Ice-Templated MXene/Ag-Epoxy Nanocomposites as High-Performance Thermal Management Materials

Enhanced thermal management of mats and yarns from polystyrene fibers through incorporation of exfoliated graphite

The energy crisis, driven by modern electronics and global warming from population growth, underscores the need for advanced textiles to regulate thermal environments. Researchers stress the need to improve high-performance polymer mats with enhanced thermal conductivity. This report delves into the morphological, mechanical, and thermal properties of exfoliated graphite (EG) when incorporated into polystyrene (PS) fiber mats and yarns through blend electrospinning. The incorporation of EG inside the fibers allowed us to obtain approximately twofold improvement in maximum stress and toughness compared to pristine PS mats. Thermal camera measurement showed significant improvement in heat transport for PS-EG fibers. The heating test showed a temperature increase of ∼2.5 °C for an EG-loaded PS mat, and in the case of a resistance wire coated with a PS fiber yarn, the increase reached 17 °C. The incorporation of EG into electrospun mats enables the recovery of more energy in the form of heat by enhancing the heating of the sample through infrared radiation. The temperature increased by 2 °C for PS and by 27 °C for PS-EG, respectively. The obtained results exhibit a great potential for the application of electrospun hybrid systems with EG in further advancement in the field of next-generation thermal management.

Boosted Efficiency of Fe2O3 for Photocatalytic CO2 Reduction via Engineering Fe-O-Ti Bonding

Visible light-driven photocatalytic CO2 reduction (CO2RR) offers a sustainable and promising solution to environmental and energy challenges. However, the design of efficient photocatalysts is hindered by poor interface interactions in heterojunctions and a limited understanding of reaction kinetics. A modified Fe2O3 photocatalyst, M-Fe2O3@MXene, is introduced featuring KH-550-modified M-Fe2O3 hollow nanocubes coated with MXene, constructed via an electrostatic and Fe-O-Ti bonding self-assembly method. This design achieves an unprecedented CO production rate of 240 µmol g⁻¹ h⁻¹ among non-noble metal catalysts (8.6 folds vs Fe2O3). The Fe-O-Ti sites enhance *COOH intermediate formation and CO production through higher electron deficiency of Fe3+ and rapid charge transfer. This study offers new insights on the use of functional metal oxides and high-quality Mxene layers to design efficient metal oxide-based photocatalysts.

Convenient in situ self-assembled formation of dual-functional Ag/MXene nanozymes for efficient chemiluminescence sensing

MXenes are attracting increasing interest as a low-cost carrier for the development of nanozymes with enhanced peroxidase or oxidase-like activity. In this work, silver nanoparticles (AgNPs) were synthesized and loaded on Ti3C2 MXene nanosheets (denoted as Ag/MXene) by a simple method, using MXene as a support and reducing agent. The synthesized Ag/MXene composites exhibited satisfactory stability and the peroxidase activity was higher than that of the single components. In the presence of luminol and hydrogen peroxide (H2O2), Ag/MXene could catalyze H2O2 to produce reactive oxygen species (ROS) and act on luminol to generate strong chemiluminescent (CL) signals. Free radical scavenging experiments and electron paramagnetic resonance spectroscopy confirmed the production of these radicals. In this regard, we fabricated a facile biosensor for glutathione (GSH) and uric acid (UA) detection and the results showed good linear relationship between GSH and UA. The linear ranges of GSH and UA were 50 nM to 20 μM and 1 μM to 35 μM, respectively, with low detection limits of 0.83 nM and 0.37 μM. The sensor platform established in this study provides the possibility for developing MXene biosensors with high sensitivity and performance, and lays the solid foundation for expanding the application of MXene in biosensors.

2D Materials-Based Thermal Interface Materials: Structure, Properties, and Applications

The challenges associated with heat dissipation in high-power electronic devices used in communication, new energy, and aerospace equipment have spurred an urgent need for high-performance thermal interface materials (TIMs) to establish efficient heat transfer pathways from the heater (chip) to heat sinks. Recently, emerging 2D materials, such as graphene and boron nitride, renowned for their ultrahigh basal-plane thermal conductivity and the capacity to facilitate cross-scale, multi-morphic structural design, have found widespread use as thermal fillers in the production of high-performance TIMs. To deepen the understanding of 2D material-based TIMs, this review focuses primarily on graphene and boron nitride-based TIMs, exploring their structures, properties, and applications. Building on this foundation, the developmental history of these TIMs is emphasized and a detailed analysis of critical challenges and potential solutions is provided. Additionally, the preparation and application of some other novel 2D materials-based TIMs are briefly introduced, aiming to offer constructive guidance for the future development of high-performance TIMs.

