Efficient Electromagnetic Interference Research Articles

Metal Mesh-Based Infrared Transparent EMI Shielding Window with Balanced Shielding Properties over a Wide Frequency Spectrum

Metal mesh films have been shown to be a promising strategy to effectively mitigate the growing issue of electromagnetic interference (EMI) in optoelectronic systems. To achieve superior shielding effectiveness, it is common to increase the thickness of the mesh film. However, mesh-based shielding materials have frequency-dependent shielding effectiveness that decreases as the frequency increases. Simply increasing the thickness of the mesh cannot effectively enhance the EMI shielding effectiveness at high frequencies. This will further lead to challenges such as increased processing difficulties and higher costs. In this paper, we present an infrared transparent electromagnetic shielding window based on metal mesh with irregular patterns and proper thickness. The mesh coating is fabricated on a sapphire substrate using ultraviolet photolithography technology and exhibits an efficient electromagnetic shielding effectiveness of more than 20 dB over the wide frequency range of 1.7–18 GHz while maintaining high infrared optical transparency. More importantly, there is no distinct variation in shielding effectiveness between low and high frequency ranges, demonstrating a balanced shielding characteristic across a broad frequency band. This work could be crucial in designing cost-effective and efficient EMI shielding windows for optoelectronic systems.

Superhydrophobic PDMS/PPy-Ag/Graphene/PET films with highly efficient electromagnetic interference shielding, UV shielding, self-cleaning and electrothermal deicing

In this work, a general strategy is reported to fabricate flexible superhydrophobic PDMS/PPy-Ag/Graphene/PET films with high conductivity and durability. The films achieved surface resistance of 6.32 Ω/□ and superhydrophobicity of 154.5° through adjusting AgNO3 concentration and reaction time. With the increase of reaction time, surface micro/nanostructure of the film became dense and the pores decreased to disappear, leading to competition between superhydrophobicity and electrical conductivity. The film had excellent heat resistance and UV resistance, good mechanical stability for sandpaper abrasion. The films could keep superhydrophobicity even they are treated with acid, alkali and salt solutions. Importantly, the coating showed excellent and stable electrothermal performance with fast response speed and rapid electrothermal deicing ability. At 5 V, ice cube with 0.5 cm3 completely melted and slid in 160 s. The films also showed excellent self-cleaning, UV shielding and electromagnetic interference shielding with an EMI SET of about 31.5 dB.

Structure design of multi-layered ABS/CNTs composite foams for EMI shielding application with low reflection and high absorption characteristics

The low-reflection and high-absorption features for electromagnetic (EM) waves are the key and significant requirements for fabricating efficient EM interference (EMI) shielding polymer-based composite foams. Herein, single-layered acrylonitrile–butadienestyrene (ABS)/carbon nanotubes (CNTs) foams with three representative pore structures (nano-pores, micro-pores and regular pores) were produced via supercritical CO2 foaming technology. Subsequently, they were stacked together to obtain multi-layered ABS/CNTs foams through structural design for achieving the high absorption and low reflection characteristics described above. Among all the unfoamed and foamed ABS/CNTs specimens, nano-porous ABS/CNTs foams could reach the maximum electrical conductivity of 3.7 S/m. The multi-layered ABS/CNTs foam with positive pore gradient structure exhibited the best EM wave absorption coefficient of 0.90. The sandwich structure formed in ABS/CNTs foam by sandwiching a middle layer of regular porous foam between nano-porous foam and micro-porous foam increased EM wave absorption properties, owing to the generation of constructive interference. This work provides new insight and methodology for the design and fabrication of multi-layered EMI shielding polymer-based composite foams with low reflection and high absorption.

