Biomimetic Porous MXene Sediment-Based Hydrogel for High-Performance and Multifunctional Electromagnetic Interference Shielding

Recent Advances of Stretchable Nanomaterial-Based Hydrogels for Wearable Sensors and Electrophysiological Signals Monitoring

Electrophysiological monitoring is a commonly used medical procedure designed to capture the electrical signals generated by the body and promptly identify any abnormal health conditions. Wearable sensors are of great significance in signal acquisition for electrophysiological monitoring. Traditional electrophysiological monitoring devices are often bulky and have many complex accessories and thus, are only suitable for limited application scenarios. Hydrogels optimized based on nanomaterials are lightweight with excellent stretchable and electrical properties, solving the problem of high-quality signal acquisition for wearable sensors. Therefore, the development of hydrogels based on nanomaterials brings tremendous potential for wearable physiological signal monitoring sensors. This review first introduces the latest advancement of hydrogels made from different nanomaterials, such as nanocarbon materials, nanometal materials, and two-dimensional transition metal compounds, in physiological signal monitoring sensors. Second, the versatile properties of these stretchable composite hydrogel sensors are reviewed. Then, their applications in various electrophysiological signal monitoring, such as electrocardiogram monitoring, electromyographic signal analysis, and electroencephalogram monitoring, are discussed. Finally, the current application status and future development prospects of nanomaterial-optimized hydrogels in wearable physiological signal monitoring sensors are summarized. We hope this review will inspire future development of wearable electrophysiological signal monitoring sensors using nanomaterial-based hydrogels.

Smart sensing hydrogel actuators conferred by MXene gradient arrangement

Smart sensing and excellent actuation abilities of natural organisms have driven scientists to develop bionic soft-bodied robots. However, most conventional robots suffer from poor electrical conductivity, limiting their application in real-time sensing and actuation. Here, we report a novel strategy to enhance the electrical conductivity of hydrogels that integrated actuation and strain-sensing functions for bioinspired self-sensing soft actuators. Conductive hydrogels were synthesized in situ by copolymerizing MXene nanosheets with thermosensitive N-isopropylacrylamide and acrylamide under a direct current electric field. The resulting hydrogels exhibited high electrical conductivity (2.11 mS/cm), good sensitivity with a gauge factor of 4.79 and long-term stability. The developed hydrogels demonstrated remarkable capabilities in detecting human motions at subtle strains such as facial expressions and large strains such as knee bending. Additionally, the hydrogel electrode patch was capable of monitoring physiological signals. Furthermore, the developed hydrogel showed good thermally induced actuation effects when the temperature was higher than 30 °C. Overall, this work provided new insights for the design of sensory materials with integrated self-sensing and actuation capabilities, which would pave the way for the development of high-performance conductive soft materials for intelligent soft robots and automated machinery.

Flexible Conformally Bioadhesive MXene Hydrogel Electronics for Machine Learning-Facilitated Human-Interactive Sensing

Wearable epidermic electronics assembled from conductive hydrogels are attracting various research attention for their seamless integration with human body for conformally real-time health monitoring, clinical diagnostics and medical treatment, and human-interactive sensing. Nevertheless, it remains a tremendous challenge to simultaneously achieve conformally bioadhesive epidermic electronics with remarkable self-adhesiveness, reliable ultraviolet (UV) protection ability, and admirable sensing performance for high-fidelity epidermal electrophysiological signals monitoring, along with timely photothermal therapeutic performances after medical diagnostic sensing, as well as efficient antibacterial activity and reliable hemostatic effect for potential medical therapy. Herein, a conformally bioadhesive hydrogel-based epidermic sensor, featuring superior self-adhesiveness and excellent UV-protection performance, is developed by dexterously assembling conducting MXene nanosheets network with biological hydrogel polymer network for conformally stably attaching onto human skin for high-quality recording of various epidermal electrophysiological signals with high signal-to-noise ratios (SNR) and low interfacial impedance for intelligent medical diagnosis and smart human-machine interface. Moreover, a smart sign language gesture recognition platform based on collected electromyogram (EMG) signals is designed for hassle-free communication with hearing-impaired people with the help of advanced machine learning algorithms. Meanwhile, the bioadhesive MXene hydrogel possesses reliable antibacterial capability, excellent biocompatibility, and effective hemostasis properties for promising bacterial-infected wound bleeding.

Lightweight, breathable and self-cleaning polypyrrole-modified multifunctional cotton fabric for flexible electromagnetic interference shielding

The thriving of wearable electronics and the emerging new requirements for electromagnetic interference (EMI) shielding have driven the innovation of EMI shielding materials towards lightweight, wearability and multifunctionality. Herein, the hierarchical polypyrrole nanotubes (PNTs)/PDMS structures are rationally constructed on the textile for obtaining multifunctional and flexible EMI shielding textiles by in-situ polymerization and surface coating. The modified cotton fabric possesses a conductivity of about 2715.8 S/m and an SET of 28.2 dB in the X band when the thickness is only 0.5 mm. After ultrasonic treatment, cyclic bending and washing, the conductivity and EMI shielding performance remain stable and exhibit long-term durability. Importantly, the textile's inherent lightweight, breathable and soft properties have been completely retained after modification. This work shows application potentiality in the field of EMI pollution protection and affords a novel path for the construction of multifunctionally wearable and durable EMI shielding materials.

Unlocking Ultrahigh Initial Coulombic Efficiency of MXene Anode via Presodiation and Electrolyte Optimization

The low initial Coulombic efficiency (ICE) greatly hinders the practical application of MXenes in sodium-ion batteries. Herein, theoretical calculations confirm that -F and -OH terminations as well as the tetramethylammonium ion (TMA+) intercalator in sediment Ti3C2Tx (s-Ti3C2Tx) MXene possess strong interaction with Na+, which impedes Na+ desorption during the charging process and results in low ICE. Consequently, Na+-intercalated sediment Ti3C2Tx (Na-s-Ti3C2Tx) is constructed through Na2S·9H2O treatment of s-Ti3C2Tx. Specifically, Na+ can first exchange with TMA+ of s-Ti3C2Tx and then combine with -F and -OH terminations, thus leading to the elimination of TMA+ and preshielding of -F and -OH. As expected, the resulting Na-s-Ti3C2Tx anode delivers considerably boosted ICE values of around 71% in carbonate-based electrolytes relative to s-Ti3C2Tx. Furthermore, electrolyte optimization is employed to improve ICE, and the results demonstrate that an ultrahigh ICE value of 94.0% is obtained for Na-s-Ti3C2Tx in the NaPF6-diglyme electrolyte. More importantly, Na-s-Ti3C2Tx exhibits a lower Na+ migration barrier and higher electronic conductivity compared with s-Ti3C2Tx based on theoretical calculations. In addition, the cyclic stability and rate performance of the Na-s-Ti3C2Tx anode in various electrolytes are comprehensively explored. The presented simple strategy in boosting ICE significantly enhances the commercialization prospect of MXenes in advanced batteries.

A Breathable Fibrous Membrane with Coaxially Heterogeneous Conductive Networks toward Personal Thermal Management and Electromagnetic Interference Shielding

The expeditious growth of wearable electronic devices has boomed the development of versatile smart textiles for personal health-related applications. In practice, integrated high-performance systems still face challenges of compromised breathability, high cost, and complicated manufacturing processes. Herein, a breathable fibrous membrane with dual-driven heating and electromagnetic interference (EMI) shielding performance is developed through a facile process of electrospinning followed by targeted conformal deposition. The approach constructs a robust hierarchically coaxial heterostructure consisting of elastic polymers as supportive "core" and dual-conductive components of polypyrrole and copper sulfide (CuS) nanosheets as continuous "sheath" at the fiber level. The CuS nanosheets with metal-like electrical conductivity demonstrate the promising potential to substitute the expensive conductive nano-materials with a complex fabricating process. The as-prepared fibrous membrane exhibits high electrical conductivity (70.38 S cm-1), exceptional active heating effects, including solar heating (saturation temperature of 69.7 °C at 1 sun) and Joule heating (75.2 °C at 2.9 V), and impressive EMI shielding performance (50.11 dB in the X-band), coupled with favorable air permeability (161.4 mm s-1 at 200 Pa) and efficient water vapor transmittance (118.9 g m-2 h). This work opens up a new avenue to fabricate versatile wearable devices for personal thermal management and health protection.