Ultrahigh Thermal Conductivity of Epoxy/Ag Flakes/MXene@Ag Composites Achieved by In Situ Sintering of Silver Nanoparticles

The growing use of high-power and integrated electronic devices has created a need for thermal conductive adhesives (TCAs) with high thermal conductivity (TC) to manage heat dissipation at the interface. However, TCAs are often limited by contact thermal resistance at the interface between materials. In this study, we synthesized MXene@Ag composites through a direct in situ reduction process. The Ag nanoparticles (Ag NPs) generated by the reduction of the MXene interlayer and surface formed effective thermally conductive pathways with Ag flakes within an epoxy resin matrix. Various characterization analyses revealed that adding MXene@Ag composites at a concentration of 3 wt % resulted in a remarkable TC of 40.80 W/(m·K). This value is 8.77 times higher than that achieved with Ag flakes and 7.9 times higher than with MXene filler alone. The improved TC is attributed to the sintering of the in situ reduced Ag NPs during the curing process, which formed a connection between MXene (a highly conductive material) and the Ag flakes, thereby reducing contact thermal resistance. This reduction in contact thermal resistance significantly enhanced the TC of the thermal interface materials (TIMs). This study presents a novel approach for developing materials with exceptionally high TC, opening new possibilities for the design and fabrication of advanced thermal management systems.

Super-Stretchable and High-Energy Micro-Pseudocapacitors Based on MXene Embedded Ag Nanoparticles

The advancement of aqueous micro-supercapacitors offers an enticing prospect for a broad spectrum of applications, spanning from wearable electronics to micro-robotics and sensors. Unfortunately, conventional micro-supercapacitors are characterized by low capacity and slopy voltage profiles, limiting their energy density capabilities. To enhance the performance of these devices, the use of 2D MXene-based compounds has recently been proposed. Apart from their capacitive contributions, these structures can be loaded with redox-active nanowires which increase their energy density and stabilize their operation voltage. However, introducing rigid nanowires into MXene films typically leads to a significant decline in their mechanical properties, particularly in terms of flexibility. To overcome this issue, super stretchable micro-pseudocapacitor electrodes composed of MXene nanosheets and in situ reconstructed Ag nanoparticles (Ag-NP-MXene) are herein demonstrated, delivering high energy density, stable operation voltage of ≈1 V, and fast charging capabilities. Careful experimental analysis and theoretical simulations of the charging mechanism of the Ag-NP-MXene electrodes reveal a dual nature charge storage mechanism involving ad(de)sorption of ions and conversion reaction of Ag nanoparticles. The superior mechanical properties of synthesized films obtained through in situ construction of Ag-NP-MXene structure show an ultra stretchability, allowing the devices to provide stable voltage and energy output even at 100% elongation.

3D-Networks Based Polymer Composites for Multifunctional Thermal Management and Electromagnetic Protection: A Mini Review

The rapid development of miniaturized, high-frequency, and highly integrated microelectronic devices has brought about critical issues in electromagnetic compatibility and thermal management. In recent years, there has been significant interest in lightweight polymer-based composites that offer both electromagnetic interference (EMI) shielding and thermal conductivity. One promising approach involves constructing three-dimensional (3D) interconnection networks using functional fillers in the polymer matrix. These networks have been proven effective in enhancing the thermal and electrical conductivity of the composites. This mini-review focuses on the preparation and properties of 3D network-reinforced polymer composites, specifically those incorporating metal, carbon, ceramic, and hybrid networks. By comparing the effects of different filler types and distribution on the composite materials, the advantages of 3D interconnected conductive networks in polymer composites are highlighted. Additionally, this review addresses the challenges faced in the field of multifunctional thermal management and electromagnetic protection materials and provides insights into future development trends and application prospects of 3D structured composites.