Facile fabrication of ultrathin graphene/cellulose composites with efficient electromagnetic interference shielding by spray deposition

Ultrathin electromagnetic interference shielding materials are commonly used to overcome electromagnetic pollution in applications including integrated and wearable electronics. This paper demonstrates a graphene composite with an ultrathin thickness of 43 μm manufactured using a facile and rapid spray deposition technique on a cellulose substrate. The graphene was highly oriented and densely stacked on the cellulose substrate by the spray deposition due to polyvinyl alcohol (PVA) and polyacrylic acid (PAA) introduced for increasing their self-adhesion and adhesion to the cellulose substrate. The interconnected graphene conductive networks on the cellulose were effectively formed, resulting in low electrical resistivity (0.003 Ω·m) and efficient electromagnetic shielding effectiveness (28.3 dB at the 10 GHz) of graphene/cellulose composites. It is expected that this research will be used for the effective development of electromagnetic shielding materials for multifunctional smart and wearable electronics.

Optimizing Electromagnetic Interference Shielding of Ultrathin Nanoheterostructure Textiles through Interfacial Engineering.

Strong electromagnetic wave reflection loss concomitant with second emission pollution limits the wide applications of electromagnetic interference (EMI) shielding textiles. Decoration of textiles by using various dielectric materials has been found efficient for the development of highly efficient EMI shielding textiles, but it is still a challenge to obtain EMI shielding composites with thin thickness. A route of interfacial engineering may offer a twist to overcome these obstacles. Here, we fabricated a Ni nanoparticle/SiC nanowhisker/carbon cloth nanoheterostructure, where SiC nanowhiskers were deposited by a simple manufacturing method, namely, laser chemical vapor deposition (LCVD), directly grown on carbon cloth. Through directly constructing a Ni/SiC interface, we find that the formation of Schottky contact can influence the interfacial polarization associated with the generation of dipole electric fields, leading to an enhancement of dielectric loss. A striking feature of this interfacial engineering strategy is able to enhance the absorption of the incident electromagnetic wave while suppressing the reflection. As a result, our Ni/SiC/carbon cloth exhibits an excellent EMI shielding effectiveness of 68.6 dB with a thickness of only 0.39 mm, as well as high flexibility and long-term duration stability benefited from the outstanding mechanical properties of SiC nanowiskers, showing potential for EMI shielding applications.

Ti3C2Tx MXene-Ferroferric Oxide/Carbon Nanotubes/Waterborne Polyurethane-Based Asymmetric Composite Aerogels for Absorption-Dominated Electromagnetic Interference Shielding

Absorption-dominated electromagnetic interference (EMI) shielding materials are more attractive to manage the increasing electromagnetic radiation pollution than conventional reflection-dominated counterparts due to their advantages of balancing the efficient EMI shielding performance while minimizing the secondary pollution of the reflected electromagnetic (EM) wave. Herein, we first fabricate ferroferric oxide/carbon nanotubes/waterborne polyurethane (Fe3O4/CNTs/WPU) aerogels and then coat Ti3C2Tx MXene at the bottom to construct an asymmetric structure. Moreover, the medium or transition layer is formed during the coating process of MXene-ferroferric oxide by the gravity and aerogel’s capillary action. This delicate design makes them with obvious absorption, transition, and reflection layers according to the progressive modular design principle. The composite aerogels show an average EMI shielding effectiveness (SE) of 20.06 dB, low reflectivity of 0.396, and specific EMI SE of SSE/t of 332.60 dB cm2 g–1 in the X-band when the MXene content is only 2.35 vol %. Additionally, the resultant aerogels exhibit remarkable flexible and mechanical properties, which could even bear weights of about 4500 times their own weight. In sum, this work provides a promising absorption-dominated EMI shielding candidate with flexible and high strength features.

MXene-cellulose nanofiber composites: toward green, multi-functional, flexible, and highly efficient electromagnetic interference shielding materials

