Electromagnetic Shielding Structures Research Articles

Flexible regenerated cellulose composite films with sandwich structures for high-performance electromagnetic interference shielding

Flexible regenerated cellulose composite films with sandwich structures for high-performance electromagnetic interference shielding

An overpressure monitoring system based on PVDF integrated Electronic sensor with enhanced noise attenuation capability

The measurement of shockwave overpressure is of great significance for the safe use of explosives. The traditional overpressure monitoring systems are based on Integrated Electronics Piezo-Electric (IEPE) ceramic sensors. However, the brittleness of piezoelectric ceramic limits the application of overpressure monitoring system in high impact overpressure testing. Herein, a novel overpressure monitoring system based on Integrated Electronic Poly (vinylidene fluoride) (PVDF) (PFIE) sensor with electromagnetic interference shielding capability and parasitic vibration noise elimination function was designed for intense overpressure acquiring. PVDF, as a polymer, can endure much higher impact pressures compared to piezoelectric ceramics. However, its larger internal resistance makes it more prone to electromagnetic interference. To address this, an electromagnetic shielding structure was designed, incorporating an impedance matching circuit that effectively reduces the sensor's output impedance. Additionally, to mitigate excessive vibration noise during overpressure testing, the differential noise reduction technique has been implemented. Both the laboratory testing and the real blast testing with 10 kg trinitrotoluene were performed to validate the PFIE overpressure monitoring system. The result shows that the electromagnetic noise suppression ability of the PFIE overpressure sensors developed for the monitoring system was improved by 45 dB, and the parasitic vibration noise could be attenuated from 30 % to 1 %, what’s more the RMS errors of the overpressure dynamic parameters obtained by the monitoring system were below 10 %. This work has successfully addressed the noise sensitivity issue inherent in PVDF when used as a pressure sensor, capitalizing on its robust impact resistance. This approach has provided a viable solution for measuring overpressure in scenarios involving intense shock pressures, leveraging the strengths of PVDF in such demanding applications.

Catechol grafted rGO/MXene heterosheet structures for high performance electromagnetic interference shielding and thermal management applications

Two-dimensional MXenes have shown extraordinary potential in various scientific areas, including energy harvesting and microwave shielding. Despite their outstanding properties, MXene-based scaffolds suffer from vulnerable mechanical fragility and environmental instability, which reduces the operational life. Here, we used a nature-inspired strong surface adhesion to assemble a stacked heterosheet structure of reduced graphene oxide (rGO) and MXene (Ti3C2TX). Catechol bonding of self-triggered polydopamine between these two-dimensional nanofillers resulted in a dense and well-ordered structure, transforming their mechanical and electrical properties to those of a freestanding sheet. The simultaneous grafting of catechol and the formation of stacked heterosheets with rGO not only protects the MXene sheets from environmental oxidation but also preserves their intrinsic transportation properties. The resulting rGO/MXene composite sheet was ordered and dense, with a tensile strength of 86 MPa and toughness 118.2 MJm−3. The ultrathin, highly flexible, and conductive (26.5 Scm−1) composite sheet exhibited specific shielding effectiveness of 16340, 19136 and 21340 dBcm2g−1 in the X, Ku, and K bands, respectively. Additionally, it showed outstanding Joule-heating properties, with a rapid thermal response of approximately 2 s and the ability to reach a saturation temperature >120 °C at a relatively low supplied voltage of <7 V. The grafted rGO/MXene composite sheet maintained its transportation properties, electromagnetic interference shielding, and electrothermal properties even after 60days of continuous exposure to ambient by suppressing oxidation attacks. The synergistic enhancement of physical properties and environmental stability in the composite sheet suggest a great potential for high-performance, flexible shielding, and thermal management applications in aerospace and automobile electronics.