Lightweight Dual-Functional Segregated Nanocomposite Foams for Integrated Infrared Stealth and Absorption-Dominant Electromagnetic Interference Shielding

Lightweight infrared stealth and absorption-dominant electromagnetic interference (EMI) shielding materials are highly desirable in areas of aerospace, weapons, military and wearable electronics. Herein, lightweight and high-efficiency dual-functional segregated nanocomposite foams with microcellular structures are developed for integrated infrared stealth and absorption-dominant EMI shielding via the efficient and scalable supercritical CO2 (SC-CO2) foaming combined with hydrogen bonding assembly and compression molding strategy. The obtained lightweight segregated nanocomposite foams exhibit superior infrared stealth performances benefitting from the synergistic effect of highly effective thermal insulation and low infrared emissivity, and outstanding absorption-dominant EMI shielding performances attributed to the synchronous construction of microcellular structures and segregated structures. Particularly, the segregated nanocomposite foams present a large radiation temperature reduction of 70.2 °C at the object temperature of 100 °C, and a significantly improved EM wave absorptivity/reflectivity (A/R) ratio of 2.15 at an ultralow Ti3C2Tx content of 1.7 vol%. Moreover, the segregated nanocomposite foams exhibit outstanding working reliability and stability upon dynamic compression cycles. The results demonstrate that the lightweight and high-efficiency dual-functional segregated nanocomposite foams have excellent potentials for infrared stealth and absorption-dominant EMI shielding applications in aerospace, weapons, military and wearable electronics.

Supergravity-Steered Generic Manufacturing of Nanosheets-Embedded Nanocomposite Hydrogel with Highly Oriented, Heterogeneous Architecture

Designing nanocomposite hydrogels with oriented nanosheets has emerged as a promising toolkit to achieve preferential performances that go beyond their disordered counterparts. Although current fabrication strategies via electric/magnetic force fields have made remarkable achievements, they necessitate special properties of nanosheets and suffer from an inferior orientation degree of nanosheets. Herein, a facile and universal approach is discovered to elaborate MXene-based nanocomposite hydrogels with highly oriented, heterogeneous architecture by virtue of supergravity to replace conventional force fields. The key to such architecture is to leverage bidirectional, force-tunable attributes of supergravity containing coupled orthogonal shear and centrifugal force field for steering high-efficient movement, pre-orientation, and stacking of MXene nanosheets in the bottom. Such a synergetic effect allows for yielding heterogeneous nanocomposite hydrogels with a high-orientation MXene-rich layer (orientation degree, f = 0.83) and a polymer-rich layer. The authors demonstrate that MXene-based nanocomposite hydrogels leverage their high-orientation, heterogeneous architecture to deliver an extraordinary electromagnetic interference shielding effectiveness of 55.2 dB at 12.4 GHz yet using a super-low MXene of 0.3 wt%, surpassing most hydrogels-based electromagnetic shielding materials. This versatile supergravity-steered strategy can be further extended to arbitrary nanosheets including MoS2, GO, and C3N4, offering a paradigm in the development of oriented nanocomposites.

MOF Derivatives with Gradient Structure Anchored on Carbon Foam for High-Performance Electromagnetic Wave Absorption

The impedance matching and high loss capabilities of composites with homogeneous distribution are limited owing to high addition and lack of structural design. Developing composites with heterogeneous distribution can achieve strong and wide electromagnetic (EM) wave absorption. However, challenges such as complex design and unclear absorption mechanisms still exist. Herein, a novel composite with a heterogeneous distribution gradient is successfully constructed via MOF derivatives Co@ nitrogen-doped carbon (Co@NC) anchored on carbon foam (CF) matrix (MDCF). Notably, the concentration of MOF can easily control the gradient structure. In particular, the morphologies of MOF derivatives on the surface of CF undergo a transition from the collapse of the inner layer to the integrity of the outer layer, accompanied by a continuous reduction in the size of Co nanoparticles. Correspondingly, enhanced interface polarization from the core-shell of Co@NC and good impedance matching of MDCF can be obtained. The optimized MDCF exhibits the minimum reflection loss of -68.18 dB at 2.01 mm and effective absorption bandwidth covering the entire X-band. Moreover, MDCF exhibits lightweight characteristics, excellent compressive strength, and low radar cross-section reduction. This work highlights the immense potential of composites with heterogeneous distribution for achieving high-performance EM wave absorption.

Structural Design for EMI Shielding: From Underlying Mechanisms to Common Pitfalls

Modern human civilization deeply relies on the rapid advancement of cutting-edge electronic systems that have revolutionized communication, education, aviation, and entertainment. However, the electromagnetic interference (EMI) generated by digital systems poses a significant threat to the society, potentially leading to a future crisis. While numerous efforts are made to develop nanotechnological shielding systems to mitigate the detrimental effects of EMI, there is limited focus on creating absorption-dominant shielding solutions. Achieving absorption-dominant EMI shields requires careful structural design engineering, starting from the smallest components and considering the most effective electromagnetic wave attenuating factors. This review offers a comprehensive overview of shielding structures, emphasizing the critical elements of absorption-dominant shielding design, shielding mechanisms, limitations of both traditional and nanotechnological EMI shields, and common misconceptions about the foundational principles of EMI shielding science. This systematic review serves as a scientific guide for designing shielding structures that prioritize absorption, highlighting an often-overlooked aspect of shielding science.

Reversible Constrained Dissociation and Reassembly of MXene Films

Enabling materials to undergo reversible dynamic transformations akin to the behaviors of living organisms represents a critical challenge in the field of material assembly. The pursuit of such capabilities using conventional materials has largely been met with limited success. Herein, the discovery of reversible constrained dissociation and reconfiguration in MXene films, offering an effective solution to overcome this obstacle is reported. Specifically, MXene films permit rapid intercalation of water molecules between their distinctive layers, resulting in a significant expansion and exhibiting confined dissociation within constrained spaces. Meanwhile, the process of capillary compression driven by water evaporation reinstates the dissociated MXene film to its original compact state. Further, the adhesive properties emerging from the confined disassociation of MXene films can spontaneously induce fusion between separate films. Utilizing this attribute, complex structures of MXene films can be effortlessly foamed and interlayer porosity precisely controlled, using only water as the inducer. Additionally, a parallel phenomenon has been identified in graphene oxide films. This work not only provides fresh insights into the microscopic mechanisms of 2D materials such as MXene but also paves a transformative path for their macroscopic assembly applications in the future.

Porifera-Inspired Lightweight, Thin, Wrinkle-Resistance, and Multifunctional MXene Foam

Transition metal carbides/nitrides (MXenes) demonstrate a massive potential in constructing lightweight, multifunctional wearable electromagnetic interference (EMI) shields for application in various fields. Nevertheless, it remains challenging to develop a facile, scalable approach to prepare the MXene-based macrostructures characterized by low density, low thickness, high mechanical flexibility, and high EMI SE at the same time. Herein, the ultrathin MXene/reduced graphene oxide (rGO)/Ag foams with a porifera-inspired hierarchically porous microstructure are prepared by combining Zn2+ diffusion induction and hard template methods. The hierarchical porosity, which includes a mesoporous skeleton and a microporous MXene network within the skeleton, not only exerts a regulatory effect on stress distribution during compression, making the foams rubber-like resistant to wrinkling but also provides more channels for multiple reflections of electromagnetic waves. Due to the interaction between Ag nanosheets, MXene/rGO, and porous structure, it is possible to produce an outstanding EMI shielding performance with the specific surface shielding effectiveness reaching 109152.4 dB cm2 g-1. Furthermore, the foams exhibit multifunctionalities, such as transverse Joule heating, longitudinal heat insulation, self-cleaning, fire resistance, and motion detection. These discoveries open up a novel pathway for the development of lightweight MXene-based materials with considerable application potential in wearable electromagnetic anti-interference devices.

