Electromagnetic Interference Shielding Materials Research Articles

Lightweight, breathable and self-cleaning polypyrrole-modified multifunctional cotton fabric for flexible electromagnetic interference shielding

The thriving of wearable electronics and the emerging new requirements for electromagnetic interference (EMI) shielding have driven the innovation of EMI shielding materials towards lightweight, wearability and multifunctionality. Herein, the hierarchical polypyrrole nanotubes (PNTs)/PDMS structures are rationally constructed on the textile for obtaining multifunctional and flexible EMI shielding textiles by in-situ polymerization and surface coating. The modified cotton fabric possesses a conductivity of about 2715.8 S/m and an SET of 28.2 dB in the X band when the thickness is only 0.5 mm. After ultrasonic treatment, cyclic bending and washing, the conductivity and EMI shielding performance remain stable and exhibit long-term durability. Importantly, the textile's inherent lightweight, breathable and soft properties have been completely retained after modification. This work shows application potentiality in the field of EMI pollution protection and affords a novel path for the construction of multifunctionally wearable and durable EMI shielding materials.

2D Transition Metal Dichalcogenides‐Based Composites for Electromagnetic Interference Shielding and Microwave Absorption Applications

Due to the advancements in the electronics industry, the demand for new electromagnetic interference (EMI) shielding and microwave absorption (MA) materials has increased significantly in recent decades. Researchers are investigating a variety of new materials to replace conventional metal sheets in response to these growing demands. Consequently, there is a growing interest in lightweight EMI shielding materials that can meet the demand for lightweight and highly integrated electronic equipment. 2D structural transition metal dichalcogenides (TMDCs) are good candidates for EMI shielding and MA due to their unique properties. This article examines the latest developments in TMDCs and their composite nanomaterials, focusing on their EMI shielding effectiveness and MA performance. The investigation includes a thorough examination of these materials’ shielding effectiveness, maximum reflection loss value, and effective absorption bandwidth. Moreover, this review analyzes the challenges and opportunities that arise in the development of TMDCs.

Ultrathin-flexible multifunctional MXene composite hydrogels with good mechanical properties-high strain sensitivity and ultra-broadband EMI shielding performances

Conductive hydrogels show excellent application potential in flexible and stretchable electromagnetic interference (EMI) shielding materials due to their water-rich porous structure and tissue-like mechanical properties. However, integrating multiple functions into EMI shielding materials remains challenging, including ultra-broadband EMI shielding, mechanical properties, strain sensitivity, flexibility, etc., with high performance. Here, through a straightforward and scalable combination of ultrasound-assisted dispersion and thermal polymerization, we have successfully synthesized the MXene/PE-CS composite hydrogels composed of acrylic acid (AA), 2-(Dimethylamino) ethyl methacrylate (DMAEMA), and chitosan (CS). It exhibits more comprehensive and excellent functionalities including high stretchability (0.47 MPa, 747 %), strain sensitivity (11.2), ultralow thickness (0.5–2.0 mm), good adhesion (0.13 MPa), and flexibility. More importantly, it achieves excellent shielding performance of more than 99.99 % in ultra-broadband (X-band, Ka-band, Ku-band, and THz-band) under ultralow thickness (0.5–2 mm) and MXene (transition metal carbides/nitrides) content (0.46 wt%), and the shielding properties can be dynamically controlled through MXene content, PE content and hydrogel thickness. Even after repeated stretching, bending, and long-term water evaporation, it still exhibits stable and high-performance EMI shielding performance. Our MXene/PE-CS composite hydrogels exhibit potential applications in ultra-broadband shielding for new generation flexible wearable electronic devices.

A review of recent advances in MXenes/polymer‐based electromagnetic interference shielding materials

AbstractThe booming development of mobile devices has remarkably improved the lives of people, but it also leads to severe electromagnetic radiation problems. Therefore, it has become significantly important to develop electromagnetic interference (EMI) shielding materials for electromagnetic protection. In recent years, MXenes have attracted much attention in the field of EMI shielding, owing to outstanding electrical conductivity, high specific surface area and hydrophilicity. Firstly, this review introduces EMI shielding mechanism and categorization of EMI shielding materials. Subsequently, the research progress of MXenes/polymer‐based EMI shielding materials is reviewed in detail, especially for preparation methods of MXenes/polymer‐based EMI shielding blocks. Finally, the key scientific problems in MXenes/polymer‐based EMI shielding materials are proposed, and their development trend are prospected.Highlights The EMI shielding mechanism and categorization of EMI shielding materials is presented. The latest research progress of MXenes/polymer‐based EMI shielding materials is reviewed. Scientific problems for MXenes/polymer‐based EMI shielding materials are proposed. Development trend of MXenes/polymer‐based EMI shielding materials is prospected.

