Electromagnetic Interference Shielding Applications Research Articles

Self-Limited ultraviolet laser sintering of liquid metal particles for μm-Thick flexible electronics devices

Lightweight, deformable and highly conductive conductors are rather appealing in flexible electronics devices such as electromagnetic interference (EMI) shielding films; however, the most commonly used metallic foils or carbon nanomaterials suffer from critical limitation of either film thickness or electrical conductivity. Herein, we present a facile approach to rapidly fabricate sintered liquid metal submicron particles (LMSPs) films in combination spray-coating with direct nanosecond ultraviolet (UV) laser sintering. High conductive, μm-thick sintered LMSPs films were prepared owing to the self-limited penetration depth of UV laser, and their sheet resistances are easily tuned at least seven orders of magnitude by the laser processing parameters. A calculated parametric map upon particle diameter and laser fluence whether or not a liquid metal particle is ruptured has been obtained and it is quite well in accordance to the experiment results. Such laser-sintered LMSPs films are finally utilized to fabricate shielding films with superior EMI shielding effectiveness (SE) of ∼33 dB and specific EMI SE over thickness (SSE/t) of ∼27500 dB•cm2•g−1, and flexible electromagnetic metamaterials with a high absorption above 99.9 % at resonance frequency of 12.9 GHz and 14.3 GHz, showing their high potential for flexible EMI shielding and electromagnetic wave absorption applications.

Multifunctional electromagnetic interference shielding composite fabrics with simultaneous high-efficiency photothermal conversion and Joule heating performance

PurposeThis study aims to fabricate a multifunctional electromagnetic interference (EMI) shielding composite fabric with simultaneous high-efficiency photothermal conversion and Joule heating performances.Design/methodology/approachA multifunctional polypyrrole (PPy) hydrogel/multiwalled carbon nanotube (MWCNT)/cotton EMI shielding composite fabric (hereafter denoted as PHMC) was prepared by loading MWCNT onto tannin-treated cotton fabric, followed by in situ crosslinking-polymerization to synthesize three-dimensional (3D) conductive networked PPy hydrogel on the surface of MWCNT-coated cotton fabric.FindingsBenefiting from the unique interconnected 3D networked conductive structure of PPy hydrogel, the obtained PHMC exhibited a high EMI-shielding effectiveness vale of 48 dB (the absorbing electromagnetic wave accounted for 84%) within a large frequency range (8.2–12.4 GHz). Moreover, the temperature of the laminated fabric reached 54°C within 900 s under 15 V, and it required more than 100 s to return to room temperature (28.7°C). When the light intensity was adjusted to 150 mW/cm2, the PHMC temperature was about 38.2°C after lighting for 900 s, indicating high-efficiency electro-photothermal effect function.Originality/valueThis paper provides a novel strategy for designing a type of multifunctional EMI shielding composite fabric with great promise for wearable smart garments, EMI shielding and personal heating applications.

Electromagnetic interference shielding of thermally exfoliated graphene/polyurethane composite foams

AbstractThermally exfoliated graphene (TEG)/polyurethane (PU) expanded composite samples were synthesized for application in electromagnetic interference shielding (EMIS) in the 8–12 GHz frequency range. The effect of TEG concentration on both the shielding efficiency (SE) and mechanical characteristics of the resultant composite foam was investigated in detail, with the goal of determining the optimal TEG concentration that delivers the best performance in terms of SE and mechanical properties. The TEG filler was characterized using x‐ray diffraction (XRD), Raman spectroscopy, and scanning electron microscopy (SEM). Whereas the prepared composite foam samples were examined by Fourier Transform Infrared (FTIR), SEM, Thermogravimetric analysis (TGA) and mechanical testing. The experimental results revealed that the composite foam sample with 5 wt% TEG content exhibits the highest SE to be −25.6 dB (−430.3 dB cm3 g−1). It was also found that the optimal loading of TEG is 3 wt%, resulting in a compromise between SE (−20.4 dB; −345.68 dB cm3 g−1) and mechanical characteristics (compressive strength of 15.5 MPa and compressive modulus of 5.06 MPa). These findings highlight the potential applicability of the synthesized composite foam to a variety of EMIS applications.

