Flexible Electromagnetic Interference Shielding Research Articles

Ti3C2Tx MXene/polyimide composites film with excellent mechanical properties and electromagnetic interference shielding properties

With the development of electronic products to miniaturization and high frequency, high-performance flexible electromagnetic interference (EMI) shielding materials are urgently needed to deal with electromagnetic pollution. Two-dimensional transition metal carbide/polyimide (Ti3C2Tx MXene/PI) films were synthesized by in situ polymerization and a simple scratch method in this paper. The Ti3C2Tx MXene nanosheets give the films good EMI shielding effectiveness (SE) and electrical conductivity. Specifically, the film with a thickness of 0.11 mm (Ti3C2Tx content of 30 wt%) exhibits an EMI SE of 34.73 dB and a specific EMI SE (SE/thickness) of 315.73 dB/mm in the frequency range of 8.2–12.4 GHz (X-band). In addition, the films have a tensile strength of 67.58 MPa, and a high decomposition temperature of 510 ℃ in N2 atmosphere. Therefore, we believe that the prepared Ti3C2Tx/PI films with good comprehensive performance have enormous potential in the field of lightweight and flexible EMI shielding materials.

Carbon nanotube films embedded with Cu@C nanocubes for electromagnetic interference shielding

AbstractFlexible carbon tube films for electromagnetic interference (EMI) shielding are assembled by mixing the well‐aligned Cu@C core‐shell nanocubes with multi‐walled carbon nanotubes (MWCNTs). The Cu@C core‐shell nanocubes are achieved by the thermal pyrolysis of polyvinylpyrrolidone (PVP) coating on Cu2O nanocubes. With the optimal PVP concentration of 1.5 mg/mL, the Cu@C/MWCNTs composite film with ultra‐thin thickness (52.2 μm) displays good conductivity of 12.5 S cm−1 and excellent specific EMI shielding value of 510.73 dB mm−1, which is higher than the pure MWCNTs film (439.50 dB mm−1) under the same weight condition. Moreover, the 1.5 mg/mL‐Cu@C/MWCNTs composite film exhibits highly mechanical repeatability after being bended for 10,000 cycles. The carbon layers protecting metal nanoparticles can partly replace precious carbon nanotubes to construction highly flexible composite film with anticipated electrical conductivity, which have a good application prospect for thin, lightweight and flexible EMI shielding fields.

Flexible Multilayered Poly(vinylidene fluoride)/Graphene-Poly(vinylidene fluoride) Films for Efficient Electromagnetic Shielding

Developing flexible electromagnetic interference shielding (EMI SE) materials is an effective strategy to protect humans from being harmed by electromagnetic radiation from electronic devices. Though the EMI SE property of such materials as graphene can exceed 100 dB, it remains a challenge to achieve high-efficiency EMI SE performance while having excellent flexibility to allow them to be wearable. Herein, we designed theoretically and fabricated experimentally the flexible multilayer structure of the poly(vinylidene fluoride)/graphene-poly(vinylidene fluoride) (PVDF/GNP-PVDF) composite films. The experimental results show that the film thickness and layer number play an important role in determining the EMI SE performance, and the multilayer film with a thickness of 0.3 mm and a layer number of 6 exhibits not only high EMI SE performance (69.7 dB on average in X-band) but also excellent flexibility and stability (98.85% EMI SE retention after bending of 60° for 1000 cycles). The theoretical study via COMSOL software matching well with the experimental data reveals that multiple reflection and absorption of electromagnetic waves between layers is responsible for the high EMI SE performance of the PVDF/GNP-PVDF multilayer film at a relatively low thickness that ensures flexibility. This work highlights the significance of designing the multilayer architecture via theoretical simulation for improving the EMI SE performance and also demonstrates the high EMI SE application prospect of PVDF/GNP-PVDF films in wearable electronic devices.

Fabrication of Ni-Encapsulated Carbon Tube/Poly(dimethylsiloxane) Composite Materials for Lightweight and Flexible Electromagnetic Interference Shielding Material.