Are MXenes suitable for soft multifunctional composites?

MXenes are a family of two-dimensional (2D) nanomaterials known for their high electrical and thermal conductivity, as well as high aspect ratios. Recent research has focused on dispersing MXenes within compliant polymer matrices, aiming to create flexible and stretchable composites that harness MXenes' exceptional conductivity and aspect ratios. Experimental findings demonstrate the potential of MXene polymer composites (MXPCs) as flexible electrical, thermal conductors, and high dielectric materials, with promising applications in soft matter engineered systems. However, the 2D structure of MXene inclusions and their relatively large elastic modulus can impart increased stiffness to the polymer matrix, posing limitations on the mechanical flexibility of these functional materials. Here, we introduce a modeling platform to predict the mechanics and functionality of MXene elastomer composites and assess their suitability as soft multifunctional materials. Our investigation primarily focuses on understanding the influence of MXenes' size, layered structure, and percolation arrangements on the effective properties of the resulting composites. Through our model, we successfully determined the elastic modulus, thermal conductivity, and dielectric constant of MXene elastomer composites, and our results exhibit strong agreement with those obtained through finite element analysis. By utilizing this framework, we can theoretically identify the necessary microstructures of MXenes and guide the experiments, enabling the creation of MXPCs with the desired synergistic mechanical and functional properties.

Creating Biomimetic Central-Radial Skeletons with Efficient Mass Adsorption and Transport

Porous skeletons play a crucial role in various applications. Their fundamental significance stems from their remarkable surface area and capacity to enhance mass adsorption and transport. Freeze-casting is a commonly utilized methodology for the production of porous skeletons featuring vertically aligned channels. Nevertheless, the resultant single-oriented skeleton displays anisotropic mass transfer characteristics and suboptimal mechanical properties. Our investigation was motivated by the intricate microstructures observed in botanical organisms, leading us to devise an advanced freeze-casting methodology. A novel central-radial skeleton with significantly enhanced capabilities has been successfully engineered. The central-radial architecture demonstrates superior refinement and uniformity in its pore structure, featuring an axial mass transfer axis and meticulously arranged radial channels. This microstructure endows the porous skeleton with a higher compression resilience, superior adsorption rate, and structural maintenance capacity. Through a rigorous examination of the thermal conductivity of skeleton-filled composites coupled with comprehensive COMSOL simulations, the exceptional characteristics of this unique structural arrangement have been definitively ascertained. Furthermore, the efficacy of implementing this skeleton in chip cooling and photothermal conversion has been convincingly substantiated. Our pioneering method of microstructure preparation, employing freeze-casting, holds immense potential in expanding its applicability and inspiring innovative concepts for the advancement of novel structures.

Cellulose-Based Intelligent Responsive Materials: A Review

Due to the rapid development of intelligent technology and the pursuit of green environmental protection, responsive materials with single response and actuation can no longer meet the requirements of modern technology for intelligence, diversification, and environmental friendliness. Therefore, intelligent responsive materials have received much attention. In recent years, with the development of new materials and technologies, cellulose materials have become increasingly used as responsive materials due to their advantages of sustainability and renewability. This review summarizes the relevant research on cellulose-based intelligent responsive materials in recent years. According to the stimuli responses, they are divided into temperature-, light-, electrical-, magnetic-, and humidity-responsive types. The response mechanism, application status, and development trend of cellulose-based intelligent responsive materials are summarized. Finally, the future perspectives on the preparation and applications of cellulose-based intelligent responsive materials are presented for future research directions.

Ti3C2Tx MXene-Based Multifunctional Tactile Sensors for Precisely Detecting and Distinguishing Temperature and Pressure Stimuli