Electromagnetic Interference Shielding Properties of Highly Flexible Poly(styrene-co-butyl acrylate)/PEDOT:PSS Films Fabricated by Latex Technology.

As the use of stretchable electronic devices increases, the importance of flexible electromagnetic interference (EMI) shielding films is emerging. In this study, a highly flexible shielding film was fabricated using poly(styrene-co-butyl acrylate) (p(St-co-BA)) latex as a matrix and poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) as a conductive filler, and then the mechanical properties and EMI shielding performance of the film were examined. Styrene and butyl acrylate were copolymerized to lower the high glass transition temperature and increase the ductility of brittle polystyrene. The latex blending technique was used to produce a shielding film in which the aqueous filler dispersion was uniformly dispersed in the emulsion polymerized resin. To determine the phase change in the copolymer matrix with temperature, the storage modulus was measured, and a time-temperature superposition master curve was constructed. The drying temperature of water-based copolymer resin suitable for film fabrication was set based on this curve. The glass transition temperature and flexibility of the blends were determined by evaluating the thermomechanical analysis and tensile tests. The EMI shielding effectiveness (SE) of the films was analyzed at frequencies from 50 MHz to 1.5 GHz, covering the VHF and UHF ranges. As the filler content increased, the SE of the blend film increased, but the elongation increased until a certain content and then decreased. The optimal content of PEDOT:PSS that satisfied both the ductility and shielding performance of the film was found to be 10 wt%. In this case, the elongation at break reached 300%, and the SE of a 1.6 mm thick film was about 35 dB. The film developed in this study can be used as an EMI shielding material that requires high flexibility.

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.

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.

Advanced Polymer Composite with Graphene Content for Emi Shielding

One of the increasingly common unexpected outcomes of the extensive usage of electronic devices and systems is electromagnetic interference (EMI). The need for efficient fillers and shielding materials to manage electromagnetic interference (EMI) and associated issues is rising. Adding more filler typically means greater production costs, poor dispersion, and unintended agglomeration, which makes polymer composites harder to work with and mechanically weak. Therefore, it is highly desired to design a strong composite with conductive filler content that nonetheless performs well as an EMI shield. Therefore, using a graphene substrate and dispersion of conducting polymers such as polyacetylene and MWCNT fillers, a hybrid polymer composite based on polyetherimide is proposed in this research. Next, the enhancement of EMI shielding efficiency is examined. The design of the graphene substrate was completed with a coating based on nano filler, and the blending methods of the polymer matrix and the reinforcing filler materials are explored. ANSYS-HFSS software is then used to assess the shield's efficacy among others, and the results demonstrated improved performance. Therefore, by putting the suggested design into practice, high-performance EMI shielding materials can be created by combining various shield fillers. As a result, the composites' mechanical, electrical, and EMI shielding qualities will all improve.

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.

Advances in carbon fiber-based electromagnetic shielding materials: Composition, structure, and application

With the swift advancement of wireless communication technology, there is increasing concern regarding the potential hazards posed by electromagnetic radiation emitted from various electronic devices. Carbon fiber (CF)-based composites have emerged as a vital component in structure function integrated electromagnetic interference (EMI) shielding research, attributable to their exceptional electrical conductivity and mechanical properties. This review summarizes recent research advances in CF-based composites for EMI shielding. Initially, it explores the influence of factors such as the geometric form of CFs on their EMI shielding properties. Since CF is inefficient when used alone for EMI shielding, so additional EMI filler materials are often introduced. Therefore, delves into an in-depth analysis of the reinforcement mechanisms provided by the incorporated second-phase materials, as well as the smart structural designs within the CF-based composites. On this basis, the applications of CF-based EMI shielding materials in the fields of thermal conductivity, flexible wearable technology, and aerospace are reviewed. Additionally, the review offers a perspective on the future development trends and prospects of CF-based composites in the field of EMI shielding based on the current research status.

Ultrathin Aramid Nanofiber Composites with Alternating Multilayered Structure of Silver Nanowires and Boron Arsenide: Toward Superior Electrically Insulating Thermoconductive Electromagnetic Interference Shielding Materials

Ultrathin Aramid Nanofiber Composites with Alternating Multilayered Structure of Silver Nanowires and Boron Arsenide: Toward Superior Electrically Insulating Thermoconductive Electromagnetic Interference Shielding Materials

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.

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.