The exploration of flexible and lightweight electromagnetic interference (EMI) shielding materials with excellent shielding effectiveness, as a means to effectively alleviate electromagnetic pollution, is still a tremendous challenge. This paper proposes a conducting material named the textured Ni-encapsulated carbon tube, which can be applied in EMI shielding material by being inserted in the center of a poly(dimethysiloxane) (PDMS) polymer. We demonstrated that Pd2+ could be absorbed by the active groups on the plant fiber surface to catalyze the reduction of Ni2+ as a catalytic center by means of a textured Ni-encapsulated plant fiber. Owing to the outstanding heat-conducting capability of the Ni coating, the inner plant fiber was carbonized and attached to the Ni-tube inside the surface during annealing. To be precise, the textured Ni-encapsulated C tube was fabricated successfully after annealing at 300 °C. On further increasing the annealing temperature, the C tube disappeared gradually with the Ni coating being oxidized to NiO. Of note, the C tube acted as a support layer for the external Ni coating, providing sufficient mechanical strength. When combined with the coating PDMS layer, a flexible and lightweight EMI shielding material is fabricated successfully. It displays an outstanding EMI shielding effectiveness of 31.34 dB and a higher specific shielding efficiency of 27.5 dB·cm3/g, especially showing excellent mechanical property and flexibility with only 2 mm thickness. This study provides a new method to fabricate outstanding EMI shielding materials.

Transparent and flexible electromagnetic interference shielding film based on Ag nanowires/ionic liquids/thermoplastic polyurethane ternary composites

Flexible and transparent electromagnetic interference (EMI) shielding films are desired in various fields. Herein, we propose a simple but effective approach to fabricate the flexible, transparent, and high EMI shielding films based on Ag nanowires (AgNWs)/ionic liquids (ILs)/thermoplastic polyurethane (TPU) ternary composites. Attributed to the formation of the low-density but highly interconnected AgNW network as well as the synergistic effect of AgNWs and ILs on composite conductivity, the as-prepared AgNWs/ILs/TPU film has a transmittance of 67% and an EMI shielding effectiveness of ∼26.8 dB at 10 GHz. Because of the low areal density of AgNWs, the absolute shielding effectiveness (SSE/t) of AgNWs/ILs/TPU film even reaches to 1.32 × 106 dB cm2 g−1 at 10 GHz, which is superior to most reported works. More interestingly, the as-prepared film also exhibits good durability and stability in the EMI shielding properties even after 1000 uninterrupted bending cycles or long-term soaking in acidic or alkali solution. These outstanding performances endow the as-prepared film with great potential in flexible and transparent EMI shielding scenarios.

A double crosslinking MXene/cellulose nanofiber layered film for improving mechanical properties and stable electromagnetic interference shielding performance

With the discovery of the two-dimensional (2D) MXene, it shows a great application potential in the field of electromagnetic interference (EMI) shielding, but the mechanical brittleness and easy oxidation of MXene limit its wide application. For this reason, a double crosslinking strategy is provided to solve the above problems in a nacre-like “brick-mortar” layered MXene/cellulose nanofiber (MXene/CNF) film. Typically, the film was firstly suffered by dopamine modification, then was further reinforced by secondary Ca2+ bridging, so as to obtain excellent mechanical properties and antioxidative EMI shielding performance. Comparing with the single crosslinking, the double crosslinking strategy reveals a higher efficiency in improving the mechanical property. The mechanical strength and toughness of the double crosslinking MXene/CNF film can increase to 142.2 MPa and 9.48 MJ/m3, respectively. More importantly, while achieving good mechanical properties, the MXene composite film still holds a very stable EMI shielding performance of more than 44.6 dB when suffering from the oxidation treatment of high-temperature annealing, showing excellent anti-oxidation ability and environment tolerance. Therefore, this work provides a universal but effective double crosslinking strategy to solve the mechanical brittleness and easy oxidation of MXene-based composites, thus showing a huge potential in flexible EMI shielding applications.

Elastomer Encapsulated Silver Nanorod Dispersed Polyacrylamide-Alginate Hydrogel for Water-Pressure-Dependent EMI Shielding Application

