Tunable Electromagnetic Interference Research Articles

Electrochemically-Switched Microwave Response of MXene in Organic Electrolyte.

The increasingly complex electromagnetic (EM) environment necessitates advanced electrically controllable electromagnetic interference (EMI) shielding materials that can adapt to varying EM conditions. This study develops a flexible electrochemically tunable EMI shielding device based on ultrathin Ti3C2Tx MXene films, exhibiting reversible shielding effectiveness (SE) modulation from 18.9 to 26.2dB in X band at 0.1 and -1.5V. Unlike the previously reported mechanism relying on interlayer spacing adjustments, the work leverages transformations of charging state and surface chemistry for tunability during the electrochemical process. The Ti3C2Tx flake size is also evidenced to play a crucial role, with smaller flakes offering higher absorption modulation despite lower SE modulation, enabling the device with high designability. When integrated with Salisbury screen structure, the device achieves adjustable absorption from 93.560% at 0.1V to 99.996% at -1V, showing a tunable reflection suppression ratio up to 32dB with an effective bandwidth of 4.2GHz. Additionally, incorporating resonant cavity structure enables absorption-dominated (over 90%) microwave-responsive switching at 0.1 and -1.5V. This work highlights significant potential of adaptive EMI shielding materials for applications in smart electronic protection, EM switch, and radar camouflage.

Polypyrrole-decorated carbonized cotton fabric derived from air atmosphere for tunable electromagnetic interference shielding performance and high fire safety

Polypyrrole-decorated carbonized cotton fabric derived from air atmosphere for tunable electromagnetic interference shielding performance and high fire safety

Direct Ink Writing of Low-Concentration MXene/Aramid Nanofiber Inks for Tunable Electromagnetic Shielding and Infrared Anticounterfeiting Applications.

MXene inks offer a promising avenue for the scalable production and customization of printing electronics. However, simultaneously achieving a low solid content and printability of MXene inks, as well as mechanical flexibility and environmental stability of printed objects, remains a challenge. In this study, we overcame these challenges by employing high-viscosity aramid nanofibers (ANFs) to optimize the rheology of low-concentration MXene inks. The abundant entangled networks and hydrogen bonds formed between MXene and ANF significantly increase the viscosity and yield stress up to 103 Pa·s and 200 Pa, respectively. This optimization allows the use of MXene/ANF (MA) inks at low concentrations in direct ink writing and other high-viscosity processing techniques. The printable MXene/ANF inks with a high conductivity of 883.5 S/cm were used to print shields with customized structures, achieving a tunable electromagnetic interference shielding effectiveness (EMI SE) in the 0.2-48.2 dB range. Furthermore, the MA inks exhibited adjustable infrared (IR) emissivity by changing the ANF ratio combined with printing design, demonstrating the application for infrared anticounterfeiting. Notably, the printed MXene/ANF objects possess outstanding mechanical flexibility and environmental stability, which are attributed to the reinforcement and protection of ANF. Therefore, these findings have significant practical implications as versatile MXene/ANF inks can be used for customizable, scalable, and cost-effective production of flexible printed electronics.

High-Precision Printing of Flexible MXene Patterns for Dynamically Tunable Electromagnetic Interference Shielding Performance.

Smart electromagnetic interference (EMI) shielding materials are of great significance in coping with the dynamic performance demands of cutting-edge electronic devices. However, smart EMI shielding materials are still in their infancy and face a variety of challenges (e.g., large thickness, limited tunable range, poor reversibility, and unclear mechanisms). Here, we report a method for controllable shielding electromagnetic (EM) waves through subwavelength structure changes regulated by the customized structure via a direct printing route. The highly conductive MXene ink is regulated with metal ions (Al3+ ions), giving superb metallic conductivity (∼5000 S cm-1) for the printed lines without an annealing treatment. The reversible tunability of EMI shielding effectiveness (SE) ranging from 8.2 dB ("off" state) to 34 dB ("on" state) is realized through the controllable modulation of subwavelength structure driven by stress. This work provides a feasible strategy to develop intelligent shielding materials and EM devices.

Sandwich-Like Flexible Breathable Strain Sensor with Tunable Thermal Regulation Capability for Human Motion Monitoring.

