Multifunctional MXene-Based Fireproof Electromagnetic Shielding Films with Exceptional Anisotropic Heat Dissipation Capability and Joule Heating Performance

Building Thermal-Conduction Nanochannels in Composite Electromagnetic Interference Shielding Film for Electromagnetic Heat Management

In the 6G era, miniaturized and highly integrated wearable communications devices require electromagnetic materials with efficient thermal-management capability to mitigate electromagnetic interference (EMI) and heat accumulation. Herein, we present a facile strategy for conducting electromagnetic heat by constructing directional thermal-conduction nanochannels within a layer-by-layer EMI shielding film. This composite film consists of polyacrylonitrile/boron nitride nanosheets@polydopamine nanofibers covered with an EMI layer based on MXene sheets. Compared with traditional materials in which the heat dissipates randomly, the one-dimensional fibrous structure can offer a directional heat dissipation pathway. Under high-power microwave irradiation, it exhibits significantly lower temperatures, ensuring robust and durable communication performance without overheating. The thin film (0.43 mm thickness) achieves an impressive specific surface shielding efficiency of 29,400 dB·cm2·g-1 at 18-24 GHz, with an EMI shielding effectiveness (SE) of 88 dB for its layer-by-layer structure counterpart. In addition, the flexible film maintains a high EMI SE after 10,000 bending times. Its lightweight, flexible, and thin design makes it suitable for robust applications in various environments. This EMI shielding and thermally conductive film provides rapid heat dissipation and effective signal shielding for wearable communication systems, showcasing the great potential for efficient thermal management in next-generation communication technologies.

Ultra-high thermally conductive graphite microplatelet/aramid nanofiber composites with reduced interfacial thermal resistances by engineered interface π-π interactions

Polymer-based thermally conductive composites with ultrahigh in-plane thermal conductivity are ideal candidates for heat dissipation applications in electronics. However, the complex interfaces between the functional filler and polymer matrix limit the significant increase in thermal conductivity of the polymer composites. In this study, we developed a one-pot strategy to prepare highly thermally conductive composite films of freeze-expansion large-size graphite microplatelets (F-GMPs) and aramid nanofibers (ANFs) with π-π interactions. The obtained F-GMP/ANF nanocomposite films present salient in-plane thermal conductivity, considerable flexibility, and outstanding long-term stability. The π-π interactions between the F-GMPs and ANFs promote the freeze-expansion exfoliation of graphite, yielding stable F-GMP/ANF precursor pastes with high-quality graphite platelets. Moreover, the π-π interactions improve the filler-matrix interfacial compatibility and reduce the interfacial thermal resistance, while the large-size F-GMP particles are directly lapped to construct a thermal transfer pathway with a reduction in the filler-filler interfacial thermal resistance. Consequently, the F-GMP/ANF composite films with 30 wt% F-GMPs exhibit unprecedentedly high in-plane thermal conductivity (56.89 W m-1 K-1) and corresponding thermal conductivity enhancement efficiency, presenting great application potential for the effective thermal management of highly integrated electronics.

Two-Dimensional MXenes: Innovative Materials for Efficient Thermal Management and Safety Solutions

MXenes, a class of 2-dimensional transition metal carbides and nitrides, have garnered important attention due to their remarkable electrical and thermal conductivity, high photothermal conversion efficiency, and multifunctionality. This review explores the potential of MXene materials in various thermal applications, including thermal energy storage, heat dissipation in electronic devices, and the mitigation of electromagnetic interference in wearable technologies. Recent advancements in MXene composites, such as MXene/bacterial cellulose aerogel films and MXene/polymer composites, have demonstrated enhanced performance in phase change thermal storage and electromagnetic interference shielding, underscoring their versatility and effectiveness. Although notable progress has been made, challenges remain, including the need for a deeper understanding of photothermal conversion mechanisms, improvements in mechanical properties, exploration of diverse MXene types, and the development of sustainable synthesis methods. This paper discusses these aspects and outlines future research directions, emphasizing the growing importance of MXenes in addressing energy efficiency, health, and safety concerns in modern applications.

Shaping Thermal Transport and Temperature Distribution via Anisotropic Carbon Fiber Reinforced Composites

With the ongoing electrification of vehicles, thermal management is on everyone's lips. To prevent overheating in electronic systems, new design strategies for thermal dissipation are needed. Thermally anisotropic materials enable targeted directional heat transport due to their anisotropic thermal conduction. Laminates made of unidirectionally aligned carbon fibers in a polymer matrix can be tailored regarding their in-plane anisotropy. Exposing the laminates to a temperature gradient reveals that the thermal transport is determined by their anisotropic properties. The corresponding heat flow can be visualized by IR thermography. The combination of anisotropic laminate discs into composite materials, similar to building with toy bricks, enables precise control of heat transport in the macroscopic composite materials. Thus, we achieve control of heat flow at the level of the individual components. In addition, we show that the orientation of anisotropy relative to the temperature gradient is crucial to guide the heat flow selectively. We found that the ratio of thermal anisotropy, the amount and arrangement of anisotropic components, and their positioning in the composite strongly influence heat transport. By combining all these factors, we are able to locally control the heat flow in composites by creating materials to either dissipate heat or block heat transport. The proposed concept can be extended to different shapes of building blocks in two or three dimensions.

Sandwich-Structured Mxene/Waste Polyurethane Foam Composites For Highly Efficient Electromagnetic Interference, Infrared Shielding and Joule Heating

Electromagnetic interference (EMI) shielding and infrared (IR) stealth materials have attracted increasing attention owing to the rapid development of modern communication and military surveillance technologies. However, to realize excellent EMI shielding and IR stealth performance simultaneously remains a great challenge. Herein, a facile strategy is demonstrated to prepare high-efficiency EMI shielding and IR stealth materials of sandwich-structured MXene-based thin foam composites (M-W-M) via filtration and hot-pressing. In this composite, the conductive Ti3C2Tx MXene/cellulose nanofiber (MXene/CNF) film serves as the outer layer, which reflects electromagnetic waves and reduces the IR emissivity. Meanwhile, the middle layer is composed of a porous waste polyurethane foam (WPUF), which not only improves thermal insulation capacity but also extends electromagnetic wave propagation paths. Owing to the unique sandwich structure of "film-foam-film", the M-W-M composite exhibits a high EMI shielding effectiveness of 83.37 dB, and in the meantime extremely low emissivity (22.17%) in the wavelength range of 7-14 µm and thermal conductivity (0.19 W m-1 K-1), giving rise to impressive IR stealth performance at various surrounding temperatures. Remarkably, the M-W-M composite also shows excellent Joule heating properties, capable of maintaining the IR stealth function during Joule heating.