Ultralight, compressible and superhydrophobic hybrid foam with highly efficient electromagnetic interference shielding in damping and high humidity environment

To expand the application range of electromagnetic interference (EMI) shielding materials, it has become an urgent issue to achieve the excellent shielding effectiveness (SE) in extreme environment. In this paper, an ultralight, compressible and superhydrophobic foam composed of melamine foam (MF), Ti 3 C 2 T x MXene and polydimethylsiloxane (PDMS) was constructed via the facile dipping and vacuum-assisted impregnation method. The MF as a skeleton can provide coated substrate for MXene sheets to realize the 3D conductive network. Meanwhile, the PDMS layer of MF/MXene/PDMS (MFMP) foam can enhance the stability and durability of its structure and capability. The obtained MFMP foam possesses the very low reduction (less than 10%) of compressive stress at a high strain of 60% after 200th compression cycles. More importantly, the MFMP foam also shows an ultrahigh absolute SE of 29088 dB cm 2 g −1 due to its excellent SE of 44.66 dB and ultralow density of 9.22 mg cm −3 . The retention rate of SE can be maintained over 85% under the different treatment of serve environment. This strategy offers a promising idea to construct the ultralight porous materials for highly efficient EMI shielding applications in damping and high humidity environment. • MFMP has superhydrophobicity. • MFMP with of 9.22 mg cm -3 possesses ultrahigh SSE/t of 29088 dB cm 2 g -1 . • MFMP exhibits shielding stability.

Lotus leaf-inspired and multifunctional Janus carbon felt@Ag composites enabled by in situ asymmetric modification for electromagnetic protection and low-voltage joule heating

Multifunctional materials with electromagnetic interference (EMI) shielding, thermal management, sensing, and comfort characteristics are greatly desirable in the application of intelligent and wearable devices. However, the multifunctional integration and low energy consumption of wearable devices remain a great challenge. Herein, inspired by the lotus leaf, a strategy of in situ asymmetric modification is proposed to construct a highly conductive and multifunctional Janus carbon felt@Ag nanoparticles (AgNPs) composite. Due to the uniform AgNPs layer together with carbon fiber, the resultant multifunctional composite demonstrates high electric conductivity with shielding effectiveness (SE) of ∼65 dB at a thickness of 270 μm. The composite also exhibits a great joule-heating property with the saturated temperature of 61.1 °C at an extremely low voltage of 1 V, as well as boosted thermal durability. More importantly, the asymmetrical feature constructed by a unique nano-micro structure endows the composite with simultaneously hydrophobic and superhydrophilic properties, which may integrate sweat removal and waterproof functions for manufacturing comfortable wearable devices. In addition, the carbon felt@AgNPs composite displays enormous potential as a sensor for human motion monitoring. Therefore, this work would provide a vital sight for fabricating advanced wearable equipment with EMI shielding, thermal management, and multifunctional applications.

Cellulose‐Based Sustainable Composites: A Review of Systems for Applications in EMI Shielding and Sensors

AbstractAdvanced functional materials that are highly efficient in shielding electromagnetic radiation and sensing applications are primarily lightweight polymeric materials. In recent years, several research works on the development of polymer‐based sensors and electromagnetic interference (EMI) shielding materials have been reported. Cellulosic materials are extensively investigated for fabricating EMI shielding gadgets and sensors. Cellulose is a naturally abundant renewable polymeric material, and the EMI shielding, and sensing performances of cellulose‐based materials depend on their conductive network architecture. Incorporating conducting nanofillers can improve the conductivity of the cellulose matrix in composites. However, a comprehensive understanding of the electrical response of nanofillers in cellulose‐based composites is necessary for the design of EMI shielding materials and sensor devices. Therefore, this work provides a critical overview of the types of processing methods used, an insight into the effects of incorporating conductive nanofillers on the architectural structure of cellulose, and the obtained shielding and sensing properties of the cellulose‐based composites. This article is expected to provide guidelines for developing sustainable polymer materials for advanced applications in the future.

