Synchronously Enhancing Mechanical Strength and Conductivity of MXene Nanofluidic Fibers with Multivalent Ion Crosslinking

Developing high-performance nanofluidic fibers with synergetic ionic and electric conductivities is promising for human–machine interface interaction. In such a scenario, inter- and intra-forces in constituent flakes are recognized as crucial factors in determining the derived nanofluidic fiber performance. In this work, the rheological properties of Ti₃C₂T_x MXene solution are systematically optimized by regulating the electrostatic interaction via introducing multivalent metal cations. As a result, such multivalent cations trigger ionic crosslinking and remarkably strengthen the interaction force between nanosheets, which even forms into a tight fiber-shaped gel network. A series of cations, such as K⁺, Na⁺, Mg²⁺, Zn²⁺, and Al³⁺, are introduced to enhance the ionic cross-linking between interconnected flakes. The thus-prepared Zn²⁺-Ti₃C₂T_x fiber exhibits a remarkable electrical conductivity of 11 200 S cm⁻¹, a tensile strength of 252 MPa, and an ionic conductivity of 2.51 × 10⁻³ S cm⁻¹. This multivalent cation crosslinking strategy could offer some insights into developing functional nanofluidic fibers for wearable or healthcare applications.     

Ultrathin Titanium Carbide (MXene) Films for High-Temperature Thermal Camouflage

Thermal camouflage has attracted increasing attention owing to the rapid development of infrared (IR) surveillance technologies. Various materials and systems have been developed to date, but the realization of high-temperature thermal camouflage using ultrathin film/coating remains a great challenge; this is of great significance, especially for IR stealth in military equipment. This work demonstrates a series of ultrathin Ti₃C₂T_x MXene films (as low as 1 µm) with superior high-temperature indoor/outdoor thermal camouflage performance: wide camouflage temperature range (from below −10 °C to over 500 °C), large reduction in radiation temperature (exceeding 300 °C for objects with temperatures over 500 °C), long-term high-temperature or fire stability, multifunctionality including disguised Joule heating capability, and high electromagnetic interference shielding efficiency. The superior high-temperature thermal camouflage performance of the ultrathin MXene film is attributed to its low mid-IR emissivity (0.19), which is comparable to that of stainless steel but far below that of other 2D nanomaterials, such as graphene. The multifunctional ultrathin MXene films prepared through simple vacuum-assisted filtration provide a feasible method for efficient high-temperature thermal camouflage using ultrathin films, demonstrating the great promise of MXene materials for thermal camouflage, IR stealth, counter-surveillance, and security protection.     

Engineering 3D Ion Transport Channels for Flexible MXene Films with Superior Capacitive Performance

2D MXene materials are of considerable interest for future energy storage. A MXene film could be used as an effective flexible supercapacitor electrode due to its flexibility and, more importantly, its high specific capacitance. However, although it has excellent electronic conductivity, sluggish ionic kinetics within the MXene film becomes a fundamental limitation to the electrochemical performance. To compensate for the relative deficiency, MXene films are frequently reduced to several micrometer dimensions with low mass loading (<1 mg cm^?2), to the point of detriment of areal performance and commercial value. Herein, for the first time, the design of a 3D porous MXene/bacterial cellulose (BC) self‐supporting film is reported for ultrahigh capacitance performance (416 F g^?1, 2084 mF cm^?2) with outstanding mechanical properties and high flexibility, even when the MXene loading reaches 5 mg cm^?2. The highly interconnected MXene/BC network enables both excellent electron and ion transport channel. Additionally, a maximum energy density of 252 µWh cm^?2 is achieved in an asymmetric supercapacitor, higher than that of all ever‐reported MXene‐based supercapacitors. This work exploits a simple route for assembling 2D MXene materials into 3D porous films as state‐of‐the‐art electrodes for high performance energy storage devices.     