Tailoring Interfaces of All-Carbon Electromagnetic Interference Shielding Materials for Boosting Comprehensive Performance

Electromagnetic interference (EMI) shielding materials with lightweight, high shielding effectiveness, excellent chemical stability, especially minimized secondary electromagnetic pollution, are urgently desired for integrated electronic systems operating in harsh working environments. Here in this study, by systematically engineering and matching the interfacial properties of carbon-based membrane materials, i.e., graphite paper, whisker carbon nanotube paper (WCNT paper), carbon nanotube film (CNT film), bucky paper (BP), and carbon cloth (CC) with three-dimensional (3D) porous carbon nanotube sponge (CNTS), we successfully constructed a series of multifunctional all-carbon EMI shielding materials, which exhibit excellent average shielding effectiveness of over 90 dB with a thickness of about 1 mm and dramatically minimized secondary electromagnetic reflection. Moreover, benefiting from the all-carbon nature and engineered interfaces, our CMC materials also exhibit excellent photothermal and Joule heating performances. These results not only provide guidance for designing advanced multifunctional all-carbon EMI shielding materials but also shed light on the hidden mechanism between interfaces and performances of composite materials.

Succulent-Inspired Implicit Structural Change for Smart "ON/OFF" Switchable and Flexible EMI Shielding Coating

Modern miniaturized intelligent electronics call for smart switchable and flexible electromagnetic interference (EMI) shielding material for highly precise applications. However, most switchable EMI shielding materials are based on an explicit structural change. Herein, we report a succulent-inspired smart switchable MXene (WR-MXene) coating film realized by inner implicit structural change, which benefits from the insertion of our reversible large-cavity yolk-shell biomicrospheres. The novel switchable yolk-shell biomicrospheres contain a soft N-isopropylacrylamide (PNIPAM) hydrogel core, an "ON/OFF" switchable cavity (over 30% volume fraction), and a porous polydopamine (p-PDA) shell. The yolk-shell biomicrospheres can be obtained by a facile two-step polymerization and a simple drying-dehydration treatment. Because of the "ON/OFF" switchable void space brought by the smart biomicrospheres and conductive framework of MXene, an optimized ultralight and flexible WR-MXene coating film (vWR-coating film) showed both large switchable change (over 60 dB) and extraordinary EMI shielding effectiveness, reaching 95 and over 50 dB in the whole X band (8.2-12.4 GHz). These novel reversible yolk-shell biomicrospheres and the succulent-inspired switchable coating films are promising for smart flexible wearable devices and many advanced multifunctional systems needing dynamic real-time response.

Enhancing the Interaction of Carbon Nanotubes by Metal-Organic Decomposition with Improved Mechanical Strength and Ultra-Broadband EMI Shielding Performance

The remarkable properties of carbon nanotubes (CNTs) have led to promising applications in the field of electromagnetic interference (EMI) shielding. However, for macroscopic CNT assemblies, such as CNT film, achieving high electrical and mechanical properties remains challenging, which heavily depends on the tube-tube interactions of CNTs. Herein, we develop a novel strategy based on metal-organic decomposition (MOD) to fabricate a flexible silver-carbon nanotube (Ag-CNT) film. The Ag particles are introduced in situ into the CNT film through annealing of MOD, leading to enhanced tube-tube interactions. As a result, the electrical conductivity of Ag-CNT film is up to 6.82 × 105 S m-1, and the EMI shielding effectiveness of Ag-CNT film with a thickness of ~ 7.8 μm exceeds 66 dB in the ultra-broad frequency range (3-40 GHz). The tensile strength and Young's modulus of Ag-CNT film increase from 30.09 ± 3.14 to 76.06 ± 6.20 MPa (~ 253%) and from 1.12 ± 0.33 to 8.90 ± 0.97 GPa (~ 795%), respectively. Moreover, the Ag-CNT film exhibits excellent near-field shielding performance, which can effectively block wireless transmission. This innovative approach provides an effective route to further apply macroscopic CNT assemblies to future portable and wearable electronic devices.

Controllable proton-reservoir ordered gel towards reversible switching and reliable electromagnetic interference shielding

Smart and dynamic electromagnetic interference (EMI) shielding materials possess a remarkable capacity to modify their EMI shielding abilities, rendering them invaluable in various civil and military applications. However, the present response mechanism of switch-type EMI shielding materials is slightly restricted, as it primarily depends on continuous pressure induction, thereby resulting in concerns regarding their durability and reliability. Herein, for the first time, we demonstrate a novel method for achieving solvent-responsive, reversible switching, and robust EMI shielding capabilities using a controlled proton-reservoir ordered gel. The gel contains polyaniline (PANI) and sodium alginate (SA). Initially, SA acts as a proton reservoir for PANI in an aqueous system, enhancing the doping level of PANI and improving its electrical conductivity. Additionally, PANI and SA chains respond to diverse polar solvents, such as water, acetonitrile, ethanol, n-hexane, and air, inducing distinct conformations that affect the degree of PANI conjugation and electron migration along the chains. This process is reversible and non-destructive to the polymer chain, ensuring the effective and uncompromised performance of the EMI shielding switch. We can achieve precise and reversible tuning (on/off) of EMI shielding with different effectiveness levels by manipulating the solvents within the framework. This work opens a new solvent-stimuli avenue for the development of EMI shielding materials with reliable and intelligent on/off switching capabilities.

A rapid and specific antimicrobial resistance detection of Escherichia coli via magnetic nanoclusters

Drinking water contamination, often caused by bacteria, leads to substantial numbers of diarrhea deaths each year, especially in developing regions. Human urine as a source of fertilizer, when handled improperly, can contaminate drinking water. One dominant bacterial pathogen in urine is Escherichia coli, which can trigger serious waterborne/foodborne diseases. Considering the prevalence of the multi-drug resistant extended-spectrum beta-lactamase (ESBL) producing E. coli, a rapid detection method for resistance is highly desired. In this work, we developed a method for quick identification of E. coli and, at the same time, capable of removal of general bacterial pathogens from human urine. A specific peptide GRHIFWRRGGGHKVAPR, reported to have a strong affinity to E. coli, was utilized to modify the PEGylated magnetic nanoclusters, resulting in a specific capture and enrichment of E. coli from the bacteria-spiked artificial urine. Subsequently, a novel luminescent probe was applied to rapidly identify the antimicrobial resistance of the collected E. coli within 30 min. These functionalized magnetic nanoclusters demonstrate a promising prospect to rapidly detect ESBL E. coli in urine and contribute to reducing drinking water contamination.

High-Performance, Multifunctional, and Designable Carbon Fiber Felt Skeleton Epoxy Resin Composites EP/CF-(CNT/AgBNs)x for Thermal Conductivity and Electromagnetic Interference Shielding

In this work, high-performance epoxy resin (EP) composites with simultaneous excellent thermal conductivity (TC) and outstanding electromagnetic shielding properties are fabricated through the structural synergy of 1D carbon nanotubes and 2D silver-modified boron nitride nanoplates (CNT/AgBNs) to erect microscopic 3D networks on long-range carbon fiber (CF) felt skeletons. The line-plane combination of CNT/AgBNs improve the interfacical bonding involving EP and CF felts and alleviate the phonon scattering at the interface. Eventually, the TC of the EP composites is enhanced by 333% (up to 0.91 W m-1 K-1 ) with respect to EP due to the efficient and orderly transmission of phonons along the 3D pathway. Meanwhile, the unique anisotropic structure of CF felt and exceptional insulating BNs diminishes the electronic conduction between CNT and CFs, which protects the through-plane insulating properties of EP composites. Furthermore, the EP composites present favorable electromagnetic shielding properties (51.36 dB) attributed to the multiple reflection and adsorption promoted by the multiple interfaces of stacked AgBNs and heterointerface among CNT/AgBNs, CF felt and EP. Given these distinguishing features, the high-performance EP composites open a convenient avenue for electromagnetic wave (EMW) shielding and thermal management applications.

