Flexible MXene-Decorated Fabric with Interwoven Conductive Networks for Integrated Joule Heating, Electromagnetic Interference Shielding, and Strain Sensing Performances

A Review on Multifunctional Polymer-MXene Hybrid Materials for Electronic Applications

MXenes, a family of two-dimensional (2D) transition metal carbides, carbonitrides, and nitrides, have emerged as a promising class of nanomaterials for interdisciplinary applications due to their unique physiochemical properties. The large surface area, excellent electrical conductivity, superior mechanical properties, and abundant possible functional groups make this layered nanomaterial an ideal candidate for multifunctional hybrid materials for electronic applications. This review highlights recent progress in MXene-based hybrid materials, focusing on their electrical, dielectric, and electromagnetic interference (EMI) shielding properties, with an emphasis on the development of multifunctionality required for advanced electronic devices. The review explores the multifunctional nature of MXene-based polymer nanocomposites and hybrid materials, covering the coexistence of a diverse range of properties, including sensory capabilities, electromagnetic interference shielding, energy storage, and the Joule heating phenomenon. Finally, the future outlook and key challenges are summarized, offering insights to guide future research aimed at improving the performance and functionality of MXene-polymer nanocomposites.

Conductive Structural Colored Cotton Fabrics with Nonangle-Dependent Colors and Dynamic Thermal Management

Textile dyeing based on structural colors has attracted great attention due to its environmental friendliness and long-lasting color fastness. However, most studies on structural colored fabrics focus on only improving the color and stability of the fabric, neglecting the increasing demand for multifunctional textiles in daily life. Herein, a simple and effective method was used for preparing conductive structural colored cotton fabrics with nonangle-dependent colors and dynamic thermal management. To prepare structural color nanospheres with higher color rendering, PMMA nanospheres were coated with black PDA. The conductive structural colored fabric was obtained by self-assembling PMMA@PDA nanospheres onto MXene-modified cotton fabric through a simple blade coating method. The prepared conductive structural colored textile retains its softness and demonstrates good electrothermal performance and durable color fastness through washing, friction, and durability tests. This work provides a novel approach for creating bifunctional structural colored textiles that are suitable for electrothermal applications.

Biomass-derived multifunctional conductive fabrics with aluminum ion coordination: Integrating hydrophobic triboelectric and electrothermal conversion properties

The accelerated depletion of fossil resources and the rising demand for environmental protection have posed significant challenges to conventional e-smart textiles, driving the need for more sustainable alternatives. This has created an urgent demand for environmentally friendly, lightweight, and renewable smart textiles. This study developed biomass-derived flexible conductive fabrics (BWPU/CNTs/Al/NF) with a microporous structure using impregnation and coating techniques guided by the wet phase transition film-forming principle. The primary materials employed in this study were soy-based waterborne polyurethane (BWPU), carboxylated carbon nanotubes (CNTs), and collagen fiber nonwovens(NF). The carboxyl groups (COOH) in BWPU and CNTs functioned as binding sites, enhancing the binding force between BWPU and CNTs. The addition of aluminum ion (Al3+) cross-linking served to reinforce the conductive network structure, enhancing conductivity and stability. The resulting BWPU/CNTs/Al/NF fabrics retain their original softness, air permeability, and water vapor permeability while exhibiting excellent electrical conductivity, hydrophobicity, chemical stability, and mechanical durability. Additionally, they demonstrate remarkable triboelectric properties, achieving an output voltage of up to 512.6 V under a 10 kPa force during a continuous 2.5 Hz "contact-detachment" cycle. Moreover, they demonstrate exceptional Joule heating performance, reaching a saturation temperature of 165.6 °C within 2 min at a drive of 12 V. Furthermore, the fabrics demonstrate excellent capabilities for removing water and ice. These exceptional properties make the fabrics promising candidates for applications in smart wearables, artificial intelligence, and outdoor electronic and electrical devices.

3D Large Space Warp-Knitted Composite Fabric with Heating and Insulation for Extremely Cold Environments

The extremely cold environment restricts certain activities, making the preparation of a material with both heating and insulation functions a significant challenge. This study presents the large space warp-knitted composite fabric (LSWCF) as an electric heating inflatable material with a three-dimensional structure. It is designed and developed from three modes to mitigate heat loss. The top layer of LSWCF is combined with the electric heating film as the heating layer, showing high electric heating efficiency (577.33 °C/(W·cm-2)), high electrothermal conversion efficiency (95%), and excellent conductivity (12.5 S/cm). The bottom layer of LSWCF is coated with TiO2/WPU coatings as a thermal radiation layer. The inflated LSWCF retains a substantial volume of still air within its middle layer and exhibits low thermal conductivity (0.037 W·m-1·K-1), with resulting minimization of heat loss due to convection and conduction. LSWCF's radiant coating, on the other hand, reduces heat loss through directed radiation. Contributed to the structural design, the LSWCF demonstrates an enhanced ability to generate heat at low temperatures (up to 35 °C at -20 °C, 980 W·m-2) compared to the existing literature. This study offers a novel strategy for the development of materials for use in extremely cold environments.

Flexible, stretchable multifunctional silver nanoparticles-decorated cotton textile based on amyloid-like protein aggregation for electrothermal and photothermal dual-driven wearable heater

The design of multifunctional, high-performance wearable heaters utilizing textile substrates has garnered increasing attention, particularly in the development of body temperature and health monitoring devices. However, fabricating these multifunctional wearable heaters while simultaneously ensuring flexibility, air permeability, Joule heating performance, electromagnetic interference (EMI) shielding and antibacterial properties remains a significant challenge. This study utilizes phase transition lysozyme (PTL) film-mediated electroless deposition (ELD) technology to deposit silver nanoparticles (Ag NPs) on the cotton fabrics surface in a mild aqueous solution at room temperature, thereby constructing a wearable heater with long-term stability, high conductivity, and exceptional photothermal properties. The textiles enriched with Ag NPs exhibit remarkable electrothermal and photothermal dual-driven heating capabilities, achieving temperatures exceeding 110 °C within 50s under 2 V, or in merely a few seconds through photothermal conversion. Importantly, these textiles retain the intrinsic flexibility and breathability of the textile substrate. Furthermore, the amyloid-like protein Ag NP integrated textiles demonstrate excellent antibacterial properties, and exhibit a high EMI shielding efficiency of 50 dB within the frequency range of 8.2-12.4 GHz. Therefore, these multifunctional Ag NPs wearable heaters were expected to find applications in areas such as smart wearable clothing and future health management.