Cellulose-derived carbon scaffolds with bidirectional gradient Fe3O4 distribution: Integration of green EMI shielding and thermal management

Cellulose papers (CPs) possess a pore structure, rendering them ideal precursors for carbon scaffolds because of their renewability. However, achieving a tradeoff between high electromagnetic shielding effectiveness and low reflection coefficient poses a tremendous challenge for CP-based carbon scaffolds. To meet the challenge, leveraging the synergistic effect of gravity and evaporation dynamics, laminar CP-based carbon scaffolds with a bidirectional gradient distribution of Fe3O4 nanoparticles were fabricated via immersion, drying, and carbonization processes. The resulting carbon scaffold, owing to the bidirectional gradient structure of magnetic nanoparticles and unique laminar arrangement, exhibited excellent in-plane electrical conductivity (96.3 S/m), superior electromagnetic shielding efficiency (1805.9 dB/cm2 g), low reflection coefficients (0.23), and a high green index (gs, 3.38), suggesting its green shielding capabilities. Furthermore, the laminar structure conferred upon the resultant carbon scaffold a surprisingly anisotropic thermal conductivity, with an in-plane thermal conductivity of 1.73 W/m K compared to a through-plane value of only 0.07 W/m K, confirming the integration of thermal insulation and thermal management functionalities. These green electromagnetic interference shielding materials, coupled with thermal insulation and thermal management properties, hold promising prospects for applications in sensitive devices.

Fabrication of innovative multifunctional dye using MXene nanosheets

The increasing demand for natural and safer alternatives to traditional hair dyes has led to the investigation of nanomaterials as potential candidates for hair coloring applications. MXene nanosheets have emerged as a promising alternative in this context due to their unique optical and electronic properties. In this study, we aimed to evaluate the potential of Ti3C2Tx (Tx = -O, -OH, -F, etc.) MXene nanosheets as a hair dye. MXene nanosheet-based dyes have been demonstrated to exhibit not only coloring capabilities but also additional properties such as antistatic properties, heat dissipation, and electromagnetic wave shielding. Additionally, surface modification of MXene using collagen reduces the surface roughness of hair and upregulates keratinocyte markers KRT5 and KRT14, demonstrating the potential for tuning its physicochemical and biological properties. This conceptual advancement highlights the potential of MXene nanosheets to go beyond simple cosmetic improvements and provide improved comfort and safety by preventing the presence of hazardous ingredients and solvents while providing versatility.

Recent advances in multifunctional electromagnetic interference shielding materials

Electromagnetic interference (EMI) shielding material is the most effective solution to protect electronic devices and human health from the harmful effects of electromagnetic radiation. The study of EMI shielding materials is intensifying in the constantly developing picture of the fourth industrial revolution. Many EMI shielding materials based on metal, carbon, emerging MXene materials, and their composites have been discovered to utilize the EMI shielding performance. However, a huge demand for compact and multi-functional devices requires the integration of new functions into EMI shielding materials. Multifunctional EMI shielding materials perform multiple functions beyond their main function of EMI shielding in a system due to their specific properties. The additional functions can either naturally exist or be specially engineered. This review summarizes the recent progress of cutting-edge multifunctional EMI shielding materials. The possibility of combining multifunction EMI shielding materials, such as strain sensing, humidity sensing, temperature sensing, thermal management, etc., and the difficulties in balancing EMI shielding performance with other functions are also discussed. Lastly, we point out challenges and propose future directions to develop research on multifunctional EMI shielding materials.

Design and Analysis of a Textured Cu-Encapsulated Ni Tube for Low-Reflection Electromagnetic Interference Shielding Material

With the frequent increase and update of electromagnetic interference (EMI) shielding materials, a low-resolution material that can absorb most electromagnetic waves, thereby effectively reducing the secondary pollution, is urgently needed. However, the excellent performance, flexibility, and low cost of these methods are usually incompatible with current reports. To address the above dilemma, we reported a facile solution for fabricating a low-reflection and high-performance EMI shielding composite by means of electroless nickel plating (EP-Ni), electroless copper plating (EP-Cu), annealing, and coating with a polydimethylsiloxane (PDMS) polymer with the structure of a Ni@Cu tube encapsulated with PDMS. The results indicate that the active groups on vegetable wool can act as active sites for the absorption of the Pd catalyst, thereby catalyzing the reduction of Ni2+, Cu2+, and the subsequent deposition on the plant fiber surface. Notably, the Ni@Cu-encapsulated plant fibers decreased during annealing at 100 °C. According to the segregated network and synergistic effect of the porous structure, the as-fabricated EMI shielding material demonstrated high absorption and low reflection, in which the power coefficient of the T value was approximately 0.0001, the R value was about 0.1764 (a decrease of 27.5% compared that of EP-Ni cotton), and the A value was approximately 0.8235.

A fire resistant MXene-based flexible film with excellent Joule heating and electromagnetic interference shielding performance

Flexible films with thermal management capability and efficient electromagnetic interference (EMI) shielding performance are highly needed for electronic devices. Moreover, it remains difficult to integrate fire safety performance into the multifunctional film. Thus, a facile multi-interfacial engineering strategy was proposed to prepare a fire resistant MXene-based flexible film with excellent Joule heating and EMI Shielding performance. Specifically, the neighboring and interlayer MXene sheets were respectively bridged by graphene oxide and carbon nanotube via multiple physical and chemical interactions, thus formed a optimized hierarchical microstructure. The resultant film possessesd outstanding Joule heating performance including wide electrical-to-thermal temperature and sensitive conversion ability. Simultaneously, the film exhibited high EMI shielding efficiency (99.97%). Most significantly, after being burned up to 60 min, the film still maintained its flexibility and multifunctional perfprmance benefiting from a large expanded protective layer. The excellent fire resistance and multi-functions endowed the film wide application prospects in advanced electronics.