Biocompatible, stretchable, and compressible cellulose/MXene hydrogel for strain sensor and electromagnetic interference shielding

ABSTRACT With the booming growth of flexible human-computer interactions and telecommunications, it is desirable to fabricate a high-sensitivity strain sensor to monitor human movement and develop an electromagnetic interference (EMI) shielding materials to protect modern microelectronics and humans from electromagnetic damage. Herein, the biocompatible, stretchable, and compressible cellulose/MXene hydrogel has been prepared to first realize the dual-functional applications in strain sensor and EMI shielding. Two-dimensional MXene nanosheets serve as conductive sensing materials and fillers to construct conductive networks. The hydrogen bond interaction between them enhances the mechanical property of hydrogel. Benefiting from the excellent electrical conductivity and good mechanical property of the cellulose/MXene hydrogel, the resultant strain sensor displays excellent tensile strain (~144.4%), high sensitivity (gauge factor ~ -6.97), adjustable detection range (0-68.7%), fast response time (~100 ms), and great stability (~1000 cycles). It can monitor human motion, including pulse beating, speech recognition, writing sensing and pressure distribution induction of 4 × 4 sensor array platform. Moreover, the cellulose/MXene hydrogel presents an absorption-predominant EMI shielding performance in the frequency of X-band. This work provides a new inspiration for the development of multifunctional hydrogel in artificial intelligence, human-computer interaction, and EMI shielding technique.

High-strength, flexible and superhydrophobic graphene/aramid nanofiber nanocomposite films for electromagnetic interference shielding application

Electromagnetic interference (EMI) shielding composite materials exhibit many amazing characteristics, including low density, excellent flexibility and corrosion resistance, compared with metals. However, it is a long-standing challenge for EMI shielding materials to overcome inferior mechanical properties and limited hydrophobic characteristics. In this work, the high-strength, flexible and superhydrophobic graphene nanosheet/aramid nanofiber (GNS/ANF) nanocomposite films with layered microstructure were prepared by the sol-gel transformation and spray coating process. The resultant film exhibits excellent mechanical properties with a high tensile strength (131.17 ± 2.77 MPa), large fracture strain (9.58 ± 0.58%), and favorable toughness (8.84 ± 0.74 MJ m−3), which are 26.2 times, 7.5 times and 221.0 times higher than those of pure GNS films. These results are attributed to synergistic effect between intensive stretching of three dimensional (3D) nanofiber network and extensive sliding of GNS produced effective energy dissipation. Moreover, the film with content of 70 wt% GNS has EMI shielding effectiveness of 31.3 dB, and its reflection coefficient is more than 0.89, revealing a reflection-dominant shielding mechanism. Meanwhile, the film possesses superhydrophobic property (158.7° ± 1.1°) and flame retardancy. The multilayered nanocomposite films have excellent potential for high-performance EMI shielding applications under some outdoor conditions.

Functional Polyaniline/MXene/Cotton Fabrics with Acid/Alkali-Responsive and Tunable Electromagnetic Interference Shielding Performances.

Although two-dimensional transition-metal carbides (MXenes) and intrinsic conductive polymers have been combined to produce functional electromagnetic interference (EMI) shielding composites, acid/alkali-responsive EMI shielding textiles have not been reported. Herein, electrically conductive polyaniline (PANI)/MXene/cotton fabrics (PMCFs) are fabricated by an efficient vacuum filtration-assisted spray-coating method for acid/alkali-responsive and tunable EMI shielding applications on the basis of the high electrical conductivity of MXene sheets and the acid/alkali doping/de-doping feature of PANI nanowires. The as-prepared PMCF exhibits a sensitive ammonia response of 19.6% at an ammonia concentration of 200 ppm. The high EMI shielding efficiency of ∼54 dB is achieved by optimizing the decorated structure of the PANI/MXene coating on the cotton fabrics. More importantly, the PMCF can act adaptively as a "switch" for EMI shielding between the efficient strong shielding of 24 dB and the inefficient weak shielding of 15 dB driven by the stimulation of hydrogen chloride and ammonia vapors. This multifunctional fabric would possess promising applications for intelligent garments, flexible electronic sensors, and smart electromagnetic wave response in special environments.

