Aerogel-Involved Triple-State Gels Resemble Natural Living Leaves in Structure and Multi-Functions.

Natural plant leaves with multiple functions, for example, spectral features, transpiration, photosynthesis, etc., have played a significant role in the ecosystem, and artificial synthesis of plant leaves with multiple functions of natural ones is still a great challenge. Herein, this work presents an aerogel-involved living leaf (AL), most similar to natural ones so far, by embedding super-hydrophobic SiO2 aerogel microparticles in polyvinyl alcohol hydrogel in the presence of hygroscopic salt and chlorophyllin copper sodium to form solid-liquid-vapor triple-state gel. The AL shows a high spectral similarity with all sampled 15 species of natural leaves and exhibits ≈4-7 times transpiration speed higher than natural leaves. More importantly, AL can achieve several times higher photosynthesis than natural leaves without the energy provided by the respiratory action of natural ones. This work demonstrates the feasibility of creating ALs with natural leaf-like triple-state gel structures and multiple functions, opening up new avenues for energy conversion, environmental engineering, and biomimetic applications.

MXene-Enabled Pneumatic Multiscale Shape Morphing for Adaptive, Programmable and Multimodal Radar-infrared Compatible Camouflage.

Achieving radar-infrared compatible camouflage with dynamic adaptability has been a long-sought goal, but faces significant challenges owing to the limited dispersion relations of conventional material systems operating in different wavelength ranges. Here, this work proposes the concept of pneumatic multiscale shape morphing and design a periodically arranged pneumatic unit consisting of MXene-based morphable conductors and intake platforms. During gas actuation, the morphable conductor transforms centimeter-scale 2D flat sheets into 3D balloon shapes to enhance microwave absorption behavior, and also reconfigures micrometer-scale MXene wrinkles into smooth planes in combination with cavity-induced low heat transfer to minimize infrared (IR) signatures. Through theory-guided reverse engineering, the final pneumatic matrix shows remarkable frequency tunability (2.64-18.0 GHz), moderate IR emissivity regulation (0.14 at 7-16.5 µm), rapid responsiveness (≈30 ms), wide-angle operation (>45°), and excellent environmental tolerance. Additionally, the multiplexed pneumatic matrix enables over 14 programmable coding sequences that independently alter thermal radiation without compromising radar stealth, and allows multimodal camouflage switching between three distinct compatible states. The approach may facilitate the evolution of camouflage techniques and electromagnetic functional materials toward multispectral, adaptability and intelligence.

Achieving Ultra-Broad Microwave Absorption Bandwidth Around Millimeter-Wave Atmospheric Window Through an Intentional Manipulation on Multi-Magnetic Resonance Behavior.

The utilization of electromagnetic waves is rapidly advancing into the millimeter-wave frequency range, posing increasingly severe challenges in terms of electromagnetic pollution prevention and radar stealth. However, existing millimeter-wave absorbers are still inadequate in addressing these issues due to their monotonous magnetic resonance pattern. In this work, rare-earth La3+ and non-magnetic Zr4+ ions are simultaneously incorporated into M-type barium ferrite (BaM) to intentionally manipulate the multi-magnetic resonance behavior. By leveraging the contrary impact of La3+ and Zr4+ ions on magnetocrystalline anisotropy field, the restrictive relationship between intensity and frequency of the multi-magnetic resonance is successfully eliminated. The magnetic resonance peak-differentiating and imitating results confirm that significant multi-magnetic resonance phenomenon emerges around 35 GHz due to the reinforced exchange coupling effect between Fe3+ and Fe2+ ions. Additionally, Mössbauer spectra analysis, first-principle calculations, and least square fitting collectively identify that additional La3+ doping leads to a profound rearrangement of Zr4+ occupation and thus makes the portion of polarization/conduction loss increase gradually. As a consequence, the La3+-Zr4+ co-doped BaM achieves an ultra-broad bandwidth of 12.5 + GHz covering from 27.5 to 40 + GHz, which holds remarkable potential for millimeter-wave absorbers around the atmospheric window of 35 GHz.

Multi-interfacial bridging engineering of flexible MXene film for efficient electromagnetic shielding and energy conversion.

