. However, the fabrication of stretchable electrodes with high electrical stability, especially high omnidirectional stretchability, remains challenging. Here, we proposed a scheme for making stretchable electrodes based on wrinkled silver nanowires (Ag NWs) through the shrinkage of electrospun polymer fibers. The Ag NWs were vacuum filtered on electrospun fluoroelastomer fiber mats, and then they formed isotropic wrinkles on the scale of several micrometers after the thermal induced shrinkage of the fibers. An ∼80% areal shrinkage was achieved in the composite fiber mat under the conditions of 7 kV applied voltage during electrospinning and 120 °C thermal treatment temperature. The co-shrunk Ag NW electrodes reached high stretchability of up to 500%. The resistance increased only by a factor of ∼0.65 under 100% strain and ∼0.1 under 50% strain. These random wrinkles endow the electrodes with high omnidirectional stretchability, no significant variation of resistance change was observed along the hexagonal stretched directions at ∼80% strain. In addition, the stretchable electrodes demonstrated good electrical stability, with only

Here we demonstrate a novel SERS-active substrate assembled by silver nanowire (Ag NW)-embedded porous polystyrene (PS) fibers. Ag NWs are synthesized through a glycerol-mediated solvothermal method firstly, then electrospun into PS porous fibers. The as-synthesized Ag NWs are embedded in PS fiber and aligned orderly along the axial direction. Porous structure appears in PS fiber due to the phase separation induced by rapid evaporation of solvents. Large amounts of holes not only greatly improve the sample collection efficiency of the SERS-active substrate, but also significantly facilitate the adsorption of target molecules on the surface of Ag NWs, thus increasing the probability of enhancement of target molecules. In addition, compared with polyvinyl alcohol (PVA) and polyvinyl pyrrolidone (PVP), PS has better solvent resistance. The detection limit of 4-aminothiophenol (4-ATP) on our fabricated electrospun fiber mats is 10−7 M, and the electrospun fiber mats showed good reproducibility of SERS signal detection. This study proposes a feasible strategy for the large-scale preparation of flexible SERS-active substrate assembled by Ag NW-embedded porous PS fibers. The produced flexible SERS substrates may have potential application in wearable sensors for the trace detection of chemical and biological molecules.