Natural Protein‐Based Biocomposites with Superior Paramagnetism and Microwave Absorbing Properties by Incorporating Nanosized Fe2O3

AbstractSoy protein is one kind of environment‐friendly nonbioactive plant protein with excellent properties. Paramagnetic γ‐Fe2O3 nanoparticles with a mean particle size of 7 nm are prepared by submerged circulative impinging stream reactor (SCISR). And a series of soy protein isolate (SPI)/Fe2O3 nanocomposites with excellent magnetic performance have been successfully prepared with glycerol as plasticizer and γ‐Fe2O3 as fillers. The results show that the strong hydrogen bonds are formed between polar amino acids of SPI and the fillers. The Fe2O3 nanoparticles exhibit homogeneous dispersion in the protein matrix. The resulting SPI/Fe2O3 nanocomposites exhibit good paramagnetism and good microwave absorbing properties at 2–18 GHz. In addition, the mechanical properties and thermal stability of soy protein materials are improved with the addition of Fe2O3 nanocomposites. The interactions between the fillers and matrix as well as between the fillers would influence the reinforcing effect of Fe2O3. These natural resources based on green functional materials would exhibit wide potential applications in electromagnetic interference shielding and packaging areas.

Ti3C2Tx MXene/carbon nanotubes/waterborne polyurethane based composite ink for electromagnetic interference shielding and sheet heater applications

Wearable and flexible electronic devices have attracted much attention in recent decades due to their novel functionalities which can be applied in diverse fields such as identification of emergency, health monitoring, safety, and protection. For these devices to work precisely, they need a protective layer to prevent electromagnetic interference (EMI) and harsh environment. Therefore, developing multifunctional materials that can shield EMI and have thermal management functions has become essential. Herein, we propose a multifunctional conductive composite ink that can be applied to fabricate EMI shielding and sheet heater applications. The composite ink, which is eco-friendly, is a mixture of carbon nanotubes (CNTs) and heat-treated Ti3C2Tx MXene in waterborne polyurethane (WPU) matrix. Using the doctor blade printing method, we fabricated composite films with large size, high electrical conductivity, and good mechanical flexibility. The composite films with a thickness from 20 to 200 µm provided a remarkable EMI shielding performance from 20 dB to 70 dB in overall X-band and Ka-band. The excellent Joule heating performance and heat dissipation of the composite films were also demonstrated through practical sheet heaters and thermal interface materials (TIM). We believe that our composite ink could be a practical approach to delivering superior EMI shielding and thermal management performance in printed wearable electronics applications.

High strength composites of carbon fiber sheets-veneers sandwich-structure for electromagnetic interference shielding materials

Due to the advantages of porous structure, anisotropy, and fiber composition, wood possesses great potential to be a high-strength electromagnetic interference (EMI) shielding material. This study used vacuum assisted resin transfer molding (VARTM) technology to fabricate EMI shielding composite material by combining carbon fiber sheets and wood veneers via infusion of epoxy resin. The shielding effectiveness of the composites against electromagnetic waves in the 8.2–12.4 GHz (X-band) can reach 40 dB. The flexural and tensile strength (i.e., 442.3 and 195.5 MPa, respectively) of the composite were 6-fold and 3-fold higher than natural poplar (i.e., 69.8 and 55.6 MPa, respectively), respectively. The composites possessed superior thermal conductivity (0.91 W m-1 K-1) compared to poplar, good water resistance and surface hydrophobicity. The addition of carbon fiber sheets not only improved the mechanical performance of samples, but also made samples possessing the ability to shielding electromagnetic waves. This work provides a novel technology to make a natural bio-based high-strength composite material for the EMI shielding applications.

Functionalised SiO2 modified icephobic nanocomposite electrospun membranes for outdoor electromagnetic shielding applications