Biomimetic Wearable Sensors: Emerging Combination of Intelligence and Electronics

Owing to the advancement of interdisciplinary concepts, for example, wearable electronics, bioelectronics, and intelligent sensing, during the microelectronics industrial revolution, nowadays, extensively mature wearable sensing devices have become new favorites in the noninvasive human healthcare industry. The combination of wearable sensing devices with bionics is driving frontier developments in various fields, such as personalized medical monitoring and flexible electronics, due to the superior biocompatibilities and diverse sensing mechanisms. It is noticed that the integration of desired functions into wearable device materials can be realized by grafting biomimetic intelligence. Therefore, herein, the mechanism by which biomimetic materials satisfy and further enhance system functionality is reviewed. Next, wearable artificial sensory systems that integrate biomimetic sensing into portable sensing devices are introduced, which have received significant attention from the industry owing to their novel sensing approaches and portabilities. To address the limitations encountered by important signal and data units in biomimetic wearable sensing systems, two paths forward are identified and current challenges and opportunities are presented in this field. In summary, this review provides a further comprehensive understanding of the development of biomimetic wearable sensing devices from both breadth and depth perspectives, offering valuable guidance for future research and application expansion of these devices.

Ti3C2Tx MXene- and Sulfuric Acid-Treated Double-Network Hydrogel with Ultralow Conductive Filler Content for Stretchable Electromagnetic Interference Shielding

Hydrogels are emerging as stretchable electromagnetic interference (EMI) shielding materials because of their tissue-like mechanical properties and water-rich porous cellular structures. However, achieving high-performance hydrogel shields remains a challenge because enhancing conductivity often results in a compromise in deformation adoptability. This work proposes a treatment strategy involving sulfuric acid/titanium carbide MXene, which can simultaneously enhance the conductivity and stretchability of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS)/poly(vinyl alcohol) (PVA) double-network hydrogels. Multiple spectroscopic characterizations reveal that sulfuric acid promotes the linear conformation transition of the PEDOT molecular chain, while MXene increases charge delocalization and hydrogen bond cross-linking sites. The hydrogels, synthesized with a combined content of 0.6 wt % of MXene and PEDOT:PSS, exhibit an average X-band EMI SE of 41 dB. This performance is sustained at 94.5%, even following stretching and release at a strain of 200%. Interestingly, the EMI SE is found to linearly increase, reaching a value of 99 dB as the frequency is increased to 26.5 GHz. This increase is attributed to the enhanced water molecular polarization process, as supported by theoretical calculations of the impedance and attenuation constant. This work introduces a post-treatment technique that optimizes double-network hydrogels, providing deep insights into their EMI shielding mechanism and enabling high-performance EMI shielding with an ultralow conductive filler content.

Drawing Inspiration from Nature: Trinitarian Strategies for Designing Polyoxometalates and Metal-Organic Framework-Based Biomimetic Microhoneycomb Electromagnetic Wave-Absorbing Materials

Trinitarian designs in the morphology, components, and microstructure remain challenging for advanced electromagnetic wave absorption (EMWA) materials with light weight, strong absorption, and well-defined structure-function relationships. Herein, a series of X-doped MoS2/Cu9S5 with multilevel honeycomb structures (X-MoS2/Cu9S5 MHs, X = P, Si, Ge) were designed by space-confined growth and in situ sulfidation of a polyoxometalate-based metal-organic framework. X-MoS2/Cu9S5 MHs possess low density, high surface area, and abundant cation-cuprum and anion-sulfur double vacancies (VCu and VS) simultaneously that are unmatched by conventional EMWA materials. Also, the systematic investigation of the doping effect of various polyoxometalate heteroatoms on VCu and VS in the microhoneycomb has been conducted. Experimental results and density functional theory calculations reveal that the excellent EMWA performance (-56.21 dB) results from the synergistic effect of morphology design, component optimization, and vacancy regulation. This study not only provides an important opportunity to understand a morphology-component-microstructure strategy in electromagnetic wave absorption but also builds a noteworthy bridge between bioinspired engineering and microscale absorbers.

Organohydrogel-based transparent terahertz absorber via ionic conduction loss

The fast-growing terahertz technologies require high-performance terahertz absorber for suppressing electromagnetic interference. Since the dissipation mechanism in terahertz band usually focuses on electronic conduction loss, almost all terahertz absorbers are constructed with electronically conducting materials being opaque, which limits their applications in scenarios requiring high visible transmittance. Here, we demonstrate a transparent terahertz absorber based on permittivity-gradient elastomer-encapsulated-organohydrogel. Our organohydrogel-based terahertz absorber exhibits a high absorbing property (average reflection loss of 49.03 dB) in 0.5-4.5 THz band with a thin thickness of 700 μm and a high average visible transmittance of 85.51%. The terahertz absorbing mechanism mainly derives from the ionic conduction loss of the polar liquid in organohydrogel. Besides, the hydrophobic and adhesive elastomer coating endows this terahertz absorber high absorbing stability and interfacial adhesivity. This work paves a viable way to designing transparent terahertz absorbers.

Robust, ultrathin and flexible electromagnetic interference shielding paper designed with all-polysaccharide hydrogel and MXene

An effective strategy was demonstrated to design an electromagnetic interference (EMI) shielding paper via a facile surface treatment on paper. TEMPO-oxidized cellulose nanofibers (TOCN) were first integrated with Ti3C2Tx MXene, and subsequently cast onto a filter paper with cationic guar gum (CGG) in a sequential way. TOCN and CGG generated a self-assembling hydrogel and formed a MXene-containing hydrogel film on top of the filter paper. The hydrogel film enhanced the tensile strength (9.49 MPa) of composite paper, and resulted in a 17 % increase as compared to the control. The composite paper containing 80 mg MXene (namely, 2.07 mg·cm-2) showed a conductivity of 3843 S·m-1 and EMI shielding effectiveness (EMI SE) of 49.37 dB. Furthermore, the 2-layer assembled TC-M 80 hydrogel composite paper achieved an EMI SE of 73.99 dB. Importantly, this composite paper showed higher EMI SE and lower thickness than a lot of reported materials. The presence of TOCN and CGG also protected MXene against several solvents and the incorporation of polydimethylsiloxane (PDMS) further improved the durability of the composite paper. This work provides a novel and simple strategy to design robust, ultrathin and flexible EMI shielding materials, and it might also inspire other work in paper-based functional materials.

Broadband electromagnetic wave absorption using pure carbon aerogel by synergistically modulating propagation path and carbonization degree

Carbon materials were widely used as electromagnetic (EM) wave absorption due to their advantages of light weight, environmental resistance and high electrical conductivity. However, conventional means were typically available by combining carbon and other materials to achieve effective absorption. Herein, a novel strategy using pure carbon aerogel with oriented structure was reported to enhance the EM wave absorption by synergistically modulating the wave propagation path and carbonization degree. The aerogel contained proposed modified carbon nanofibers (MCNF) derived from bacterial cellulose (BC), and core-shell carbon nanofibers @ reduced oxide graphene (CNF@RGO). The oriented structure was induced by the temperature field, which manifests anisotropic EM constitutive parameters (εx ≠ εz) at different directions of incident wave. The carbonization degree was adjusted by varying the carbonization temperature. At the carbonization temperature of 700 °C, the maximum reflection loss and effective absorption bandwidth reached -53.94 dB and 7.14 GHz, respectively, enabling the aerogel to outperform its previous counterparts. To clarify the EM wave mode-of-action in conjunction, physical models of the aerogel were established in addition to finite element simulation and theoretical analysis. Notably, the aerogel with a density of 3.6 mg/cm3 featured ultra-light weight, superhydrophobicity, superior compressibility, and thermal insulation. Our work offers an efficient strategy for designing broadband and multifunctional EM wave absorption materials (EWAMs), promising great potentials in complex stealth equipment.

