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

Ultrastrong MXene film induced by sequential bridging with liquid metal

Assembling titanium carbide (Ti3C2Tx) MXene nanosheets into macroscopic films presents challenges, including voids, low orientation degree, and weak interfacial interactions, which reduce mechanical performance. We demonstrate an ultrastrong macroscopic MXene film using liquid metal (LM) and bacterial cellulose (BC) to sequentially bridge MXene nanosheets (an LBM film), achieving a tensile strength of 908.4 megapascals. A layer-by-layer approach using repeated cycles of blade coating improves the orientation degree to 0.935 in the LBM film, while a LM with good deformability reduces voids into porosity of 5.4%. The interfacial interactions are enhanced by the hydrogen bonding from BC and the coordination bonding with LM, which improves the stress-transfer efficiency. Sequential bridging provides an avenue for assembling other two-dimensional nanosheets into high-performance materials.

Annual Energy-Saving Smart Windows with Actively Controllable Passive Radiative Cooling and Multimode Heating Regulation

Smart windows with radiative heat management capability using the sun and outer space as zero-energy thermodynamic resources have gained prominence, demonstrating a minimum carbon footprint. However, realizing on-demand thermal management throughout all seasons while reducing fossil energy consumption remains a formidable challenge. Herein, an energy-efficient smart window that enables actively tunable passive radiative cooling (PRC) and multimode heating regulation is demonstrated by integrating the emission-enhanced polymer-dispersed liquid crystal (SiO2@PRC PDLC) film and a low-emission layer deposited with carbon nanotubes. Specifically, this device can achieve a temperature close to the chamber interior ambient under solar irradiance of 700 W m-2, as well as a temperature drop of 2.3 °C at sunlight of 500 W m-2, whose multistage PRC efficiency can be rapidly adjusted by a moderate voltage. Meanwhile, synchronous cooperation of passive radiative heating (PRH), solar heating (SH), and electric heating (EH) endows this smart window with the capability to handle complicated heating situations during cold weather. Energy simulation reveals the substantial superiority of this device in energy savings compared with single-layer SiO2@PRC PDLC, normal glass, and commercial low-E glass when applied in different climate zones. This work provides a feasible pathway for year-round thermal management, presenting a huge potential in energy-saving applications.

A novel strategy to prepare high performance multifunctional composite films by combining electrostatic assembly, crosslinking, topology enhancement and sintering

Currently, polymer-fiber composite films face the challenge of striking a balance between good mechanical properties and multi-functionalities. Here, aramid fibers (ANFs), chitosan (CS) dendritic particles, and silver nanowires (AgNWs) were used to create high-performance multifunctional composite films. AgNWs and polymer dendritic particles form an interpenetrating segregated network that ensures both a continuous conductive filler and a polymer network. Electrostatic assembly eliminates repulsion between negatively charged ANFs, cross-linked CS particles generate a stable three-dimensional network, and a "brick-mortar" structure composed of multiple materials contributes to topological enhancement. Sintering encourages local overlap and fusing of the AgNWs while reducing their internal flaws. Based on the above strategy, these films achieve a strength of 306.5 MPa, a toughness of 26.5 MJ m-3, and a conductivity of 392 S cm-1. Density functional theory (DFT) and Comsol simulations demonstrate that the introduction of CS thin layers leads to strong hydrogen bonds and three-dimensional continuous conductive networks. With its outstanding mechanical and electrical properties, the AgNW@ANF/CS-CH film demonstrates excellent electromagnetic shielding (22 879.1 dB cm2 g-1) and Joule heating (70 °C within 10 s) capabilities. This work presents a novel approach to fabricate high-performance conductive films and expand their potential applications in lightweight wearable electronics and electrothermal therapy.

Large-Scale, Mechanically Robust, Solvent-Resistant, and Antioxidant MXene-Based Composites for Reliable Long-Term Infrared Stealth

MXene-based thermal camouflage materials have gained increasing attention due to their low emissivity, however, the poor anti-oxidation restricts their potential applications under complex environments. Various modification methods and strategies, e.g., the addition of antioxidant molecules and fillers have been developed to overcome this, but the realization of long-term, reliable thermal camouflage using MXene network (coating) with excellent comprehensive performance remains a great challenge. Here, a MXene-based hybrid network comodified with hyaluronic acid (HA) and hyperbranched polysiloxane (HSi) molecules is designed and fabricated. Notably, the presence of appreciated HA molecules restricts the oxidation of MXene sheets without altering infrared stealth performance, superior to other water-soluble polymers; while the HSi molecules can act as efficient cross-linking agents to generate strong interactions between MXene sheets and HA molecules. The optimized MXene/HA/HSi composites exhibit excellent mechanical flexibility (folded into crane structure), good water/solvent resistance, and long-term stable thermal camouflage capability (with low infrared emissivity of ≈0.29). The long-term thermal camouflage reliability (≈8 months) under various outdoor weathers and the scalable coating capability of the MXene-coated textile enable them to disguise the IR signal of various targets in complex environments, indicating the great promise of achieved material for thermal camouflage, IR stealth, and counter surveillance.