Outdoor electronic equipment such as signal stations, radar units, and cellular base stations would benefit from electromagnetic interference (EMI) shielding systems, but ice accretion on the surface of these facilities often causes critical challenges, especially in cold regions and winter season. In this study, icephobic nanocomposite electrospun membranes were developed via a two-step process from recycled polyethylene terephthalate (r-PET), which exhibited high electromagnetic shielding efficiency with superhydrophobic and icephobic performance. The surface superhydrophobicity and icephobicity of the membrane were achieved after surface modification using fluorinated silane functionalised SiO2 nanoparticles (FSFS). Superhydrophobicity with less than 5° of contact angle hysteresis was observed on the nanocomposite electrospun membranes, and the ice adhesion strength was approximately 50 kPa after the FSFS modification, which was ∼6 times lower than aluminium reference. Furthermore, with the addition of 20 wt% magnetite nanopowders, the r-PET nanocomposite electrospun membranes demonstrated a high magnetic response, around 4.22 emu/g, in the range of −10 and + 10 kOe, and a high electromagnetic shielding efficiency between 11 and 22 dB in the frequency range of 400 MHz to 6 GHz. The icephobic r-PET electrospun membranes incorporated with magnetite are promising candidate materials for outdoor EMI shielding applications.

Magnetite/graphene oxide/Prussian blue composite with robust effectiveness for electromagnetic interference shielding

Considering the promising efficiency of composites, in the current study, a graphene oxide (GO)-magnetite-Prussian blue (PB) composite material was prepared. The composite exhibited electrical conductivity, magnetic permeability, and permittivity nature, and was evaluated using electromagnetic interference (EMI) shielding studies. GO was developed by the Hummer's method, ferrite (Fe 3 O 4 ) was incorporated by the sol-gel method, and PB was introduced in the mixture by an in-situ process. The fabricated samples were studied by X-ray diffraction, Raman Spectroscopy, Fourier-transform infrared spectroscopy along with EMI shielding efficiency (SE) evaluation. The SE of −71.66 dB of reflection losses was measured at a frequency of 1.5 MHz. The GO/Fe 3 O 4 /PB composite provided the best results for the detection in the 1–18 MHz frequency range because of its excellent electric and magnetic properties. The obtained results demonstrated that the GO/Fe 3 O 4 /PB composite has promising potential applications in EMI shielding.

Near-Instantaneously Self-Healing Coating toward Stable and Durable Electromagnetic Interference Shielding

HighlightsStable and durable electromagnetic interference (EMI) shielding performance was achieved in harsh environments by applying a thin protective coating of hydrophobic 1H,1H,2H,2H-perfluorooctyltriethoxysilane (POTS) on polypyrrole (PPy)-modified fabrics.The damaged POTS layer can be instantaneously self-healed (~ 4 s) for the first time by the microwave heating effect of PPy.The self-healing process is repeatable even after severe damages, highlighting the great potential to exploit EMI shielding materials’ instant microwave heating effects to enable robust and durable EMI shielding applications.

Recent Advances in MXene/Polyaniline-Based Composites for Electrochemical Devices and Electromagnetic Interference Shielding Applications.

Due to serious global warming and environmental issues, the demand for clean and sustainable energy storage devices is significantly increased. Often accompanied by rapid growth of portable electronic vehicles and devices, massive electromagnetic wave pollution becomes unavoidable. To mitigate the above two issues, this mini-review summaries preparation methods and recent developments of MXene/polyaniline-based composites for their applications in electrochemical devices and electromagnetic interference shielding. Based on excellent synergistic effects between single compounds and designed hierarchical structures, MXene/polyaniline-based composites usually exhibit enhanced physical and chemical properties, showing great potentials in sustainable electrochemical properties and electromagnetic wave protections for human health as well as normal operation of precise electronic devices.

Multifunctional carbon fiber@NiCo/polyimide films with outstanding electromagnetic interference shielding performance

The electromagnetic interference (EMI) shielding materials with low reflection characteristics are highly desirable for integrated communication and microelectronics systems to shield EM waves and their secondary pollution. In this study, the EMI shielding materials with outstanding absorption performance were fabricated via the two-step pyrolysis and followed by vacuum assisted filtration approach. The chopped carbon fibers (CFs) wrapped with NiCo2O4 nanowire arrays (CF@NiCo2O4) were prepared by the hydrothermal reaction initially. After annealing, the NiCo2O4 nanowires transformed into NiCo alloy nanoparticles and evenly embedded in the CFs, endowing the CF@NiCo composites with efficient magnetic loss and dielectric loss capacity. After vacuum filtration and encapsulation with polyimide, the obtained flexible CF@NiCo/polyimide composite film displays superior EMI shielding effectiveness of 87 dB with a thickness of only 1.08 mm. Particularly, the composite film exhibits extremely low SER characteristics of ~6 dB, which surpasses those of most previously reported composites materials with similar thickness. In addition, the composite films present outstanding flexibility, mechanical properties and Joule heating performances. Therefore, the prepared flexible composite films have broad prospect for EMI shielding and thermal management applications in advanced microelectronic systems.