Multifunctional Flexible MXene/AgNW Composite Thin Film with Ultrahigh Conductivity Enabled by a Sandwich-Structured Assembly Strategy

Flexible composite films have attracted considerable attention due to great potential for healthcare, telecommunication, and aerospace. However, it is still challenging to achieve high conductivity and multifunctional integration, mainly due to poorly designed composite structures of these films. Herein, a novel sandwich-structured assembly strategy is proposed to fabricate flexible composite thin films made of Ag nanowire (AgNW) core and MXene layers by combination of spray coating and vacuum filtration process. In this case, ultrathin MXene layers play crucial roles in constructing compact composite structures strongly anchored to substrate with extensive hydrogen-bonding interactions. The resultant sandwich-structured MXene/AgNW composite thin films (SMAFs) exhibit ultrahigh electrical conductivity (up to 27193 S cm-1 ), resulting in exceptional electromagnetic interference shielding effectiveness of 16 223.3 dB cm2 g-1 and impressive Joule heating performance with rapid heating rate of 10.4 °C s-1 . Moreover, the uniform SMAFs can also be facilely cut into kirigami-patterned interconnects, which indicate superior strain-insensitive conductance even after long-term exposure to extreme temperatures. The demonstrated strategy offers a significant paradigm to construct multifunctional composite thin films for next-generation integrated flexible electronics with practical applications.

Liquid metal assisted fabrication of MXene-based films: Toward superior electromagnetic interference shielding and thermal management

The development of thin and flexible films that possess both electromagnetic interference (EMI) shielding and thermal management capabilities has always been an intriguing pursuit, but itisnevertheless a crucialproblemtoaddress. Inspired by the deformability of liquid metal (LM) and film forming capacity of MXene, here we present a series of ternary compositing films prepared via cellulose nanofiber (CNF) assisted vacuum filtration technology. Originating from the highly conductive LM/MXene network, the MLMC film presents a maximum EMI shielding effectiness (EMI SE) of 78 dB at a tiny thickness of 45 μm, together with a high specific EMI SE of 3046 dB mm-1. Meanwhile, these compositing films also deliver excellent flexibility and mechanical reliability, showing no obvious decline in EMI shielding performance even after 1000 bending and 500 folding cycles, respectively. Moreover, notable anisotropic thermal conductive property was successfully achieved, allowing for a highly desirable in-plane thermal conductivity of 7.8 W m-1 K-1. This accomplishment also yielded an exceptional electro-thermal conversion capacity, enabling efficient low-voltage (3 V) heating capabilities. These captivating features are expected to greatly drive the widespread adoption of LM-based films in future flexible electronic and wearable technologies.

Rapid Fabrication of Flexible Cu@Ag Flake/SAE Composites with Exceptional EMIS and Joule Heating Performance

High electromagnetic interference shielding (EMIS) effectiveness and good thermal management properties are both required to meet the rapid development of integrated electronic components. However, it remains challenging to obtain environmentally friendly and flexible films with high EMIS and thermal management performance in an efficient and scalable way. In this paper, an environmentally friendly strategy is proposed to synthesize multifunctional waterborne Cu@Ag flake conductive films using water as the solvent and silicone-acrylic emulsion (SAE) as a matrix. The obtained films show high electrical conductivity and exceptional EMI SE and electrothermal conversion properties. The EMI SE in the X-band is higher than 76.31 dB at a thickness of 60 μm owing to the ultrahigh electrical conductivity of 1073.61 S cm-1. The film warms up quickly to 102.1 °C within 10 s under a low voltage of 2.0 V. In addition, the shielding coating is sufficiently flexible to retain a conductivity of 93.4% after 2000 bending-release cycles with a bending radius of 3 mm. This work presents an alternative strategy to produce high EMIS effectiveness and Joule heating films for highly integrated and flexible electronic components in a green, scalable, and highly efficient way.

Scalable Fabrication of Nacre-Structured Graphene/Polytetrafluoroethylene Films for Outstanding EMI Shielding Under Extreme Environment

In this work, inspired by the great advantage of the unique "brick-mortar" layered structure as electromagnetic interference (EMI) shielding materials, a multifunctional flexible graphene nanosheets (GNS)/polytetrafluoroethylene (PTFE) composite film with excellent EMI shielding effects, impressive Joule heating performance, and light-to-heat conversion efficiency is fabricated based on the self-emulsifying process of PTFE. Both PTFE microspheres and nanofibers are employed together for the first time as "sand and cement" to build unique nacre-structured EMI shielding materials. Such configuration can obviously enhance the adhesion of composites and improve their mechanical property for the application under extreme environment. Moreover, the simple and effective repetitive roll pressing method can be used for the scalable production in industrialization. The GNS/PTFE composite film shows a high EMI shielding effectiveness (SE) of 50.85 dB. Furthermore, it has a high thermal conductivity of 16.54 W (m K)-1 , good flexibility, and recyclable properties. The excellent fire-resistant and hydrophobic properties of GNS/PTFE film also ensure its reliability and safety in practical application. In conclusion, the GNS/PTFE film demonstrates the potential for industrial manufacturing, and outstanding EMI shielding performance with high stability and durability, which has a broad application prospect for electronic devices in practical extreme outdoor environments.

Effective Surface Modification of 2D MXene toward Thermal Energy Conversion and Management

Thermal energy management is a crucial aspect of many research developments, such as hybrid and soft electronics, aerospace, and electric vehicles. The selection of materials is of critical importance in these applications to manage thermal energy effectively. From this perspective, MXene, a new type of 2D material, has attracted considerable attention in thermal energy management, including thermal conduction and conversion, owing to its unique electrical and thermal properties. However, tailored surface modification of 2D MXenes is required to meet the application requirements or overcome specific limitations. Herein, a comprehensive review of surface modification of 2D MXenes for thermal energy management is discussed. First, this work discusses the current progress in the surface modification of 2D MXenes, including termination with functional groups, small-molecule organic compound functionalization, and polymer modification and composites. Subsequently, an in situ analysis of surface-modified 2D MXenes is presented. This is followed by an overview of the recent progress in the thermal energy management of 2D MXenes and their composites, such as Joule heating, heat dissipation, thermoelectric energy conversion, and photothermal conversion. Finally, some challenges facing the application of 2D MXenes are discussed, and an outlook on surface-modified 2D MXenes is provided.

Ti3 C2 TX MXene Ink Direct Writing Flexible Sensors for Disposable Paper Toys

Flexible electronics have gained great attention in recent years owing to their promising applications in biomedicine, sustainable energy, human-machine interaction, and toys for children. Paper mainly produced from cellulose fibers is attractive substrate for flexible electronics because it is biodegradable, foldable, tailorable, and light-weight. Inspired by daily handwriting, the rapid prototyping of sensing devices with arbitrary patterns can be achieved by directly drawing conductive inks on flat or curved paper surfaces; this provides huge freedom for children to design and integrate "do-it-yourself (DIY)" electronic toys. Herein, viscous and additive-free ink made from Ti3 C2 TX MXene sediment is employed to prepare disposable paper electronics through a simple ball pen drawing. The as-drawn paper sensors possess hierarchical microstructures with interweaving nanosheets, nanoflakes, and nanoparticles, therefore exhibiting superior mechanosensing performances to those based on single/fewer-layer MXene nanosheets. As proof-of-concept applications, several popular children's games are implemented by the MXene-based paper sensors, including "You say, I guess," "Emotional expression," "Rock-Paper-Scissors," "Arm wrestling," "Throwing game," "Carrot squat," and "Grab the cup," as well as a DIY smart whisker for a cartoon mouse. Moreover, MXene-based paper sensors are safe and disposable, free from producing any e-waste and hazard to the environment.