Although skin-like sensors that can simultaneously detect various physical stimuli are of fair importance in cutting-edge human-machine interaction, robotic, and healthcare applications, they still face challenges in facile, scalable, and cost-effective production using conventional active materials. The emerging two-dimensional transition metal carbide, Ti3C2Tx MXene, integrated with favorable thermoelectric properties, metallic-like conductivity, and a hydrophilic surface, is promising for solving these problems. Herein, skin-like multifunctional sensors are designed to precisely detect and distinguish temperature and pressure stimuli without cross-talk by decorating elastic and porous substrates with MXene sheets. Because the combination of the thermoelectric and conductive MXene with the thermally insulating, elastic, and porous substrate integrates efficient Seebeck and piezoresistive effects, the resultant sensor exhibits not only an ultralow detection limit (0.05 K), high signal-to-noise ratio, and excellent cycling stability for temperature detection but also high sensitivity, fast response time, and outstanding durability for pressure detection. Based on the impressive dual-mode sensing properties and independent temperature and pressure detections, a multimode input terminal and an electronic skin are created, exhibiting great potential in robotic and human-machine interaction applications. This work provides a scalable fabrication of multifunctional tactile sensors for precisely detecting and distinguishing temperature and pressure stimuli.

Review of Design Routines of MXene Materials for Magnesium-Ion Energy Storage Device

Renewable energy storage using electrochemical storage devices is extensively used in various field applications. High-power density supercapacitors and high-energy density rechargeable batteries are some of the most effective devices, while lithium-ion batteries (LIBs) are the most common. Due to the scarcity of Li resources and serious safety concerns during the construction of LIBs, development of safer and cheaper technologies with high performance is warranted. Magnesium is one of the most abundant and replaceable elements on earth, and it is safe as it does not generate dendrite following cycling. However, the lack of suitable electrode materials remains a critical issue in developing electrochemical energy storage devices. 2D MXenes can be used to construct composites with different dimensions, owing to their suitable physicochemical properties and unique magnesium-ion adsorption structure. In this study, the construction strategies of MXene in different dimensions, including its physicochemical properties as an electrode material in magnesium ion energy storage devices are reviewed. Research advancements of MXene and MXene-based composites in various kinds of magnesium-ion storage devices are also analyzed to understand its energy storage mechanisms. Finally, current opportunities, challenges, and future prospects are also briefly discussed to provide crucial information for future research.

3D-Printed Polyamide 12/Styrene-Acrylic Copolymer-Boron Nitride (PA12/SA-BN) Composite with Macro and Micro Double Anisotropic Thermally Conductive Structures

Anisotropic thermally conductive composites are very critical for precise thermal management of electronic devices. In this work, in order to prepare a composite with significant anisotropic thermal conductivity, polyamide 12/styrene-acrylic copolymer-boron nitride (PA12/SA-BN) composites with macro and micro double anisotropic structures were fabricated successfully using 3D printing and micro-shear methods. The morphologies and thermally conductive properties of composites were systematically characterized via SEM, XRD, and the laser flash method. Experimental results indicate that the through-plane thermal conductivity of the composite is 4.2 W/(m·K) with only 21.4 wt% BN, which is five times higher than that of the composite with randomly oriented BN. Simulation results show that the macro-anisotropic structure of the composite (caused by the selective distribution of BN) as well as the micro-anisotropic structure (caused by the orientation structure of BN) both play critical roles in spreading heat along the specified direction. Therefore, as-obtained composites with double anisotropic structures possess great potential for the application inefficient and controllable thermal management in various fields.

Advances in the synthesis and applications of 2D MXene-metal nanomaterials

MXenes, two-dimensional (2D) materials that consist of transition metal carbides, nitrides and/or carbonitrides, have recently attracted much attention in energy-related and biomedicine fields. These materials have substantial advantages over traditional carbon graphenes: they possess high conductivity, high strength, excellent chemical and mechanical stability, and superior hydrophilic properties. Furthermore, diverse functional groups such as -OH, -O, and -F located on the surface of MXenes aid the immobilization of numerous noble metal nanoparticles (NP). Therefore, 2D MXene composite materials have become an important and convenient option of being applied as support materials in many fields. In this review, the advances in the synthesis (including morphology studies, characterization, physicochemical properties) and applications of the currently known 2D MXene-metal (Pd, Ag, Au, and Cu) nanomaterials are summarized based on critical analysis of the literature in this field. Importantly, the current state of the art, challenges, and the potential for future research on broad applications of MXene-metal nanomaterials have been discussed.