Poly(arylene ether nitrile) composite foams with magnetically and electrically separated structures for frequency-selective electromagnetic interference shielding

With the rapid development of communication technology and modern intelligent electronic systems, the demand for frequency-selective electromagnetic interference (EMI) shielding materials has grown. In this work, poly(arylene ether nitrile) (PEN) composite foams with separated magnetic and conductive layers were prepared via delayed non-solvent induced phase separation, where the distribution of magnetic and conductive layers was designed to construct double-layer asymmetric structures and sandwich structures. Benefiting from destructive interference between electromagnetic waves (EMWs) in the magnetically and electrically separated porous structures, the double-layer asymmetric composites (M−C) exhibited outstanding absorption-dominated EMI shielding performance with favorable frequency selectivity, which did not occur in conventional double-layer composites. Specifically, M−C achieved a maximum shielding efficiency (SE) of 49.3 dB and a maximum average absorption ratio (Ar) of 93.9 %. Meanwhile, increasing the thickness of the magnetic layer of M−C can lower the characteristic frequency (fc) of the shielding peak and enhance average SE and average Ar. Moreover, M−C could show higher fc, average Ar, and average adsorption coefficient in the X-band when the incident EMWs first met with the magnetic layer, which was unavailable in frequency-selective PEN-based sandwich-structured composites. This effort offers a novel, flexible design to fabricate absorption-dominated EMI shielding materials with frequency selectivity.

Health Monitoring via Heart, Breath, and Korotkoff Sounds by Wearable Piezoelectret Patches.

Real-time monitoring of vital sounds from cardiovascular and respiratory systems via wearable devices together with modern data analysis schemes have the potential to reveal a variety of health conditions. Here, a flexible piezoelectret sensing system is developed to examine audio physiological signals in an unobtrusive manner, including heart, Korotkoff, and breath sounds. A customized electromagnetic shielding structure is designed for precision and high-fidelity measurements and several unique physiological sound patterns related to clinical applications are collected and analyzed. At the left chest location for the heart sounds, the S1 and S2 segments related to cardiac systole and diastole conditions, respectively, are successfully extracted and analyzed with good consistency from those of a commercial medical device. At the upper arm location, recorded Korotkoff sounds are used to characterize the systolic and diastolic blood pressure without a doctor or prior calibration. An Omron blood pressure monitor is used to validate these results. The breath sound detections from the lung/ trachea region are achieved a signal-to-noise ration comparable to those of a medical recorder, BIOPAC, with pattern classification capabilities for the diagnosis of viable respiratory diseases. Finally, a 6×6 sensor array is used to record heart sounds at different locations of the chest area simultaneously, including the Aortic, Pulmonic, Erb's point, Tricuspid, and Mitral regions in the form of mixed data resulting from the physiological activities of four heart valves. These signals are then separated by the independent component analysis algorithm and individual heart sound components from specific heart valves can reveal their instantaneous behaviors for the accurate diagnosis of heart diseases. The combination of these demonstrations illustrate a new class of wearable healthcare detection system for potentially advanced diagnostic schemes.

Fabrication of dual-function conductive cellulose-based composites with layered conductive network structures for supercapacitors and electromagnetic shielding

In this work, a conductive TEMPO-cellulose nanofibers(TONF)/conductive carbon black(CCB)/ Vinasse activated carbon(VAC)(TCA) composite was constructed by electrostatic adsorption, freeze-drying, and hot pressing. In this composite, a conductive TONF composite with good electrical conducting properties was constructed by electrostatic adsorption between TONF and CCB. And the conductive TONF can be used as an ideal dispersant to effectively prevent accumulation between VACs. In addition, TONF imparts TCA composites with excellent mechanical properties. Due to the layered conductive network structure formed by the effective tight stacking between the highly conductive TONF layer and the VAC, the assembled supercapacitor exhibits a high specific capacitance of 263F g−1 (672 mF cm−2), energy density of 23.8 Wh kg−1, and power density of 5.7 KW kg−1. What's more, the assembled supercapacitor can exhibit excellent cycle stability after 12,000 cycles. In addition, An intelligent electromagnetic(EMI) shielding TCA-V composite material with shape memory function was prepared by introducing a dynamically cross-linked polymer Vitrimer. In summary, TCA composites have excellent integration properties, especially electrochemical properties with good stability performance and excellent EMI shielding properties. These remarkable features make nano cellulose/carbon-matrix composites have great attraction and potential in the field of supercapacitors and intelligent EMI shielding.