Flexible and Durable Conducting Fabric Electrodes for Next-Generation Wearable Supercapacitors

This study presents the fabrication of highly conducting Au fabric electrodes using a layer-by-layer (LBL) approach and its application toward energy storage. Through the ligand-exchange mechanism, the alternating layers of tris(2-aminoethyl)amine (TREN) and gold nanoparticles (Au NPs) encapsulated with tetraoctylammonium bromide (TOABr) ligands (Au-TOABr) were deposited onto the fabric to achieve a highly conducting Au fabric (0.12 Ω/□) at room temperature in just two LBL cycles. In contrast to several existing techniques, the current study realizes highly conducting Au fabric (7-15 Ω/□) in a layer-by-layer coating. The obtained Au fabrics demonstrate excellent stability against various deformations and abrasions, and its sheet resistance remained unaltered even after multiple cycles of bending, twisting, scotch tape adhesions, and sandpaper abrasions. In addition, the prepared Au fabrics exhibit high robustness toward various chemical media, highlighting their anticorrosive properties. Although Au fabrics showed a slight increase in sheet resistance postwashing and ultrasonication tests, it was got ridden by coating a thin layer of a biocompatible polydimethylsiloxane (PDMS) polymer. Besides enhancing the adhesion of Au NPs, PDMS coating offered a hydrophobic surface to fabrics rendering their use toward self-cleaning applications. High-performing energy storage devices integrated with wearable technologies are in great demand. In this context, here, electropolymerized polyaniline (PANI)-coated Au fabrics were employed to develop supercapacitors with remarkable energy-storing capability. In a symmetric two-electrode configuration, the device offered a maximum areal capacitance of 660 mF/cm2 with high areal energy and power densities of 58.64 μWh/cm2 and 22.86 mW/cm2, respectively. The solid-state supercapacitor device (SSD) fabricated using Au/PANI-30 electrodes exhibited an areal capacitance of 495 mF/cm2 with energy and power densities of 33 μWh/cm2 and 10,660 μW/cm2, respectively. This LBL method offers a significant advantage over existing techniques by offering simple room-temperature fabrication with excellent conductivity and adaptability to various substrates and with ease of scalability.

A Review on MXene/Nanocellulose Composites: Toward Wearable Multifunctional Electromagnetic Interference Shielding Application

With the rapid development of mobile communication technology and wearable electronic devices, the electromagnetic radiation generated by high-frequency information exchange inevitably threatens human health, so high-performance wearable electromagnetic interference (EMI) shielding materials are urgently needed. The 2D nanomaterial MXene exhibits superior EMI shielding performance owing to its high conductivity, however, its mechanical properties are limited due to the high porosity between MXene nanosheets. In recent years, it has been reported that by introducing natural nanocellulose as an organic framework, the EMI shielding and mechanical properties of MXene/nanocellulose composites can be synergically improved, which are expected to be widely used in wearable multifunctional shielding devices. In this review, the electromagnetic wave (EMW) attenuation mechanism of EMI shielding materials is briefly introduced, and the latest progress of MXene/nanocellulose composites in wearable multifunctional EMI shielding applications is comprehensively reviewed, wherein the advantages and disadvantages of different preparation methods and various types of composites are summarized. Finally, the challenges and perspectives are discussed, regarding the performance improvement, the performance control mechanism, and the large-scale production of MXene/nanocellulose composites. This review can provide guidance on the design of flexible MXene/nanocellulose composites for multifunctional electromagnetic protection applications in the future intelligent wearable field.

Cellulose-based functional textiles through surface nano-engineering with MXene and MXene-based composites

The emergence of smart textiles with the ability to regulate body temperature, monitor human motion, exhibit antibacterial properties, sound fire alarms, and offer fire resistance has sparked considerable interest in recently. MXene displays remarkable attributes like high metallic conductivity, electromagnetic shielding capability, and photothermal/electrothermal properties. Furthermore, due to the highly polar surface groups, MXene nanosheets show exceptional hydrophilic properties and are able to establish strong connections with the polar surfaces of natural fabrics. This review focuses on the most recent developments in altering the surface of cellulosic textiles with MXene and MXene-based composites. The combination of MXene with other modifier agents, such as phosphorous compounds, graphene, carbon nanotube, conductive polymers, antibacterial macromolecules, superhydrophobic polymers, and metal or metal oxide nanoparticles, imparts diverse functionalities to textiles, such as self-cleaning and fire resistance. Moreover, the synergistic effects between these modifier agents with MXenes can improve MXene-related properties like antibacterial, photothermal, electrothermal, and motion- and fire-sensing characteristics.

High-Performance Flexible Pressure Sensor with Micropyramid Structure for Human Motion Signal Detection and Electromagnetic Interference Shielding

Flexible pressure sensors have a wide range of applications in the field of human motion signal detection, but the electromagnetic radiation generated during the monitoring process has become an unavoidable problem. Nowadays, it is still a challenge to develop high-performance pressure sensors with excellent electromagnetic interference (EMI) shielding performance. Herein, the Ti3C2TX MXene/carbon fiber/multiwalled carbon nanotube/polydimethylsiloxane (MXene/CMP) films with a micropyramidal structure were developed by the technology of vacuum high-temperature hot pressing and spray deposition. Benefiting from the dielectric loss of the conductive fillers and the presence of the microstructure, the MXene/CMP film exhibits excellent EMI shielding performance, and the EMI shielding efficiency (SE) can reach 49.37 dB. Besides, the introduction of CF effectively improves the mechanical properties of the MXene/CMP films, and the MXene nanosheets deposited on the surface of the film can reduce stress concentration, which in turn delays the expansion of cracks. Furthermore, the MXene/CMP sensor exhibits high sensitivity (89.76 kPa-1) and fast response/recovery time (61/60 ms). The deformation of microstructure and the construction of conductive networks enable the sensor to realize the monitoring of human motion signals (such as finger bending, knee bending, wrist bending, etc.). Meanwhile, the sensor maintains sensing stability even after 2000 pressure cycles, which can be attributed to the improvement in mechanical properties. In summary, the developed high-performance flexible pressure sensor with micropyramid structure has great application prospects in wearable devices and healthcare.