Structure Design and Processing Strategies of MXene-Based Materials for Electromagnetic Interference Shielding

The development of new materials for electromagnetic interference (EMI) shielding is an important area of research, as it allows for the creation of more effective and high-efficient shielding solutions. In this sense, MXenes, a class of 2D transition metal carbides and nitrides have exhibited promising performances as EMI shielding materials. Electric conductivity, low density, and flexibility are some of the properties given by MXene materials, which make them very attractive in the field. Different processing techniques have been employed to produce MXene-based materials with EMI shielding properties. This review summarizes processes and the role of key parameters like the content of fillers and thickness in the desired EMI shielding performance. It also discusses the determination of power coefficients in defining the EMI shielding mechanism and the concept of green shielding materials, as well as their influence on the real application of a produced material. The review concludes with a summary of current challenges and prospects in the production of MXene materials as EMI shields.

Progress of high performance Ti3C2Tx MXene nanocomposite films for electromagnetic interference shielding

With the rapid growth of 5G communication technology, it is imperative to produce electromagnetic interference (EMI) shielding materials to combat the growing electromagnetic radiation pollution. For new shielding applications, EMI shielding materials with high flexibility, light weight and good mechanical strength are in high demand. Due to their light weight, high flexibility, excellent EMI shielding performance, high mechanical properties, and multifunctionality, Ti₃C₂T_x MXene nanocomposite films have shown absolute benefits in EMI shielding in recent years. Consequently, numerous lightweight and flexible high-performance Ti₃C₂T_x MXene nanocomposite films have been generated quickly. In this article, we discuss not only the present state of EMI shielding material research, but also the synthesis and electromagnetic properties of Ti₃C₂T_x MXene. In addition, the loss mechanism of EMI shielding is described, with an emphasis on the analysis and summary of the research progress of diverse layer structured Ti₃C₂T_x MXene nanocomposite films for EMI shielding. Finally, the current issues of design and fabrication for Ti₃C₂T_x MXene nanocomposite films that need to be addressed are proposed, as well as the future research direction for Ti₃C₂T_x MXene nanocomposite films.

Improved Mechanical Strength of Dicatechol Crosslinked MXene Films for Electromagnetic Interference Shielding Performance

Pristine MXene films express outstanding excellent electromagnetic interference (EMI) shielding properties. Nevertheless, the poor mechanical properties (weak and brittle nature) and easy oxidation of MXene films hinder their practical applications. This study demonstrates a facile strategy for simultaneously improving the mechanical flexibility and the EMI shielding of MXene films. In this study, dicatechol-6 (DC), a mussel-inspired molecule, was successfully synthesized in which DC as mortars was crosslinked with MXene nanosheets (MX) as bricks to create the brick-mortar structure of the MX@DC film. The resulting MX@DC-2 film has a toughness of 40.02 kJ·m^-3 and Young's modulus of 6.2 GPa, which are improvements of 513% and 849%, respectively, compared to those of the bare MXene films. The coating of electrically insulating DC significantly reduced the in-plane electrical conductivity from 6491 S·cm^-1 for the bare MXene film to 2820 S·cm^-1 for the MX@DC-5 film. However, the EMI shielding effectiveness (SE) of the MX@DC-5 film reached 66.2 dB, which is noticeably greater than that of the bare MX film (61.5 dB). The enhancement in EMI SE resulted from the highly ordered alignment of the MXene nanosheets. The synergistic concurrent enhancement in the strength and EMI SE of the DC-coated MXene film can facilitate the utilization of the MXene film in reliable, practical applications.

High-strength, low infrared-emission nonmetallic films for highly efficient Joule/solar heating, electromagnetic interference shielding and thermal camouflage

High-strength nonmetallic materials with low infrared (IR) emission are rare in nature, yet highly anticipated especially in military and aerospace fields for thermal camouflage, IR stealth, energy-saving heating. Here, we reported a high-strength (422 MPa) nonmetallic film with very low IR emissivity (12%), realized by constructing alternating multilayered structures consisting of successive MXene functionalized outer layers and continuous GO reinforced inner layers. This nonmetallic film is capable of competing with typical stainless steel (415 MPa, 15.5%), and exhibits remarkable thermal camouflage performance (ΔT = 335 °C), ultrahigh Joule heating capability (350 °C at 2 V), excellent solar-to-thermal conversion efficiency (70.2%), and ultrahigh specific electromagnetic interference shielding effectiveness (83 429 dB cm^-1). Impressively, these functionalities can be maintained well after prolonged outdoor aging, and even after undergoing harsh application conditions including strong acid/alkali and boiling water immersion, and cryogenic (-196 °C) temperature.

Advanced perspectives on MXene composite nanomaterials: Types synthetic methods, thermal energy utilization and 3D-printed techniques

MXene, 2D material, can be synthesized as single flake with 1 nm thickness by using phase change material, polymer and graphene oxide. Meanwhile, the MXene and its composite derivative materials have been applied widely in electro-to-thermal conversion, photo-to-thermal conversion, thermal energy storage, and 3D printing ink aspects. Furthermore, the forward-looking utilization of the MXene nanomaterials in hydrogen energy storage, radio frequency field application, CO₂ capture and remediation of environmental pollution, is explored. This article reveals that the efficiencies of the photo-to-thermal and electro-to-thermal energy conversions with the MXene nanomaterials could reach about 80-90%. In parallel, it is demonstrated that the MXene printed ink has the excellent rheological property and high viscosity and stability of liquid, which contribute to arranging the multi-dimensional architectures with functional materials and controlling the flow rate of the MXene ink in the range of 0.03-0.15 mL/min for speedily printing and various printing structures.