Smart electromagnetic interference (EMI) shielding materials with tunable EMI shielding effectiveness (SE) have garnered huge attention in the fabrication of next generation EM devices as well as innovative wearable electronics. Here, we report a polydimethylsiloxane (PDMS) encapsulated soft, flexible, and stretchable polyacrylamide (PAM)-alginate (Alg)-hydrogel/silver nanorod (AgNR) composite system for EMI SE application. The PDMS encapsulation not only enhances the tensile strength of the system from ∼0.057 MPa to ∼0.724 MPa but also restricts the evaporation of water from the hydrogel matrix. Consequently, at 14.5 GHz frequency, the EMI SE (∼48.72 dB) of the hydrogel was reduced to ∼10.52 dB (72 h at 30 °C) and ∼6.44 dB (72 h at 40 °C) and ∼8.03 dB after 1 week of settlement at ambient conditions. However, for the encapsulated hydrogel, the EMI SE (∼40.65 dB) value was marginally reduced to ∼33.86 dB, ∼31.45 dB, and ∼32.42 dB, respectively, under the same conditions. Moreover, by changing the sample thickness (increasing holding pressure in a VNA sample holder), the shielding performance can be altered from ∼48.72 to ∼53.63 dB for the hydrogel and from ∼40.65 to ∼44.03 dB for the encapsulated hydrogel. Thus, these findings provide an innovative strategy to fabricate a flexible and stretchable EMI shielding material with adjustable SE by varying the content of water and applying pressure for futuristic development in smart electronics.

Double layered design for electromagnetic interference shielding with ultra-low reflection features: PDMS including carbon fibre on top and graphene on bottom

Electromagnetic interference (EMI) shielding materials with low reflection features have become necessary for a new generation of electronic devices to reduce secondary electromagnetic pollution. Here, a novel strategy is adopted to provide flexible polydimethylsiloxane (PDMS) composite films with ultra-low reflection EMI shielding performance by constructing a double-layer structure with uniformly dispersed carbon fibres (CFs) in the upper layer as an impedance-matching absorption layer and continuous graphene fibres (GFs) located at the bottom layer as a conductive reflection layer. The resulting specific structure significantly reduces the reflectivity of the composite film at extremely low carbon conductive fillers (0.01 wt% CFs and 1.00 wt% GFs) through the process of “absorption-reflection-reabsorption” when incident electromagnetic waves (EMWs) pass through the composite film: the total shielding effectiveness (SETotal) achieves 34.4 dB at 18.0 GHz, while the shielding effectiveness of reflection (SER) is only 0.1 dB, and reflection coefficient (R) is as low as 0.018. This phenomenon indicates that 1.8% of the incident EMWs are reflected in the propagation process when 99.96% are attenuated. In addition, the shielding mechanism of the double-layer EMI shielding composite films with low reflection features is studied in depth. This study provides a reliable idea for designing flexible EMI shielding materials with ultra-low reflection to alleviate secondary electromagnetic radiation pollution.

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.

Lightweight and textured Ni@Cu-encapsulated carbon tube with outstanding electromagnetic interference shielding performance

The low-reflection electromagnetic interference (EMI) shielding material is highly desirable, which would facilitate the reduction of the EM-wave secondary pollution, but classic conflict between performance and density makes it very challenging in practical application. Herein, a textured Ni@Cu-encapsulated carbon tube was designed and fabricated as a conducting material inserted into the middle of polydimethylsiloxane (PDMS) polymer and its application in flexible, light-weight and low-reflection EMI shielding material. Results showed that the active groups on the plant fiber surface could absorb Pd2+, acting as catalytic center, which can catalyze electroless nickel plating (EP Ni) on its surface by means of textured Ni-encapsulated plant fiber. The inside plant fiber was carbonized and attached to Ni-tube inside surface after annealing, owning to the outstanding heat-conducting capability of Ni coating. To be precise, textured Ni encapsulated C tube was fabricated successfully after annealing at 300 °C. Interestingly, the surface Ni tube could catalyze the EP Cu on its surface by means of textured Ni@Cu-encapsulated carbon tube structure, endowing the composites with efficient dielectric loss and magnetic loss capacity. Combined with PDMS coating, a flexible, light-weight and low-reflection EMI shielding material is fabricated successfully. More importantly, it displays outstanding EMI shielding effectiveness of 35.4 dB, lower reflection one of 0.9 dB, higher specific one of 28.7 dB cm3/g, superior flexibility and mechanical properties with a thickness of only 2 mm. This work open a new window for fabricating EMI shielding materials with outstanding EMI shielding performance.

Directional Migration and Distribution of Magnetic Microparticles in Polypropylene-Matrix Magnetic Composites Molded by an Injection Molding Assisted by External Magnetic Field.