High-performance flexible strain sensors with synergistic and outstanding thermal regulation function are poised to make a significant impact on next-generation multifunctional sensors. However, it has long been intractable to optimize the sensing performance and high thermal conductivity simultaneously. Herein, a novel flexible sandwich-like strain sensor with advanced thermal regulation capability was prepared by assembling electrospun thermoplastic polyurethane (TPU) fibrous membrane, MXene layer, and TPU/boron nitride nanosheet (BNNS) composite films. The as-prepared sensor demonstrates a wide strain working range (∼100% strain), an ultrahigh gauge factor (2080.9), and a satisfactory reliability. Meanwhile, benefiting from the uniform dispersion and promising orientation of BNNSs in TPU composites, the sensor possesses a high thermal conductivity of 1.5 W·m-1·K-1, guaranteeing wearer comfort. Additionally, the unique structure endows the sensor with high stretchability, breathability, biocompatibility, and tunable electromagnetic interference shielding performances. Furthermore, an integrated wireless motion monitoring device based on this sensor is rationally designed. It exhibits a fast response time, a wide recognition range, and the ability to maintain skin temperature during prolonged physical activity. These encouraging findings provide a new and feasible approach to designing high-performance and versatile flexible strain sensors with broad applications in advanced wearable technology.

Multifunctional heterostructured composite foam with tunable electromagnetic interference shielding

Multifunctional composite materials with adjustable electromagnetic interference (EMI) shielding properties hold significant promise in the emerging field of combating electromagnetic radiation pollution. Herein, we construct a heterostructured composite foam with tunable EMI shielding performance by adjusting the thickness and spatial distribution of Ag conductive network in the porous sponge, coupled with the incorporation of CNTs/WPU aerogel. The remarkable conductivity of 3D Ag network within the composite foam enables it possesses excellent shielding performance at X-band (47.1 dB), fast sensing response time (∼0.2 s), and high temperature of 101.8 °C through efficient joule heating even at a low voltage of 3 V. Importantly, controllable tuning of EMI shielding effectiveness (from 25.0 to 40.1 dB), are successfully achieved by changing the position of the Ag layer or compression strain of the composite foam. These achievements underscore the substantial potential of this material for creating electromagnetic shielding solutions with adaptable characteristics.

Highly tunable rGO composites for EMI shielding inks: A tailored approach to modulate broadband EMI shielding

In this study, we demonstrate the ability to design tunable electromagnetic interference (EMI) shielding by controlling the dominant shielding mechanism, whether it is absorption or reflection, using graphene-based nanocomposites. We synthesized four different composites and their corresponding acrylic- based inks to investigate the impact of additives on the EMI shielding mechanism. We conducted measurements on both liquid and printable structures, and the results were highly promising. The coatings exhibited a maximum shielding efficiency of over 200 dB/mm. To achieve targeted shielding for specific frequency bands (here 10 GHz), we tested metastructures printed with the synthesized inks for their shielding effectiveness. Remarkably, these structures, when screen printed on flexible and transparent polyvinyl chloride substrate, achieved over 90% microwave attenuation. Overall, this research highlights the potential of printable EMI shielding solutions, enabled by graphene-based nanocomposites, to effectively address microwave interference issues in a wide range of electronic devices and defence applications.

A Smart Amorphous Wire Composite with Tunable Electromagnetic Shielding

Nowadays, in view of the increasingly serious problems of electromagnetic interference (EMI) and radiation pollution, smart EMI shielding materials with tunable shielding effectiveness (SE), especially “On/Off” switchable capability, are highly desirable. Herein, Co‐based amorphous wires (AWs) with excellent soft magnetic and mechanical properties are regularly arranged on a 3D‐printed mold as tunable EMI shielding composites. The EMI SE can be easily tuned in the range of ≈0.6–24.7 dB by way of rotation, which has been confirmed to be an effective way to achieve free tuning of EMI SE by simulation. In addition, by compositing AWs with reduced graphene oxide and constructing a double‐layer structure with a gap of 1/4 wavelength in the X‐band, a much wider SE tuning range of ≈1.0–57.7 dB is further realized. The representative “On/Off” switchable shielding capability that can switch between EM transmission and effective shielding, together with the wide SE tuning range larger than 50 dB, shows the great potential of Co‐based AW composites in smart EMI shielding applications.