Yarn-Based Degradable Janus PPDO Fabric for Multifunctional Applications

The growing high standard of people's wear has put forward requirements for fabrics, and multifunctional fabrics have been developed precisely in response to the requirements of the times. However, the incineration of waste fabrics produces a large amount of pollutants, resulting in a massive waste of resources and environmental pollution. Herein, the degradable nanofiber yarns (NYs) with self-cleaning properties were fabricated by in situ growth of SiO2 nanoparticles on the surface of the electrospun poly(p-dioxanone) (PPDO) NYs using the Stöber method. Then, the PPDO NYs were blended with carbon fibers and the PPDO/SiO2 NYs with themselves to form the Janus PPDO fabrics, respectively. The Janus PPDO fabric offered asymmetric wettability and dual personal thermal management properties. The PPDO/C side of the Janus PPDO fabric provided 65.8 °C at 1.5 V or 58.5 °C under one sunlight intensity for radiative heating. The PPDO/SiO2 side exhibited high solar reflectivity (81.8%) and mid-infrared (MIR) emissivity (99.1%), which reduced the skin temperature by 4.6 °C, resulting in radiative cooling. Moreover, the Janus PPDO fabrics display an excellent electromagnetic interference (EMI) shielding performance (53.3 dB). Therefore, yarn-based degradable Janus fabric has a promising future in multifunctional wearable products.

Advanced functional materials based on nanocellulose/Mxene: A review

The escalating need for a sustainable future has driven the advancement of renewable functional materials. Nanocellulose, derived from the abundant natural biopolymer cellulose, demonstrates noteworthy characteristics, including high surface area, crystallinity, mechanical strength, and modifiable chemistry. When combined with two-dimensional (2D) graphitic materials, nanocellulose can generate sophisticated hybrid materials with diverse applications as building blocks, carriers, scaffolds, and reinforcing constituents. This review highlights the progress of research on advanced functional materials based on the integration of nanocellulose, a versatile biopolymer with tailorable properties, and MXenes, a new class of 2D transition metal carbides/nitrides known for their excellent conductivity, mechanical strength, and large surface area. By addressing the challenges and envisioning future prospects, this review underscores the burgeoning opportunities inherent in MXene/nanocellulose composites, heralding a sustainable frontier in the field of materials science.

Multilayer Core-Shell Fiber Device for Improved Strain Sensing and Supercapacitor Applications

1D fiber devices, known for their exceptional flexibility and seamless integration capabilities, often face trade-offs between desired wearable application characteristics and actual performance. In this study, a multilayer device composed of carbon nanotube (CNT), transition metal carbides/nitrides (MXenes), and cotton fibers, fabricated using a dry spinning method is presented, which significantly enhances both strain sensing and supercapacitor functionality. This core-shell fiber design achieves a record-high sensitivity (GF ≈ 4500) and maintains robust durability under various environmental conditions. Furthermore, the design approach markedly influences capacitance, correlating with the percentage of active material used. Through systematic optimization, the fiber device exhibited a capacitance 26-fold greater than that of a standard neat CNT fiber, emphasizing the crucial role of innovative design and high active material loading in improving device performance.

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.

MXene Composite Electromagnetic Shielding Materials: The Latest Research Status

MXene emerges as a premier candidate for electromagnetic shielding owing to its unique properties as a novel two-dimensional material. Its exceptional electrical conductivity, chemical reactivity, surface tunability, and facile processing render it highly suitable for diverse electromagnetic shielding applications. The research status of MXene and MXene-based electromagnetic shielding materials is systematically discussed in this paper. First, the research status of MXene as a single-component electromagnetic shielding material is briefly introduced. Subsequently, the research status of composite structures constructed by MXene with polymers, carbon derivatives, and ferrites is introduced in detail. Furthermore, the research progress of MXene-based ternary and quaternary composite electromagnetic shielding materials is further focused. Finally, the application of MXene-based composite electromagnetic shielding materials is prospected. A deeper understanding of MXene's electromagnetic shielding properties is facilitated by this paper, providing the direction for the future development of two-dimensional materials in the design and processing of electromagnetic shielding materials.

Recent advances in multifunctional electromagnetic interference shielding materials

Electromagnetic interference (EMI) shielding material is the most effective solution to protect electronic devices and human health from the harmful effects of electromagnetic radiation. The study of EMI shielding materials is intensifying in the constantly developing picture of the fourth industrial revolution. Many EMI shielding materials based on metal, carbon, emerging MXene materials, and their composites have been discovered to utilize the EMI shielding performance. However, a huge demand for compact and multi-functional devices requires the integration of new functions into EMI shielding materials. Multifunctional EMI shielding materials perform multiple functions beyond their main function of EMI shielding in a system due to their specific properties. The additional functions can either naturally exist or be specially engineered. This review summarizes the recent progress of cutting-edge multifunctional EMI shielding materials. The possibility of combining multifunction EMI shielding materials, such as strain sensing, humidity sensing, temperature sensing, thermal management, etc., and the difficulties in balancing EMI shielding performance with other functions are also discussed. Lastly, we point out challenges and propose future directions to develop research on multifunctional EMI shielding materials.

In Situ Synthesis of Liquid Metal Conductive Fibers toward Smart Cloth

To meet the diverse needs of humans, smart cloth has become a potential research hotspot to replace traditional cloth. However, it is challenging to manufacture a flexible fabric with multiple functions. Here, we introduce a smart cloth based on liquid metal (LM) conductive fibers. Ga2O3 nanoparticles are obtained through ultrasonic pretreatment. Furthermore, a coordination bond is formed between thiol groups on the surface of protein fibers and Ga2O3 through a scraping method, allowing Ga2O3 particles to be grafted onto the surface of protein fibers in situ. Finally, LM conductive fibers are encapsulated using a photocuring adhesive. In addition, a wearable smart cloth integrated with multiple sensors has been developed based on LM conductive fibers. Users can not only monitor their movement trajectory and the surrounding environment in real time but also have their data supervised by family members through a client, achieving remote and continuous monitoring. The development of this wearable smart cloth provides strong support for future wearable, flexible electronic devices.

Architectural design and affecting factors of MXene-based textronics for real-world application

Today, textile-based wearable electronic devices (textronics) have been developed by taking advantage of nanotechnology and textile substrates. Textile substrates offer flexibility, air permeability, breathability, and wearability, whereas, using nanomaterials offers numerous functional properties, like electrical conductivity, hydrophobicity, touch sensitivity, self-healing properties, joule heating properties, and many more. For these reasons, textronics have been extensively used in many applications. Recently, new emerging two-dimensional (2D) transition metal carbide and nitride, known as MXene, nanomaterials have been highly considered for developing textronics because the surface functional groups and hydrophilicity of MXene nanoflakes allow the facile fabrication of MXene-based textronics. In addition, MXene nanosheets possess excellent electroconductivity and mechanical properties as well as large surface area, which also give numerous opportunities to develop novel functional MXene/textile-based wearable electronic devices. Therefore, this review summarizes the recent advancements in the architectural design of MXene-based textronics, like fiber, yarn, and fabric. Regarding the fabrication of MXene/textile composites, numerous factors affect the functional properties (e.g. fabric structure, MXene size, etc.). All the crucial affecting parameters, which should be chosen carefully during the fabrication process, are critically discussed here. Next, the recent applications of MXene-based textronics in supercapacitors, thermotherapy, and sensors are elaborately delineated. Finally, the existing challenges and future scopes associated with the development of MXene-based textronics are presented.