Significantly Enhanced Electromagnetic Interference Shielding Performances of Epoxy Nanocomposites with Long-Range Aligned Lamellar Structures

High‑efficiency electromagnetic interference (EMI) shielding materials are of great importance for electronic equipment reliability, information security and human health. In this work, bidirectional aligned Ti₃C₂T_x@Fe₃O₄/CNF aerogels (BTFCA) were firstly assembled by bidirectional freezing and freeze-drying technique, and the BTFCA/epoxy nanocomposites with long-range aligned lamellar structures were then prepared by vacuum-assisted impregnation of epoxy resins. Benefitting from the successful construction of bidirectional aligned three-dimensional conductive networks and electromagnetic synergistic effect, when the mass fraction of Ti₃C₂T_x and Fe₃O₄ are 2.96 and 1.48 wt%, BTFCA/epoxy nanocomposites show outstanding EMI shielding effectiveness of 79 dB, about 10 times of that of blended Ti₃C₂T_x@Fe₃O₄/epoxy (8 dB) nanocomposites with the same loadings of Ti₃C₂T_x and Fe₃O₄. Meantime, the corresponding BTFCA/epoxy nanocomposites also present excellent thermal stability (T_{heat-resistance index} of 198.7 °C) and mechanical properties (storage modulus of 9902.1 MPa, Young's modulus of 4.51 GPa and hardness of 0.34 GPa). Our fabricated BTFCA/epoxy nanocomposites would greatly expand the applications of MXene and epoxy resins in the fields of information security, aerospace and weapon manufacturing, etc.

Rheology-Guided Assembly of a Highly Aligned MXene/Cellulose Nanofiber Composite Film for High-Performance Electromagnetic Interference Shielding and Infrared Stealth

Delicately aligned structures of two-dimensional (2D) MXene nanosheets have demonstrated positive effects on applications, especially in electromagnetic interference (EMI) shielding and infrared (IR) stealth. However, precise regulation of structural assembly by theory-guided solution processing is still a great challenge. Herein, one-dimensional (1D) cellulose nanofibers (CNFs) with a high aspect ratio are applied as a reinforcing agent and a rheological modifier for MXene/CNF colloids to fabricate aligned MXene-based materials for EMI shielding and IR stealth. Notably, a systematical rheological study of the MXene/CNF colloids is proposed to determine the optimal solution-processing conditions for finely oriented component arrangement requirements and provides in-depth information on the interactions between the components. The delicately regulated orientation structure assembled by shear inducement is convincingly demonstrated through micro-CT and wide-angle X-ray diffraction/small-angle X-ray scattering (WAXD/SAXS), which endows the MXene/CNF film with a significantly enhanced electrical conductivity of 46 685 S m^-1, a tensile strength of 281.7 MPa, and Young's modulus of 14.8 GPa. Furthermore, the highly aligned structure of the ultrathin film possesses a great enhancement in EMI shielding effectiveness (50.2 dB) and IR stealth (0.562 emissivity). These findings provide a fruitful understanding of the optimized fabrication in solution processing of high-performance MXene-based functional composite films and open up a great opportunity for the development of multifunctional stealth materials.

MXene based nanocomposite films

Since the first report in 2011, two-dimensional transition metal carbide/nitride MXenes have aroused widespread attention owing to the particular structure and physiochemical properties. In the last few years, MXene-based nanocomposite films have been widely investigated, showing promising applications in many fields. However, poor mechanical properties and thermal/electrical conductivities of MXene-based nanocomposite films still limited their practical applications. Herein, we summarize the fabrication approach of MXene-based nanocomposite films and discuss the mechanical properties and other applications, including electromagnetic interference shielding, thermal conductivity, and supercapacitors. Then, several vital factors for fabricating high performance MXene based nanocomposite films have been refined. To further fabricate high performance MXene-based nanocomposite films, some effective sequential bridging strategies are also discussed. Lastly, a conclusion of the challenges and opportunities of MXene-based nanocomposite films is provided to facilitate their development and application for various purposes in the future of scientific research.

Structural evolution of MXenes and their composites for electromagnetic interference shielding applications

Nowadays, the extensive utilization of electronic devices and equipment inevitably leads to severe electromagnetic interference (EMI) issues. Therefore, EMI shielding materials have drawn considerable attention, and great effort has been devoted to the exploration of high-efficiency EMI shielding materials. As a novel kind of 2D transition metal carbide material, MXenes have been widely investigated for EMI shielding in the past few years due to their extraordinary electrical conductivity, large specific surface area, light weight, and easy processability. In view of the great achievements in MXene-based materials for EMI shielding, herein, we reviewed the recent studies on the structural design and evolution of MXenes and their composites for EMI shielding. First, the methods for structural control of MXenes, including HF etching, in situ HF etching, fluorine-free etching, electrochemical etching, and molten salt etching, are systematically summarized. Then we illustrate the fundamental relationship between the microstructure of MXenes and the EMI shielding mechanism. In the following, the effects of different synthesis methods and structures of MXene-based composite materials as well as their EMI shielding performances are comprehensively discussed. Lastly, future prospects for the development of MXene-based composite materials in EMI shielding applications are commented on.

Thermal Properties of MXenes and Relevant Applications

The properties and applications of MXenes (a family of layered transition metal carbides, nitrides, and carbonitrides) have aroused enormous research interests for a decade since the successful synthesis of few-layer transition metal carbides in 2011. Though MXenes, as the building blocks, have already been applied in various fields (such as wearable electronics) owing to the distinctive optical, mechanical and electrical properties, their thermal stability and intrinsic thermal properties were less thoroughly investigated compared to other characteristics in early reports. The pioneering theoretical prediction of the thermoelectric nature of MXenes was performed in 2013 while the first experiment-based report concerning the degradation behavior of the 2D structure at elevated temperatures in a controlled atmosphere was published in 2015, followed by numerous discoveries regarding the thermal properties of MXenes. Herein, after a brief description of the synthesis, this Review summarized the latest insights into the thermal stability and thermophysical properties of MXenes, and further associated these unique properties with relevant applications by multiple examples. Finally, current hurdles and challenges in this field were provided along with some advices on potential research directions in the future.

Scalable MXene and PEDOT-CNT Nanocoatings for Fibre-Reinforced Composite De-Icing

In this study, the de-icing performance is investigated between traditional carbon fibre-based coatings and novel MXene and poly(3,4-ethylenedioxythiophene)-coated single-walled carbon nanotube (PEDOT-CNT) nanocoatings, based on simple and scalable coating application. The thickness and morphology of the coatings are investigated using atomic force microscopy and scanning electron microscopy. Adhesion strength, as well as electrical properties, are evaluated on rough and glossy surfaces of the composite. The flexibility and electrical sensitivity of the coatings are studied under three-point bending. Additionally, the influence of ambient temperature on coating’s electrical resistance is investigated. Finally, thermal imaging and Joule heating are analysed with high-accuracy infrared cameras. Under the same power density, the increase in average temperature is 84% higher for MXenes and 117% for PEDOT-CNT, when compared with fibre-based coatings. Furthermore, both nanocoatings result in up to three times faster de-icing. These easily processable nanocoatings offer fast and efficient de-icing for large composite structures such as wind turbine blades without adding any significant weight.