In the current fast-paced digital world, electronic devices have become an inevitable part of our lives, contributing to increasing electromagnetic interference (EMI) that may unfavorably affect our health as well as the precision of miniaturized electronics. Therefore, developing efficient multi-functional EMI shielding materials is of immense interest and importance. EMI shielding technology requires materials possessing high conductivity, permeability, permittivity, processability, and corrosion resistance while being cost-effective and environmentally friendly. The EMI shielding characteristics of MXene, as a novel flourishing 2D material, have been extensively explored in recent years owing to its excellent electrical, thermal, and mechanical properties. Cellulose nanofibers (CNFs) that can be obtained from biomass and upcycling waste, benefiting from numerous advantages such as biodegradability, high aspect ratio, processability, and low cost, can be utilized as a matrix, binder, or derived carbon material. Amalgamating the outstanding properties of these two materials, this paper reviews recent advancements in the field of CNF/MXene nanocomposites. After a brief introduction on CNF and MXene, the role of the structure in the mechanism of attenuation of the electromagnetic wave is discussed. Emphasis is given to the effect of the type and content of the conductive material, thickness, and fabrication method on EMI shielding effectiveness and conductivity. An elaborate discussion on the gaps in achieving multi-functional and flexible composites based on CNF and MXene exhibiting high EMI shielding and potential application in aerospace and wearable sensors is reported as well.

Superhydrophobic and Durable Silver-Coated Fabrics for Efficient Electromagnetic Interference Shielding

Superhydrophobic surfaces present promising potential for improving the mechanical and chemical durability of electromagnetic interference (EMI) shielding materials. However, integrating superhydrophobicity and EMI shielding is still a challenge due to the complex structural design. Herein, superhydrophobic and highly durable fabrics with excellent EMI shielding effectiveness were fabricated. First, the meta-aramid nonwoven fabrics were functionalized by a polydopamine layer. Then, with the assistance of the metal-binding ability of polydopamine, silver nanoparticles were immobilized on the fiber surface by electroless plating. Finally, after the introduction of fluorine-containing agents via a facile dipping method, a superhydrophobic surface was successfully obtained. The as-prepared fabrics showed excellent EMI shielding effectiveness of 111 dB due to superior electrical conductivity (234 S/cm). Moreover, thanks to the low surface energy of fluorine-containing molecules as well as the micro-nanoroughness created by the stacking of silver nanoparticles, the composite fabrics exhibited a large water contact angle of 152° and a low sliding angle of 5°. It was noted that the composite fabrics still maintain superhydrophobicity and high EMI shielding effectiveness (110 dB) even after the acid and alkali corrosion, bending, abrading, and salt fog test, respectively, demonstrating their durability under harsh environments.

Ice-templated assembly strategy to construct oriented porous Ti3SiC2 ceramics for thermal management and electromagnetic interference shielding in harsh thermal environments

Given the electromagnetic interference (EMI) and heat aggregation issue faced by electronic components, an urgent need exists to integrate EMI shielding and thermal conductivity in one material. Herein, a novel lightweight porous Ti3SiC2 ceramic with ordered structural arrangement was fabricated by using budget-friendly raw materials through ice template design and in-situ reaction synthesis. Leveraging the excellent conductivity and thermal conductivity of Ti3SiC2, a dual-functional advanced material with efficient EMI shielding and thermal management capabilities was obtained. At room temperature, porous Ti3SiC2 ceramics can achieve a shielding effectiveness of 35.44 dB and a thermal conductivity of 12.17 W/mK, with performance that can be tuned by porosity. In further, the porous Ti3SiC2 ceramic can work stably in thermal environments from room temperature to 700 °C or in corrosive environments rich in acid, alkali, and salts due to its excellent high temperature oxidation resistance and corrosion resistance. In view of the dual-functional characteristics and the stability of operation in harsh thermal environments, ordered porous Ti3SiC2 ceramics are promising for modern maritime and aerospace applications.

Versatile Electronic Textile Enabled by a Mixed-Dimensional Assembly Strategy.