Deep eutectic supramolecular polymer functionalized MXene for enhancing mechanical properties, photothermal conversion, and bacterial inactivation of cellulose textiles

Two-dimensional (2D) transition metal carbides (Ti3C2Tx MXene) have gained significant attention for their potential in constructing diverse functional materials, However, MXene is easily oxidized and weakly bound to the cellulose matrix, which pose challenges in developing MXene-decorated non-woven fabric with strong bonding and stable thermal management properties. Herein, we successfully prepared deep eutectic supramolecular polymer (DESP) functionalized MXene to address these issues. MXene can be wrapped with DESP to be insulated from water and protected from being oxidized. Subsequently, we achieved an efficient in-situ deposition of DESP-functionalized MXene onto fibers through a combination of dip coating and photopolymerization technique. The resulting nonwoven fabric (CNs-DESP@M) exhibited excellent photothermal conversion properties along with rapid thermal response and functional stability. Interestingly, the interface bonding between MXene and the fiber surface was significantly enhanced due to the abundant pyrogallol groups in DESP, resulting in the composite textile exhibiting commendable mechanical properties (2.68 MPa). Moreover, the as-prepared textile demonstrates outstanding bactericidal efficacy against both Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). The multifunctional textile, created through a facile and efficient approach, demonstrates remarkable potential for applications in smart textiles, catering to the diverse needs of individuals in the future.

Ti3C2Tx MXene-based hybrid nanocoating for flame retardant, early fire-warning and piezoresistive tension sensing smart polyester fabrics

Flammability feature of textiles is a big underlying risk causing fire disasters. The fabrication of reliable fire resistant and quick fire warning fabrics is imperative but challenging. Herein, three types of early fire-warning polyester fabrics, namely, FPP@AM-X, FPP@PM-X and FPP@AX-M1, with good flame retardant and piezoresistive sensing performance were developed by fabricating polyethyleneimine (PEI), ammonium polyphosphate (APP), phytic acid (PA) and MXenes onto phosphorus-containing flame retardant polyethylene terephthalate (FRPET) via polydopamine (PDA) mediated layer-by-layer self-assembly. Owing to the improved thermoelectric properties of MXenes, FPP@A5-M1 exhibited a maximum thermoelectric voltage of 0.59 mV at a temperature difference of 130 °C and can provide an ideal cyclic early fire warning response within 4 s. In addition, due to the synergistic flame retardant effect of MXenes and APP in the coating layer, FPP@A5-M1 could be self-extinguished within 2 s after ignition and the value of peak heat release ratio and total smoke production decreased by 41.9% and 30.4%, respectively. Besides, the MXene-based hybrid coated fabric can detect the movement of human fingers and elbows, illustrating its potential application in piezoresistive tension sensing. This work provides a new route to designing and developing multi-functional and smart fire protection fabrics.

Multifunctional MnFe2O4/TiO2/Ti3C2Tx composites based on in-situ grown TiO2 for efficient microwave absorption, high hydrophobicity, and heat dissipation properties

Despite the fact that the 2D structure Ti3C2Tx with abundant defects and functional groups contributes to the high microwave absorption (MA) performance, it is difficulty to improve the strength and bandwidth by pursuing higher conductivity or loading more groups due to the limitation of intrinsic properties. Therefore, it is important to ingeniously design efficient Ti3C2Tx based MA composites assembling the features of abundant surface groups, good dispersibility, multiple composition, and precise structure. Inspired by the fact that Ti3C2Tx contains thermodynamically metastable marginal Ti atoms, TiO2 nanoparticles can be grown in-situ on Ti3C2Tx nanosheets uniformly and increase the spacing of Ti3C2Tx layers, and then MnFe2O4 nanoparticles are introduced into the layers of Ti3C2Tx by electrostatic self-assembly method for optimized impedance matching. This designed hierarchical MnFe2O4/TiO2/Ti3C2Tx composites shows excellent MA performance, and the minimum reflection loss (RLmin) reaches -46.91 dB with a thickness of 2.5 mm at frequency of 10.4 GHz. The high MA performance mainly comes from the enhanced interfacial polarization induced by edges location and interface region among TiO2, MnFe2O4, and Ti3C2Tx. In addition, the conduction loss existed in the interior untreated Ti3C2Tx, the dielectric loss generated by multiple composition, the multiple scattering from improved large surface specific area all contribute to the excellent MA performance. Meanwhile, the simple preparation process and good stability storage at room temperature under air atmosphere of the MnFe2O4/TiO2/Ti3C2Tx composites promote its exploration on practical use, and the lab-gown cloth coated with MnFe2O4/TiO2/Ti3C2Tx composites shows better electromagnetic shielding properties, hydrophobicity, and heat transfer ability than pure fabric, showing the potential for practical application.

Tunable construction of fire safe and mechanically strong hierarchical composites towards electromagnetic interference shielding

Cotton fabric composites were designed to be protected by fire safe thermoplastic polyurethane (TPU) composites for developing electromagnetic interference (EMI) shielding polymer composites with superior mechanical properties. Herein, the as-prepared MXene was coated onto the fiber surface of cotton and then thermally compressed with TPU composites, which were filled with the sodium dodecyl sulfate modified layered double hydroxides functionalized the short carbon fiber hybrids through melt blending method. Then, a series of highly fire safe cotton/TPU hierarchical composites were constructed by a designed thermal compression technique. For instance, the obtained cotton/TPU hierarchical sample showed greatly reduced peak of heat release rate, peak of carbon monoxide production rate and peak of carbon dioxide production rate of TPU by 50.1%, 52.1% and 55.4%, respectively. Furthermore, the cotton/TPU hierarchical composites possessed the EMI shielding effectiveness of 40.0 dB in the X band and 54.6 dB in the K band. The mechanical property of the cotton/TPU hierarchical composites was also reinforced, where the elongation at break and toughness values of the TPU/SCF/mLDH1/C2 hierarchical composite were 21.47 and 18.30 times higher than those of pure TPU, respectively. These mechanically strong hierarchical composites have brought a promising attempt to broaden their practical application, removing the fire hazards and electromagnetic waves radiation from the environment.

