Electromagnetic Interference Shielding Effectiveness Research Articles

Absorption‐Dominant Electromagnetic Interference (EMI) Shielding across Multiple mmWave Bands Using Conductive Patterned Magnetic Composite and Double‐Walled Carbon Nanotube Film

AbstractThe revolution of millimeter‐wave (mmWave) technologies is prompting a need for absorption‐dominant EMI shielding materials. While conventional shielding materials struggle in the mmWave spectrum due to their reflective nature, this study introduces a novel EMI shielding film with ultralow reflection (<0.05 dB or 1.5%), ultrahigh absorption (>70 dB or 98.5%), and superior shielding (>70 dB or 99.99999%) across triple mmWave frequency bands with a thickness of 400 µm. By integrating a magnetic composite layer (MCL), a conductive patterned grid (CPG), and a double‐walled carbon nanotube film (DWCNTF), specific resonant frequencies of electromagnetic waves are transmitted into the film with minimized reflection, and trapped and dissipated between the CPG and the DWCNTF. The design factors for resonant frequencies, such as the CPG geometry and the MCL refractive index, are systematically investigated based on electromagnetic wave propagation theories. This innovative approach presents a promising solution for effective mmWave EMI shielding materials, with implications for mobile communication, radar systems, and wireless gigabit communication.

An ultralight all‐fiber‐structure sponge with thermal and electromagnetic integrated insulation property

AbstractThe integration of thermal and electromagnetic interference (EMI) insulation is of great significance for fields such as aerospace that face extreme environments. The challenge lies in ensuring that the protective layer is lightweight while simultaneously possessing the ability to suppress heat conduction, heat convection, thermal radiation, and electromagnetic radiation. To address these challenges, we propose a novel ultralight all‐fiber‐structure composite sponge, yttria‐stabilized zirconia/polyvinyl butyral‐supported silver (YAP) nanofiber sponge, with ultralight mass (∼65 mg/cm3), exceptionally low thermal conductivity (21 mW/m K at 25°C, and 329 mW/m K at 500°C), and remarkable EMI shielding effectiveness (∼62.6 dB). Moreover, benefiting from its all‐fiber‐structure, the YAP nanofiber sponge can endure 100 cycles of compression up to 50% of its original volume while retaining its mechanical properties with minimal degradation. These characteristics render YAP nanofiber sponge an ideal material for integrated thermal and EMI insulation, offering a promising solution to the rigorous demands of extreme environment protection such as space exploration.

Morphology and electrical conductivity of carbon-coated nickel reinforced high-performance polymer nanocomposites.

Novel nanocomposites of poly(ether-ketone) (PEK) reinforced with carbon-coated Nickel nanoparticles (CCNi) were synthesized through a sequential process involving cost-effective ball milling and hot compaction. Scanning electron microscopy revealed an excellent dispersion and a 3-dimensional (3-D) network of CCNi nanoparticles in the matrix, causing a significant improvement in the electrical conductivity and electromagnetic interference shielding effectiveness (SE). Carbon coating of about 5 nm thick over Ni nanoparticle probably helps in uniform dispersion, avoids its oxidation and reduces its agglomeration in the matrix. An exceptionally low percolation threshold of 2.1 vol.% CCNi was found, and eight-orders of magnitude enhancement in the dc-electrical conductivity was achieved. The highest dc- and ac-electrical conductivities achieved were more than 0.01 S/cm at 5.89 vol.% CCNi nanoparticles content which were the highest values amongst reported Ni-filled polymer composites and comparable with those of carbon nanotubes filled PEK nanocomposites. Electromagnetic interference SE of the CCNi/PEK nanocomposites was measured in the X-band, and a total SE (SET) of 17.52 dB was obtained for 5.89 vol.% CCNi reinforced PEK nanocomposite.