Industry-Scale and Environmentally Stable Ti3C2Tx MXene Based Film for Flexible Energy Storage Devices

MXenes, 2D transition metal carbides, and nitrides have attracted tremendous interest because of their metallic conductivity, solution processability, and excellent merits in energy storage and other applications. However, the pristine MXene films often suffer from poor ambient stability and mechanical properties that stem from their polar terminal groups and weak interlayer interactions. Here, a heteroatom doping strategy is developed to tailor the surface functionalities of MXene, followed by the addition of large-sized reduced graphene oxide (rGO) as conductive additives to achieve a scalable production of S, N-MXene/rGO (SNMG-40) hybrid film with high mechanical strength ( ≈ 45 MPa) and energy storage properties (698.5 F cm⁻³). Notably, the SNMG-40 film also demonstrates long-term cycling stability ( ≈ 98% capacitance retention after 30 000 cycles), which can be maintained under ambient condition or immersed in H₂SO₄ electrolyte for more than 100 days. The asymmetric supercapacitor (aMGSC) based on SNMG-40 film shows an ultrahigh energy density of 22.3 Wh kg⁻¹, which is much higher than those previously reported MXene-based materials. Moreover, the aMGSC also provides excellent mechanical durability under different deformation conditions. Thus, this strategy makes MXene materials more competitive for real-world applications such as flexible electronics and electromagnetic interference shielding.     

Reversible Crumpling of 2D Titanium Carbide (MXene) Nanocoatings for Stretchable Electromagnetic Shielding and Wearable Wireless Communication

In the emerging Internet of Things, stretchable antennas can facilitate wireless communication between wearable and mobile electronic devices around the body. The proliferation of wireless devices transmitting near the human body also raises interference and safety concerns that demand stretchable materials capable of shielding electromagnetic interference (EMI). Here, an ultrastretchable conductor is fabricated by depositing a crumple‐textured coating composed of 2D Ti₃C₂T_x nanosheets (MXene) and single‐walled carbon nanotubes (SWNTs) onto latex, which can be fashioned into high‐performance wearable antennas and EMI shields. The resulting MXene‐SWNT (S‐MXene)/latex devices are able to sustain up to an 800% areal strain and exhibit strain‐insensitive resistance profiles during a 500‐cycle fatigue test. A single layer of stretchable S‐MXene conductors demonstrate a strain‐invariant EMI shielding performance of ≈30 dB up to 800% areal strain, and the shielding performance is further improved to ≈47 and ≈52 dB by stacking 5 and 10 layers of S‐MXene conductors, respectively. Additionally, a stretchable S‐MXene dipole antenna is fabricated, which can be uniaxially stretched to 150% with unaffected reflected power <0.1%. By integrating S‐MXene EMI shields with stretchable S‐MXene antennas, a wearable wireless system is finally demonstrated that provides mechanically stable wireless transmission while attenuating EM absorption by the human body.     

MXene Composite and Coaxial Fibers with High Stretchability and Conductivity for Wearable Strain Sensing Textiles

The integration of nanomaterials with high conductivity into stretchable polymer fibers can achieve novel functionalities such as sensing physical deformations. With a metallic conductivity that exceeds other solution‐processed nanomaterials, 2D titanium carbide MXene is an attractive material to produce conducting and stretchable fibers. Here, a scalable wet‐spinning technique is used to produce Ti₃C₂T_x MXene/polyurethane (PU) composite fibers that show both conductivity and high stretchability. The conductivity at a very low percolation threshold of ≈1 wt% is demonstrated, which is lower than the previously reported values for MXene‐based polymer composites. When used as a strain sensor, the MXene/PU composite fibers show a high gauge factor of ≈12900 (≈238 at 50% strain) and a large sensing strain of ≈152%. The cyclic strain sensing performance is further improved by producing fibers with MXene/PU sheath and pure PU core using a coaxial wet‐spinning process. Using a commercial‐scale knitting machine, MXene/PU fibers are knitted into a one‐piece elbow sleeve, which can track various movements of the wearer's elbow. This study establishes fundamental insights into the behavior of MXene in elastomeric composites and presents strategies to achieve MXene‐based fibers and textiles with strain sensing properties suitable for applications in health, sports, and entertainment.     