Surface-functionalized polymer composites with spherical particles as fillers offer great qualities and have been widely employed in applications of sensors, pharmaceutical industries, anti-icing, and flexible electromagnetic interference shielding. The directional migration and dispersion theory of magnetic microparticles in polypropylene (PP)-matrix magnetic composites must be studied to better acquire the functional surface with remarkable features. In this work, a novel simulation model based on multi-physical field coupling was suggested to analyze the directed migration and distribution of magnetic ferroferric oxide (Fe3O4) particles in injection molding assisted by an external magnetic field using COMSOL Multiphysics® software. To accurately introduce rheological phenomena of polymer melt into the simulation model, the Carreau model was used. Particle size, magnetic field intensity, melt viscosity, and other parameters impacting particle directional motion were discussed in depth. The directional distribution of particles in the simulation model was properly assessed and confirmed by experiment results. This model provides theoretical support for the control, optimization, and investigation of the injection-molding process control of surface-functionalized polymer composites.

Carbon black incorporated carbon nanofiber based polydimethylsiloxane composite for electromagnetic interference shielding

High-performance electromagnetic interference (EMI) shielding materials that are very elastic and flexible, hydrophobic, and of low density are desperately needed to address the rising electromagnetic pollution problem. This study describes the preparation and characterization of an elastic EMI shielding material which is hydrophobic and of low density. Carbon nanofibers (CNFs) incorporated with carbon black super P ([email protected]NFs) based polydimethylsiloxane (PDMS) composites were fabricated using a combination of electrospinning followed by heat treatment and manual lay-up process. The high electrical conductivity of 2.5 S cm−1 imparted excellent EMI shielding property to [email protected] With a thickness of 0.06 mm and a density of 0.63 g cm−3, [email protected] exhibited high EMI shielding effectiveness (EMI SE) over a wide frequency range (8.2-26.5 GHz). The highest and average values of EMI SE in the range were 55.8 and 50.7 dB respectively. Composites of [email protected] with PDMS also showed similar behaviour. The [email protected] with 9 wt% and 16.6 wt% loading of CBSP exhibited 24,837 and 14741 dB cm2 g−1 of absolute EMI SE (SSEt), respectively, which is remarkably higher than the most reported EMI shielding materials. These results suggest that [email protected] based PDMS composites would be promising for applications as thin, flexible, stretchable, and light EMI shielding materials.

Investigation of flexible warp-knitted metal meshes for electromagnetic interference shielding

This paper develops four novel warp-knitted structures with two bars of the one-in one-out threading mode and describes the investigation of electromagnetic interference (EMI) shielding metal meshes composed of contiguous ultra-fine metal wires fabricated using warp-knitting technology. The mechanical properties, electrical conductivity, and microwave shielding effectiveness (SE) of the flexible meshes are assessed in terms of the mesh structure, mesh material, and warp run-in parameter. The results reveal that the metal mesh has a flexible and stable mechanical property, good electrical conductivity, and optimal EMI performance when the mesh structure is open lap atlas. The gold-coated molybdenum mesh exhibits the lowest electrical resistivity (5.18 × 10−5 ohm/sq) and optimal average EMI SE (–21.04 dB), making it a candidate for EMI shields for intelligent wearable electronic devices. The warp run-in can adjust the EMI SE, and the optimum average EMI SE (–25.52 dB) can be obtained when the warp run-in is set at the 2580 rack. Moreover, the warp-knitted metal meshes show desirable EMI shielding efficiency persisting at >70% even at large strain deformations and under cyclic bending and twisting deformations. Conductive warp-knitted meshes with a millimeter period and micron-scale wire diameter exhibit an adequately large scale, satisfactory mechanical stability, excellent flexibility, permanent conductivity, and strong microwave reflection, simultaneously. Moreover, the EMI SE of warp-knitted metal mesh reaches the protection level (–20 dB) prescribed by standard electronic devices. Therefore, the warp-knitted metal meshes show great potential in flexible and wearable EMI shielding devices.