A PVDF/MWCNTs/GO@MWCNTs/AgNWs bilayer structured composite film with ultra‐high EMI shielding and conductivity performance

AbstractElectromagnetic interference (EMI) shielding materials with easy processing, high electrical conductivity, and excellent absorption loss are urgently needed in aerospace, military stealth and portable electronic devices. In this study, a polyvinylidene fluoride/multi‐walled carbon nanotubes (PVDF/MWCNTs)‐3 wt% composite film prepared by simple solution mixing and polyethylene terephthalate (PET) nonwoven scraping method was used as the substrate, and the PVDF/MWCNTs/graphene oxide@multi‐walled carbon nanotubes (PVDF/MWCNTs/GO@MWCNTs) and PVDF/MWCNTs/GO@MWCNTs/silver nanowires (PVDF/MWCNTs/GO@MWCNTs/AgNWs) bilayer composite films were prepared by vacuum‐assisted filtration (VAF). When the amount of GO@MWCNTs was 20 mL, the conductivity of PVDF/MWCNTs/GO@MWCNTs film is 3.5 × 101 S m−1, the total EMI shielding effectiveness (EMI SET) was 15.5 dB and the EMI absorption efficiency (EMI SEA) was 10.7 dB, the specific EMI SE (SSE/T) was 539.5 dB/ dB/(cm−2 g). When the amount of AgNWs was 25 mL, the conductivity of PVDF/MWCNTs/GO@MWCNTs/AgNWs film with 0.47 mm thickness was 1.6 × 104 S m−1, the EMI SET was 69.1 dB, the EMI SEA was 61.1 dB, and the SSE/T was 2320.0 dB cm2 g−1. The results show that the absorption was played a dominant role in the EMI shielding mechanism of obtained films. The addition of GO@MWCNTs/AgNWs increases the electrical conductivity and EMI shielding performance of the film more than the addition of GO@MWCNTs. This is mainly because GO， MWCNTs and AgNWs formed a novel three‐dimensional conductive network structure inside the composite film due to their hydrogen bonding and van der Waals forces, which increases the carrier channels and promotes the interaction between the internal microcurrents and the electromagnetic waves, achieving the purpose of attenuating the electromagnetic waves. The obtained PVDF/MWCNTs/GO@MWCNTs/AgNWs film has good potential in EMI shielding in aerospace, military and electronic intelligence applications.Highlights Well‐dispersed and highly conductive GO@MWCNTs were prepared by hydrothermal synthesis. AgNWs with good conductivity and high aspect ratio were prepared. PVDF‐based bilayer composite films with novel 3D conductive network were prepared. The synergistic EMI shielding mechanism of the film is discussed.

Strain‐Tolerant Nanocomposite Conductors with Engineered Bicontinuous Phase System by Additive Liquid/Solid Assembly

AbstractIntrinsically stretchable conductors are vital components in next‐generation flexible electronics. However, solid conductive networks are generally vulnerable to external deformations due to their incompatible mechanical properties with the highly elastic substrates or matrixes. It is still challenging to achieve precisely controlled conductive structure with stable electromechanical performances. Herein, a nanocomposite conductor with 3D engineered bicontinuous phase system is developed, which is constructed by alternately arranged robust solid‐phase and conductive liquid‐phase via additive liquid/solid assembly. The proper rheological properties and extraordinary structural compatibility of the liquid‐phase prompt the formation of bridged structure within the 3D periodic solid‐phase main skeleton, giving rise to stable and even strain‐enhanced electrical and electromagnetic interference (EMI) shielding properties under external deformation. A negative resistance change of −37% along with unabated EMI shielding effectiveness and mechanical properties are obtained at 100% strain, showing negligible performance degradation even after 10,000 cycles of rigorous stretching and releasing. A strain‐tolerant pressure‐sensing device is further demonstrated using the liquid/solid nanocomposite structure, delivering a unique function of precisely recognizing the local pressure at large tensile loading interference. This work provides a new paradigm for the manufacturing of nanocomposites with desired functionalities using the adequate nanofiller reserve toward practical strain‐tolerant applications.

Nanofiber derived MXene composite paper for electromagnetic shielding and thermal management

Despite the urgent demands in protecting wearable electronics from electromagnetic interference (EMI) in various conditions, it remains challenging to attain mechanically robust and flexible materials with both excellent EMI shielding and thermal managing performance. Herein, we report MXene composite paper that can provide multifunction with superior mechanical properties. To construct a hierarchical composite with 2D/0D reinforcements, the MXene paper is fabricated by hot pressing of electrospun Poly (vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) nanofibers incorporated with MXene nanosheets and carbon black nanoparticles. Due to the laminated structure connected by nanoparticles, the flexible composite paper shows remarkable mechanical strength and fatigue resistance that can provide stable EMI shielding effectiveness of 500 dB/mm even after 10000th cyclic rolling. Moreover, the high in-plane electrical conductivity and out-of-plane thermal conductivity allow a fast electrothermal heating and cooling behavior, which qualifies the MXene paper as multifunctional surface for wearable electronics.