Accompanied by the progressive development of electronic equipment, excellent electromagnetic interference (EMI) shielding materials display a satisfying prospect in protecting electronic devices against electromagnetic pollution/radiation, while integrating energy conversion. Heretofore, it remains a conundrum to availably construct thin films with multi-interfacial bridging engineering as multifunctional shielding devices. To effectively achieve electromagnetic wave attenuation and integrate energy conversion, a co-mixed vacuum-assisted filtration strategy is designed to synthesize Au@MXene/cellulose nanocrystal/dodecylbenzenesulfonic acid-doped polyaniline (AMCP) films. Profited from the interfacial engineering, the total EMI shielding effectiveness (SE) can be increased by 27 % with the highest value of 67.9 dB. MXene with localized surface plasmon resonance characteristics gives the composite films good energy conversion performance, that is, the composite film can be rapidly heated up to 100 °C under the irradiation of an infrared lamp, and its surface temperature remains stable after continuous irradiation. Additionally, the infrared emissivity is as low as 0.173 within the 8-14 µm, which is necessary to adapt various application scenarios. Therefore, it is reliable that the AMCP films constructed by multicomponent offer a facile strategy for MXene-based EMI shielding devices with integration characteristics.

Dendrimer-assisted defect and morphology regulation for improving optical, hyperthermia, and microwave-absorbing features.

Electromagnetic pollution and cancer are phenomena that essentially endanger the future of humanity. Herein, multiple approaches are being proposed to solve the aforementioned issues. Recent studies have demonstrated that by regulating the morphology, defect, and phase of materials, their microwave absorbing, optical, and hyperthermia properties are tunable. Calcium ferrite with proper dielectric, magnetic, and biocompatible characteristics was chosen as a substantial candidate to promote its microwave-absorbing properties by regulating its structure. Spinel CaFe2O4 was synthesized through sol-gel and solvothermal routes and its phase, defect, and morphology were manipulated using innovative procedures. Glucose was applied as conventional defecting and templating agent; interestingly, a dendrimer was designed to bear and form nanoparticles. More importantly, a novel reductive process was designed to fabricate one-put Ca/Fe3O4 using a solvothermal method. Particularly, polypropylene (PP) was employed as a practical polymeric matrix to fabricate the eventual product. Structures were molded at a low filling ratio to evaluate their optical and microwave-absorbing performance. As expected, defects, morphology, and phase play a pivotal role in tuning the optical and microwave-absorbing properties of calcium ferrite derivates. Interestingly, the dendrimer-assisted (D-A) formation of CaFe2O4 demonstrated a fascinating reflection loss (RL) of 70.11 dB and an efficient bandwidth (RL ≤ -20 dB) of 7.03 GHz with ultralow thickness (0.65 mm) and filling ratio (10 wt%), attaining proper shielding efficiency (SE) and hyperthermia desirable for its practical application as a material for shielding buildings and cancer therapy. The presented perspective develops new inspirations for architecting microwave absorbing/shielding materials with advanced applications in therapeutic issues.

Pneumatic Structural Deformation to Enhance Resonance Behavior for Broadband and Adaptive Radar Stealth.

Ideal radar absorbing materials (RAMs) require instantaneous, programmable, and spontaneous adaptability to cope with a complex electromagnetic (EM) environment across the full working frequency. Despite various material systems and adaptive mechanisms having been demonstrated, it remains a formidable challenge to integrate these benefits simultaneously. Here, we present a pneumatic matrix that couples morphable MXene/elastomer conductors with dielectric spacers, which leverages controllable airflow to reconfigure the spatial structure between a flat sheet and a hemispherical crown while maintaining resistance stability via wrinkle folding and unfolding. The interdimensional reconfigurations drastically induce multiple resonance behavior, enabling the matrix remarkable frequency tunability (144.5%), ultrawide bandwidth (15 GHz), weak angular dependence (45° incidence), ultrafast responsiveness (∼30 ms), and excellent reproducibility (1000 cycles). With multichannel fluidic and conceptual automated control systems, the final pneumatic device demonstrates a multiplexed, programmable, and autonomous transformable mode that builds a promising platform for smart radar cloaking.

Electronic Modulation Strategy for Mass-Producible Ultrastrong Multifunctional Biomass-Based Fiber Aerogel Devices: Interfacial Bridging.