Construction of designable and high-temperature resistant composite foams for tunable electromagnetic shielding

Conductive polymer composite (CPC) foams have been extensively studied for electromagnetic interference (EMI) shielding due to their lower density and relatively low EM reflectivity. However, most CPC foams are difficult to structurally design to regulate performance, and also limited in high-temperature application scenarios owing to the low-temperature resistance of the matrix themselves. Herein, high-performance expanded polyetherimide (EPEI) foam beads were fabricated by subcritical foaming technology with organic solvents/CO2 as co-blowing agents, and designable EPEI/CNS (carbon nanostructures) composite foams with segregated networks and high-temperature resistance were then manufactured through CNS dip-coating and epoxy bonding. The resultant EPEI/CNS composite foams showed the shielding effectiveness (SE) of ∼11.9–39.5 dB with CNS loading of only ∼0.25–0.72 vol%, along with R coefficient of only ∼0.26–0.56. The construction of asymmetric gradient structure in the foams via orderly assembling can further reduce the EM reflection in comparison with uniform structure, thereby remitting the secondary EM pollution. Moreover, the EPEI/CNS composite foams can not only maintain the structural integrity after being treated at ∼200 °C, but also maintain relatively stable EMI SE and most of their mechanical properties, enabling their applications in high-temperature environments. This work provides a simple and effective method for constructing high-temperature resistant CPC foams for tunable EMI shielding.

Multi-layer carbon fiber paper @reduced graphene oxide/Co/C composite with adjustable electromagnetic interference shielding properties

Paper-based composite materials exhibit a marked tendency towards thinner and lighter profiles in the context of electromagnetic interference (EMI) shielding. Carbon fiber paper (CFP) has excellent electrical conductivity and Lightweight base characteristics. However, its single electrical loss characteristic and uncontrollable EMI shielding performance are limited in application. Therefore, we prepared CFP@ graphene oxide (GO)/ZIF-67 composites by chemical bonding and in-situ polymerization, and then prepared CFP@rGO/Co/C composites with integrated structure and function by heat treatment. Layer-by-layer assembly technology was employed to develop composite materials with tunable EMI shielding performance. The composite material has excellent high conductivity (2475.86 S/m) and excellent EMI shielding performance (average X-band EMI efficiency (SE)38.46 dB, absolute shielding effectiveness (SSE/t) = 14388.56 dB cm2 g−1). Through the layer-by-layer assembly technology, the EMI SE performance of the 7-layer assembled material reached 85.83 dB, and the EMI SSE/t reached 32110.51 dB cm2 g−1. Through simulation verification, the EMI shielding performance of the materials is compared, and ideas for EMI material design are provided. In addition, the material also has excellent Joule heating performance, fast electrothermal response and good temperature controllability. The material exhibits remarkable resilience against harsh environmental conditions, including strong acids, bases, organic reagents, ultrasonic waves, combustive processes, and extremely low temperatures. Despite these severe treatments, its performance remains above 90 % intact. This study proposes a magnetic-dielectric synergistic, performance-adjustable CFP-based shielding material, which has great application potential in the future wearable, defense, and aerospace fields.

Liquid-Templating Aerogels.

Modern materials science has witnessed the era of advanced fabrication methods to engineer functionality from the nano- to macroscales. Versatile fabrication and additive manufacturing methods are developed, but the ability to design a material for a given application is still limited. Here,a novel strategy that enables target-oriented manufacturing of ultra-lightweight aerogels with on-demand characteristics is introduced. The process relies on controllable liquid templating through interfacial complexation to generate tunable, stimuli-responsive 3D-structured (multiphase) filamentous liquid templates. The methodology involves nanoscale chemistry and microscale assembly of nanoparticles (NPs) at liquid-liquid interfaces to produce hierarchical macroscopic aerogels featuring multiscale porosity, ultralow density (3.05-3.41mg cm-3 ), and high compressibility (90%) combined with elastic resilience and instant shape recovery. The challenges are overcome facing ultra-lightweight aerogels, including poor mechanical integrity and the inability to form predefined 3D constructs with on-demand functionality, for a multitude of applications. The controllable nature of the coined methodology enables tunable electromagnetic interference shielding with high specific shielding effectiveness (39 893dB cm2 g-1 ), and one of the highest-ever reported oil-absorption capacities (487 times the initial weight of aerogel for chloroform), to be obtained. These properties originate from the engineerable nature of liquid templating, pushing the boundaries of lightweight materials to systematic function design and applications.