Diverse Structural Design Strategies of MXene-Based Macrostructure for High-Performance Electromagnetic Interference Shielding

There is an urgent demand for flexible, lightweight, mechanically robust, excellent electromagnetic interference (EMI) shielding materials. Two-dimensional (2D) transition metal carbides/nitrides (MXenes) have been potential candidates for the construction of excellent EMI shielding materials due to their great electrical electroconductibility, favorable mechanical nature such as flexibility, large aspect ratios, and simple processability in aqueous media. The applicability of MXenes for EMI shielding has been intensively explored; thus, reviewing the relevant research is beneficial for advancing the design of high-performance MXene-based EMI shields. Herein, recent progress in MXene-based macrostructure development is reviewed, including the associated EMI shielding mechanisms. In particular, various structural design strategies for MXene-based EMI shielding materials are highlighted and explored. In the end, the difficulties and views for the future growth of MXene-based EMI shields are proposed. This review aims to drive the growth of high-performance MXene-based EMI shielding macrostructures on basis of rational structural design and the future high-efficiency utilization of MXene.

Directional-Freezing-Enabled MXene Orientation toward Anisotropic PVDF/MXene Aerogels: Orientation-Dependent Properties of Hybrid Aerogels

Polymer hybrid materials that contain reinforcements with a preferred orientation have received growing attention because of their unique properties and promising applications in multifunctional fields. Herein, anisotropic poly(vinylidene fluoride) (PVDF)/MXene hybrid aerogels with highly ordered delaminated MXene nanosheets and anisotropic porous structures were successfully fabricated by unidirectional freezing of thermoreversible gels followed by a freeze-drying process. The strong interfacial interactions between PVDF chains and abundant functional groups on the surface of MXene enabled the orientation of MXene nanosheets at the boundaries of ice crystals as the semicrystalline PVDF and delaminated MXene nanosheets are squeezed along the freezing direction. These aerogels display distinct properties along the freezing and perpendicular to the freezing (transverse) directions. These anisotropic aerogels are flexible and flame-retardant and possess an anisotropic compression performance, heat transfer, electrical conductivity, and electromagnetic interference (EMI) shielding. Further, by increasing the MXene loadings, the electrical conductivity and EMI shielding performances of hybrid aerogels were significantly improved. The PVDF aerogel showed sticky hydrophobicity with a contact angle of 139°, whereas the contact angle increased significantly in hybrid aerogels (153°) with low water adhesion, making them suitable as self-cleaning materials. The combination of the above characteristics makes these hybrid aerogels potential candidates for a wide range of electronic applications.

Regulatable Phase Manipulation-Enhanced Polarization and Conductance Loss Enabling Hierarchical 3D Microsphere-like MoS2 with Efficient Microwave Absorption

Molybdenum disulfide (MoS2) has become a new type of microwave absorption (MA) material due to the abundant functional groups and defects, high polarization effect, and controllable structural design. However, the development of MoS2 has been limited by its inherently low conductance losses and imperfect impedance matching. This study employs ammonium ion (NH4+) intercalation as a phase manipulation strategy to enhance dielectric loss and form heterogeneous structures by incorporating highly conductive 1T phase into the 2H-MoS2 crystal phase. Additionally, the implementation of CTAB as a soft template agent for constructing layered three-dimensional microsphere structures improves impedance matching. The experimental findings demonstrate that the MA performance of MoS2 can be effectively regulated by controlling the 1T phase content and morphological structure design. It is worth noting that A-MoS2-2 possesses excellent multifrequency absorption capability. A-MoS2-2 has a minimum reflection loss (RL) of -53 dB at a coating thickness of 1.99 mm and an effective absorption bandwidth (EAB) of 5.6 GHz at a thinner coating thickness of 1.77 mm. This work improves the MA properties of MoS2 by introducing metallic phases and unique structural design, which opens up new ideas for the development of MA materials.

Bionic ordered structured hydrogels: structure types, design strategies, optimization mechanism of mechanical properties and applications

Natural organisms, such as lobsters, lotus, and humans, exhibit exceptional mechanical properties due to their ordered structures. However, traditional hydrogels have limitations in their mechanical and physical properties due to their disordered molecular structures when compared with natural organisms. Therefore, inspired by nature and the properties of hydrogels similar to those of biological soft tissues, researchers are increasingly focusing on how to investigate bionic ordered structured hydrogels and render them as bioengineering soft materials with unique mechanical properties. In this paper, we systematically introduce the various structure types, design strategies, and optimization mechanisms used to enhance the strength, toughness, and anti-fatigue properties of bionic ordered structured hydrogels in recent years. We further review the potential applications of bionic ordered structured hydrogels in various fields, including sensors, bioremediation materials, actuators, and impact-resistant materials. Finally, we summarize the challenges and future development prospects of bionic ordered structured hydrogels in preparation and applications.

Anion Exchange of Metal Particles on Carbon-Based Skeletons for Promoting Dielectric Equilibrium and High-Efficiency Electromagnetic Wave Absorption

The combination of carbon materials and magnetic elements is considered as an effective strategy to obtain high-performance electromagnetic wave (EMW) absorption materials. However, using nanoscale regulation to the optimization of composite material dielectric properties and enhanced magnetic loss properties is facing significant challenges. Here, the dielectric constant and magnetic loss capability of the carbon skeleton loaded with Cr compound particles are further tuned to enhance the EMW absorption performance. After 700 °C thermal resuscitation of the Cr3-polyvinyl pyrrolidone composite material, the chromium compound is represented as a needle-shaped structure of nanoparticles, which is fixed on the carbon skeleton derived from the polymer. The size-optimized CrN@PC composites are obtained after the substitution of more electronegative nitrogen elements using an anion-exchange strategy. The minimum reflection loss value of the composite is -105.9 dB at a CrN particle size of 5 nm, and the effective absorption bandwidth is 7.68 GHz (complete Ku-band coverage) at 3.0 mm. This work overcomes the limitations of impedance matching imbalance and magnetic loss deficiency in carbon-based materials through size tuning, and opens a new way to obtain carbon-based composites with ultra-high attenuation capability.

Asymmetric and Flexible Ag-MXene/ANFs Composite Papers for Electromagnetic Shielding and Thermal Management

Lightweight, flexible, and electrically conductive thin films with high electromagnetic interference (EMI) shielding effectiveness and excellent thermal management capability are ideal for portable and flexible electronic devices. Herein, the asymmetric and multilayered structure Ag-MXene/ANFs composite papers (AMAGM) were fabricated based on Ag-MXene hybrids and aramid nanofibers (ANFs) via a self-reduction and alternating vacuum-assisted filtration process. The resultant AMAGM composite papers exhibit high electrical conductivity of 248,120 S m-1, excellent mechanical properties with tensile strength of 124.21 MPa and fracture strain of 4.98%, superior EMI shielding effectiveness (62 dB), ultra-high EMI SE/t (11,923 dB cm2 g-1) and outstanding EMI SE reliability as high as 96.1% even after 5000 cycles of bending deformation benefiting from the unique structure and the 3D network at a thickness of 34 μm. Asymmetric structures play an important role in regulating reflection and absorption of electromagnetic waves. In addition, the multifunctional nanocomposite papers reveal outstanding thermal management performances such as ultrafast thermal response, high heating temperatures at low operation voltage, and high heating stability. The results indicate that the AMAGM composite papers have excellent potential for high-integration electromagnetic shielding, wearable electronics, artificial intelligence, and high-performance heating devices.