Copper-nickel electroplating of 3D-printed acrylonitrile butadiene styrene for interference and radiation shielding applications

In this study, electromagnetic and radiation shielding structures were fabricated by 3D printing acrylonitrile butadiene styrene (ABS) structures via fused filament fabrication and electroplating with copper (Cu) and nickel (Ni) metals. Prior to electroplating, the printed ABS materials were made conductive by surface electrodepositon of polypyrrole (PPy). ABS adsorbs the pyrrole monomer, which subsequently polymerizes via oxidation forming conductive PPy layer on the printed structures. The successful anchoring of PPy layer can be attributed to its hydrogen bonding and electrostatic interactions with ABS. Thermal analysis, optical, and electron microscopy equipped with energy dispersive X-ray were employed to characterize the printed shielding structures, while the interference and radiation shielding effectiveness were evaluated using a spectrum analyzer and dosimeter, respectively. The interference shielding was found to be effective at 60 ± 5 dB over relatively small frequency range. Shielding was also apparent against gamma and X-ray ionizing rays, but more significantly effective against beta rays. Furthermore, the Cu/Ni coating was able to reduce any heat-induced dimensional changes for the 3D printed ABS substrate without compromising the mechanical integrity.

Recent Developments of Shielding Effectiveness for Electronics and Information Devices

With the increase wireless communications, many wireless devices and equipment have been invented for special applications, resulting in mutual interference that might destroy the systems or distort signal in-transmission. One of the effective methods to reduce or eliminate interference is to devise a shielding to block the unwanted interference in between the approaching systems, circuits, devices, etc. Thus, shielding and estimation of its effectiveness are very important in order to protect the information devices from potential interference and to improve the performance of information equipment. In this survey, we present the recent developments of the shielding and shielding effectiveness techniques and methods, and give a design for an electromagnetic shielding structure.

Machine Learning Empowered Magnetic Substrate Coupled Broadband and Miniaturized Frequency Selective Surface

This works offers a polarization-insensitive, wide angular stable, and wideband electromagnetic interference shielding structure using an integration of frequency selective surface (FSS) with magnetic substrates. The equivalent circuit model (ECM) together with the analytical model is derived to figure out the physics of the shielding structure. The overall inductance of the shielding structure is increased using a magnetic ferrite sheet and magnetic silicon rubber sheet as substrates. Further, four different deep neural network configurations are investigated with inverse modeling to predict the shielding structure parameters within a fraction of seconds. The mse between expected and predicted output is only 2.92 × <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$10^{-8}$</tex-math></inline-formula> . The entire X-band is shielded with a minimum 10-dB shielding effectiveness (SE) and with SE of 56 dB at resonance. The FSS unit cell size is only 0.21 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\lambda$</tex-math></inline-formula> × 0.21 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\lambda$</tex-math></inline-formula> . Furthermore, the proposed shielding structure shows stable transmission performance up to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$75^{\circ}$</tex-math></inline-formula> angle of incidence for both perpendicular and parallel polarization. Finally, a prototype is fabricated and measured using nondestructive free space measurement. Good agreement among the simulated, ECM, analytical model, and measured results demonstrate the efficacy of the proposed technique for building an effective shielding structure.

Waste flame-retardant polyurethane foam/ground tire rubber/carbon nanotubes composites with hierarchical segregated structures for high efficiency electromagnetic interference shielding

Recently, flexible conductive polymer composites (CPCs) have attracted increasing interests for their promise in electromagnetic interference (EMI) shielding. Inspired by the “steel reinforced concrete” structure, we proposed in this study a novel method to prepare a CPC with high EMI shielding performance from waste flame-retardant polyurethane foam (WFPUF) and ground tire rubber (GTR). In this CPC, WFPUF coated with carbon nanotubes (CNT) and cellulose nanofibers (CNF) served as a strong and conductive skeleton like the “steel” in “steel reinforced concrete”. Meanwhile, the GTR and CNT composite with a segregated structure occupied the pore space of WFPUF/CNT/CNF (WCC) to form the WCC/GTR/CNT composite, similar to the “concrete” in “steel reinforced concrete”. Owing to such a hierarchical structure, the resultant WCC/GTR/CNT demonstrated some coveted properties, including the enhanced mechanical properties, high electrical conductivity (84.0 S·m−1), excellent EMI shielding performance (53.8 dB), and long-term durability. Remarkably, the composite also showed great flame retardancy due to the presence of WFPUF. This work provided a promising strategy for the preparation of eco-friendly, low cost, flexible and efficient CPCs from polymer wastes, which showed high potential in EMI shielding.