Thermally Conductive MXene

MXene materials, which consist of nitrides, carbides, or carbonitrides of transition metals, possess a distinctive multilayered structure resulting from the specific etching of the "A" layer from MAX phase precursors. This unique structure allows for tunable properties through intercalation and surface modification. Beyond their structural novelty, MXenes exhibit exceptional thermal conductivity, mechanical resilience, and versatile surface functionalization capabilities, rendering them highly versatile for a wide range of applications. They are particularly renowned for their multifaceted utility and are emerging as outstanding candidates in applications requiring robust thermal conductivity. MXenes, when integrated into textile, fiber, and film forms, have gained increasing relevance in fields where efficient heat management is essential. This work provides a comprehensive exploration of MXene materials, delving into their inherent structure and thermal properties. This Perspective places particular emphasis on their crucial role in efficient heat dissipation, which is vital for the development of wearable heaters and related technologies. Engineered compounds such as MXenes have become indispensable for personal and industrial heating applications, and the advancement of wearable electronic devices necessitates heaters with specific properties, including transparency, mechanical reliability, and adaptability. Recent advancements in emergent thermally conductive MXene compounds are discussed in this study, shedding light on their potential contributions across various domains, including wearable heaters and biosensors for healthcare and environmental monitoring. Furthermore, the versatile nature of MXene materials extends to their application in interfacial solar steam generation, representing a breakthrough approach for solar water desalination. This multifaceted utility underscores the vast potential of MXenes in addressing various pressing challenges.

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.

Mechanically Tough and Highly Stretchable Hydrogels Based on Polyurethane for Sensitive Strain Sensor

Hydrogels with flexible and stretchable properties are ideal for applications in wearable sensors. However, traditional hydrogel-based sensors suffer from high brittleness and low electrical sensitivity. In this case, to solve this dilemma, a macromolecular polyurethane crosslinking agent (PCA) was designed and prepared; after that, PCA and two-dimensional (2D) MXene nanosheets were both introduced into a covalently crosslinked network to enhance the comprehensive mechanical and electrochemical properties of the hydrogels. The macromolecular polyurethane crosslinking agent promotes high-tensile strength and highly stretchable capacity by suitable covalent crosslinking. The optimized hydrogel, which exhibited maximum tensile strength and maximum elongation at break, had results of 1.21 MPa and 644%, respectively. Two-dimensional MXene nanosheets provide hydrogel with high electrical conductivity and strain sensitivity, producing a wearable device for the continuous monitoring of human movements and facial microexpressions. This study demonstrated an efficient structure design strategy for building mechanically tough, highly stretchable, and sensitive dual-mode MXenes-based wearable sensors.

Thermoplastic Electromagnetic Shielding Materials from the Integral Recycling of Waste from Electronic Equipment

The European Green Deal's goals are anticipated to be fulfilled in large part thanks to the New Circular Economy Action Plan. It is believed that recycling materials will have a significant positive impact on the environment, particularly in terms of reducing greenhouse gas emissions and the impacts this will have on preventing climate change. Due to the complexity of the issue and its significant practical ramifications, the activity of Waste Electrical and Electronic Equipment (WEEE) collection networks is a subject of interest for researchers and managers, in accordance with the principles that recent laws have addressed in a large number of industrialized countries. The goal of this paper is to characterize and obtain composite materials using an injection process with a matrix of LDPE, PP, and HDPE, with up to a 10% addition of nonmetallic powders from PCBs and electronic parts from an integrated process of WEEE recycling. The composites present relevant thermal, electrical, and mechanical properties. Such composite materials, due to their relevant dielectric properties, may be further tested for applications in electromagnetic shielding at frequencies above 1 kHz, or for electromagnetic interference/electromagnetic compatibility (EMI/EMC and ESD) applications at lower frequencies due to their superior dielectric loss factor values, associated with relevant behaviors around exploitation temperatures, mainly for the electric, electronic, or automotive industries.

Effect of Atmospheric Temperature on Epoxy Coating Reinforced with Carbon Nanotubes for De-Icing on Road Systems

Traffic accidents caused by road icing are a serious global problem, and conventional de-icing methods like spraying chemicals have several limitations, including excessive manpower management, road damage, and environmental pollution. In this study, the carbon nanotubes reinforced de-icing coating for the road system with a self-heating function was developed as part of the development of a new system to prevent accidents caused by road icing. The electrical characteristics of the fabricated coating were analyzed, and the carbon nanotube coating heating performance experiment was conducted to measure the temperature increments by applying a voltage to the coating at a sub-zero temperature using an environmental chamber. In addition, the coating was installed on the road pavement and the applicability was investigated through a heating test in winter. As a result of the experiment, the coating made with the higher carbon nanotube concentration presented higher heating owing to its higher electrical conductivity. In addition, the coating showed sufficient heating performance, although the maximum temperature by Joule heating decreased for the entire coating at sub-zero temperatures. Finally, field tests demonstrated the potential of electrically conductive coatings for de-icing applications.

Pattern design of a liquid metal-based wearable heater for constant heat generation under biaxial strain

As the wearable heater is increasingly popular due to its versatile applications, there is a growing need to improve the tensile stability of the wearable heater. However, maintaining the stability and precise control of heating in resistive heaters for wearable electronics remains challenging due to multiaxial dynamic deformation with human motion. Here, we propose a pattern study for a circuit control system without complex structure or deep learning of the liquid metal (LM)-based wearable heater. The LM direct ink writing (DIW) method was used to fabricate the wearable heaters in various designs. Through the study about the pattern, the significance of input power per unit area for steady average temperature with tension was proven, and the directionality of the pattern was shown to be a factor that makes feedback control difficult due to the difference in resistance change according to strain direction. For this issue, a wearable heater with the same minimal resistance change regardless of the tension direction was developed using Peano curves and sinuous pattern structure. Lastly, by attaching to a human body model, the wearable heater with the circuit control system shows stable heating (52.64°C, with a standard deviation of 0.91°C) in actual motion.

Recent Progress in Emerging Novel MXenes Based Materials and their Fascinating Sensing Applications

Early transition metals based 2D carbides, nitrides and carbonitrides nanomaterials are known as MXenes, a novel and extensive new class of 2D materials family. Since the first accidently synthesis based discovery of Ti₃ C₂ in 2011, more than 50 additional compositions have been experimentally reported, including at least eight distinct synthesis methods and also more than 100 stoichiometries are theoretically studied. Due to its distinctive surface chemistry, graphene like shape, metallic conductivity, high hydrophilicity, outstanding mechanical and thermal properties, redox capacity and affordable with mass-produced nature, this diverse MXenes are of tremendous scientific and technological significance. In this review, first we'll come across the MXene based nanomaterials possible synthesis methods, their advantages, limitations and future suggestions, new chemistry related to their selected properties and potential sensing applications, which will help us to explain why this family is growing very fast as compared to other 2D families. Secondly, problems that help to further improve commercialization of the MXene nanomaterials based sensors are examined, and many advances in the commercializing of the MXene nanomaterials based sensors are proposed. At the end, we'll go through the current challenges, limitations and future suggestions.