Hofmeister Effect Assisted Dual-Dynamic-Bond Cross-Linked Organohydrogels with Enhanced Ionic Conductivity and Balanced Mechanical Properties for Flexible Sensors

For soft electronic applications, the simultaneous incorporation of conductivity and mechanical robustness remains a grand constraint, not to mention being able to operate at wide temperatures ranges. Herein, a novel conductive platform is proposed by designing skin-inspired ionic organohydrogels based on Hofmeister effect and glycerol/water system, which simultaneously realize balanced conductivity, mechanical strength, and versatile properties. The comprehensive performances are broadly and simultaneously altered via tuning the aggregation states of polymer chains by kosmotropes or chaotropes. With various ions, the conductivity and mechanical strength are continuously in situ modulated over a large window: conductivity from 0.08 to 4.8 S m⁻¹, strength from 0.01 to 17.30 MPa, toughness from 5.4 to 9236.9 kJ m⁻³, and modulus from 5.1 to 2258.9 kPa. The ion transport process is inseparable from the changes of water content and pore structures caused by cross-linking density. Meanwhile, the mechanical properties greatly depend on the densification or loosing of polymer chains and crystalline domains. Furthermore, oil/water system exhibits low temperature tolerance at ≈−65–15 °C and long-term stability. Finally, the champion organohydrogels are applied as wearable electronic sensors and artificial skins. The mechanism proposed in this work advances the understanding of the ions contribution to organohydrogels for electronic applications.     

Achieving of Flexible,Free‐Standing,Ultracompact Delaminated Titanium Carbide Films for High Volumetric Performance and Heat‐Resistant Symmetric Supercapacitors

The volumetric performance of supercapacitors (SCs), besides the gravimetric performance, is attracting an increasing attention due to the fast development of electric vehicles and smart devices. Here, a unique design of symmetric supercapacitor material is reported with a tight face‐to‐face architecture by applying a high pressure to the delaminated Ti₃C₂ (d‐Ti₃C₂) films. The high pressure makes the d‐Ti₃C₂ films achieve an increased density, high electron conductivity, good wettability, and abundant interconnected mesopore channels to promote ion transport efficiently, that is, more cations can intercalate/deintercalate in the charging–discharging process. As a result, with the increase of the applying pressure, the d‐Ti₃C₂ film pressured at 40 MPa in 1 m Li₂SO₄ exhibits an ultrahigh capacitance of over 633 F cm^?3, outstanding energy density, and cyclic stability. Especially, the corresponding SC in 1 m 1‐ethyl‐3‐methylimidazolium tetrafluoroborate/acetonitrile organic electrolyte shows a high volumetric energy density of 41 Wh L^?1, which is the highest value reported for the SCs based on MXene materials in organic electrolytes. The outstanding volumetric electrochemical performance and thermal stability of the SCs based on the ultracompact d‐Ti₃C₂ film demonstrate their promising potential as forceful power sources for small electronic devices.     

高Al组分AlxGa1-xN薄膜的弹性-塑性力学性质

采用纳米压痕方法,研究了AlN/sphire模板上的高Al组分AlxGa1-xN薄膜的力学性质,特别是弹性-塑性转变行为.研究表明,AlxGa1-xN薄膜的杨氏模量E随着Al组分的增加而增大,薄膜中产生塑性形变所必要的剪切应力也随着Al组分的增加而增大.在AlxGa1-xN薄膜纳米压痕实验中,观察到位移不连续的跳断("pop-in")行为,并且发现"pop-in"行为强烈依赖于Al组分,Al组分的增加导致这种行为的减少.我们认为随着Al组分的增加,AlxGa1-xN中键能的增强和由于AlxGa1-xN与AlN/sapphire模板之间晶格失配减少这两个因素增加了AlxGa1-xN中新位错形成的阻力,从而导致了AlxGa1-xN薄膜中的"pop-in"行为随Al组分增加而减少.     