The emergence of green flexible aerogel electronics based on natural materials is expected to solve part of the global environmental and energy crisis. However, it is still challenging to achieve large-scale production and multifunctional stable applications of natural biomass fiber aerogel (BFA) materials. Herein, we exploit the interfacial bridging between the flower-type titanium dioxide nanoarray (FTNA) and natural fiber substrates to modulate the electronic structure and loss mechanism to achieve multifunctional properties. Specifically, the fibrous substrate with wrinkled features induces lattice strain in titania through precise interfacial bridging, effectively improving the intrinsic properties of the BFA materials. This interfacial bridging regulation strategy is also confirmed by X-ray absorption fine structure spectroscopy (XAS). More importantly, the construction of BFA products for different macroscopic and multifunctional applications through simple processing methods will facilitate the transition from natural materials to multifunctional flexible electronics. Therefore, the as-prepared blanket-type BFA (TCBFA) has good mechanical properties, electromagnetic protection properties, thermal stealth properties, high-temperature flame retardancy, and UV resistance. Meanwhile, the membrane-type (TCBFAM) multifunctional wearable fiber aerogel device exhibits superior flexibility, efficient Joule heating performance, and a smart response. This regulation strategy provides another concept for the design and innovation of green multifunctional fiber-integrated aerogels.

"Three-in-One" Multi-Scale Structural Design of Carbon Fiber-Based Composites for Personal Electromagnetic Protection and Thermal Management.

Wearable devices with efficient thermal management and electromagnetic interference (EMI) shielding are highly desirable for improving human comfort and safety. Herein, a multifunctional wearable carbon fibers (CF) @ polyaniline (PANI) / silver nanowires (Ag NWs) composites with a "branch-trunk" interlocked micro/nanostructure were achieved through "three-in-one" multi-scale design. The reasonable assembly of the three kinds of one-dimensional (1D) materials can fully exert their excellent properties i.e., the superior flexibility of CF, the robustness of PANI, and the splendid conductivity of AgNWs. Consequently, the constructed flexible composite demonstrates enhanced mechanical properties with a tensile stress of 1.2 MPa, which was almost 6 times that of the original material. This is mainly attributed to the fact that the PNAI (branch) was firmly attached to the CF (trunk) through polydopamine (PDA), forming a robust interlocked structure. Meanwhile, the composite possesses excellent thermal insulation and heat preservation capacity owing to the synergistically low thermal conductivity and emissivity. More importantly, the conductive path of the composite established by the three 1D materials greatly improved its EMI shielding property and Joule heating performance at low applied voltage. This work paves the way for rational utilization of the intrinsic properties of 1D materials, as well as provides a promising strategy for designing wearable electromagnetic protection and thermal energy management devices.

An Adaptive Multispectral Mechano-Optical System for Multipurpose Applications.

Mechano-optical systems with on-demand adaptability and a broad spectrum from the visible to microwave are critical for complex multiband electromagnetic (EM) applications. Most existing material systems merely have dynamic optical or microwave tunability because their EM wave response is strongly wavelength-dependent. Inspired by cephalopod skin, we develop an adaptive multispectral mechano-optical system based on bilayer acrylic dielectric elastomer (ADE)/silver nanowire (AgNW) films, which reconfigures the surface morphology between wrinkles and cracks via mechanical contraction and stretching. Such morphological evolution regulates the direct transmission/reflection and scattering behavior of visible-infrared light and simultaneously alters the conductive network in a AgNW film to influence its microwave characteristics. The designed system features switching between visible-infrared-microwave transparency and opacity, continuous regulation, wide spectral window (0.38-15.5 µm and 24,200-36,600 µm), excellent recyclability (500 times), and rapid response time (<1 s). These grant the system great potential as platforms for various promising applications such as smart windows, switchable EM devices, dynamic thermal management, adaptive visual stealth, and human motion detection.

Multi-interfacial engineering in the hierarchical self-assembled micro-nano dielectric aerogel for wide-band absorption and low infrared emissivity.