Anisotropic Shape Memory Composite for Dynamically Adjustable Electromagnetic Interference Shielding

Smart electromagnetic interference (EMI) shielding materials that enable dynamical adjustment of electromagnetic wave transmission are highly desirable for various applications. Nevertheless, ordinary materials show nonadjustable EMI shielding performance after deployment. Herein, an anisotropic smart EMI shielding composite is presented, which shows tunable EMI shielding effectiveness by rotation, shape memory, and simple stacking. The composite possesses a sandwich structure consisting of two graphene fibrous films (GFFs) with intermediate shape memory poly(ethylene-co-vinyl acetate) (EVA). Owing to the aligned graphene fibers of GFF, the GFF/EVA composite showed anisotropic mechanical property, shape memory property, and shielding effectiveness. The composite shows high tensile strength but declined shape memory property in the axial direction (0°) of the graphene fibers. In the 0° direction of the GFF/EVA composite, a total shielding effectiveness (SET) of >40.8 dB in the X-band is observed, which is much higher than that in the 90° direction (vertical, <8.1 dB). The rotation-modulated EMI shielding of GFF/EVA is achieved by the anisotropy-dependent EMI shielding performance. Moreover, tunable EMI shielding is demonstrated through the shape memory process of the composite and the average SET can be adjusted in the range from 43.2 to 33.1 dB by fixing a tensile strain from 0 to 100%. Furthermore, the EMI shielding of the multilayered composite can be modulated by stacking individual GFF/EVA composites at different angles. The smart GFF/EVA composite with tunable and function-switchable features is demonstrated, which will contribute to the development of smart EMI shielding materials and devices for electromagnetic applications in various fields.

Multifunctional shape memory foam composites integrated with tunable electromagnetic interference shielding and sensing

Porous polymer-based conductive composites are highly regarded for their accomplishments of being applied in the field of electromagnetic interference (EMI) shielding, but fabrication of high-performance porous EMI shielding materials with the ability to realize self-fixable shielding effectiveness (SE) adjustment is still challenging. Herein, ethylene–vinyl acetate copolymer (EVA)@polypyrrole (PPy)@Ag (EPA) foam composites are fabricated by modifying EVA foams with PPy and Ag nanoparticles (AgNPs) in succession. In this system, EVA foam serves as shape memory frameworks to endow this composite with shape memory effect (SME), and PPy is employed to reinforce the interaction between the Ag layers and the EVA foam. Profiting from the reinforced conductive network, the EPA foam composites exhibit electro-thermal performance with a heating temperature of 81.1 °C at a voltage of 1 V and EMI shielding performance with a SE of 107.45 dB within the X-band. Importantly, depending on the SME, the SE of the EPA foams can be easily tuned by controlling and fixing the compressive strain. Moreover, the EPA foams can also serve as sensors for monitoring different actions. By virtue of the above merits, the EPA foams are promising to serve as multifunctional electronics, involving smart EM protection devices and wearable sensors.

Flame-retardant aramid fabric with durable, self-cleaning, hydrophobic, and tunable electromagnetic interference shielding properties

Flame-retardant aramid fabric with durable, self-cleaning, hydrophobic, and tunable electromagnetic interference shielding properties

Scalable production of bioinspired MXene/black phosphorene nanocoatings for hydrophobic and fire-safe textiles with tunable electromagnetic interference and exceeding thermal management

Multifunctional fire-safe textiles are urgently needed to meet the application requirements under harsh environments, e.g., high-frequency environments. However, it is rather tough to realize scalable production of multifunctional fire-safe textiles by constructing coatings. To tackle the hurdles above, multifunctional fire-safe cotton fabric was prepared though a blade-coating strategy (using black phosphorus and Ti3C2Tx nano-dispersion ink), followed by hydrophobic treatment with poly (dimethylsiloxane) coating. The resultant textiles with the coating of micra-like structure exhibit excellent water resistance with a water contact angle of up to 93° and excellent heat response within 10 s to the original temperature. Furthermore, the as-designed textiles demonstrate high flame retardancy and superior shielding effectiveness (SE) of 58 dB, which is much better than the reported treated fabric. The final treated fabric with high electromagnetic interference shielding effectiveness is suitable for most commercial applications. This work provides a promising strategy to produce functional textiles with superior electromagnetic interference and exceeding thermal management at a large scale, showing potential applications in electronic, electrical, and military fields.