Highly Conductive and Environmentally Stable Organic Transparent Electrodes Laminated with Graphene

Improving the lifetime and the operational and thermal stability of organic thin‐film materials while maintaining high conductivity and mechanical flexibility is critical for flexible electronics applications. Here, it is reported that highly conductive and environmentally stable organic transparent electrodes (TEs) can be fabricated by mechanically laminating poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) films containing dimethylsulfoxide and Zonyl fluorosurfactant (PDZ films) with a monolayer graphene barrier. The proposed lamination process allows graphene to be coated onto the PDZ films uniformly and conformally with tight interfacial binding, free of wrinkles and air gaps. The laminated films exhibit an outstanding room‐temperature hole mobility of ≈85.1 cm² V^?1 s^?1 since the graphene can serve as an effective bypass for charge carriers. The significantly improved stability of the graphene‐laminated TEs against high mechanical/thermal stress, humidity, and ultraviolet irradiation is particularly promising. Furthermore, the incorporation of the graphene barrier increases the expected lifetime of the TEs by more than two orders of magnitude.     

Suppression of Ionic and Electronic Conductivity by Multilayer Heterojunctions Passivation Toward Sensitive and Stable Perovskite X-Ray Detectors

Organic-inorganic hybrid perovskites are promising candidates for direct X-ray detection and imaging. The relatively high dark current in perovskite single crystals (SCs) is a major limiting factor hindering the pursuit of performance and stability enhancement. In this study, the contribution of dark current is disentangled from electronic (σ_e) and ionic conductivity (σ_i) and shows that the high σ_i dominates the dark current of MAPbBr₃ SCs. A multilayer heterojunctions passivation strategy is developed that suppresses not only the σ_i by two orders of magnitude but also σ_e by a factor of 1.6. The multilayer heterojunctions passivate the halide vacancy defects and increase the electron and hole injection barrier by inducing surface p-type doping of MAPbBr₃. This enables the MAPbBr₃ SC X-ray detectors to obtain a high sensitivity of 19 370 µC Gy_air⁻¹ cm⁻² under a high electric field of 100 V cm⁻¹, a record high sensitivity for bromine self-powered devices, and a low detection limit of 42.3 nGy_air s⁻¹. The unencapsulated detectors demonstrate a stable baseline after storage for 210 days and outstanding operational stability upon irradiation with an accumulated dose of up to 1944 mGy_air.     

高Al组分AlxGa1-xN薄膜的弹性-塑性力学性质

采用纳米压痕方法,研究了AlN/sphire模板上的高Al组分AlxGa1-xN薄膜的力学性质,特别是弹性-塑性转变行为.研究表明,AlxGa1-xN薄膜的杨氏模量E随着Al组分的增加而增大,薄膜中产生塑性形变所必要的剪切应力也随着Al组分的增加而增大.在AlxGa1-xN薄膜纳米压痕实验中,观察到位移不连续的跳断("pop-in")行为,并且发现"pop-in"行为强烈依赖于Al组分,Al组分的增加导致这种行为的减少.我们认为随着Al组分的增加,AlxGa1-xN中键能的增强和由于AlxGa1-xN与AlN/sapphire模板之间晶格失配减少这两个因素增加了AlxGa1-xN中新位错形成的阻力,从而导致了AlxGa1-xN薄膜中的"pop-in"行为随Al组分增加而减少.     

Effect of Microstructural Development on Mechanical and Electrical Properties of Inkjet-Printed Ag Films

The microstructural characterization of inkjet-printed Ag films sintered at various conditions was carried out to analyze the effect of microstructure on mechanical and electrical properties. As expected, the films became denser with grain growth with increasing sintering time and temperature, which resulted in improvement in mechanical properties. However, the resistivity of the films reached a minimum value of 3.0 μΩ cm before full densification. In order to improve the mechanical properties, pressure-assisted sintering was introduced. As a result, inkjet-printed Ag films sintered at 250°C under 5 MPa showed a tensile strength of 550 MPa, elongation of 2.4%, Young’s modulus of 55 GPa, and resistivity of ~3.0 μΩ cm.     