Robust ZTO-reinforced Ag nanowire hybrid transparent conductive thin films with absorption-enhanced electromagnetic interference shielding property

Technological advances have accelerated the pursuit of transparent conducting thin films (TCFs) with superior mechanical properties, durability, efficient optoelectrical performance and substrate compatibility as a pivotal focus in the realm of flexible transparent electronics. Against this background, this work investigates the fabrication of multilayer silver nanowire (AgNW) thin films reinforced by zinc tin oxide (ZTO) thin film encapsulation on polycarbonate substrates by a combination of sputtering and spin-coating techniques. An investigation of the influence of AgNW percolation networks on the optoelectrical properties of ZTO/AgNW/ZTO hybrid thin films was carried out. The impact of ZTO protective layers on the enhancement of electrical properties, adhesivity, flexibility and environmental stability of the multilayer TCF was elucidated. Additionally, to explore the compatibility of the fabricated TCF in integrated device and stealth applications, its electromagnetic interference shielding properties were investigated. The hybrid TCF showed 99.47% EMI shielding efficiency with an absorption-dominant EMI shielding effectiveness of 22.7 dB in the x-band region.

Recyclable Polymer Composites with a Wrinkled Core-Shell Structure for Highly Efficient EMI Shielding and Low Reflection.

Green electromagnetic interference (EMI) shielding materials not only require high shielding effectiveness (SE) and low reflection but also need to be recyclable after damage; however, it is challenging to strike a balance in practice. Here, a polyacrylamide (PAM) composite composed of numerous chemically cross-linked PAM@carbon nanotube (cPAM@CNT) core-shell particles featuring rich wrinkled microstructures was prepared using an adsorption-drying-shrinking strategy. The wrinkled microstructures enable the incident electromagnetic waves (EMWs) to undergo attenuation within the composites, achieving an average EMI SE of 67.5 dB in the X band. Due to the hygroscopicity of hydrophobically associated PAM (hPAM, an adhesive for cPAM@CNTs core-shell particles), the average EMI SE of the composites further increased to 83.2 dB after exposure to 91% relative humidity for 24 h, with only a 2.7 dB low reflection. Additionally, the composites also demonstrated excellent Joule heating, photothermal performance, and recyclability, which exhibit substantial promise for advanced EMI shielding applications.

Smart windows with adjustable electromagnetic interference shielding using hydrogel technology

Thermochromic smart windows with adjustable electromagnetic interference (EMI) shielding capability are integral elements in modernized buildings, especially in military applications, due to their energy-saving benefits and ability to mitigate electromagnetic pollution. However, its application is limited by the relatively poor light transmission of conductive substances and the high demand for light transmission of thermochromic smart windows. Maintaining the thermochromic performance of smart windows while adjusting EMI shielding effectiveness (SE) poses a significant challenge. Here, we propose a straightforward approach to create a smart EMI shielding material with adaptable properties, including light transmission, shape, and EMI SE. This method involves a layer-by-layer polymerisation process followed by solvent substitution. The resulting hydrogel exhibits tunable optical properties, making it suitable for use as a smart window that responds to external conditions and offers local tunability. Noteworthy characteristics include high light transmittance (80.87 %), ultra-fast response time (16 s), multiple shape adjustments, adjustable EMI SE ranging from 0 to 27.64 dB, and strong adhesion, among other features. These findings suggest that the obtained hydrogels have significant potential to provide a substantial advantage in developing next-generation soft and intelligent smart EMI shielding windows.

Electromagnetic interference shielding and DFT study of barium hexaferrites nanoparticles coated polyaniline with heterointerface polarization behavior

Barium-hexaferrite-nanoparticles (BHNs) and polyaniline-nanoparticles (PNs) were prepared individually with average particle sizes of 50 nm and 42 nm. The two nanoparticles were then combined to create hybrid nanoparticles (HNs) with a ferritic core and a conductive surface, by chemically coating polyaniline onto the surface of BHNs via in-situ polymerization. The nanoparticle shape, size, structural, and morphological properties were analyzed using SEM, XRD, and PSA. The nanoparticles were dispersed into a PVDF matrix to produce nanocomposite-films (NFs) for testing EMI shielding effectiveness. The NFs exhibited excellent blocking of near infrared radiation and a shielding effectiveness of more than 50 dB in the microwave region when 30 wt% of HNs was used in the PVDF matrix. Density-function-theory (DFT) based on first-principle was used to confirm the interfacial polarization contribution at the heterointerface, revealing different electron occupied states and considerable charge transfer and accumulation at the interface, enhancing the EMI shielding effectiveness.