Enhanced ultra high frequency EMI shielding with controlled ITO nano-branch width via different tin material types

The development of technologies for electromagnetic wave contamination has garnered attention. Among the various electromagnetic wave frequencies, for high frequencies such as those in the K and Ka ranges, there is a limitation of using only the properties of a single material. Therefore, it is necessary to improve the absorption coefficients by increasing the path of electromagnetic waves through internal scattering at an interface or a structure inside the material. Here, we accurately demonstrated the role of Sn in the growth of an indium tin oxide (ITO) nano-branch structure and grew high-density ITO nano-branches with the lowest thickness possible. Consequently, we obtained shielding efficiencies of 21.09 dB (K band) and 17.81 dB (Ka band) for a film with a thickness of 0.00364 mm. Owing to the significantly high specific shielding efficiency and low thickness and weight, it is expected to be applied in various fields.

Multifunctional amorphous FeCoNiTixSi high-entropy alloys with excellent electromagnetic-wave absorption performances

Amorphous high-entropy alloys (HEAs) as electromagnetic-wave absorbing materials have been rarely reported. In this work, amorphous FeCoNiTixSi HEAs were synthesized by introducing a high content of large-atom Ti using the high-energy ball-milling technique. This amorphous structure could improve the saturated magnetization and coercivity of HEAs, but slightly degraded the mechanical and oxidation resistance properties. In terms of electromagnetic properties, FeCoNiTi0.01Si and FeCoNiTiSi exhibit excellent electromagnetic-wave absorption performances, with significant absorptions of -68.4 dB at 6.14 GHz and -63.4 dB at 9.12 GHz, corresponding to bandwidths of 5.15 GHz (1.69 mm) and 3.64 GHz (1.43 mm), respectively. Overall, the prepared FeCoNiTixSi HEAs exhibited superior comprehensive performances compared to other HEA absorption materials. This work provided a novel strategy for the development of new electromagnetic-wave absorption materials with low weight, high absorption efficiency, and resistance to harsh environments.

Structural Electromagnetic Absorber Based on MoS2 /PyC-Al2 O3 Ceramic Metamaterials

Limited by the types of suitable absorbents as well as the challenges in engineering the nanostructures (e.g., defects, dipoles, and hetero-interface) using state-of-the-art additive manufacturing (AM) techniques, the electromagnetic (EM) wave absorption performance of the current ceramic-based materials is still not satisfying. Moreover, because of the high residual porosity and the possible formation of cracks during sintering or pyrolysis, AM-formed ceramic components may in many cases exhibit low mechanical strength. In this work, semiconductive MoS2 and conductive PyC modified Al2 O3 (MoS2 /PyC-Al2 O3 ) ceramic-based structural EM metamaterials are developed by innovatively harnessing AM, precursor infiltration and pyrolysis (PIP), and hydrothermal methods. Three different meta-structures are successfully created, and the ceramic-based nanocomposite benefit from its optimization of EM parameters. Ultra-broad effective absorption bandwidth (EAB) of 35 GHz is achieved by establishment of multi-loss mechanism via nanostructure engineering and fabrication of meta-structures via AM. Due to the strengthening by the PyC phase, the bending strength of the resulting ceramics can reach ≈327 MPa, which is the highest value measured on 3D-printed ceramics of this type that has been reported so far. For the first time, the positive effect deriving from the engineering of the microscopic nano/microstructure and of the macroscopic meta-structure of the absorber on the permittivity and EM absorption performance is proposed. Integration of outstanding mechanical strength and ultra-broad EAB is innovatively realized through a multi-scale design route. This work provides new insights for the design of advanced ceramic-based metamaterials with outstanding performance under extreme environment.

Structural design and preparation of Ti3C2Tx MXene/polymer composites for absorption-dominated electromagnetic interference shielding

Electromagnetic interference (EMI) is a pervasive and harmful phenomenon in modern society that affects the functionality and reliability of electronic devices and poses a threat to human health. To address this issue, EMI-shielding materials with high absorption performance have attracted considerable attention. Among various candidates, two-dimensional MXenes are promising materials for EMI shielding due to their high conductivity and tunable surface chemistry. Moreover, by incorporating magnetic and conductive fillers into MXene/polymer composites, the EMI shielding performance can be further improved through structural design and impedance matching. Herein, we provide a comprehensive review of the recent progress in MXene/polymer composites for absorption-dominated EMI shielding applications. We summarize the fabrication methods and EMI shielding mechanisms of different composite structures, such as homogeneous, multilayer, segregated, porous, and hybrid structures. We also analyze the advantages and disadvantages of these structures in terms of EMI shielding effectiveness and the absorption ratio. Furthermore, we discuss the roles of magnetic and conductive fillers in modulating the electrical properties and EMI shielding performance of the composites. We also introduce the methods for evaluating the EMI shielding performance of the materials and emphasize the electromagnetic parameters and challenges. Finally, we provide insights and suggestions for the future development of MXene/polymer composites for EMI shielding applications.

Nanofiber Composite Reinforced Organohydrogels for Multifunctional and Wearable Electronics

Composite organohydrogels have been widely used in wearable electronics. However, it remains a great challenge to develop mechanically robust and multifunctional composite organohydrogels with good dispersion of nanofillers and strong interfacial interactions. Here, multifunctional nanofiber composite reinforced organohydrogels (NCROs) are prepared. The NCRO with a sandwich-like structure possesses excellent multi-level interfacial bonding. Simultaneously, the synergistic strengthening and toughening mechanism at three different length scales endow the NCRO with outstanding mechanical properties with a tensile strength (up to 7.38 ± 0.24 MPa), fracture strain (up to 941 ± 17%), toughness (up to 31.59 ± 1.53 MJ m-3) and fracture energy (up to 5.41 ± 0.63 kJ m-2). Moreover, the NCRO can be used for high performance electromagnetic interference shielding and strain sensing due to its high conductivity and excellent environmental tolerance such as anti-freezing performance. Remarkably, owing to the organohydrogel stabilized conductive network, the NCRO exhibits superior long-term sensing stability and durability compared to the nanofiber composite itself. This work provides new ideas for the design of high-strength, tough, stretchable, anti-freezing and conductive organohydrogels with potential applications in multifunctional and wearable electronics.

Bioinspired Additive Manufacturing of Hierarchical Materials: From Biostructures to Functions

Throughout billions of years, biological systems have evolved sophisticated, multiscale hierarchical structures to adapt to changing environments. Biomaterials are synthesized under mild conditions through a bottom-up self-assembly process, utilizing substances from the surrounding environment, and meanwhile are regulated by genes and proteins. Additive manufacturing, which mimics this natural process, provides a promising approach to developing new materials with advantageous properties similar to natural biological materials. This review presents an overview of natural biomaterials, emphasizing their chemical and structural compositions at various scales, from the nanoscale to the macroscale, and the key mechanisms underlying their properties. Additionally, this review describes the designs, preparations, and applications of bioinspired multifunctional materials produced through additive manufacturing at different scales, including nano, micro, micro-macro, and macro levels. The review highlights the potential of bioinspired additive manufacturing to develop new functional materials and insights into future directions and prospects in this field. By summarizing the characteristics of natural biomaterials and their synthetic counterparts, this review inspires the development of new materials that can be utilized in various applications.

Structure Design and Processing Strategies of MXene-Based Materials for Electromagnetic Interference Shielding

The development of new materials for electromagnetic interference (EMI) shielding is an important area of research, as it allows for the creation of more effective and high-efficient shielding solutions. In this sense, MXenes, a class of 2D transition metal carbides and nitrides have exhibited promising performances as EMI shielding materials. Electric conductivity, low density, and flexibility are some of the properties given by MXene materials, which make them very attractive in the field. Different processing techniques have been employed to produce MXene-based materials with EMI shielding properties. This review summarizes processes and the role of key parameters like the content of fillers and thickness in the desired EMI shielding performance. It also discusses the determination of power coefficients in defining the EMI shielding mechanism and the concept of green shielding materials, as well as their influence on the real application of a produced material. The review concludes with a summary of current challenges and prospects in the production of MXene materials as EMI shields.