A Constrained Assembly Strategy for High-Strength Natural Nanoclay Film

Developing high-performance materials from existing natural materials is highly desired because of their environmental friendliness and low cost; two-dimensional nanoclay exfoliated from layered silicate minerals is a good building block to construct multilayered macroscopic assemblies for achieving high mechanical and functional properties. Nevertheless, the efforts have been frustrated by insufficient inter-nanosheet stress transfer and nanosheet misalignment caused by capillary force during solution-based spontaneous assembly, degrading the mechanical strength of clay-based materials. Herein, a constrained assembly strategy that is implemented by in-plane stretching a robust water-containing nanoclay network with hydrogen and ionic bonding is developed to adjust the 2D topography of nanosheets within multilayered nanoclay film. In-plane stretching overcomes capillary force during water removal and thus restrains nanosheet conformation transition from nearly flat to wrinkled, leading to a highly aligned multilayered nanostructure with synergistic hydrogen and ionic bonding. It is proved that inter-nanosheet hydrogen and ionic bonding and nanosheet conformation extension generate profound mechanical reinforcement. The tensile strength and modulus of natural nanoclay film reach up to 429.0 MPa and 43.8 GPa and surpass the counterparts fabricated by normal spontaneous assembly. Additionally, improved heat insulation function and good nonflammability are shown for the natural nanoclay film and extend its potential for realistic uses.

Bioinspired, High-Strength, and Flexible MXene/Aramid Fiber for Electromagnetic Interference Shielding Papers with Joule Heating Performance

High-strength, flexible, and multifunctional characteristics are highly desirable for electromagnetic interference (EMI) shielding materials in the field of electric devices. In this work, inspired by natural nacre, we fabricated large-scale, layered MXene/amarid nanofiber (ANF) nanocomposite papers by blade-coating process plus sol-gel conversion step. The as-synthesized papers possess excellent mechanical performance, that is, exceptional tensile strength (198.80 ± 5.35 MPa), large strain (15.30 ± 1.01%), and good flexibility (folded into various models without fracture), which are ascribed to synergetic interactions of the interconnected three-dimensional network frame and hydrogen bonds between MXene and ANF. More importantly, the papers with extensive continuous conductive paths formed by MXene nanosheets present a high EMI shielding effectiveness of 13188.2 dB cm² g^-1 in the frequency range of 8.2-12.4 GHz. More interestingly, the papers show excellent Joule heating performance with a fast thermal response (<10 s) and a low driving voltage (≤4 V). As such, the large-scale MXene/ANF papers are considered as promising alternatives in a wide range of applications in electromagnetic shielding and thermal management.

Healable Strain Sensor Based on Tough and Eco-Friendly Biomimetic Supramolecular Waterborne Polyurethane

Stretchable sensors are essential for flexible electronics, which can be made with polymer elastomers as the matrix. The main challenge in producing practical devices is to obtain polymers with mechanical stability, eco-friendliness, and self-healing properties. Herein, we introduce urea bonds and 2-ureido-4[1H]-pyrimidinone (UPy) to synthesize tailored waterborne polyurethanes (WPU-UPy-x) with a hierarchical hydrogen bond (H-bond). Accordingly, sound tensile performance (strength: 53.33 MPa, toughness: 128.97 MJ m^-3), satisfying deformation recovery, and good self-healing capability of the WPU-UPy-x film are demonstrated. With atomic force microscope characterization, we find that UPy groups contribute to the highly improved microphase separation of WPU-UPy-x, responsible for good mechanical properties. As a proof of concept, a strain sensor is successfully configured, thanks to the good interfacial interactions between the polyurethane matrix and the Ti₃C₂T_x MXene conductive filler, which features sensitive and stable performance for monitoring diverse human and mechanical motions. Intriguingly, this sensor is capable of self-healing after cutting and displays well-retained sensitivity to detect the stretched signal. The as-proposed design concept for healable and sensitive strain sensors can shed light on future wearable electronics.

Ti3C2Tx/rGO Aerogel Towards High Electromagnetic Wave Absorbing and Thermal Resistance

Facing the fast development of telecommunication technology, traditional electromagnetic wave absorption materials are unable to meet the microwave shielding requirements in practical application. Herein, a Ti3C2Tx MXene/rGO composite aerogel was...

Directional Electromagnetic Interference Shielding Based on Step-Wise Asymmetric Conductive Networks

Some precision electronics such as signal transmitters need to not only emit effective signal but also be protected from the external electromagnetic (EM) waves. Thus, directional electromagnetic interference (EMI) shielding materials (i.e., when the EM wave is incident from different sides of the sample, the EMI shielding effectiveness (SE) is rather different) are strongly required; unfortunately, no comprehensive literature report is available on this research field. Herein, Ni-coated melamine foams (Ni@MF) were obtained by a facile electroless plating process, and multiwalled carbon nanotube (CNT) papers were prepared via a simple vacuum-assisted self-assembly approach. Then, step-wise asymmetric poly(butylene adipate-co-terephthalate) (PBAT) composites consisting of loose Ni@MF layer and compact CNT layer were successfully fabricated via a facile solution encapsulation approach. The step-wise asymmetric structures and electrical conductivity endow the Ni@MF/CNT/PBAT composites with unprecedented directional EMI shielding performances. When the EM wave is incident from Ni@MF layer or CNT layer, Ni@MF-5/CNT-75/PBAT exhibits the total EMI SE (SET) of 38.3 and 29.5 dB, respectively, which illustrates the ΔSET of 8.8 dB. This work opens a new research window for directional EMI shielding composites with step-wise asymmetric structures, which has promising applications in portable electronics and next-generation communication technologies.

Holocellulose nanofibrils assisted exfoliation to prepare MXene-based composite film with excellent electromagnetic interference shielding performance

A high-yield and straightforward method is proposed to obtain an electromagnetic interference (EMI) shielding film based on multilayered Ti₃C₂T_x (m-Ti₃C₂T_x). Holocellulose nanofibrils modified by sulfamic acid (SHCNF) with unique "core-shell" structure can act as a dispersant and a binder to assist in exfoliating m-Ti₃C₂T_x into delaminated-Ti₃C₂T_x (d-Ti₃C₂T_x) and fabricate flexible Ti₃C₂T_x/SHCNF composite films with a high-yield value. The "brick-and-mortar" composite films exhibit a superior electromagnetic interference (EMI) shielding effectiveness (SE) of 45.02 dB with an ultrathin thickness of 40 μm at the 12.4 GHz. Moreover, these flexible and strong integrated Ti₃C₂T_x/SHCNF composite films also display excellent specific EMI SE of SSE/t (4437 dB cm² g^-1) and high EMI shielding efficiency (99.996%). Therefore, the SHCNF-assisted method provides a cost-effective approach to fabricate a strong and flexible MXene-based nanocomposite films toward EMI shielding application.