A review on accelerated development of skin-like MXene electrodes: from experimental to machine learning

Foreshadowing future needs has catapulted the progress of skin-like electronic devices for human-machine interactions. These devices possess human skin-like properties such as stretchability, self-healability, transparency, biocompatibility, and wearability. This review highlights the recent progress in a promising material, MXenes, to realize soft, deformable, skin-like electrodes. Various structural designs, fabrication strategies, and rational guidelines adopted to realize MXene-based skin-like electrodes are outlined. We explicitly discussed machine learning-based material informatics to understand and predict the properties of MXenes. Finally, an outlook on the existing challenges and the future roadmap to realize soft skin-like MXene electrodes to facilitate technological advances in the next-generation human-machine interactions has been described.

Conductive fibers for biomedical applications

Bioelectricity has been stated as a key factor in regulating cell activity and tissue function in electroactive tissues. Thus, various biomedical electronic constructs have been developed to interfere with cell behaviors to promote tissue regeneration, or to interface with cells or tissue/organ surfaces to acquire physiological status via electrical signals. Benefiting from the outstanding advantages of flexibility, structural diversity, customizable mechanical properties, and tunable distribution of conductive components, conductive fibers are able to avoid the damage-inducing mechanical mismatch between the construct and the biological environment, in return to ensure stable functioning of such constructs during physiological deformation. Herein, this review starts by presenting current fabrication technologies of conductive fibers including wet spinning, microfluidic spinning, electrospinning and 3D printing as well as surface modification on fibers and fiber assemblies. To provide an update on the biomedical applications of conductive fibers and fiber assemblies, we further elaborate conductive fibrous constructs utilized in tissue engineering and regeneration, implantable healthcare bioelectronics, and wearable healthcare bioelectronics. To conclude, current challenges and future perspectives of biomedical electronic constructs built by conductive fibers are discussed.

Versatile Electronic Textile Enabled by a Mixed-Dimensional Assembly Strategy

Electronic textiles (e-textiles) hold great promise for serving as next-generation wearable electronics owing to their inherent flexible, air-permeable, and lightweight characteristics. However, these e-textiles are of limited performance mainly because of lacking powerful materials combination. Herein, a versatile e-textile through a simple, high-efficiency mixed-dimensional assembly of 2D MXene nanosheets and 1D silver nanowires (AgNWs) are presented. The effective complementary actions of MXene and AgNWs endow the e-textiles with superior integrated performances including self-powered pressure sensing, ultrafast joule heating, and highly efficient electromagnetic interference (EMI) shielding. The textile-based self-powered smart sensor systems obtained through the screen-printed assembly of MXene-based supercapacitor and pressure sensor are flexible and lightweight, showing ultrahigh specific capacitance (2390 mF cm^-2 ), robust areal energy density (119.5 µWh cm^-2 ), excellent sensitivity (474.8 kPa^-1 ), and low detection limit (1 Pa). Furthermore, the interconnected conductive MXene/AgNWs network enables the e-textile with ultrafast temperature response (10.4 °C s^-1 ) and outstanding EMI shielding effectiveness of ≈66.4 dB. Therefore, the proposed mixed-dimensional assembly design creates a multifunctional e-textile that offers a practical paradigm for next-generation smart flexible electronics.

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.

Multifunctional MoSe2 @MXene Heterostructure-Decorated Cellulose Fabric for Wearable Thermal Therapy

A booming demand for wearable electronic devices urges the development of multifunctional smart fabrics. However, it is still facing a challenge to fabricate multifunctional smart fabrics with satisfactory mechanical property, excellent Joule heating performance, highly efficient photothermal conversion, outstanding electromagnetic shielding effectiveness, and superior anti-bacterial capability. Here, a MoSe₂ @MXene heterostructure-based multifunctional cellulose fabric is fabricated by depositing MXene nanosheets onto cellulose fabric followed by a facile hydrothermal method to grow MoSe₂ nanoflakes on MXene layers. A low-voltage Joule heating therapy platform with rapid Joule heating response (up to 230 °C in 25 s at a supplied voltage of 4 V) and stable performance under repeated bending cycles (up to 1000 cycles) is realized. Besides, the multifunctional fabric also exhibits excellent photothermal performance (up to 130 °C upon irradiation for 25 s with a light intensity of 400 mW cm^-2 ), outstanding electromagnetic interference shielding effectiveness (37 dB), and excellent antibacterial performances (>90% anti-bacterial rate toward Escherichia coli, Bacillus subtilis, and Staphylococcus aureus). This work offers an efficient avenue to fabricate multifunctional wearable thermal therapy devices for mobile healthcare and personal thermal management.

Fabrication of Porous Carbon Nanofibers from Polymer Blends Using Template Method for Electrode-Active Materials in Supercapacitor

Porous carbon nanofibers (PCNFs) with excellent physical and chemical properties have been considered candidate materials for electrodes used in supercapacitors. Herein, we report a facile procedure to fabricate PCNFs through electrospinning blended polymers into nanofibers followed by pre-oxidation and carbonization. Polysulfone (PSF), high amylose starch (HAS), and phenolic resin (PR) are used as three different kinds of template pore-forming agents. The effects of pore-forming agents on the structure and properties of PCNFs have been systematically studied. The surface morphology, chemical components, graphitized crystallization, and pore characteristics of PCNFs are analyzed by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and nitrogen adsorption and desorption test, respectively. The pore-forming mechanism of PCNFs is analyzed by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Fabricated PCNF-R have a specific surface area as high as ~994 m²/g, a total pore volume as high as ~0.75 cm³/g, and a good graphitization degree. When PCNF-R are used as active materials to fabricate into electrodes, the PCNF-R electrodes show a high specific capacitance ~350 F/g, a good rate capability ~72.6%, a low internal resistance ~0.55 Ω, and an excellent cycling stability ~100% after 10,000 charging and discharging cycles. The design of low-cost PCNFs is expected to be widely applicable for the development of high-performance electrodes for an energy storage field.