Recent Progress in MXene Hydrogel for Wearable Electronics

Recently, hydrogels have attracted great attention because of their unique properties, including stretchability, self-adhesion, transparency, and biocompatibility. They can transmit electrical signals for potential applications in flexible electronics, human-machine interfaces, sensors, actuators, et al. MXene, a newly emerged two-dimensional (2D) nanomaterial, is an ideal candidate for wearable sensors, benefitting from its surface's negatively charged hydrophilic nature, biocompatibility, high specific surface area, facile functionalization, and high metallic conductivity. However, stability has been a limiting factor for MXene-based applications, and fabricating MXene into hydrogels has been proven to significantly improve their stability. The unique and complex gel structure and gelation mechanism of MXene hydrogels require intensive research and engineering at nanoscale. Although the application of MXene-based composites in sensors has been widely studied, the preparation methods and applications of MXene-based hydrogels in wearable electronics is relatively rare. Thus, in order to facilitate the effective evolution of MXene hydrogel sensors, the design strategies, preparation methods, and applications of MXene hydrogels for flexible and wearable electronics are comprehensively discussed and summarized in this work.

CNT-MXene ultralight membranes: fabrication, surface nano/microstructure, 2D-3D stacking architecture, ion-transport mechanism, and potential application as interlayers for Li-O2 batteries

Multiwalled carbon nanotubes (MWCNTs) have shown effectiveness in improving the suitability of MXenes for energy-related applications. However, the ability of individually dispersed MWCNTs to control the structure of MXene-based macrostructures is unclear. Here, the correlation among composition, surface nano- and microstructure, MXenes' stacking order, structural swelling, and Li-ion transport mechanisms and properties in individually dispersed MWCNT-Ti₃C₂ films was investigated. The compact surface microstructure of MXene film, characterized by prominent wrinkles, is dramatically changed as MWCNTs occupy MXene/MXene edge interfaces. The 2D stacking order is preserved up to 30 wt% MWCNTs despite a significant swelling of ∼400%. Such alignment is completely disrupted at 40 wt%, and a more pronounced surface opening and internal expansion of ∼770% are realized. Both 30 wt% and 40 wt% membranes show stable cycling performance under a significantly higher current density due to faster transport channels. Notably, for the 3D membrane, the overpotential during repeated Li deposition/dissolution reactions is further reduced by ∼50%. Ion-transport mechanisms in the absence and presence of MWCNTs are discussed. Furthermore, ultralight yet continuous hybrid films comprising up to ∼0.027 mg cm^-2 Ti₃C₂ can be prepared using aqueous colloidal dispersions and vacuum filtration for specific applications. The potential application of such ultralight membranes as interlayers for Li-O₂ batteries is briefly examined.

High-Sensitivity Wearable Sensor Based On a MXene Nanochannel Self-Adhesive Hydrogel

To address the shortcomings of traditional filler-based wearable hydrogels, a new type of nanochannel hydrogel sensor is fabricated in this work through a combination of the unique structure of electrospun fiber textile and the properties of a double network hydrogel. Unlike the traditional Ti₃C₂T_x MXene-based hydrogels, the continuously distributed Ti₃C₂T_x MXene in the nanochannels of the hydrogel forms a tightly interconnected structure similar to the neuron network. As a result, they have more free space to flip and perform micromovements, which allows one to significantly increase the electrical conductivity and sensitivity of the hydrogel. According to the findings, the Ti₃C₂T_x MXene nanochannel hydrogel has excellent mechanical properties as well as self-adhesion and antifreezing characteristics. The hydrogel sensor successfully detects different human motions and physiological signals (e.g., low pulse signals) with high stability and sensitivity. Therefore, the proposed Ti₃C₂T_x MXene-based hydrogel with a unique structure and properties is very promising in the field of flexible wearable devices.

Controlled Distributed Ti3 C2 Tx Hollow Microspheres on Thermally Conductive Polyimide Composite Films for Excellent Electromagnetic Interference Shielding

Flexible multifunctional polymer-based electromagnetic interference (EMI) shielding composite films have important applications in the fields of 5G communication technology, wearable electronic devices, and artificial intelligence. Based on the design of a porous/multilayered structure and using polyimide (PI) as the matrix and polymethyl methacrylate (PMMA) microspheres as the template, flexible (Fe₃ O₄ /PI)-Ti₃ C₂ T_x -(Fe₃ O₄ /PI) composite films with controllable pore sizes and distribution of Ti₃ C₂ T_x hollow microspheres are successfully prepared by sacrificial template method. Owing to the porous/multilayered structure, when the pore size of the Ti₃ C₂ T_x hollow microspheres is 10 µm and the mass ratio of PMMA/Ti₃ C₂ T_x is 2:1, the (Fe₃ O₄ /PI)-Ti₃ C₂ T_x -(Fe₃ O₄ /PI) composite film has the most excellent EMI shielding performance, with EMI shielding effectiveness (EMI SE) of 85 dB. It is further verified by finite element simulation that the composite film has an excellent shielding effect on electromagnetic waves. In addition, the composite film has good thermal conductivity (thermal conductivity coefficient of 3.49 W (m·K)^-1 ) and mechanical properties (tensile strength of 65.3 MPa). This flexible (Fe₃ O₄ /PI)-Ti₃ C₂ T_x -(Fe₃ O₄ /PI) composite film with excellent EMI shielding performance, thermal conductivity, and mechanical properties has demonstrated great potential for applications in EMI shielding protection for high-power, portable, and wearable flexible electronic devices.

Research Progress with Membrane Shielding Materials for Electromagnetic/Radiation Contamination

As technology develops at a rapid pace, electromagnetic and radiation pollution have become significant issues. These forms of pollution can cause many important environmental issues. If they are not properly managed and addressed, they will be everywhere in the global biosphere, and they will have devastating impacts on human health. In addition to minimizing sources of electromagnetic radiation, the development of lightweight composite shielding materials to address interference from radiation has become an important area of research. A suitable shielding material can effectively reduce the harm caused by electromagnetic interference/radiation. However, membrane shielding materials with general functions cannot effectively exert their shielding performance in all fields, and membrane shielding materials used in different fields must have specific functions under their use conditions. The aim of this review was to provide a comprehensive review of these issues. Firstly, the causes of electromagnetic/radiation pollution were briefly introduced and comprehensively identified and analyzed. Secondly, the strategic solutions offered by membrane shielding materials to address electromagnetic/radiation problems were discussed. Then, the design concept, technical innovation, and related mechanisms of the existing membrane shielding materials were expounded, the treatment methods adopted by scholars to study the environment and performance change laws were introduced, and the main difficulties encountered in this area of research were summarized. Finally, on the basis of a comprehensive analysis of the protection provided by membrane shielding materials against electromagnetic/radiation pollution, the action mechanism of membrane shielding materials was expounded in detail, and the research progress, structural design and performance characterization techniques for these materials were summarized. In addition, the future challenges were prospected. This review will help universities, research institutes, as well as scientific and technological enterprises engaged in related fields to fully understand the design concept and research progress of electromagnetic/radiation-contaminated membrane shielding materials. In addition, it is hoped that this review will facilitate efforts to accelerate the research and development of membrane shielding materials and offer potential applications in areas such as electronics, nuclear medicine, agriculture, and other areas of industry.