Radar-infrared (IR) compatible stealth can satisfy the characteristics of excellent electromagnetic wave attenuation property and low infrared emissivity. However, concurrently satisfying these demands is still a great challenge at present. Herein, multi-interfacial engineering strategy was proposed for the preparation of radar-IR compatible stealth materials. ZnO has a high electron binding energy and a large band gap at room temperature, and doping with sulphide can increase the concentration of unconstrained carriers. Therefore, bimetallic sulphide aerogels loaded with ZnO were prepared by means of carbonization and vulcanization, combined with freeze-drying method. When the filling ratio is 20 %, an absorption bandwidth (fe) of 6.62 GHz at a matching thickness of 2.0 mm and a reduction in IR emissivity from 0.920 to 0.539 in the 8-14 µm band are achieved. This work provides a guidance to design and synthesize high-performance absorbers by multi-interfacial engineering for IR-radar compatible stealth application.

Green, Sustainable Architectural Bamboo with High Light Transmission and Excellent Electromagnetic Shielding as a Candidate for Energy-Saving Buildings.

Currently, light-transmitting, energy-saving, and electromagnetic shielding materials are essential for reducing indoor energy consumption and improving the electromagnetic environment. Here, we developed a cellulose composite with excellent optical transmittance that retained the natural shape and fiber structure of bamboo. The modified whole bamboo possessed an impressive optical transmittance of approximately 60% at 6.23 mm, illuminance of 1000 luminance (lux), water absorption stability (mass change rate less than 4%), longitudinal tensile strength (46.40 MPa), and surface properties (80.2 HD). These were attributed to not only the retention of the natural circular hollow structure of the bamboo rod on the macro, but also the complete bamboo fiber skeleton template impregnated with UV resin on the micro. Moreover, a multilayered device consisting of translucent whole bamboo, transparent bamboo sheets, and electromagnetic shielding film exhibited remarkable heat insulation and heat preservation performance as well as an electromagnetic shielding performance of 46.3 dB. The impressive optical transmittance, mechanical properties, thermal performance, and electromagnetic shielding abilities combined with the renewable and sustainable nature, as well as the fast and efficient manufacturing process, make this bamboo composite material suitable for effective application in transparent, energy-saving, and electromagnetic shielding buildings.

Broadband and High-Efficiency Microwave Absorbers Based on Pyramid Structure.

Microwave-absorbing materials with wide bandwidth and high absorptivity are increasingly playing an important role in over-the-air (OTA) testing. In this work, a kind of pyramid absorbing material was prepared using flame-retardant absorbers as the filler. In addition, a coating was used to further improve the flame-retardant properties of the microwave-absorbing material. To obtain excellent microwave absorption performance (MWAP), a high-frequency structure simulator (HFSS) was adopted to design structural materials. Here, the total height, the base height, the decapitation height of the pyramid tip, the distance between the pyramids, and other parameters were analyzed; then, the actual processing and molding were realized. The MWAP of -30 dB was achieved at 2.7-18 GHz, and the MWAP of -10 dB was also met at 2-18 GHz. In particular, the study also investigated the MWAP of large angle, which can meet the MWAP of -10 dB at 2-18 GHz and MWAP of -30 dB at 4-18 GHz. Most importantly, the absorption mechanism of the pyramid structure was explored. The influence of the tip was proved by the distribution of the electromagnetic field in the pyramid. It can be regarded as a multilayer microwave-absorbing material due to the impedance gradient of the pyramid, which can provide an effective research idea and method for future engineering applications.

A Lightweight, Elastic, and Thermally Insulating Stealth Foam With High Infrared-Radar Compatibility.

The development of infrared-radar compatible materials/devices is challenging because the requirements of material properties between infrared and radar stealth are contradictory. Herein, a composite of poly(3, 4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) coated melamine foam is designed to integrate the advantages of the dual materials and the created heterogeneous interface between them. The as-designed PEDOT:PSS@melamine composite shows excellent mechanical properties, outstanding thermal insulation, and improved thermal infrared stealth performance. The relevant superb radar stealth performance including the minimum reflection loss value of -57.57 dB, the optimum ultra-wide bandwidth of 10.52 GHz, and the simulation of radar cross section reduction value of 17.68 dB m2 , can be achieved. The optimal specific electromagnetic wave absorption performance can reach up as high as 3263.02 dB·cm3 g-1 . The average electromagnetic interference shielding effectiveness value can be 30.80 dB. This study provides an approach for the design of high-performance stealth materials with infrared-radar compatibility.