Multifunctional asymmetric foam with Compression-Enhanced EMI shielding effectiveness exhibits Real-Time tunability of Reflection/Absorption ratio and pressure sensing

Traditional electromagnetic interference (EMI) shielding materials usually have constant shielding effectiveness and fixed absorption/reflection ratio, and cannot respond to the real-time changing shielding requirements of smart wearable electronic devices. Herein, smart asymmetric foams (AF) composed of chromium dioxide decorated graphene (CrO2@G)/thermoplastic polyurethane-poly vinyl alcohol (TP) foams and a eutectic gallium-indium liquid metal (LM)/TP layer were developed via an efficient ‘split conductive modular design/assembly’ strategy. The AF with compressive stress-controlled conductivity can capture and attenuate electromagnetic (EM) waves in the form of absorption-dominated or reflection-dominated by adjusting the compressive strain in real time. The optimized AF achieved a low average reflection coefficient (R) of 0.12 and a minimum value of 0.05, holding the lowest record for LM-based EMI shielding materials with comparable SEt. As the compressive strain increases from 0 to 90 %, the AF alter its SEt from 63.8 ± 3 dB to 92.7 ± 2 dB, while reducing the average EM wave absorption efficiency from 88 % to 39 %, allowing it to be adjusted in real time as needed to block EM waves. Furthermore, the AF demonstrated its application as a strain sensor to monitor human motions. This work provides an effective strategy for the design and preparation of multifunctional smart EMI shielding materials.

Robust ultrahigh electromagnetic interference shielding effectiveness based on engineered structures of carbon nanotube films

High-performance electromagnetic interference (EMI) shielding materials with ultrathin, flexible, and pliable mechanical properties are highly desired for high-end equipments, yet there remain large challenges in the manufacture of these materials. Here, carbon nanotube film (CNTF)/copper (Cu) nanoparticle (NP) composite films are fabricated via a facile electrodeposition method to achieve high electromagnetic shielding efficiency. Notably, a CNTF/Cu NP composite film with 15μm thickness can achieve excellent EMI shielding efficiency of ∼248 dB and absolute EMI shielding effectiveness as high as 2.17×105 dB cm2 g-1, which are the best values for composite EMI shielding materials with similar or greater thicknesses. These engineered composite films exhibit excellent deformation tolerance, which ensures the robust reliability of EMI shielding efficiency after 20,000 cycles of repeated bending. Our results represent a critical breakthrough in the preparation of ultrathin, flexible, and pliable shielding films for applications in smart, portable and wearable electronic devices, and 5G communication.

Electromagnetic interference shielding composite aerogels with asymmetric structures developed in aid of neural network

Along with the increasingly serious electromagnetic interference (EMI) pollution, it is in urgent need of exploiting high-performance EMI shielding materials. However, the conventional experimental methods always require a series of tedious preparation and characterization processes, resulting in the long period and high cost. Herein, a fully connected neural network (FCNN) was applied to aid in exploiting silver nanowires/waterborne polyurethan/multi-walled carbon nanotubes (AgNWs/WPU/MWCNTs) EMI shielding aerogels with asymmetric structures to optimize new material evolution and reduce experiment burden. Firstly, the special AgNWs/WPU/MWCNTs aerogels were fabricated with various MWCNTs content (0 wt%, 2 wt%, and 4 wt%) and AgNWs mass (10 mg, 20 mg, 30 mg, and 40 mg) via a combination of directional freezing and spraying procedures, leading to 12 distinct samples. AgNWs/WPU/MWCNTs aerogels hold excellent EMI shielding properties and absorption-dominant shielding mechanism. The experimental EMI shielding effectiveness (SE) data at different frequency were leveraged to establish, train, and test the FCNN model based on Adam optimizer (Adam-FCNN). It is worth noting that Adam-FCNN model predictions are in good accordance with the EMI SE of the physically measured samples, with the lowest root mean square error RMSE of 0.7899, the highest correlation coefficient (R) of 0.9895, and excellent computational efficiency and reliability. Moreover, Adam-FCNN can accurately prognosticate EMI SE of unobtained AgNWs/WPU/MWCNTs aerogels in mechanics-intuitions to reduce repeated preparation and characterizing conditions. Thereby, Adam-FCNN soft model approach opens significant potential for alleviating the experimental burden, accelerating the discovery of innovative materials, and exploring the complex mechanism.