Highly conductive calcium ion-reinforced MXene/sodium alginate aerogel meshes by direct ink writing for electromagnetic interference shielding and Joule heating

• The MXene/sodium alginate ink is suitable for direct writing customized structures. • The Ca 2+ ion enhances mechanical and electrical properties of the aerogel meshes. • A wide range of tunable EMI shielding efficiencies from 45 to 100 dB is achieved. • The printed meshes present excellent Joule heating performance and stability. Although MXene sheets possess high electrical conductivity and rich surface chemistry and are well suitable for fabricating electrically conductive nanocomposites for electromagnetic interference (EMI) shielding applications, it remains challenging for MXene nanocomposites to achieve tunable EMI shielding performances and customized geometries. Herein, an aqueous MXene/sodium alginate ink is developed to print aerogel meshes with customized geometries using a direct ink writing approach. An ion-enhanced strategy is proposed to reinforce the printed aerogel meshes by multi-level cross-linking. The resultant 3D-printed aerogel mesh exhibits an ultrahigh electrical conductivity of 2.85 × 10 3 S m −1 , outstanding mechanical properties, and excellent structural stability in wet environment. More importantly, a wide range of tunable EMI shielding efficiencies from 45 to 100 dB is achieved by the structural design of the 3D printed ion-enhanced MXene/sodium alginate aerogel meshes. As a Joule heater, in addition, the printed aerogel meshes can achieve a wide temperature range of 40-135°C at low driving voltages. This work demonstrates a direct ink writing approach for the fabrication of ion-enhanced MXene/sodium alginate aerogel meshes with tunable EMI shielding properties and multi-functionalities for applications in various scenarios.

Electrochemically modulated interaction of MXenes with microwaves.

Dynamic control of electromagnetic wave jamming is a notable technological challenge for protecting electronic devices working at gigahertz frequencies. Foam materials can adjust the reflection and absorption of microwaves, enabling a tunable electromagnetic interference shielding capability, but their thickness of several millimetres hinders their application in integrated electronics. Here we show a method for modulating the reflection and absorption of incident electromagnetic waves using various submicrometre-thick MXene thin films. The reversible tunability of electromagnetic interference shielding effectiveness is realized by electrochemically driven ion intercalation and de-intercalation; this results in charge transfer efficiency with different electrolytes, accompanied by expansion and shrinkage of the MXene layer spacing. We finally demonstrate an irreversible electromagnetic interference shielding alertor through electrochemical oxidation of MXene films. In contrast with static electromagnetic interference shielding, our method offers opportunities to achieve active modulation that can adapt to demanding environments.

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.

Top-down construction strategy toward sustainable cellulose composite paper with tunable electromagnetic interference shielding

Cellulose-based electromagnetic interference (EMI) shielding composites have aroused enormous attention due to their advantages of environmental protection, low cost, and abundant resources. However, it is still a great challenge to develop a method with low energy consumption, scalability, and short synthesis time to prepare cellulose-based shielding materials. Herein, a cellulose/polyaniline (PANI) composite paper directly from wood was synthesized via a facile top-down strategy. By adjusting the concentration of aniline and the polymerization time, the prepared composite paper exhibits the shielding effectiveness (SE) of 21.4 dB, which can block 99% of incident electromagnetic waves. What's more, the composite paper inherits the anisotropic feature of pristine wood, presenting an excellent mechanical performance with a tensile strength of about 54 MPa in the longitudinal direction. In short, this work provides a feasible strategy to prepare the green, scalable, and low-cost cellulose/PANI composite paper, which may be promising in the field of EMI shielding.

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.