Scalable Fabrication of Ti3C2Tx MXene/RGO/Carbon Hybrid Aerogel for Organics Absorption and Energy Conversion

High aspect ratio two-dimensional Ti₃C₂T_x MXene flakes with extraordinary mechanical, electrical, and thermal properties are ideal candidates for assembling elastic and conductive aerogels. However, the scalable fabrication of large MXene-based aerogels remains a challenge because the traditional preparation method relies on supercritical drying techniques such as freeze drying, resulting in poor scalability and high cost. Herein, the use of porous melamine foam as a robust template for MXene/reduced graphene oxide aerogel circumvents the volume shrinkage during its natural drying process. Through this approach, we were able to produce large size (up to 600 cm³) MXene-based aerogel with controllable shape. In addition, the aerogels possess an interconnected cellular structure and display resilience up to 70% of compressive strain. Some key features also include high solvent absorption capacity (∼50-90 g g^-1), good photothermal conversion ability (an average evaporation rate of 1.48 kg m^-2 h^-1 for steam generation), and an excellent electrothermal conversion rate (1.8 kg m^-2 h^-1 at 1 V). More importantly, this passive drying process provides a scalable, convenient, and cost-effective approach to produce high-performance MXene-based aerogels, demonstrating the feasibility of commercial production of MXene-based aerogels toward practical applications.

High-Performance, Lightweight, and Flexible Thermoplastic Polyurethane Nanocomposites with Zn2+-Substituted CoFe2O4 Nanoparticles and Reduced Graphene Oxide as Shielding Materials against Electromagnetic Pollution

The development of flexible, lightweight, and thin high-performance electromagnetic interference shielding materials is urgently needed for the protection of humans, the environment, and electronic devices against electromagnetic radiation. To achieve this, the spinel ferrite nanoparticles CoFe2O4 (CZ1), Co0.67Zn0.33Fe2O4 (CZ2), and Co0.33Zn0.67Fe2O4 (CZ3) were prepared by the sonochemical synthesis method. Further, these prepared spinel ferrite nanoparticles and reduced graphene oxide (rGO) were embedded in a thermoplastic polyurethane (TPU) matrix. The maximum electromagnetic interference (EMI) total shielding effectiveness (SET) values in the frequency range 8.2-12.4 GHz of these nanocomposites with a thickness of only 0.8 mm were 48.3, 61.8, and 67.8 dB for CZ1-rGO-TPU, CZ2-rGO-TPU, and CZ3-rGO-TPU, respectively. The high-performance electromagnetic interference shielding characteristics of the CZ3-rGO-TPU nanocomposite stem from dipole and interfacial polarization, conduction loss, multiple scattering, eddy current effect, natural resonance, high attenuation constant, and impedance matching. The optimized CZ3-rGO-TPU nanocomposite can be a potential candidate as a lightweight, flexible, thin, and high-performance electromagnetic interference shielding material.

Anisotropic conductive networks for multidimensional sensing

In the past decade, flexible physical sensors have attracted great attention due to their wide applications in many emerging areas including health-monitoring, human-machine interfaces, smart robots, and entertainment. However, conventional sensors are typically designed to respond to a specific stimulus or a deformation along only one single axis, while directional tracking and accurate monitoring of complex multi-axis stimuli is more critical in practical applications. Multidimensional sensors with distinguishable signals for simultaneous detection of complex postures and movements in multiple directions are highly demanded for the development of wearable electronics. Recently, many efforts have been devoted to the design and fabrication of multidimensional sensors that are capable of distinguishing stimuli from different directions accurately. Benefiting from their unique decoupling mechanisms, anisotropic architectures have been proved to be promising structures for multidimensional sensing. This review summarizes the present state and advances of the design and preparation strategies for fabricating multidimensional sensors based on anisotropic conducting networks. The fabrication strategies of different anisotropic structures, the working mechanism of various types of multidimensional sensing and their corresponding unique applications are presented and discussed. The potential challenges faced by multidimensional sensors are revealed to provide an insightful outlook for the future development.

Flexible Sandwich-Structured Electromagnetic Interference Shielding Nanocomposite Films with Excellent Thermal Conductivities

With the rapid development and popularization of smart, portable, and wearable flexible electronic devices, urgent demands have been raised for flexible electromagnetic interference (EMI) shielding films to solve related electromagnetic pollution problems. With polyvinyl alcohol (PVA) as polymer matrix, the sandwich-structured EMI shielding nanocomposite films are prepared via electrospinning-laying-hot pressing technology, where Fe₃ O₄ /PVA composite electrospun nanofibers in the top and bottom layers and Ti₃ C₂ T_x /PVA composite electrospun nanofibers in the middle layer. Owing to the electrospinning process and the successful construction of the sandwich structure, when the amounts of Ti₃ C₂ T_x and Fe₃ O₄ are respectively only 13.3 and 26.7 wt%, the EMI shielding effectiveness (EMI SE) of the sandwich-structured EMI shielding nanocomposite films reach 40 dB with the thickness of 75 µm, higher than that of (Fe₃ O₄ /Ti₃ C₂ T_x )/PVA EMI shielding nanocomposite films (21 dB) prepared based on blending-electrospinning-hot pressing process under the same amounts of fillers. Furthermore, the prepared sandwich-structured EMI shielding nanocomposite films possess excellent thermal conductivities and mechanical properties. This novel kind of flexible sandwich-structured EMI shielding nanocomposite films with excellent EMI shielding performances, thermal conductivities, and mechanical properties presents broad application prospects in the fields of EMI shielding and protection for high-power, portable, and wearable flexible electronic devices.