A self-healing and flexible Ag@carbon fiber/polyurethane composite based on disulfide bonds and application in electromagnetic interference shielding

With the wide application of electronic equipment, the demand for the efficient performance of electromagnetic interference (EMI) shielding materials has become increasingly urgent to meet different requirements and electromagnetic environments. In this study, a flexible composite with both self-healing and reliable EMI shielding functions was facilely developed. Firstly, we synthesize Ag@Carbon fiber (CF) by electroless plating method, and we can see that the silver layer wrapped CF completely by scanning electron microscope (SEM). Then we synthesize polyurethane (PU) with disulfide, and mix Ag@CF with PU mechanically to prepare Ag@CF/PU composite. Ag@CF/PU achieved satisfactory mechanical properties, EMI shielding performance and self-healing performance. When the filler content was 3 wt%, the tensile strength of composite was 1.63 MPa, the highest EMI shielding effectiveness (SE) was 10.3 dB at X-band, and self-healing efficiency of tensile strength was 96%. With the increase of filler content, the tensile strength and EMI SE of composite improved, and self-healing efficiency decrease. When the filler content was 20 wt%, the tensile strength was 7.95 MPa, the highest EMI SE was 26 dB and self-healing efficiency of tensile strength was 28%. This work demonstrated a self-healing flexible EMI shielding composite material that ensured reliability.

Facile fabrication of MXene/cellulose fiber composite film with homogeneous and aligned structure via wet co-milling for enhancing electromagnetic interference shielding performance

MXene/cellulose nanofiber (MXene/CNF) composites have demonstrated promising performance in various areas. Here, we propose a one-pot wet co-milling strategy to produce homogeneous delaminated-MXene nanosheets/micro-fibrillated cellulose fibers slurry from multilayer-MXene particles/raw cellulose fibrils mixture on a large scale. The vacuum-filtrated MXene/CNF composite films can be fabricated from the well-dispersed slurry with a homogeneous and aligned structure which is convincingly demonstrated through laser scanning confocal microscopy (LSCM) and small-angle X-ray scattering (SAXS). Owning to the well-refined structure, the mechanical properties, conductivity, and electromagnetic interference (EMI) shielding performance of MXene/CNF composite films exhibit significant enhancement with 13882.8%, 3725.5%, and 63.5%, respectively. More importantly, the excellent EMI shielding performance of MXene/CNF composite films reaches up to 36.51 dB at a thickness of 20 μm. This wet co-milling strategy demonstrates potential in the facile manufacture of high-performance MXene-based composite materials for flexible EMI shielding materials.

Self‐Assembled Woven Ag‐Nanowire 3D Network Film for Ultrathin, Transparent, and Flexible Surface Electromagnetic Interference Shielding

AbstractA kind of pollution known as electromagnetic interference (EMI), which results from ubiquitous usage of various electronic communication and military radar equipment, has received increasing attention recently. However, it is still a big challenge to obtain good EMI shielding in transparent and/or curved surfaces. In this paper, a light, ultrathin, transparent, and flexible EMI shielding film based on woven silver nanowire (Ag‐NW) 3D networks is successfully prepared via a room‐temperature template production method. For transparent application scenario, Ag‐NWs with 91% transmittance in visible range show ≈27 dB shielding efficiency. This sample shows ≈27 dB shielding efficiency, although with a low density of Ag‐NWs (≈0.0168 mg cm−2), which implies that this material has a cost‐effectiveness. Moreover, total shielding as high as ≈40 dB is obtained by using thickened Ag‐NW grids. The EMI has not changed remarkedly after bended 1200 times, which indicates the as‐prepared flexible film has a relative stability of the EMI performance. Considering the facile production technology, this material can be readily applied in transparent EMI shielding.

Hierarchically structured elastomer for absorption-dominated electromagnetic interference shielding in an ultra-wide band

Flexible electromagnetic interference (EMI) shielding materials with low secondary electromagnetic radiation are urgently required for next-generation precise electronic devices and wearable electronics. However, realizing ultra-low microwave reflectivity and sustaining strong absorption feature in a wide frequency range remains a great challenge. Here, natural rubber-based flexible hierarchical composites were fabricated by combination of honeycomb-like 3D networks with selectively distributed ferro/ferric oxide modified graphene (F@rLG) magnetic particles and densely interconnected conductive networks (RL) with fulfilled multiwall carbon nanotubes (MWCNTs) via latex compounding together with co-vulcanization method. The resulting hierarchical bilayer elastomer has the EMI shielding coefficient of 34.4 dB at RL thickness of 0.18 mm, and achieves minimum electromagnetic wave reflection coefficient of 0.1. Moreover, in almost entire Ku band, over 80% incident electromagnetic waves can be absorbed, indicating its excellent capability in minimizing the secondary electromagnetic pollution. And this double-layered flexible material exhibits excellent stability in EMI shielding performance after the deformation cycles of 500 times. In addition, both the influence of precisely manipulated distribution of nanoparticles on the EMI property and the absorption-dominated approach via coupled layers were investigated in depth. This work paves a way for designing flexible EMI shielding materials with low secondary electromagnetic contamination.