Flexible Ti3C2Tx@Al electrodes with Ultrahigh Areal Capacitance: In Situ Regulation of Interlayer Conductivity and Spacing

Although Ti₃C₂ MXene has shown great potential in energy storage field, poor conductivity and restacking between MXene flakes seriously hinders the maximization of its capacitance. Herein, a new strategy to solve the problems is developed. Gallery Al atoms in Ti₃AlC₂ are partially removed by simple hydrothermal etching to get Ti₃C₂T_x reserving appropriate Al interlayers (Ti₃C₂T_x@Al). Ti₃C₂T_x@Al keeps stable layered structure rather than isolated Ti₃C₂T_x flakes, which avoids flake restacking. The removal of partial Al frees up space for easy electrolyte infiltration while the reserved Al as “electron bridges” ensures high interlayer conductivity. As a result, the areal capacitance reaches up to 1087 mF cm^?2 at 1 mA cm^?2 and over 95% capacitance is maintained after 6000 cycles. The all‐solid‐state supercapacitor (ASSS) based on Ti₃C₂T_x@Al delivers a high capacitance of 242.3 mF cm^?2 at 1 mV s^?1 and exhibits stable performance at different bending states. Two ASSSs in tandem can light up a light‐emitting diode under the planar or wrapping around an arm. The established strategy provides a new avenue to improve capacitance performances of MXenes.     

高强铝合金的激光焊接头组织及力学性能

采用CO2激光器对高强铝合金2519-T87进行焊接,研究了其激光焊接头组织和力学性能特征,并与熔化极气体保护焊(MIG)焊接头的组织和力学性能进行了对比。实验结果表明,激光焊焊缝组织细小,晶界共晶相呈短棒状均匀分布,时效后焊缝中有大量细小θ′相均匀析出,且熔合线附近没有形成等轴晶区,而熔化极气体保护焊焊缝组织晶粒粗大,晶界共晶相呈长条网络状分布,时效后焊缝中的θ′相尺寸大,数量少,且分布不均匀,熔合线附近还存在一个较宽的等轴晶区。焊后时效激光焊接头抗拉强度可达到母材的74%,并且随着焊接速度的增加,接头抗拉强度随之增加,而熔化极气体保护焊焊接头抗拉强度仅仅只有母材的61%,且激光焊接头的热影响区(HAZ)中没有明显的软化区。     

Interactions between Primary Neurons and Graphene Films with Different Structure and Electrical Conductivity

Graphene-based materials represent a useful tool for the realization of novel neural interfaces. Several studies have demonstrated the biocompatibility of graphene-based supports, but the biological interactions between graphene and neurons still pose open questions. In this work, the influence of graphene films with different characteristics on the growth and maturation of primary cortical neurons is investigated. Graphene films are grown by chemical vapor deposition progressively lowering the temperature range from 1070 to 650 °C to change the lattice structure and corresponding electrical conductivity. Two graphene-based films with different electrical properties are selected and used as substrate for growing primary cortical neurons: i) highly crystalline and conductive (grown at 1070 °C) and ii) highly disordered and 140-times less conductive (grown at 790 °C). Electron and fluorescence microscopy imaging reveal an excellent neuronal viability and the development of a mature, structured, and excitable network onto both substrates, regardless of their microstructure and electrical conductivity. The results underline that high electrical conductivity by itself is not fundamental for graphene-based neuronal interfaces, while other physico–chemical characteristics, including the atomic structure, should be also considered in the design of functional, bio-friendly templates. This finding widens the spectrum of carbon-based materials suitable for neuroscience applications.     

Flexible Transparent Bifunctional Capacitive Sensors with Superior Areal Capacitance and Sensing Capability based on PEDOT:PSS/MXene/Ag Grid Hybrid Electrodes

Flexible transparent supercapacitors (FTSs) have aroused considerable attention. Nonetheless, balancing energy storage capability and transparency remains challenging. Herein, a new type of FTSs with both excellent energy storage and superior transparency is developed based on PEDOT:PSS/MXene/Ag grid ternary hybrid electrodes. The hybrid electrodes can synergistically utilize the high optoelectronic properties of Ag grids, the excellent capacitive performance of MXenes, and the superior chemical stability of PEDOT:PSS, thus, simultaneously demonstrating excellent optoelectronic properties (T: ≈89%, R_s: ≈39 Ω sq⁻¹), high areal specific capacitance, superior mechanical softness, and excellent anti-oxidation capability. Due to the excellent comprehensive performances of the hybrid electrodes, the resulting FTSs exhibit both high optical transparency (≈71% and ≈60%) and large areal specific capacitance (≈3.7 and ≈12 mF cm⁻²) besides superior energy storage capacity (P: 200.93, E: 0.24 µWh cm⁻²). Notably, the FTSs show not only excellent energy storage but also exceptional sensing capability, viable for human activity recognition. This is the first time to achieve FTSs that combine high transparency, excellent energy storage and good sensing all-in-one, which make them stand out from conventional flexible supercapacitors and promising for next-generation smart flexible energy storage devices.     