Rapid Photothermal Responsive Conductive MXene Nanocomposite Hydrogels for Soft Manipulators and Sensitive Strain Sensors

Stimulus-responsive hydrogels are of great significance in soft robotics, wearable electronic devices, and sensors. Near-infrared (NIR) light is considered an ideal stimulus as it can trigger the response behavior remotely and precisely. In this work, a smart flexible stimuli-responsive hydrogel with excellent photothermal property and decent conductivity are prepared by incorporating MXene nanosheets into the physically cross-linked poly(N-isopropyl acrylamide) hydrogel matrix. Because of outstanding photothermal effect and dispersion of MXene, the composite hydrogel exhibits rapid photothermal responsiveness and excellent photothermal stability under the NIR irradiation. Furthermore, the anisotropic bilayer hydrogel actuator shows fast and controllable light-driven bending behavior, which can be used as a light-controlled soft manipulator. Meanwhile, the hydrogel sensor exhibits cycling stability and good durability in detecting various deformation and real-time human activities. Therefore, the present study involving the fabrication of MXene nanocomposite hydrogels for potential applications in remotely controlled actuator and wearable electronic device provides a new method for the development of photothermal responsive conductive hydrogels.

Ti3C2Tx MXene-Decorated Nanoporous Polyethylene Textile for Passive and Active Personal Precision Heating

Heating the human body to maintain a relatively constant temperature is pivotal for various human functions. However, most of the current heating strategies are energy-consuming and energy-wasting and cannot cope with the complex and changing environment. Developing materials and systems that can heat the human body precisely via an efficient energy-saving approach no matter indoors/outdoors, day/night, and sunny/cloudy is highly anticipated for mitigating the growing energy crisis and global warming but is still a great challenge. Here, we demonstrate the low mid-infrared radiative (mid-IR) emissivity characteristic of Ti₃C₂T_x MXene and then apply it for energy-free passive radiative heating (PRH) on the human body. Our strategy is realized by simply decorating the cheap nanoporous polyethylene (nanoPE) textile with MXene. Impressively, the as-obtained 12 μm thick MXene/nanoPE textile shows a low mid-IR emissivity of 0.176 at 7-14 μm and outstanding indoor PRH performance on the human body, which enhances by 4.9 °C compared with that of traditional 576 μm thick cotton textile. Meanwhile, the MXene/nanoPE textile exhibits excellent active outdoor solar heating and indoor/outdoor Joule heating capability. The three heating modes integrated in this wearable MXene/nanoPE heating system can be switched easily or combined arbitrarily, making this thin heating system able to heat the human body precisely in various scenarios like indoors/outdoors, day/night, and sunny/cloudy, providing multiple promising and energy-saving solutions for future all-day personal precision thermal management.

Facile Fabrication of Densely Packed Ti3C2 MXene/Nanocellulose Composite Films for Enhancing Electromagnetic Interference Shielding and Electro-/Photothermal Performance

The development of modern electronics has raised great demand for multifunctional materials to protect electronic instruments against electromagnetic interference (EMI) radiation and ice accretion in cold weather. However, it is still a great challenge to prepare high-performance multifunctional films with excellent flexibilty, mechanical strength, and durability. Here, we propose a layer-by-layer assembly of cellulose nanofiber (CNF)/Ti₃C₂T_x nanocomposites (TM) on a bacterial cellulose (BC) substrate via repeated spray coating. CNFs are hybridized with Ti₃C₂T_x nanoflakes to improve the mechanical properties of the functional coating layer and its adhesion with the BC substrate. The densely packed hierarchical structure and strong interfacial interactions endows the TM/BC films with good flexibility, ultrahigh mechanical strength (>250 MPa), and desirable toughness (>20 MJ cm^-3). Furthermore, benefiting from the densely packed hierarchical structure, the resultant TM/BC films present outstanding EMI shielding effictiveness of 60 dB and efficient electro-/photothermal heating performance. Silicone encapsulation further imparts high hydrophobicity and exceptional durability against solutions and deformations to the multifunctional films. Impressively, the silicone-coated TM/BC film (Si-TM/BC) exhibits desirable low voltage-driven Joule heating and excellent photoresponsive heating performance, which demonstrates great feasibility for efficient thermal deicing under actual conditions. Therefore, we believe that the Si-TM/BC film with excellent mechanical properties and durability holds great promise for the practical applications of EMI shielding and ice accretion elimination.

High-Performance Joule Heating and Electromagnetic Shielding Properties of Anisotropic Carbon Scaffolds

Highly efficient electrical heaters along with excellent electromagnetic interference (EMI) shielding properties are urgently required for the progress of miniaturization electronics, artificial intelligence, and smart heating management setups. Herein, lignin removal, which comprises two efficient and versatile steps, followed by carbonization produces multifunctional carbon monoliths derived from natural wood. The obtained carbonized wood exhibits a high specific surface area (655.14 m²/g) and electrical (17.5 S/cm) and thermal conductivity (0.58 W/m·K), superhydrophilicity (contact angle of ∼0°), and excellent EMI shielding ability and Joule heating performance. The high electrical conductivity renders a low-voltage-actuated Joule heating performance and fascinating EMI shielding effectiveness of 55 dB, primarily resulting from the absorption mechanism. Moreover, regulation of the carbonized woods derived from the longitudinal to the radial direction enables transformation of hydrophilicity, strong thermal conductivity, and absorption-dominated EMI shielding to hydrophobicity, thermal insulation, and reflection-dominated EMI shielding. This is attributed to the unique anisotropic microstructure of carbon scaffolds. It is believed that these multifunctional carbon scaffolds can be used for intelligent electronics, EMI shielding, and thermal heating instruments.

Multifunctional MXene/Chitosan-Coated Cotton Fabric for Intelligent Fire Protection

Multifunctional intelligent fireproof cotton fabrics are urgently demanded in the era of the Internet of Things. Herein, a novel high fire safety cotton fabric (denoted as MXene/CCS@CF) with temperature sensing, fire-warning, piezoresistivity, and Joule heating performance was developed by coating MXene nanosheet and carboxymethyl chitosan (CCS) via an eco-friendly layer-by-layer assembly method. Benefiting from the thermoelectric characteristic and high conductivity of MXene nanosheet, MXene/CCS@CF exhibited accurate wide-range temperature sensing performance. When being burned, it could repeatedly trigger the fire-warning system in less than 10 s. More importantly, MXene/CCS@CF showed outstanding flame retardancy because of the synergistic carbonization between MXene and CCS. The limiting oxygen index of MXene/CCS@CF was as high as 45.5%, and the char length was only 33 mm after the vertical burning test. Meanwhile, its peak heat release rate reduced more than 66%. Besides, the obtained fabric could detect a variety of human motions. Moreover, the controllable Joule heating performance enabled the fabric to be used in extreme cold weather. This work provides a facile approach to fabricating a next-generation high fire safety cotton fabric, showing promising applications in firefighting, home automation, and smart transportation.