Electronic textiles (e-textiles) hold great promise for serving as next-generation wearable electronics owing to their inherent flexible, air-permeable, and lightweight characteristics. However, these e-textiles are of limited performance mainly because of lacking powerful materials combination. Herein, a versatile e-textile through a simple, high-efficiency mixed-dimensional assembly of 2D MXene nanosheets and 1D silver nanowires (AgNWs) are presented. The effective complementary actions of MXene and AgNWs endow the e-textiles with superior integrated performances including self-powered pressure sensing, ultrafast joule heating, and highly efficient electromagnetic interference (EMI) shielding. The textile-based self-powered smart sensor systems obtained through the screen-printed assembly of MXene-based supercapacitor and pressure sensor are flexible and lightweight, showing ultrahigh specific capacitance (2390 mF cm-2 ), robust areal energy density (119.5 µWh cm-2 ), excellent sensitivity (474.8 kPa-1 ), and low detection limit (1Pa). Furthermore, the interconnected conductive MXene/AgNWs network enables the e-textile with ultrafast temperature response (10.4°C s-1 ) and outstanding EMI shielding effectiveness of ≈66.4dB. Therefore, the proposed mixed-dimensional assembly design creates a multifunctional e-textile that offers a practical paradigm for next-generation smart flexible electronics.

Broadband transparent and flexible silver mesh for efficient electromagnetic interference shielding and high-quality free-space optical communication

A broadband transparent and flexible silver (Ag) mesh is presented experimentally for the first time for both efficient electromagnetic interference (EMI) shielding in the X band and high-quality free-space optical (FSO) communication. High transmission is achieved in a broad wavelength range of 0.4-2.0 µm. The transmittance of the Ag mesh relative to the substrate is around 92% and the sheet resistance is as low as 7.12 Ω/sq. The Ag mesh/polyethylene (PE) achieves a high average EMI shielding effectiveness (SE) of 28.8 dB in the X band with an overall transmittance of 80.9% at 550 nm. High-quality FSO communication with small power penalty is attributed to the high optical transmittance and the low haze at 1550 nm, superior to those of the Ag NW networks. With a polydimethylsiloxane (PDMS) coating, the average EMI SE is still up to 26.2 dB and the overall transmittance is increased to 84.5% at 550 nm due to antireflection. The FSO communication does not change much due to the nearly unchanged optical property at 1550 nm. Both the EMI shielding performance and the FSO communication function maintain after 2-hour chemical corrosions as well as after 1000 bending cycles and twisting. Our PDMS/Ag mesh/PE sandwiched film can be self-cleaned, suitable for outdoor applications.

Low-temperature treated polypyrrole coated cotton fabrics for efficient electromagnetic interference shielding

Low-temperature treated polypyrrole coated cotton fabrics for efficient electromagnetic interference shielding

NiFe-doped CoP network-structured nanocomposites for efficient electromagnetic interference shielding

The highly integrated electronics put forward an urgent demand for ultrathin and high-performance electromagnetic interference (EMI) shielding materials. Herein, NiFe doped CoP network-structured nanocomposites support on titanium mesh were prepared by hydrothermal method, the resulting composites with EMI SE of 63.9 dB at 150 µm thickness exhibit excellent EMI shielding performance. Neat flower-like CoP and NiFe nanoparticles are tightly attached to the surface of titanium mesh, while NiFe doped CoP exhibits loose needle-like structure accompanied by nanoparticles attachment. The resulting reticulated nanocomposites show efficient EMI shielding mainly based on absorption loss. CoP with good conductivity promotes the dielectric loss of electromagnetic waves, the penetration of magnetic NiFe strengthens the impedance of the composites, and the synergistic effect of CoP and NiFe with loose structure are conducive to further absorption and attenuation of electromagnetic waves, thus titanium mesh based NiFe-doped CoP composites possess excellent EMI shielding. These high-performance ultrathin EMI shielding materials would show superior application prospects in electronics and electrical appliances.

Rational design of heterointerface between MoO2 and N-doped carbon with tunable electromagnetic interference shielding capacity

Exploring highly efficient electromagnetic interference (EMI) shielding filler is urgently desired for next-generation wireless communication and integrated electronics. In this regard, a series of heterogeneous MoO2/N-doped carbon (MoO2/NC) nanorods with tunable conductivity have been successfully synthesized by regulating the pyrolysis temperature within 600, 700 and 800 °C. Profiting from the rational design of heterointerface and low-dimensional structure, the MoO2/NC powder achieves stronger EMI shielding capacity with the incremental temperature. It is found that the MoO2/NC-800 nanorods exhibit the optimal average EMI shielding effectiveness (SE) of 57.2 dB at a thickness of ∼0.3 mm in the X band. Meanwhile, the corresponding shielding mechanisms of MoO2/NC nanorods are also elaborately explained. More interestingly, the increase of sintering temperature makes an obvious effect on absorption loss but has little influence on reflection loss, demonstrating that adjusting the pyrolysis temperature is an effective strategy to strengthen the electromagnetic energy dissipation.