Transparent and Flexible Electromagnetic Interference Shielding Film Using ITO Nanobranches by Internal Scattering.

A transparent and flexible film capable of shielding electromagnetic waves over a wide range of frequencies (X and Ku bands, 8-18 GHz) is prepared. The electromagnetic wave shielding film is fabricated using the excellent transmittance, electrical conductivity, and thermal stability of indium tin oxide (ITO), a representative transparent conductive oxide. The inherent mechanical brittleness of oxide ceramics is overcome by adopting a nanobranched structure. In addition, mechanical stability is maintained even after repeated bending experiments (200 000 times). The produced transparent and flexible shielding film is applied to practical GHz devices (Wi-Fi and LTE devices), and signal sensitivity is confirmed to decrease. Therefore, it can be widely applied to various transparent and flexible electronic devices.

Flexible transparent electromagnetic interference shielding films with silver mesh fabricated using electric-field-driven microscale 3D printing

In order to address the challenging issue regarding the high-efficiency and low-cost fabrication of high-performance flexible transparent electromagnetic interference (EMI) shielding films, a novel approach is proposed to produce flexible transparent EMI shielding film with silver mesh based on electric-field-driven (EFD) microscale 3D printing. The manufacturing principle and the reasonable process parameters are revealed with a series of experiments. Following this fabricating scheme and self-developed EFD micro-scale 3D printer, three flexible transparent EMI shielding films having a size of 60 mm × 60 mm and a line width of 26 μm are achieved utilizing the low-temperature nano silver paste (75% silver content and 350 dPa·s (25 °C) dynamic viscosity). The experimental result shows that the adhesive force between the sintered silver mesh and the polyethylene terephthalate (PET) substrate is measured to be 5B with 3 M scotch tape. The bending experiment proves the excellent mechanical flexibility of the flexible transparent EMI shielding film. In different chemical environments and ultrasonic vibration environments, the silver mesh flexible transparent EMI shielding film can still maintain good electrical properties. When the pitch of the silver mesh is 500 μm, the optical transmittance is 90.5% and the EMI shielding efficiency for the common medium-high frequency electromagnetic wave is greater than 26 dB. When the pitch is 300 μm, the optical transmittance is 84% and the shielding efficiency is higher than 32 dB. When the pitch is 150 μm, the optical transmittance is 69% and the shielding efficiency is higher than 34 dB. As a result, the proposed method provides a promising solution for mass producing high-performance silver mesh flexible transparent EMI shielding films at low cost and high throughput.

Metallic fusion of nanocrystal thin films for flexible and high-performance electromagnetic interference shielding materials

Low-cost flexible electromagnetic interference (EMI) shielding materials are attracting considerable attention because of the rapid development of wearable smart electronics, such as wearable health monitoring systems, and flexible energy storage and harvesting systems. In the present study, we developed ultrathin, flexible, and high-performance EMI shielding materials using Ag nanocrystals (NCs) through low-cost, room-temperature wet chemical processes conducted at atmospheric pressure. Sequential ligand-exchange and reduction processes not only substantially reduced the distance between the Ag NCs but also induced intensive metallic fusion of the Ag NCs, resulting in large-scale three-dimensional interconnected conductive pathways. The fused Ag NC thin films exhibited high electrical conductivity (∼24,000 S/cm for a film ∼800 nm thick) and outstanding mechanical stability, offering stable EMI shielding performance over 1000 cycles of various mechanical deformations, including twisting, crumpling, and folding. In addition, compared with most previously reported solution-based materials, our Ag NC thin films demonstrated an excellent EMI shielding effectiveness value of ∼60 dB in the X-band range 8.2–12.2 GHz at much thinner thickness (∼1.3 μm). With the advantages of easy processing, good mechanical flexibility, and high-performance EMI shielding, the fused NC thin films developed in the present work represent innovative potential EMI shielding materials for next-generation wearable smart electronics.