Flexible Pb(Zr0.52,Ti0.48)O3 thin film acoustic emission sensor for monitoring partial discharge in power cable

Piezoelectric acoustic emission sensors can be used detect the sound emitted by the target structure when it is damaged and have important applications in the field of structure health monitoring. However, due to the mismatch of the interface acoustic impedance, it is hard for the conventional ultrasonic sensor to monitor the acoustic emission in a pipe structure. In this work, a flexible sensor by the deposition of a Pb(Zr0.52,Ti0.48)O3 thin film on a mica substrate was fabricated, and the acoustic emission generated by the partial discharge of a 110 kV power cable was detected by using the flexible sensor. The flexible sensor was designed with an electromagnetic shielding structure and, therefore, can screen most of the electromagnetic interference. The flexible sensor shows a relatively flat response in the frequency range from 100 to 1000 kHz with a sensitivity over 47.5 dB, which is beneficial for pattern recognition studies of acoustic emission. This work not only provides a flexible, anti-electromagnetic interference and broadband sensor for acoustic emission detection but also promotes the development and application of flexible ferroelectric materials.

FDM-3D printing LLDPE/BN@GNPs composites with double network structures for high-efficiency thermal conductivity and electromagnetic interference shielding

Towards the high-frequency and miniaturization of modern electronic devices, the multi-functional materials with high-efficiency thermal management and electromagnetic interference shielding performance are urgently demanded. The contributions in materials are mostly focused on a single function, and difficult to meet the requirement of the precision device with complicated structures. Herein, linear low-density polyethylene (LLDPE)/boron nitride (BN)@graphene nanoplatelets (GNPs) composite parts with double network structures were designed and realized by combining ball-milling strategy and fused deposition modeling (FDM) 3D printing technology. The FDM-3D printed parts could exhibit a thermal conductivity of 3.11 W/(m·K) along the printing direction at 3.51 vol% GNPs loading, achieving an improvement of ∼2.88 and ∼8.33 times over that of flat printing parts and pure LLDPE, respectively. The long-range aligned network along the printing direction is formed due to the shear extrusion effect during FDM-3D printing. Also, FDM-3D printing is applied to print heat sinks with excellent thermal conductive property in vertical direction. Furthermore, the ball milling process could enable the GNPs to form thermal and electrical conductivity pathways in LLDPE/BN composites. The printed parts accordingly exhibit good electromagnetic shielding performance (27.8 dB) and electrical conductivity (12.5 S/m). This study not only enriches the strategy for preparation of multifunctional FDM 3D printed parts, but also paves the way for further applications in advanced thermal management and protection against electromagnetic irradiation.

Three-Dimensional Printing to Fabricate Graphene-Modified Polyolefin Elastomer Flexible Composites with Tailorable Porous Structures for Electromagnetic Interference Shielding and Thermal Management Application

Three-Dimensional Printing to Fabricate Graphene-Modified Polyolefin Elastomer Flexible Composites with Tailorable Porous Structures for Electromagnetic Interference Shielding and Thermal Management Application

Graphene and MXene-based porous structures for multifunctional electromagnetic interference shielding

Graphene and MXene-based porous structures for multifunctional electromagnetic interference shielding

Wide-Band Electromagnetic Radiation Shielding Construction Based on Pseudooval Scattering Elements for Information Protection Against Leakage Via Electromagnetic Channel

The paper considers the results of a study of the influence of the relative position of moisture-containing pseudooval scattering elements with linear dimensions of 10…20, 2…4, 1…4 and 1…2 mm on the electromagnetic radiation reflection coefficients values of the electromagnetic radiation shielding structures, including these elements, and the effective scattering surface of the ground objects, on the surface of which the indicated structures are fixed or applied. Placement of three- or two-layer structures formed on the basis of pseudooval elements with linear dimensions of 2...4, 1...4, 1...2 mm, between two monolayers made on the basis of elements with dimensions of 10...20 mm, leads to the decrease up to –17,6 dB of the electromagnetic radiation reflection coefficients values in the frequency range of 2–12 GHz of the electromagnetic radiation shielding structures, including these elements. The values of the effective scattering surface of ground objects, on the surface of which the indicated electromagnetic radiation shielding structures are located, vary within 0,08...11,80 m 2 , which is the reason of a significant difficulty in intercepting information about the location and characteristics of ground objects by means of technical intelligence in the frequency range of their operation.