Nickel-Fe3O4@Graphene coated lightweight carbonized wood for efficient electromagnetic interference shielding

The miniaturization and integration of electronic equipment promote electromagnetic effect radiation pollution more and more serious. The lightweight, renewable electromagnetic interference (EMI) shielding materials is urgently needed. This study developed a high temperature carbonization, Fe3O4@Graphene impregnation, and electroless Ni technique to construct a carbonized wood composite with strong EMI shielding performance using sustainable natural wood as the raw material. The Fe3O4@Graphene is distributed throughout the carbonized wood to provide the conductivity and magnetism of the reinforced composite material, and provide more interfaces to increase the dielectric loss and magnetic loss, thereby exhibiting excellent EMI shielding performance. The results show that at low thickness (2 mm) and ultra-low density (0.284 g/cm3), the CWN-7 composite exhibits excellent EMI shielding effectiveness of up to 84.2 dB in the whole X-band (8.2–12.4 GHz). At the same time, it has extraordinary compressive strength and good thermal insulation performance. This study offers a different method for creating composite multifunctional electromagnetic shields out of carbonized green wood.

Lightweight polyimide/silica aerogel composite foams and their derived carbon foams for excellent flame retardancy, thermal insulation and EMI shielding performance

Multifunctional porous materials demonstrate ubiquitous applications in the fields of flame retardancy, thermal insulation and electromagnetic interference (EMI) shielding. In this work, a series of lightweight polyimide/silica aerogel (PIF/SiA) foams with exceptional thermal stability, flame retardancy and thermal insulation performance were prepared by employing microwave-assisted foaming and thermal imidization treatment, using polyester ammonium salt/silica aerogel (PEAS/SiA) powders as the derivative precursors. The limiting oxygen index and fire growth rate reached as high as 58.2% and as low as 0.1 kW/(m2·s) for PIF/SiA composite foams, respectively, which was a result of the formation of micro/nano multi-scale pore structure of PIF skeleton and the “pearl-necklace-like” skeletal network of nano SiA. In addition, the PIF/SiA composite foams exhibited excellent thermal insulation and infrared stealth performance, which demonstrate a potential for long service life in fire protection use. Furthermore, the carbonized PIF/SiA (i.e., PICF/SiA) foams possessed enhanced mechanical (improvement of 117.6%) and EMI shielding performance (specific EMI shielding effectiveness: 8541.9 dB/(g/cm2)) when compared with the original PIF/SiA composite foams. To sum up, a facile method was proposed to fabricate multifunctional PIF-based composite foams and their derived carbon foams for flame retardancy, thermal insulation and EMI shielding applications in high-end engineering sectors.

A Highly Deficient Medium-Entropy Perovskite Ceramic for Electromagnetic Interference Shielding under Harsh Environment.

Materials that can provide reliable electromagnetic interference (EMI) shielding in highly oxidative atmosphere at elevated temperature are indispensable in the fast-developing aerospace field. However, most of conductor-type EMI shielding materials such as metals can hardly withstand the high-temperature oxidation, while the conventional dielectric-type materials cannot offer sufficient shielding efficiency in gigahertz (GHz) frequencies. Here, a highly deficient medium-entropy (ME) perovskite ceramic as an efficient EMI shielding material in harsh environment, is demonstrated. The synergistic effect of entropy stabilization and aliovalent substitution on A-site generate abnormally high concentration of Ti and O vacancies that are stable under high-temperature oxidation. Due to the clustering of vacancies, the highly deficient perovskite ceramic exhibits giant complex permittivity and polarization loss in GHz, leading to the specific EMI shielding effectiveness above 30dB/mm in X-band even after 100 h of annealing at 1000°C in air. Along with the low thermal conductivity, the aliovalent ME perovskite can serve as a bifunctional shielding material for applications in aircraft engines and reusable rockets.