Multilayer RGOx＆PESy films for efficient electromagnetic shielding performance in a wide temperature range

In this work, the alternating multi-layer structured reduced graphene oxide＆polyether sulfone (RGOx&PESy) film is fabricated via a facile thermal pressure process, which has independently aligned packing layers to ensure the conductive network. The electromagnetic interference (EMI) shielding performance of the RGOx＆PESy film can be adjusted with facility by controlling the layer number of the pure RGO and PES films. At a fixed thickness of 0.35 mm, the shielding performance of the multi-layer structured films increases with the increased layer number of the RGO films. Especially, when the number of RGO film is seven, the RGO7&PES6 film provides an efficient EMI shielding performance of about 45 dB in the whole X-band with a low filler content of 7.39 wt%. Moreover, due to the excellent temperature stability of both RGO and PES, the effective EMI shielding performance can be maintained in the wide temperature range of 298 ∼ 473 K. This study provides a facile method for preparing the RGO-based EMI shielding film materials with excellent high-temperature resistance and ultra-low filler content.

Effects of pore structure on wide-frequency electromagnetic interference shielding performance of carbonized wood

Carbonized wood attracts widespread attention in the field of electromagnetic interference (EMI) shielding thanks to its layered porous structure and high electrical conductivity. Understanding the correlation between pore structure and shielding performance is crucial for constructing efficient EMI shielding materials. Herein, pore structures are monitored by changing the compression ratio during the hot pressing. Carbonized wood with a 40% compression ratio displays a superior EMI shielding effectiveness (SE) up to 71.69 dB in K-band, owing to the optimal structure. EMI shielding characteristics of carbonized wood in different frequency ranges are also studied. The effects of pore structure on the shielding performance are further illuminated by finite element analysis. After structure optimization, carbonized wood can demonstrate high EMI shielding performance, wide-frequency coverage, terahertz band use, and excellent heat dissipation. This work inspires the design of next-generation sustainable EMI shielding materials.

Lightweight poly(vinylidene fluoride) based quaternary nanocomposite foams with efficient and tailorable electromagnetic interference shielding properties

AbstractDriven by rapidly growing demands in fields such as mobile electronics, aerospace and military, the need for functional materials with lightweight, good environmental stability and efficient electromagnetic interference (EMI) shielding properties has rose sharply. In this paper, quaternary nanocomposite foams comprising of poly(vinylidene fluoride) (PVDF), carbon nanotubes (CNTs), graphene nanoplatelets (GNPs) and Ni were developed by a melt blending and supercritical CO2foaming technology. Compared with pure PVDF, the crystallization temperature of PVDF/2CNTs/2GNPs/12Ni nanocomposite increased remarkably from 139.0 to 144.9°C. Rising the nanofiller loading from 0 to 16 wt% led to the enhancements of around four orders of magnitude in the storage modulus of PVDF nanocomposites as well as about three orders of magnitude in their complex viscosity. For a typical PVDF/2CNTs/2GNPs/12Ni nanocomposite, its EMI shielding effectiveness reached 32.2 dB, brought by dielectric loss and magnetic loss. The electrical conductivity and EMI shielding effectiveness of PVDF nanocomposite foam achieved the optimum values of 0.84 S/m and 19.4 dB, respectively, which originated from the introduction of pore structure and the gradual generation of nanofiller‐nanofiller conductive networks. This study took a promising way toward the fabrication of materials with adjustable EMI shielding property in the fields of electronics and aerospace industries.