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.

A Polymer Nanocomposite with Strong Full-Spectrum Solar Absorption and Infrared Emission for All-Day Thermal Energy Management and Conversion

Realizing efficient energy utilization from the heat source of the sun and the cold source of outer space is of great significance for addressing the global energy and environmental crisis. Materials with ideal full-spectrum solar absorption and infrared emission are highly desirable for adapting to the continuous weather dynamic throughout the day, nonetheless, their development remains challenging. Here, a polymer nanocomposite with full-spectrum strong solar (280-2500 nm) absorption ranging from 88.8% to 94.8% with an average value of 93.2% and full-spectrum high infrared (8-13 µm) emission ranging from 81.3% to 90.0% with an average value of 84.2%, is reported by melt-processing polypropylene and uniformly dispersed low-loading MXene nanosheets (1.9 vol%). The nanocomposite can achieve daytime photothermal enhancement of ≈50 °C and nighttime radiative cooling of 8 °C. The temperature difference throughout the day ensures all-day uninterrupted thermoelectric generation, yielding a power density output of 1.5 W m-2 (daytime) and 7.9 mW m-2 (nighttime) in real outdoor environment without any additional energy consumption. This work provides an impressive polymer nanocomposite with ideal full-spectrum solar absorption and infrared emission for all-day uninterrupted thermal energy management and conversion.

Revealing Surface/Interface Chemistry of the Ordered Aramid Nanofiber/MXene Structure for Infrared Thermal Camouflage and Electromagnetic Interference Shielding

The past decade has witnessed the advances of infrared (IR) thermal camouflage materials, but challenges remain in breaking the trade-off nature between emissivity and mechanical properties. In response, we identify the key role of a moderate reprotonation rate in the aramid nanofiber (ANF)/MXene film toward a surface-to-bulk alignment. Theoretical simulation demonstrates that the ordered ANF/MXene surface eliminates the local high electric field by field confinement and localization, responsible for the low IR emissivity. By scrutinizing the surface/interface chemistry, the processing optimization is achieved to develop an ordered and densely stacked ANF/MXene film, which features a low emissivity of 16%, accounting for sound IR thermal camouflage performances including a wide camouflage temperature range of 50-200 °C, a large reduction in radiation temperature from 200.5 to 63.6 °C, and long-term stability. This design also enables good mechanical performance such as a tensile strength of 190.8 MPa, a toughness of 12.1 MJ m-3, and a modulus of 7.9 GPa, responsible for better thermal camouflage applications. The tailor-made ANF/MXene film further attains an electromagnetic interference (EMI) shielding effectiveness (40.4 dB) in the X-band, manifesting its promise for IR stealth compatible EMI shielding applications. This work will shed light on the dynamic topology reconstruction of camouflage materials for boosting thermal management technology.

Robust and Multifunctional Ti3 C2 Tx /Modified Sawdust Composite Paper for Electromagnetic Interference Shielding and Wearable Thermal Management

Robust, ultrathin, and environmental-friendliness papers that synergize high-efficiency electromagnetic interference (EMI) shielding, personal thermal management, and wearable heaters are essential for next-generation smart wearable devices. Herein, MXene nanocomposite paper with a nacre-like structure for EMI shielding and electrothermal/photothermal conversion is fabricated by vacuum filtration of Ti3 C2 Tx MXene and modified sawdust. The hydrogen bonding and highly oriented structure enhance the mechanical properties of the modified sawdust/MXene composite paper (SM paper). The SM paper with 50 wt% MXene content shows a strength of 23 MPa and a toughness of 13 MJ·M-3 . The conductivity of the SM paper is 10 195 S·m-1 , resulting in an EMI shielding effectiveness (SE) of 67.9 dB and a specific SE value (SSE/t) of 8486 dB·cm2 ·g-1 . In addition, the SM paper exhibits excellent thermal management performance including high light/electro-to-thermal conversion, rapid Joule heating and photothermal response, and sufficient heating stability. Notably, the SM paper exhibits low infrared emissivity and distinguished infrared stealth performance, camouflaging a high-temperature heater surface of 147-81 °C. The SM-based e-skin achieves visualization of Joule heating and realizes human motions monitoring. This work presents a new strategy for designing MXene-based wearable devices with great EMI shielding, artificial intelligence, and thermal management 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.

A Bioinspired Bilevel Metamaterial for Multispectral Manipulation toward Visible, Multi-Wavelength Detection Lasers and Mid-Infrared Selective Radiation

Manipulation of the electromagnetic signature in multiple wavebands is necessary and effective in civil and industrial applications. However, the integration of multispectral requirements, particularly for the bands with comparable wavelengths, challenges the design and fabrication of current compatible metamaterials. Here, a bioinspired bilevel metamaterial is proposed for multispectral manipulation involving visible, multi-wavelength detection lasers and mid-infrared (MIR), along with radiative cooling. The metamaterial, consisting of dual-deck Pt disks and a SiO2 intermediate layer, is inspired by the broadband reflection splitting effect found in butterfly scales and achieves ultralow specular reflectance (average of 0.013) over the entire 0.8-1.6 µm with large scattering angles. Meanwhile, tunable visible reflection and selective dual absorption peaks in MIR can be simultaneously realized, providing structural color, effective radiative thermal dissipation at 5-8 µm and 10.6 µm laser absorption. The metamaterial is fabricated by a low-cost colloidal lithography method combined with two patterning processes. Multispectral manipulation performances are experimentally demonstrated and a significant apparent temperature drop (maximum of 15.7 °C) compared to the reference is observed under a thermal imager. This work achieves optical response in multiple wavebands and provides a valuable way to effectively design multifunctional metamaterials inspired by nature.