Ultrabroad Microwave Absorption Ability and Infrared Stealth Property of Nano-Micro CuS@rGO Lightweight Aerogels.

Developing ultrabroad radar-infrared compatible stealth materials has turned into a research hotspot, which is still a problem to be solved. Herein, the copper sulfide wrapped by reduced graphene oxide to obtain three-dimensional (3D) porous network composite aerogels (CuS@rGO) were synthesized via thermal reduction ways (hydrothermal, ascorbic acid reduction) and freeze-drying strategy. It was discovered that the phase components (rGO and CuS phases) and micro/nano structure (microporous and nanosheet) were well-modified by modulating the additive amounts of CuS and changing the reduction ways, which resulted in the variation of the pore structure, defects, complex permittivity, microwave absorption, radar cross section (RCS) reduction value and infrared (IR) emissivity. Notably, the obtained CuS@rGO aerogels with a single dielectric loss type can achieve an ultrabroad bandwidth of 8.44 GHz at 2.8 mm with the low filler content of 6 wt% by a hydrothermal method. Besides, the composite aerogel via the ascorbic acid reduction realizes the minimum reflection loss (RLmin) of - 60.3 dB with the lower filler content of 2 wt%. The RCS reduction value can reach 53.3 dB m2, which effectively reduces the probability of the target being detected by the radar detector. Furthermore, the laminated porous architecture and multicomponent endowed composite aerogels with thermal insulation and IR stealth versatility. Thus, this work offers a facile method to design and develop porous rGO-based composite aerogel absorbers with radar-IR compatible stealth.

Multifunctional Integrated Transparent Film for Efficient Electromagnetic Protection.

Silver nanowire (Ag NW) has been considered as the promising building block for the fabrication of transparent electromagnetic interference (EMI) shielding films. However, the practical application of Ag NW-based EMI shielding films has been restricted due to the unsatisfactory stability of Ag NW. Herein, we proposed a reduced graphene oxide (rGO) decorated Ag NW film, which realizes a seamless integration of optical transparency, highly efficient EMI shielding, reliable durability and stability. The Ag NW constructs a highly transparent and conductive network, and the rGO provides additional conductive path, showing a superior EMI shielding effectiveness (SE) of 33.62 dB at transmittance of 81.9%. In addition, the top rGO layer enables the hybrid film with reliable durability and chemical stability, which can maintain 96% and 90% EMI SE after 1000 times bending cycles at radius of 2 mm and exposure in air for 80 days. Furthermore, the rGO/Ag NW films also possess fast thermal response and heating stability, making them highly applicable in wearable devices. The synergy of Ag NW and rGO grants the hybrid EMI shielding film multiple desired functions and meanwhile overcomes the shortcomings of Ag NW. This work provides a reference for preparing multifunctional integrated transparent EMI shielding film.

Enhanced interfacial polarization of biomass-derived porous carbon with a low radar cross-section.

Ultra-thin microwave absorbers have been urgently demanded for electromagnetic applications in recent years. Herein, porous carbon with a "flower cluster" microstructure was synthesized from biomass waste (mango seeds) by a facile activation and carbonization method. The novel structure reduced the density and also improved the impedance matching, dipole polarization, and provided many carbon matrix-air interfaces for interfacial polarization, resulting in superior microwave absorption performance. At an ultra-thin thickness of 1.5 mm, extraordinary microwave absorption was achieved, with a reflection loss (RL) of -42 dB. The effective absorption bandwidth reached 4.2 GHz. The RL can be further improved to -68.4 dB by adjusting the amount of activator to manipulate the structure of porous carbon. In addition, from the simulated radar scattering results, the maximum reduction in the radar cross-section (RCS) reached 30.4 dBm2, which can greatly reduce the probability of equipment being detected by radar. This work provides a low-cost and high-performance microwave absorber for electromagnetic stealth technologies.

A breathable and flexible fiber cloth based on cellulose/polyaniline cellular membrane for microwave shielding and absorbing applications.