Graphene Oxide/Carbon Tube Composite Films with Tunable Porous Structures for Electromagnetic Interference Shielding

Graphene Oxide/Carbon Tube Composite Films with Tunable Porous Structures for Electromagnetic Interference Shielding

Theoretical and experimental analysis of the dielectric properties of 3D orthogonal woven GFRP composites in the terahertz frequency range

A novel method to calculate the dielectric constant (εr′) of three-dimensional orthogonal woven glass fiber-reinforced polymer-matrix (3DOW-GFRP) composites in the terahertz (THz) frequency range is developed and experimentally verified using the THz time-domain spectroscopy (THz-TDS). The dielectric anisotropy is demonstrated through simulation by considering a single propagation direction of the THz waves and three different fiber orientations in unidirectional GFRP composites. Simulation results are compared to those obtained from the classic rule-of-mixture equations to determine the representative equations for the three different cases of fiber orientations in the (x,y,z)-coordinate system and a new model is developed to calculate εr′ of 3DOW-GFRP composites based on electromagnetic modeling principles. As opposed to previously reported lumped circuit models, our model addresses the issue of orthogonality of fiber and considers the shape and spatial disposition of the composite with respect to the polarization direction of the THz waves for accurate determination of εr′. A comparison between the measured and calculated εr′ indicates that the proposed method is highly accurate with ≤ 2.68% maximum error, while the latter reaches 7.82% for the classic rule-of-mixture equations. This method is potentially useful for the design of 3DOW-GFRP with desired εr′ for applications such as electromagnetic shielding and electrostatic discharging structures.

An investigation of electromagnetic interference shielding effectiveness with multilayer thin films material

This study prepared a thin films composite material sputtered with multi-layer good conductors on the surface of lightweight condensation polymer, which can be applied to electromagnetic interference shielding materials in the range of 1–6 GHz. Sub-micrometer grade silver (Ag), nickel (Ni), titanium (Ti), and graphite films were sputtered on a nylon (PA12) substrate by physical vapor deposition. The shielding effectiveness of the multilayer thin films composite was measured in accordance with a standard procedure, and the shielding index of the multilayer thin films composite was calculated. Three different electromagnetic interference shielding structures were tested in this study and gave statistically similar results with electromagnetic interference shielding effectiveness varying from 58 dB to 35 dB. The prediction results of a composite mathematical simulator were developed, including the theoretical formula model and the comprehensive prediction results of the multiple regression model, which are conducive to the development and evaluation of related composite materials in the future.

Improving Accuracy After Stability Enforcement in the Loewner Matrix Framework

The Loewner matrix (LM) is a powerful macromodeling technique that uses sampled data in the frequency domain for representing dynamical systems in a descriptor form. As stability cannot be enforced during the construction process, a postprocessing step is required to ensure a stable macromodel, which reduces its accuracy. In this article, two techniques are incorporated and evaluated with the LM framework in this postprocessing phase. The first one is an efficient sign-pole-flipping technique for stability enforcement. The other one is a matrix updating technique applied after the stability enforcement of the model. The proposed approaches are evaluated using data in the scattering parameter form for printed circuit board via interconnects examples and an electromagnetic shielding structure and compared to the state-of-the-art stability enforcement algorithms. For completeness, we will also compare the results with respect to the macromodels created by the vector fitting algorithm. It was found that by the proposed flipping and matrix updating approaches, an error reduction by a factor between 2 and 20 was achieved with respect to the previously reported methods.

Recent advances in 3D printed structures for electromagnetic wave absorbing and shielding

In this review, the 3D printing techniques on fabricating complex structures for electromagnetic wave absorbing and/or shielding, as well as the current challenges and future prospects, are emphatically summarized.