Tailoring Ultrahigh Energy Density and Stable Dendrite-Free Flexible Anode with Ti3C2Tx MXene Nanosheets and Hydrated Ammonium Vanadate Nanobelts for Aqueous Rocking-Chair Zinc Ion Batteries

Exploiting Zn metal-free anode materials would be an effective strategy to resolve the problems of Zn metal dendrites that severely hinder the development of Zn ion batteries (ZIBs). However, the study of Zn metal-free anode materials is still in their infancy, and more importantly, the low energy density severely limits their practical implementations. Herein, a novel (NH₄)₂V₁₀O₂₅ · 8H₂O@Ti₃C₂T_x (NHVO@Ti₃C₂T_x) film anode is proposed and investigated for constructing “rocking-chair” ZIBs. The NHVO@Ti₃C₂T_x electrode shows a capacity of 514.7 mAh g⁻¹ and presents low potential which is 0.59 V (vs Zn²⁺/Zn) at 0.1 A g⁻¹. The introduction of Ti₃C₂T_x not only affords an interconnected conductive network, but also stabilizes the NHVO nanobelts structure for a long cycle life (84.2% retention at 5.0 A g⁻¹ over 6000 cycles). As a proof-of-concept, a zinc metal-free full battery is successfully demonstrated, which delivers the highest capacity of 131.7 mAh g⁻¹ (mass containing anodic and cathodic) and energy density of 97.1 Wh kg⁻¹ compared to all reported aqueous “rocking-chair” ZIBs. Furthermore, a long cycling span of 6000 cycles is obtained with capacity retention reaching up to 92.1%, which is impressive. This work is expected to provide new moment toward V-based materials for “rocking-chair” ZIBs.     

Recyclable Nacre-Like Aramid-Mica Nanopapers with Enhanced Mechanical and Electrical Insulating Properties

The emerging aramid-mica nanopapers, composed of aramid nanofibers (ANFs) and mica nanosheets (Mica), exhibit superiority in the field of electrical insulation compared with commercial aramid-mica micropapers. Unfortunately, their mechanical and electrical insulating properties are still less than ideal due to insufficient control of their microstructures. Herein, it is presented that by integrating ANFs and Mica into nacre-like aramid-mica nanopapers with improved structural orderliness, densification, and interlayer interaction, simultaneously improved mechanical and electrical insulating properties are achieved. Their maximum tensile strength and breakdown strength reach ≈292 MPa and ≈176 kV mm⁻¹, respectively, which are superior to those of the state-of-the-art ANFs-based nanopapers. Particularly, the aramid-mica nanopapers show high resistance to high-temperature (250–300 °C) and oil-bath (100 °C) environments commonly involved in practical applications, and can be recycled many times, demonstrating their great potential as high-performance sustainable electrical insulating papers to be applied in advanced electrical equipment.     

Ultrathin Supported Lipid Monolayer with Unprecedented Mechanical and Dielectric Properties

The development of ultrathin dielectrics for low power electronics operations, flexible and printed electronics, and field‐effect‐transistor‐based sensors is still a challenge. Here, monolayers of engineered lipids supported on silicon are reported presenting exceptional mechanical and dielectric properties. The lipid monolayers are stabilized using a simple procedure based on a two‐stage reticulation process in both their aliphatic chains and their head‐group. With a thickness lower than 3 nm, such layers are demonstrated to offer exceptional mechanical and dielectric stability with unprecedented low leakage current and dielectric strength. Surprisingly, the mechanical and dielectric pressures required to rupture/breakdown the monolayers are shown to be similar. These results suggest the presence of a strong correlation between mechanical and dielectric properties, as well as between the mechanisms of rupture and breakdown.