Multilayer Ultrathin MXene@AgNW@MoS2 Composite Film for High-Efficiency Electromagnetic Shielding

Structure and material composition is crucial in realizing high electromagnetic interference (EMI) shielding effectiveness (SE). Herein, an ultrathin MXene@AgNW@MoS₂ (MAM) composite film that resembles the structure of a pork belly and exhibits superior EMI shielding performance was fabricated via the vacuum-assisted suction filtration process and atomic layer deposition (ALD). The staggered AgNWs form skeletons and intersperse in MXene sheets to build a doped layer with three-dimensional network structures, which improves the electrical conductivity of the film. Based on the optimal dispersion concentration of Ag in doped and single layers, the MXene/AgNW doped layer and AgNW single layer are alternately vacuum-assisted-filtered to obtain laminated structures with multiple heterogeneous interfaces. These interfaces generate interface polarization and increase multiple reflection and scattering, resulting in the increased electromagnetic (EM) wave losses. On the other hand, MoS₂ outer nanolayers fabricated precisely by ALD effectively increases the absorption proportion of electromagnetic waves, reduces the secondary reflection, and improves the stability of EMI shielding properties. Ultimately, an ultrathin MAM film (a thickness of 0.03 mm) with five alternating internal layers and MoS₂ outer layers exhibits an excellent EMI SE of 86.3 dB in the X-band.

Multifunctional Superamphiphobic Cotton Fabrics with Highly Efficient Flame Retardancy, Self-Cleaning, and Electromagnetic Interference Shielding

Here, a facile method is reported to prepare multifunctional cotton fabrics with high flame retardancy, high electrical conductivity, superamphiphobicity, and high electromagnetic shielding. The cotton fabric surface was first modified with phytic acid (PA), which promoted dehydration and carbonization of cellulose to increase flame retardancy in the process of pyrolysis. Tannic acid (TA) and 3-aminopropyltriethoxysilane (APTES) coating with nanospheres as interlayers created hierarchical roughness that facilitated the construction of superamphiphobic surfaces and provided adhesion sites for silver nanoparticles. In addition, the TA-APTES coating improved flame retardancy because the APTES-containing silicon could form silicon carbon layers to isolate heat and oxygen. Subsequently, the surface energy of the composite cotton fabric was reduced by fluorine-containing molecules. The prepared composite cotton fabric exhibited excellent superamphiphobicity with contact angles of 160.3 and 152° for water and olive oil, respectively. The conductivity and EMI shielding efficiency of the prepared composite cotton fabric reached 629.93 S/cm and 76 dB, respectively. Importantly, the composite cotton fabric maintained a relatively stable EMI shielding efficiency even after cyclic bending and abrasion tests. Moreover, the composite cotton fabric possessed a high limiting oxygen index (LOI) of 45.3% and self-extinguishing properties with the peak heat release rate (PHHR) and total heat release (THR) reduced by 73 and 67%, respectively, than the pure cotton fabric, indicating the outstanding flame retardancy.

Flexible Pressure Sensor Decorated with MXene and Reduced Graphene Oxide Composites for Motion Detection, Information Transmission, and Pressure Sensing Performance

Although fiber-based flexible piezoresistive pressure sensors have received extensive attention because of their simple fabrication and easy integration, the common practice of using a single material as the sensing layer often leads to unsatisfactory sensitivity and a limited sensing range. Herein, we exploit the combination of reduced graphene oxide (rGO) and two-dimensional transition-metal carbides and nitrides (MXene), use a polyester filament (PET) as the fiber matrix, and fabricate an MX/rGO PET-based flexible pressure sensor using the "dipping-drying" method. A systematic study is conducted concerning the effect of the dip-coating sequence and material combination on the sensor's resistance and sensitivity, which reveals that MX/rGO PET has the smallest resistance and the highest sensitivity (1.24 kPa^-1). A series of tests are conducted to evaluate the pressure sensing characteristics of the MX/rGO PET-based pressure sensor, confirming its good linearity, fast response speed, low detection limit, and stable performance. In addition, the sensor has been successfully used to monitor various human joint activities and physiological signals such as breathing, demonstrating great application potential in the field of personal health care. To further enhance the practical utility, an APP has been designed to analyze and display the collected signals, and the constructed sensor network also provides an ingenious method for information encryption and transmission via pressure sensing. In all, the MX/rGO PET-based pressure sensor proposed in this work is expected to provide a competitive scheme for wearable flexible electronic devices in information transmission and human-computer interaction in the future.

Generation of cost-effective MXene@polydopamine-decorated chitosan nanofibrous wound dressing for promoting wound healing

Herein, we designed and fabricated a MXene@polydopamine (MXene@PDA)-decorated chitosan non-woven fabric (M-CNF) hemostatic dressing with super hydrophilic properties for wound repair and regeneration. The M-CNF exhibit excellently wettability characteristics which can rapidly absorb water from blood. Moreover, M-CNF with 15 mg/mL MXene@PDA (M-CNF-15) show better antibacterial performance, excellent blood-clotting performance, better blood cell and platelet adhesion ability than CNF, displaying both active and passive hemostatic mechanisms to accelerate blood clotting in mouse-liver injury model. In addition, the M-CNF-15 also shows better wound healed performance than Tegaderm™ film in a full-thickness skin defect model, and further demonstrating that the MXene@PDA can promote fibrinogen reformation the at the initial phases of the wound healing process. Therefore, this strategy for designing and manufacturing of multi-functional M-CNF wound dressing will have great potential for active local hemostasis and wound repair and regeneration.

Structural evolution of MXenes and their composites for electromagnetic interference shielding applications

Nowadays, the extensive utilization of electronic devices and equipment inevitably leads to severe electromagnetic interference (EMI) issues. Therefore, EMI shielding materials have drawn considerable attention, and great effort has been devoted to the exploration of high-efficiency EMI shielding materials. As a novel kind of 2D transition metal carbide material, MXenes have been widely investigated for EMI shielding in the past few years due to their extraordinary electrical conductivity, large specific surface area, light weight, and easy processability. In view of the great achievements in MXene-based materials for EMI shielding, herein, we reviewed the recent studies on the structural design and evolution of MXenes and their composites for EMI shielding. First, the methods for structural control of MXenes, including HF etching, in situ HF etching, fluorine-free etching, electrochemical etching, and molten salt etching, are systematically summarized. Then we illustrate the fundamental relationship between the microstructure of MXenes and the EMI shielding mechanism. In the following, the effects of different synthesis methods and structures of MXene-based composite materials as well as their EMI shielding performances are comprehensively discussed. Lastly, future prospects for the development of MXene-based composite materials in EMI shielding applications are commented on.