Efficient electromagnetic interference shielding performance of poly(amide imide)/MWCNT‐based nanocomposites

AbstractThe establishment of conducting network in a polymer matrix is essential for the improvement in electrical conductivity and electromagnetic interference (EMI) shielding performance. Here, we report the fabrication of nanocomposites comprising polyamideimide and multiwalled carbon nanotubes (MWCNTs) (from 0.5 to 5.0 wt%). The effect of MWCNTs on electrical conductivity, morphology, and EMI shielding behavior has been examined. The morphology of nanocomposites was investigated by scanning electron microscope and x‐ray diffraction, which confirms the uniform dispersion of MWCNTs in the matrix. The electrical conductivity increases from 1.4 × 10−12 to 0.145 × 10−4 S/cm by the inclusion of MWCNTs. The composite PACNT‐5 exhibits a good EMI shielding efficiency of −17 dB in the X‐band region by employing only 5.0 wt% of MWCNTs. The incorporation of MWCNTs formed an interconnected conducting network, which boost the transferability of electrons or charge carriers. This work demonstrates a feasible, simple, and effective strategy for the fabrication of potential PAI/MWCNT composites for highly efficient EMI shielding materials.

Three-layered PBAT/CNTs composite foams prepared by supercritical CO2 foaming for electromagnetic interference shielding

Plastic pollution and electromagnetic radiation cause serious environmental problems. Herein, biodegradable poly(butylene adipate-co-terephthalate) (PBAT) and carbon nanotubes (CNTs) composite foams with three-layered structure for electromagnetic interference (EMI) shielding application were prepared by an environmentally friendly supercritical CO2 foaming method. For the CNTs content of 4.9 vol%, the EMI shielding efficiency (SE) of three-layered composite was 23.4 dB, which was improved by 125 % compared with that of single-layered composite with a CNTs content of 4.7 vol% owing to high conductivity in skin layer and multiple reflection between interfaces. The CNTs content in core has little effect on the EMI SE when the CNTs content in skin was 16 wt%. After foaming, SE values slightly decreased due to a decreased volume content of CNTs. However, considering the decreased density of foam, the specific EMI SE was improved by 26.2% after foaming when the CNTs content was 16 wt% in skin and 0 in core. This work provided a facile and green method for preparing lightweight EMI shielding materials.

Shear-Induced Fabrication of Cellulose Nanofibril/Liquid Metal Nanocomposite Films for Flexible Electromagnetic Interference Shielding and Thermal Management.

To address electromagnetic interference (EMI) pollution in modern society, the development of ultrathin, high-performance, and highly stable EMI shielding materials is highly desired. Liquid metal (LM) based conductive materials have received enormous amounts of attention. However, the processing approach of LM/polymer composites represents great challenges due to the high surface tension and cohesive energy of LMs. In this study, we develop a universal one-step fabrication strategy to directly process composites containing LMs and cellulose nanofibrils (CNFs) and successfully fabricate the ultrathin, flexible, and stable EMI shielding films with an average specific EMI shielding efficiency (EMI SE) value of 429 dB/mm and small thickness of only 70 μm in the wide frequency range of 8.2-18 GHz. In addition, the resulting films also exhibit excellent mechanical performance and flexibility, which endow the film with the ability to withstand repeated folding, bending, and folding into complex shapes without producing cracks or fractures. Besides, the resulting films display excellent thermal conductivity with a λ of 4.90 W/(m K) and an α of 3.17 mm2/s. Thus, the presented approach shows great potential in fabricating advanced materials for EMI shielding applications.

Succulent-Inspired Implicit Structural Change for Smart "ON/OFF" Switchable and Flexible EMI Shielding Coating.

Modern miniaturized intelligent electronics call for smart switchable and flexible electromagnetic interference (EMI) shielding material for highly precise applications. However, most switchable EMI shielding materials are based on an explicit structural change. Herein, we report a succulent-inspired smart switchable MXene (WR-MXene) coating film realized by inner implicit structural change, which benefits from the insertion of our reversible large-cavity yolk-shell biomicrospheres. The novel switchable yolk-shell biomicrospheres contain a soft N-isopropylacrylamide (PNIPAM) hydrogel core, an "ON/OFF" switchable cavity (over 30% volume fraction), and a porous polydopamine (p-PDA) shell. The yolk-shell biomicrospheres can be obtained by a facile two-step polymerization and a simple drying-dehydration treatment. Because of the "ON/OFF" switchable void space brought by the smart biomicrospheres and conductive framework of MXene, an optimized ultralight and flexible WR-MXene coating film (vWR-coating film) showed both large switchable change (over 60 dB) and extraordinary EMI shielding effectiveness, reaching 95 and over 50 dB in the whole X band (8.2-12.4 GHz). These novel reversible yolk-shell biomicrospheres and the succulent-inspired switchable coating films are promising for smart flexible wearable devices and many advanced multifunctional systems needing dynamic real-time response.