Additive manufacturing of carbon nanotube/polylactic acid films with efficient electromagnetic interference shielding and electrical heating performance via fused deposition modeling

In the wake of developments in 5th generation mobile communication technology and Internet of Things, traditional electromagnetic interference (EMI) shielding materials are not satisfied with the booming demand of suppressing electromagnetic pollution. In view of the characteristics of low-cost, easy-operating and functional materials applicability of fused deposition modeling (FDM), in this work, a multifunctional carbon nanotube (CNT)/ polylactic acid (PLA) film with electromagnetic shielding and electric heating properties was prepared by using FDM process. The effects of CNT content, FDM-printed film thickness, and FDM process parameters on electromagnetic shielding performance were studied. The results indicate that the additions of CNT increase the EMI shielding performance by forming the conductive paths in the CNT/PLA FDM-printed films. The EMI shielding value of the 4 wt% CNT/PLA film with a thickness of 4 mm is 68 dB at 12.3Ghz. In addition, the improved electrical conductivity provides the good electric heating performance of the CNT/PLA film. At a safe voltage (16 V), the heating temperature of the 4 wt% and 8 wt% CNT/PLA films reached 67.8 °C and 139 °C, respectively. The good repeatability and stability of CNT/PLA films for electric heating were verified. The obtained CNT/PLA FDM-printed films have excellent electromagnetic shielding and low-voltage electric heating properties by adjusting the CNT contents and the FDM process parameters, which expands the application potential of EMI shielding materials and FDM technology.

Extreme environment-bearable polyimide film with a three-dimensional Ag microfiber conductive network for ultrahigh electromagnetic interference shielding

To ensure the normal operation of electronic equipment and provide protection from electromagnetic radiation, polymer-based electromagnetic interference (EMI) shielding materials are widely developed in the electronic communication field. However, it remains a challenge to prepare EMI shielding composites with ultrahigh EMI shielding efficiency (EMI SE), low thickness, high durability, and flexibility in harsh environments, such as extremely high or low temperatures in aerospace. In this study, we used blow spinning and compression molding to construct a highly efficient EMI shielding polyimide (PI) film containing a Ag microfiber sponge (AgMS). The three-dimensional (3D) conductive network constructed by 28-vol% AgMS endows the AgMS/PI film with very high electrical conductivity of 4.5 × 106 S m−1 and an EMI SE of up to 90.6 dB, at only 20-µm thickness. Even after working at −196 or 250°C for 120 h, the excellent EMI shielding performance is maintained, with EMI SE retention higher than 85.1 dB. Furthermore, AgMS/PI film exhibits outstanding thermal management performance, achieving a high saturation temperature of 200.2°C at very low supplied voltage (1.1 V), revealing a quick response time (3.1 s), excellent cyclic heating stability, and outstanding reliability. These outstanding properties indicate the great potential of AgMS/PI films in the electronic communication field under harsh environments and artificial intelligence.

Wearable nonwoven fabric decorated with Fe3O4/rGO/PANI/Ni-P for efficient electromagnetic interference shielding

The design of three-dimensional (3D) architectures with different multi-interface and the identification of suitable nanomaterials have significantly progressed in recent years. However, balancing increasing electrical conductivity and optimising impedance matching is substantially important and requires special architecture. Here, we devised lightweight wearable electromagnetic interference (EMI) shielding materials with promising microwave absorption performances. Layer-by-layer integration of conducting and magnetic nanomaterials onto the porous structure of the nonwoven fabric was performed using dielectric and magnetic loss to enhance the absorption capability of the composite. The EMI shielding effectiveness of the 1-layer, 2-layer, and 3-layer reach up to 27, 42, and 81 dB, respectively, revealing excellent performances in the X-band. The synthesis of hierarchical Ni-P nanospheres on fibres with heterojunctions and multi-interfaces as polarisation centres results in excellent microwave absorption performance. Furthermore, Ni-P electroless plating and Ni-B chemical deposition were conducted to improve permittivity, conductivity, and permeability in addition to increasing the impedance matching of the EM shielding material. It provides an avenue for the architecture of promising wearable functional materials with superior absorption activity, flexibility, durability, and breathability.