Durability Study of Thermal Transfer Printed Textile Electrodes for Wearable Electronic Applications

Textile-based electronics hold great promise because they can endow wearable devices with soft and comfortable characteristics. However, the inherent porosity and fluffiness of fabrics result in high surface roughness, which presents great challenges in the manufacture of high-performance fabric electrodes. In this work, we propose a thermal transfer printing method to address the above challenges, in which electrodes or circuits of silver flake/thermoplastic polyurethane (TPU) composites are prefabricated on a release film by coating and laser engraving and then laminated by hot-pressing to a variety of fabrics and textiles. This universal and scalable production technique enables fabric electrodes to be made without compromising the original wearability, washability, and stretchability of textiles. The prepared fabric electrodes exhibit high conductivity (5.48 × 10⁴ S/cm), high adhesion (≥1750 N/m), good abrasion/washing resistance, high patterning resolution (∼40 μm), and good electromechanical performance up to 50% strain. To demonstrate the potential applications, we developed textile-based radio frequency identification (RFID) tags for remote identification and a large-sized heater for wearable thermotherapy. More importantly, the solvent-free thermal transfer printing technology developed in this paper enables people to DIY interesting flexible electronics on clothes with daily tools, which can promote the commercial application of smart textile-based electronics.

High Sensitivity and a Wide Sensing Range Flexible Strain Sensor Based on the V-Groove/Wrinkles Hierarchical Array

Flexible strain sensors occupying a large part of human body detection and wearable electronics, which have a wide sensing range and high sensitivity, are crucial in fully monitoring human motion signals. This study proposed a strategy to construct flexible strain sensors based on the V-groove/wrinkles hierarchical array. The V-groove array was prepared on a polydimethylsiloxane (PDMS) substrate through mold transfer printing. The gold film was sputtered on the prestretching PDMS substrate, and the V-groove/wrinkles hierarchical array was formed after strain release. Compared with the sensors based on single-scale wrinkle structures and a V-groove array, the fabricated strain sensor with the hierarchical array showed high sensitivity (maximum gauge factor up to 2,557.71) and a wide sensing range (up to 45%). In addition, the dynamic characteristics of the sensor were investigated in detail, indicating that the sensor had a fast response (less than 130 ms), a low detection limit (0.1% strain), and good stability (almost no performance loss after 10,000 cycles). In practical applications, the sensor was used to detect sizable physical motion and weak physiological signals, demonstrating great potential application value in human motion detection. This study could provide new ideas for preparing high-performance flexible strain sensors.

Fully Printed Stretchable and Multifunctional E-Textiles for Aesthetic Wearable Electronic Systems

Electronic textiles (e-textiles) that combine the wearing comfort of textiles and the functionality of soft electronics are highly demanded in wearable applications. However, fabricating robust high-performance stretchable e-textiles with good abrasion resistance and high-resolution aesthetic patterns for high-throughput manufacturing and practical applications remains challenging. Herein, the authors report a new multifunctional e-textile fabricated via screen printing of the water-based silver fractal dendrites conductive ink. The as-fabricated e-textiles spray-coated with the invisible waterproofing agent exhibit superior flexibility, water resistance, wearing comfort, air permeability, and abrasion resistance, achieving a low sheet resistance of 0.088 Ω sq^-1 , high stretchability of up to 154%, and excellent dynamic stability for over 1000 cyclic testing (ε = 100%). The printed e-textiles can be explored as strain sensors and ultralow voltage-driven Joule heaters driven for personalized thermal management. They finally demonstrate an integrated aesthetic smart clothing made of their multifunctional e-textiles for human motion detection and body-temperature management. The printed e-textiles provide new opportunities for developing novel wearable electronics and smart clothing for future commercial applications.

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

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

PDMS-Encapsulated MXene@Polyester Fabric Strain Sensor for Multifunctional Sensing Applications

Flexible strain sensors based on 2D materials have been proven effective for wearable health monitoring devices, human motion detection, and fitness applications. These sensors are flexible, light, and user-friendly, but their sensitivity and detection range need to be enhanced. Among many 2D materials, MXene attracts much interest due to its remarkable properties, such as high electrical conductivity, excellent mechanical properties, flexibility, and good hydrophilicity. However, it is a challenge to fabricate strain sensors with extreme sensitivity and a wide sensing range. In this work, a multifunctional, cost-effective, and highly sensitive PDMS-encapsulated MXene@polyester fabric strain sensor was fabricated. Firstly, complete adsorption of MXene within the fabric formed conductive networks, and then PDMS was used to endow superhydrophobicity and corrosion resistance. The strain sensor demonstrated multifunctional applications and outstanding performance, such as long-term stability (over 500 cycles) and a wide sensing range (8%). The proposed sensor has promising potential for wearable electronic devices such as health monitoring systems and physiological sensing applications.

Ti3C2Tx MXene-Based Flexible Piezoresistive Physical Sensors

MXenes have received increasing attention due to their two-dimensional layered structure, high conductivity, hydrophilicity, and large specific surface area. Because of these distinctive advantages, MXenes are considered as very competitive pressure-sensitive materials in applications of flexible piezoresistive sensors. This work reviews the preparation methods, basic properties, and assembly methods of MXenes and their recent developments in piezoresistive sensor applications. The recent developments of MXene-based flexible piezoresistive sensors can be categorized into one-dimensional fibrous, two-dimensional planar, and three-dimensional sensors according to their various structures. The trends of multifunctional integration of MXene-based pressure sensors are also summarized. Finally, we end this review by describing the opportunities and challenges for MXene-based pressure sensors and the great prospects of MXenes in the field of pressure sensor applications.

Multifunctional Phase Change Composites Based on Elastic MXene/Silver Nanowire Sponges for Excellent Thermal/Solar/Electric Energy Storage, Shape Memory, and Adjustable Electromagnetic Interference Shielding Functions

Multifunctional phase change materials (PCMs) are highly desirable for the thermal management of miniaturized and integrated electronic devices. However, the development of flexible PCMs possessing heat energy storage, shape memory, and adjustable electromagnetic interference (EMI) shielding properties under complex conditions remains a challenge. Herein, the multifunctional PCM composites were prepared by encapsulating poly(ethylene glycol) (PEG) into porous MXene/silver nanowire (AgNW) hybrid sponges by vacuum impregnation. Melamine foams (MFs) were chosen as a template to coat with MXene/AgNW (MA) to construct a continuous electrical/thermal conductive network. The MF@MA/PEG composites showed a high latent heat (141.3 J/g), high dimension retention ratio (96.8%), good electrical conductivity (75.3 S/m), and largely enhanced thermal conductivity (2.6 times of MF/PEG). Moreover, by triggering the phase change of the PEG, the sponges displayed a significant photoinduced shape memory function with a high shape fixation ratio (∼100%) and recovery ratio (∼100%). Interestingly, the EMI shielding effectiveness (SE) can be adjusted from 12.4 to 30.5 dB by a facile compression-recovery process based on shape memory properties. Furthermore, a finite element simulation was conducted to emphasize the advantage of the MF@MA/PEG composites in the thermal management of chips. Such flexible PCM composites with high latent heat storage, light-actuated shape memory, and adjustable EMI shielding functions exhibit great potential as smart thermal management materials in military and aerospace applications.