Ti3C2Tx Electromagnetic Shielding Performance: Investigating Environmental Influences and Structural Changes

AbstractMXenes, a promising family of 2D transition metal carbides/nitrides, are renowned for their exceptional electronic conductivity and mechanical stability, establishing them as highly desirable candidates for advanced electromagnetic interference (EMI) shielding material. Despite these advantages, challenges persist in optimizing MXene synthesis methods and improving their oxidation resistance. Surface defects on MXenes significantly impact their electronic properties, impeding charge transport and catalyzing the oxidation process. In this study, a novel synthesis protocol derived from the conventional, minimally invasive layer delamination (MILD) method, is presented. Two additional steps are introduced aiming at enhancing process yield, addressing a crucial issue as conventional methods often yield high‐quality individual MXene flakes but struggle to generate sufficient quantities for bulk material production. This approach successfully yields Ti3C2Tx films with excellent conductivity (3973.72 ±121.31 Scm−1) and an average EMI shielding effectiveness (SE) of 56.09 ± 1.60 dB within the 1.5 to 10 GHz frequency range at 35% relative humidity (RH). Furthermore, this investigation delves into the long‐term oxidation stability of these films under varying RH conditions. These findings underscore the effectiveness of this innovative synthesis approach in elevating both the conductivity and EMI shielding capabilities of MXene materials. This advancement represents a significant step toward harnessing MXenes for practical applications requiring robust EMI shielding solutions. Additionally, insights into long‐term stability offer critical considerations for implementing MXenes in real‐world environments.

Effects of surface modification on mechanical properties and electromagnetic interference shielding properties of carbon fiber/silk fiber hybrid composites

AbstractIn this paper, a hybrid approach was employed by integrating a high‐modulus, high‐tensile‐strength carbon fiber fabric (CFF) with a low‐density, high‐toughness silk nonwoven fabric (SNWF) to fabricate CFF‐SNWF reinforced epoxy (CFF‐SNWF/EP) hybrid composites. Through the surface freeze‐induced self‐assembly process, the multiscale hybrid modified layers were successfully constructed on the surfaces of both CFF and SNWF. This novel approach effectively enhanced the interfacial strength of the hybrid fibers (HFs). Comparing the performance of the modified composites with unmodified CFF reinforced epoxy (CFF/EP), significant improvements in both tensile strength and interlaminar shear strength were observed. Specifically, the tensile strength and interlaminar shear strength of the modified composites reached 626.7 and 39.16 MPa, a rise scope of 17.1% and 14.8%, respectively. In addition, the hybrid fibers reinforced polymers (HFRPs) exhibited a superior electromagnetic interference (EMI) shielding capabilities. For insistence, the modified CFF/EP with a thickness of 2.0 mm showed an impressive EMI shielding effectiveness value of 50 dB. These findings underscore the promising application potential of CFF‐SNWF/EP hybrid composites, particularly in the field of consumer electronics.Highlights The surface of hybrid fiber was modified by PDA‐GO‐OCNTs‐WPU. Multi‐scale structure contributes a lot in composite performance. Hybrid effect before and after interfacial modification is performed. The hybrid interface modification and hybrid structure were analyzed.

Synergistically enhanced electromagnetic interference shielding and mechanical properties of epoxy resin composites with a preconstructed hierarchical structure

AbstractElectromagnetic interference (EMI) shielding materials have attracted extensive attention as highly integrated electronic devices generate large amounts of electromagnetic pollution. Here, PNF/NGx‐EP composites with excellent EMI shielding properties and superior flexural strength were reported, where nickel‐plated carbon fiber (NF) felts and NH2‐Graphene (NG) were adopted to pre‐construct a hierarchical structure within epoxy resin (EP). The macroscopic NF network constructed a continuous conductive pathway and the NG grafted on the surface of NF formed a second microscopic conductive network. Consequently, the PNF/NG0.5 felts exhibited a quite high electrical conductivity of 138.4 S/cm, and the PNF/NG0.5‐EP composites presented excellent EMI shielding effectiveness (EMI SE) (57.4 dB at 11.9 GHz). Intriguingly, the flexural strength of the NF/EP composites was enhanced after the incorporation of NG, which was attributed to the mechanical locking effect and covalent bonding. In summary, this approach reconciles the contradiction between EMI shielding properties and mechanical properties of EP composites, and allows them to be promisingly employed for EMI shielding and protection in aerospace, weaponry, and communications.Highlights A hierarchical structure of PNF/NGx felts was preconstructed within EP via Michael addition/Schiff base reaction. The PNF/NGx‐EP composites exhibited remarkable EMI shielding properties (57.4 dB) and superior flexural strength (137.0 MPa), which are expected to realize practical applications in EMI shielding.