Asymmetric and Flexible Ag-MXene/ANFs Composite Papers for Electromagnetic Shielding and Thermal Management

Lightweight, flexible, and electrically conductive thin films with high electromagnetic interference (EMI) shielding effectiveness and excellent thermal management capability are ideal for portable and flexible electronic devices. Herein, the asymmetric and multilayered structure Ag-MXene/ANFs composite papers (AMAGM) were fabricated based on Ag-MXene hybrids and aramid nanofibers (ANFs) via a self-reduction and alternating vacuum-assisted filtration process. The resultant AMAGM composite papers exhibit high electrical conductivity of 248,120 S m-1, excellent mechanical properties with tensile strength of 124.21 MPa and fracture strain of 4.98%, superior EMI shielding effectiveness (62 dB), ultra-high EMI SE/t (11,923 dB cm2 g-1) and outstanding EMI SE reliability as high as 96.1% even after 5000 cycles of bending deformation benefiting from the unique structure and the 3D network at a thickness of 34 μm. Asymmetric structures play an important role in regulating reflection and absorption of electromagnetic waves. In addition, the multifunctional nanocomposite papers reveal outstanding thermal management performances such as ultrafast thermal response, high heating temperatures at low operation voltage, and high heating stability. The results indicate that the AMAGM composite papers have excellent potential for high-integration electromagnetic shielding, wearable electronics, artificial intelligence, and high-performance heating devices.

Achieving fast interfacial solar vapor generation and aqueous acid purification using Ti3C2Tx MXene/PANI non-woven fabrics

Acid rain is a worldwide problem because of the emission of acidic gases into the atmosphere, leading to the acidification of first-order streams and aggravation of fresh water shortage. Therefore, it is of great importance to develop an environmentally friendly method for removing acid from water. Herein, an advanced technology that can achieve aqueous acid purification using solar energy is realized with Ti₃C₂T_x MXene/polyaniline (PANI) hybrid non-woven fabrics (MPs) through interfacial solar vapor generation, with PANI acting as an acid absorber through the doping process. Benefiting from the porous structure and crumpled micro-surface of MPs, a high evaporation rate of 2.65 kg m^-2 h^-1 with an efficiency of 93.7% can be achieved under one-sun illumination. Moreover, MPs present an even higher evaporation rate of 2.83 kg m^-2 h^-1 in high concentration aqueous acid and can generate clean water with a pH higher than 6.5. More importantly, thanks to the unique reversible doping process of PANI, when used as an aqueous acid purifier, MPs show good stability and reusability after dedoping. Our work sheds light on an efficient strategy for dealing with aqueous acid and acid rain.

Research Progress with Membrane Shielding Materials for Electromagnetic/Radiation Contamination

As technology develops at a rapid pace, electromagnetic and radiation pollution have become significant issues. These forms of pollution can cause many important environmental issues. If they are not properly managed and addressed, they will be everywhere in the global biosphere, and they will have devastating impacts on human health. In addition to minimizing sources of electromagnetic radiation, the development of lightweight composite shielding materials to address interference from radiation has become an important area of research. A suitable shielding material can effectively reduce the harm caused by electromagnetic interference/radiation. However, membrane shielding materials with general functions cannot effectively exert their shielding performance in all fields, and membrane shielding materials used in different fields must have specific functions under their use conditions. The aim of this review was to provide a comprehensive review of these issues. Firstly, the causes of electromagnetic/radiation pollution were briefly introduced and comprehensively identified and analyzed. Secondly, the strategic solutions offered by membrane shielding materials to address electromagnetic/radiation problems were discussed. Then, the design concept, technical innovation, and related mechanisms of the existing membrane shielding materials were expounded, the treatment methods adopted by scholars to study the environment and performance change laws were introduced, and the main difficulties encountered in this area of research were summarized. Finally, on the basis of a comprehensive analysis of the protection provided by membrane shielding materials against electromagnetic/radiation pollution, the action mechanism of membrane shielding materials was expounded in detail, and the research progress, structural design and performance characterization techniques for these materials were summarized. In addition, the future challenges were prospected. This review will help universities, research institutes, as well as scientific and technological enterprises engaged in related fields to fully understand the design concept and research progress of electromagnetic/radiation-contaminated membrane shielding materials. In addition, it is hoped that this review will facilitate efforts to accelerate the research and development of membrane shielding materials and offer potential applications in areas such as electronics, nuclear medicine, agriculture, and other areas of industry.