Carbon nanotubes chemical bonding with cotton/spandex blended fabric via thiol-epoxy click chemistry for durable electromagnetic interference shielding

Despite flexible and wearable electromagnetic interference (EMI) shielding fabrics have aroused accelerated attention in recent years, problem such as detachment caused by traditional physical bonding methods still remains a huge challenge. Click chemistry, as a type of chemical reaction that generate substances by joining small units together with heteroatom links, is an emerging surface modification technology. Herein, thiol-epoxy click chemistry is utilized to connect thiol-modified carbon nanotubes (CNTs) and cotton/spandex blended fabric (CSF). The resultant fabric exhibits good hydrophobicity with water contact angle of 121.4° in conjunction with a high X-band shielding effectiveness (SE) of 27.30 dB with coating thickness of only ~140 μm. More importantly, benefiting from the constructed strong chemical bond with CNTs coating and fiber, the obtained fabric shows high resistance to bending test, strong acid/alkali solutions (pH = 2.0/12.0), liquid nitrogen and so on. Our work demonstrates that the EMI shielding fabrics with excellent corrosion resistance and stability prepared by thiol-epoxy click chemistry potentially suitable for long-term EMI shielding applications even in extreme environments.

Free-standing laser-induced graphene films for high-performance electromagnetic interference shielding

Although laser-induced graphene (LIG) has great advantages in the cost and manufacturing process, it has been seldom reported in the field of electromagnetic interference (EMI) shielding due to its unobtrusive conductivity and the limitation of inherent substrates. In this work, polybenzoxazine is chosen as precursor to fabricate the LIG via a one-step defocused lasing process. As a result of favorable porous structures and high conductivity, the as-produced LIG exhibits the EMI shielding effectiveness up to 24.8 dB in X-band at the thickness of 68 μm. And the EMI shielding effectiveness of LIG/Fe3O4 composite is increased to 32.7 dB at a smaller thickness of 53 μm which is obtained by a solvent-free approach. When considering the thickness and lightweight properties, the absolute shielding effectiveness is also surpassing most of the other carbon-based shielding materials. More importantly, taking advantage of the difference in the thermal expansion coefficient of carbon material and polymeric substrate, we develop a rapid quench-peeling (RQP) strategy for the separation of LIG from polymeric substrate to obtain the free-standing LIG film. Moreover, the structures and properties of LIG are well preserved. The free-standing LIG films after peeling have wider adaptability in practical EMI shielding applications, and also opened up possibilities for use in other fields, such as Joule heating device.

Hierarchically porous wood-derived carbon scaffold embedded phase change materials for integrated thermal energy management, electromagnetic interference shielding and multifunctional application

The increasing growth of powerful and sophisticated electronic devices have an urgent need for excellent heat dissipation and electromagnetic interference shielding materials. However, few studies are focusing on one material with these properties. In this work, a novel hierarchically porous wood-derived carbon scaffold embedded phase change material was prepared via facile pyrolysis and vacuum infiltration process. Notably, the raw wood was pretreated by a delignification strategy, which makes great contributions to forming a hierarchically porous network and expanding the internal area after pyrolyzing. The results demonstrate that the honeycomb-like structure of the wood carbon scaffold was well maintained after calcination, which can provide a great number of channels for energy transmission and multi-reflection of electromagnetic waves. Moreover, the paraffin wax component as phase change material not only stores and releases numerous energies during the melting and solidification processes, but also endows the composite outstanding self-cleaning function. The present composite shows excellent energy storage property (the latent heat of 122.25 J/g) and satisfied electromagnetic interference shielding performance (average shielding effectiveness of 24.4 dB). Therefore, the synthesized porous wood carbon scaffold/paraffin wax composite has great potential in multifunctional, environmentally friendly thermal energy management and electromagnetic interference shielding applications.