Specific capture of Pseudomonas aeruginosa for rapid detection of antimicrobial resistance in urinary tract infections

Urinary tract infections (UTIs) are among the most predominant microbial diseases, leading to substantial healthcare burdens and threatening human well-being. UTIs can become more critical when caused by Pseudomonas aeruginosa, particularly by antimicrobial-resistant types. Thereby a rapid diagnosis and identification of the antimicrobial-resistant P. aeruginosa can support and guide an efficient medication and an effective treatment toward UTIs. Herein, we designed a platform for prompt purification, and effective identification of P. aeruginosa to combat the notorious P. aeruginosa associated UTIs. A peptide (QRKLAAKLT), specifically binding to P. aeruginosa, was grafted onto PEGylated magnetic nanoclusters and enabled a successful capture and enrichment of P. aeruginosa from artificial human urine. Rapid identification of antimicrobial resistance of the enriched P. aeruginosa can be moreover accomplished within 30 min. These functionalized magnetic nanoclusters demonstrate a prominent diagnostic potential to combat P. aeruginosa associated UTIs, which can be extended to other P. aeruginosa involved infections.

Ultrathin Cellulose Nanofiber Assisted Ambient-Pressure-Dried, Ultralight, Mechanically Robust, Multifunctional MXene Aerogels

Ambient-pressure-dried (APD) preparation of transition metal carbide/nitrides (MXene) aerogels is highly desirable yet remains highly challenging. Here, ultrathin, high-strength-to-weight-ratio, renewable cellulose nanofibers (CNFs) are efficiently utilized to assist in the APD preparation of ultralight yet robust, highly conductive, large-area MXene-based aerogels via a facile, energy-efficient, eco-friendly, and scalable freezing-exchanging-drying approach. The strong interactions of large-aspect-ratio CNF and MXene as well as the biomimetic nacre-like microstructure induce high mechanical strength and stability to avoid the structure collapse of aerogels in the APD process. Abundant functional groups of CNFs facilitate the chemical crosslinking of MXene-based aerogels, significantly improving the hydrophobicity, water resistance, and even oxidation stability. The ultrathin, 1D nature of the CNF renders the minimal MXenes' interlayered gaps and numerous heterogeneous interfaces, yielding the excellent conductivity and electromagnetic interference (EMI) shielding performance of aerogels. The synergies of the MXene, CNF, and abundant pores efficiently improve the EMI shielding performance, photothermal conversion, and absorption of viscous crude oil. This work shows great promises of the APD, multifunctional MXene-based aerogels in electromagnetic protection or compatibility, thermal therapy, and oil-water separation applications.

Ultrafast Determination of Antimicrobial Resistant Staphylococcus aureus Specifically Captured by Functionalized Magnetic Nanoclusters

Sepsis, the systemic response to infection, is a life-threatening situation for patients and leads to high mortality, especially when caused by antimicrobial resistant pathogens. Prompt diagnosis and identification of the pathogenic bacteria, including their antibiotic resistance, are highly desired to yield a timely decision for treatment. Here, we aim to develop a platform for rapid isolation and efficient identification of Staphylococcus aureus, the most frequently occurring pathogen in sepsis. A peptide (VPHNPGLISLQG, SA5-1), specifically binding to S. aureus, was conjugated to the PEGylated magnetic nanoclusters, successfully enabling the specific capture and enrichment of S. aureus from blood serum. Consequently, fast detection of the antimicrobial resistance of the collected S. aureus was achieved within 30 min using a novel luminescent probe. These magnetic nanoclusters manifest a promising diagnostic prospect to combat sepsis.

Bicontinuous, High-Strength, and Multifunctional Chemical-Cross-Linked MXene/Superaligned Carbon Nanotube Film

Lightweight, thin, large-area, and ultraflexible chemical-cross-linked MXene/superaligned carbon nanotube composite films with a bicontinuous structure are manufactured. The films exhibit high mechanical strength, good electrical conductivity, hydrophobicity, and oxidation stability, as well as wearable multifunctionalities involving electromagnetic interference (EMI) shielding, electrothermal conversion, and photothermal antibacterial performance. An X-band EMI shielding effectiveness (SE) of 24 to 70 dB at the thickness of 8 to 28 μm and an SE of more than 60 dB in ultrabroadband frequency range of 8.2-40 GHz are accomplished. A surface specific SE of 122 368 dB·cm²·g^-1 is achieved, significantly outperforming other typical shields reported. The good electro-/photothermal performance of the films leads to high-efficiency deicing and antibacterial performance. Combined with the efficient and scalable manufacturing approach, the multifunctional wearable bicontinuous films show great potential for applications in wearable devices, defense, antibacterials, and the Internet of Things.

MXene-Based Porous Monoliths

In the past decade, a thriving family of 2D nanomaterials, transition-metal carbides/nitrides (MXenes), have garnered tremendous interest due to its intriguing physical/chemical properties, structural features, and versatile functionality. Integrating these 2D nanosheets into 3D monoliths offers an exciting and powerful platform for translating their fundamental advantages into practical applications. Introducing internal pores, such as isotropic pores and aligned channels, within the monoliths can not only address the restacking of MXenes, but also afford a series of novel and, in some cases, unique structural merits to advance the utility of the MXene-based materials. Here, a brief overview of the development of MXene-based porous monoliths, in terms of the types of microstructures, is provided, focusing on the pore design and how the porous microstructure affects the application performance.

From MXene Trash to Ultraflexible Composites for Multifunctional Electromagnetic Interference Shielding

The development of flexible composites based on the transition metal carbides/nitrides (MXenes) is gaining popularity because of MXenes' high application potentials for electromagnetic interference (EMI) shields. Here, we prepare a new type of ultraflexible composite films composed of "trashed" MXene sediment (MS) and waterborne polyurethane using a simple, facile solution casting approach. In addition to the outstanding mechanical strength and electrical conductivity, an extremely wide-range of MS contents can be achieved for the composites, resulting in EMI shielding effectiveness (SE) that may be controlled over a wide range. The X-band EMI SE of the flexible, low-density composites containing 70 wt % MS reaches 45.3 dB at a thickness of merely 0.51 mm. Moreover, the SE values of more than 34.5 dB in the ultrabroadband gigahertz frequency range including X-band, P-band, K-band, and R-band, are accomplished for the thin composites. Furthermore, the MS/WPU composite films show excellent electrothermal and photothermal performance, demonstrating the multifunctionalities of the MS-based EMI shields. Combined with the cost-efficient, sustainable, and scalable preparation approach, the ultraflexible, multifunctional composites from "trashed MXene" show great potentials for next-generation electronics. This work also opens a new avenue for the creation of innovative, high-performance, multifunctional flexible composites.

Machine learning ensures rapid and precise selection of gold sea-urchin-like nanoparticles for desired light-to-plasmon resonance

Sustainable energy strategies, particularly solar-to-hydrogen production, are anticipated to overcome the global reliance on fossil fuels. Thereby, materials enabling the production of green hydrogen from water and sunlight are continuously designed, e.g., ZnO nanostructures coated by gold sea-urchin-like nanoparticles, which employ the light-to-plasmon resonance to realize photoelectrochemical water splitting. But such light-to-plasmon resonance is strongly impacted by the size, the species, and the concentration of the metal nanoparticles coating on the ZnO nanoflower surfaces. Therefore, a precise prediction of the surface plasmon resonance is crucial to achieving an optimized nanoparticle fabrication of the desired light-to-plasmon resonance. To this end, we synthesized a substantial amount of metal (gold) nanoparticles of different sizes and species, which are further coated on ZnO nanoflowers. Subsequently, we utilized a genetic algorithm neural network (GANN) to obtain the synergistically trained model by considering the light-to-plasmon conversion efficiencies and fabrication parameters, such as multiple metal species, precursor concentrations, surfactant concentrations, linker concentrations, and coating times. In addition, we integrated into the model's training the data of nanoparticles due to their inherent complexity, which manifests the light-to-plasmon conversion efficiency far from the coupling state. Therefore, the trained model can guide us to obtain a rapid and automatic selection of fabrication parameters of the nanoparticles with the anticipated light-to-plasmon resonance, which is more efficient than an empirical selection. The capability of the method achieved in this work furthermore demonstrates a successful projection of the light-to-plasmon conversion efficiency and contributes to an efficient selection of the fabrication parameters leading to the anticipated properties.