High-performance electromagnetic (EM) wave absorption and shielding materials integrating with flexibility, air permeability, and anti-fatigue characteristics are of great potential in portable and wearable electronics. These materials usually prepared by depositing metal or alloy coatings on fabrics. However, the shortcomings of heavy weight and easy corrosion hamper its application. In this work, the cellulose nanofiber (CF) fabric was prepared by electrospinning technology. Then, conductive polyaniline (PANI) was deposited on the CF surface via a facile in-situ polymerization process. The interweaving cellulose/polyaniline nanofiber (CPF) composite constructs a conductive network, and the electrical conductivity can be adjusted by polymerization time. Benefiting from optimal impedance matching, strong conductive loss, as well as interfacial polarization, the CPF possesses excellent EM absorption performance. The minimum reflection loss (RLmin) value is -49.24 dB, and the effective absorption bandwidth (RL < -10 dB, fe) reaches 6.90 GHz. Furthermore, the CPF also exhibits outstanding electromagnetic interference (EMI) shielding capability with shielding efficiency (SE) of 34.93 dB in the whole X band. Most importantly, the lightweight CPF fabrics have the merits of mechanical flexibility, breathability and wash resistance, which is highly applicable for wearable devices.

Flexible and transparent silver nanowires/biopolymer film for high-efficient electromagnetic interference shielding.

Flexible and transparent conductive films are highly desirable in some optoelectronic devices, such as smart windows, touch panels, as well as displays and electromagnetic protection field. Silver nanowire (Ag NW) has been considered as the best material to replace indium tin oxide (ITO) to fabricate flexible transparent electromagnetic interference (EMI) shielding films due to its superior comprehensive performance. However, the common substrates supporting Ag NWs require surface modification to enhance the adhesion with Ag NWs. In this work, a flexible and transparent Ag NWs EMI shielding film with sandwich structure through a facile rod-coating method, wherein Ag NWs network were embedded between biodegradable gelatin-based substrate and cover layer. The interfacial adhesion between Ag NWs and gelatin-based layers was enhanced by hydrogen-bonding interaction and swelling effect without any pretreatment. The shielding effectiveness (SE) of the G/Ag NW/G (G represents gelatin-based layer) film reaches 37.74 dB at X band with an optical transmittance of 72.0 %. What's more, the flexible gelatin-based layer and encapsulated structure endow the resultant G/Ag NW/G film integrating excellent mechanical properties, reliable durability, antioxidation, as well as anti-freezing performance. This work paves a new way for fabricating flexible transparent EMI shielding films.

Heterointerface Engineering in Electromagnetic Absorbers: New Insights and Opportunities.

Electromagnetic (EM) absorbers play an increasingly essential role in the electronic information age, even toward the coming "intelligent era". The remarkable merits of heterointerface engineering and its peculiar EM characteristics inject a fresh and infinite vitality for designing high-efficiency and stimuli-responsive EM absorbers. However, there still exist huge challenges in understanding and reinforcing these interface effects from the micro and macro perspectives. Herein, EM response mechanisms of interfacial effects are dissected in depth, and with a focus on advanced characterization as well as theoretical techniques. Then, the representative optimization strategies are systematically discussed with emphasis on component selection and structural design. More importantly, the most cutting-edge smart EM functional devices based on heterointerface engineering are reported. Finally, current challenges and concrete suggestions are proposed, and future perspectives on this promising field are also predicted.

Enhanced Microwave Absorbing Ability of Carbon Fibers with Embedded FeCo/CoFe2O4 Nanoparticles.

In the face of increasingly severe electromagnetic (EM) wave pollution, the research of EM wave absorbing materials is an effective solution. To reduce the density of traditional absorbing materials, in this work, FeCo/CoFe2O4/carbon nanofiber composites were successfully prepared by electrospinning for the EM wave attenuation application. Benefiting from the loss ability of interface polarization, dipole polarization, and magnetic loss, the composites obtained a bandwidth of 5.0 GHz at a 1.95 mm thickness and an absorption peak of -52.3 dB. More importantly, the radar cross section (RCS) reduction of composite coatings calculated by ANSYS Electronics Desktop 2018 (HFSS) can reach 34.5 dBm2, and the RCS value is almost less than -10 dBm2 when the incident angle is greater than 20°, demonstrating great scattering ability of the material coating to EM waves. This work, combined with the exploration of the mechanism and the simulation analysis of the absorbing coating, will be of significance for the development of absorbing materials.