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 83.37dB, and in the meantime extremely low emissivity (22.17%) in the wavelength range of 7-14µm and thermal conductivity (0.19W 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 Scalable and Robust Personal Health Management Textile with Multiple Desired Thermal Functions and Electromagnetic Shielding.

The development of functional textiles combining conventional apparel with advanced technologies for personal health management (PHM) has garnered widespread attention. However, the current PHM textiles often achieve multifunctionality by stacking functional modules, leading to poor durability and scalability. Herein, a scalable and robust PHM textile is designed by integrating electrical, radiative, and solar heating, electromagnetic interference (EMI) shielding, and piezoresistive sensing performance onto cotton fabric. This is achieved through an uncomplicated screen-printing process using silver paste. The conductivity of the PHM textile is ≈1.6 × 104Sm-1, ensuring an electric heating temperature of ≈134°C with a low voltage of 1.7V, as well as an EMI shielding effectiveness of ≈56 dB, and human motion monitoring performance. Surprisingly, the radiative/solar heating capability of the PHM textile surpasses that of traditional warm leather. Even after undergoing rigorous physical and chemical treatments, the PHM textile maintains terrific durability. Additionally, the PHM textile possesses maneuverable scalability and comfortable wearability. This innovative work opens up new avenues for the strategic design of PHM textiles and provides an advantageous guarantee of mass production.

Wearable EMI Shielding Composite Films with Integrated Optimization of Electrical Safety, Biosafety and Thermal Safety.

Biomaterial-based flexible electromagnetic interference (EMI) shielding composite films are desirable in many applications of wearable electronic devices. However, much research focuses on improving the EMI shielding performance of materials, while optimizing the comprehensive safety of wearable EMI shielding materials has been neglected. Herein, wearable cellulose nanofiber@boron nitride nanosheet/silver nanowire/bacterial cellulose (CNF@BNNS/AgNW/BC) EMI shielding composite films with sandwich structure are fabricated via a simple sequential vacuum filtration method. For the first time, the electrical safety, biosafety, and thermal safety of EMI shielding materials are optimized integratedly. Since both sides of the sandwich structure contain CNF and BC electrical insulation layers, the CNF@BNNS/AgNW/BC composite films exhibit excellent electrical safety. Furthermore, benefiting from the AgNW conductive networks in the middle layer, the CNF@BNNS/AgNW/BC exhibit excellent EMI shielding effectiveness of 49.95dB and ultra-fast response Joule heating performance. More importantly, the antibacterial property of AgNW ensures the biosafety of the composite films. Meanwhile, the AgNW and the CNF@BNNS layers synergistically enhance the thermal conductivity of the CNF@BNNS/AgNW/BC composite film, reaching a high value of 8.85W m‒1 K‒1, which significantly enhances its thermal safety when used in miniaturized electronic device. This work offers new ideas for fabricating biomaterial-based EMI shielding composite films with high comprehensive safety.

Synergistic magnetic/dielectric loss and layered structural design of Ni@carbon fiber/Ag@graphene fiber/polydimethylsiloxane composite for high-absorption EMI shielding

Simultaneously achieving excellent shielding effectiveness (SE) and high absorption rate of flexible electromagnetic interference (EMI) shielding materials has become a growing demand for the new generation of highly integrated electronic devices. This study constructed a double-layer polydimethylsiloxane (PDMS) EMI shielding composite film, with the upper layer using Ni-plated carbon fiber (Ni@CF) as the high absorption loss part and the lower layer using Ag-plated graphene fiber (Ag@GF) as the reflection attenuation part. Due to the synergistic magnetic/dielectric loss effect in the upper layer, high electrical conductivity in the lower layer, and the shielding mechanism of “absorption-reflection-reabsorption” induced by the double-layer structure, this composite film achieves efficient EMI shielding performance and high absorption characteristics in the X-band. The EMI SE values of the 2 mm thick film containing 0.03 wt% Ni@CF and 1.2 wt% Ag@GF reach 33.7 dB, while shielding effectiveness of reflection (SER) and absorption (SEA) is 0.8 dB and 32.9 dB, respectively. This result means that the composite film only reflects 17.2 % of the microwaves while shielding 99.9 % and absorbs nearly 82.7 %, exhibiting a significant absorption-dominated shielding mechanism. This flexible and efficient shielding film with a high absorption rate suits portable and wearable intelligent electronic products to reduce secondary electromagnetic pollution.