Nanopolyhybrids: Materials, Engineering Designs, and Advances in Thermal Management

The fundamental requirements for thermal comfort along with the unbalanced growth in the energy demand and consumption worldwide have triggered the development and innovation of advanced materials for high thermal-management capabilities. However, continuous development remains a significant challenge in designing thermally robust materials for the efficient thermal management of industrial devices and manufacturing technologies. The notable achievements thus far in nanopolyhybrid design technologies include multiresponsive energy harvesting/conversion (e.g., light, magnetic, and electric), thermoregulation (including microclimate), energy saving in construction, as well as the miniaturization, integration, and intelligentization of electronic systems. These are achieved by integrating nanomaterials and polymers with desired engineering strategies. Herein, fundamental design approaches that consider diverse nanomaterials and the properties of nanopolyhybrids are introduced, and the emerging applications of hybrid composites such as personal and electronic thermal management and advanced medical applications are highlighted. Finally, current challenges and outlook for future trends and prospects are summarized to develop nanopolyhybrid materials.

Radiation synthesis of MXene/Ag nanoparticle hybrids for efficient photothermal conversion of polyurethane films

Flexible conductive films based on light-to-heat conversion are promising for the next-generation electronic devices. A flexible waterborne polyurethane composite film (PU/MA) with excellent photothermal conversion performance was obtained by combination of PU and silver nanoparticle decorated MXene (MX/Ag). The silver nanoparticles (AgNPs) uniformly decorated on the MXene surface by γ-ray irradiation induced reduction. Because of the synergistic effect of MXene with outstanding light-to-heat conversion efficiency and the AgNPs with plasmonic effect, the surface temperature of the PU/MA-II (0.4%) composite with lower MXene content increased from room temperature to 60.7 °C at 5 min under 85 mW cm^-2 light irradiation. Besides, the tensile strength of PU/MA-II (0.4%) increased from 20.9 MPa (pure PU) to 27.5 MPa. The flexible PU/MA composite film shows great potential in the field of thermal management of flexible wearable electronic devices.

A portable electrochemical microsensor for in-site measurement of dissolved oxygen and hydrogen sulfide in natural water

Dissolved oxygen (O₂) and hydrogen sulfide (H₂S) are two important indicators of water quality, their levels are of intimate dependence and varying over time. It is of great significance to monitoring of dissolved O₂ and H₂S simultaneously in natural water, yet has not been reported because of lack of effective approaches. In this work, a portable electrochemical microsensor was developed for simultaneously quantifying dissolved O₂ and H₂S. Here, Pd@Ni nanoparticles (NPs) were self-assembled onto the microelectrode by MXene titanium carbide (Ti₃C₂T_x), which were of responsibility towards O₂ and H₂S detection within single electrochemical reduction process. On this regard, Pd NPs facilitated catalyzing the electrochemical reduction of O₂, while Ni NPs were employed as recognition element for H₂S detection. With the electrochemical reduction sweep, the initial application of a positive voltage rendered the Ni to be oxidized to be Ni ions, contributing to their following capture of surrounding S^2- to form nickel sulfide. Nickel sulfide with highly electrochemical activity were capable of generating detecting reduction current. In consequence, the as-designed microsensor can simultaneously determine O₂ concentrations ranging from 36 to 318 μM and H₂S levels ranging from 0.1 to 2.5 μM with high selectivity. Finally, the portable microsensor was successfully applied to simultaneous detection dissolved O₂ and H₂S in natural water in-site, the results of which were comparable to the classical methods.

Tough and Conductive Nacre-inspired MXene/Epoxy Layered Bulk Nanocomposites

A long-standing quest in materials science has been the development of tough epoxy resin nanocomposites for use in numerous applications. Inspired by nacre, here we report tough and conductive MXene/epoxy layered bulk nanocomposites. The orientation of MXene lamellar scaffolds is enhanced by annealing treatment. The improved interfacial interactions between MXene lamellar scaffold and epoxy through surface chemical modification resulted in a synergistic effect. Tailoring the interlayer spacing of MXene nanosheets to a critical distance resulted in a fracture toughness about eight times higher than that of pure epoxy, surpassing other epoxy nanocomposites. Our nacre-inspired MXene/epoxy layered bulk nanocomposites also show high electrical conductivity that provides self-monitoring capability for structural integrity and exhibits an excellent electromagnetic interference shielding efficiency. Our proposed strategy provides an avenue for fabricating high-performance epoxy nanocomposites.

Recent Advances in MXene/Epoxy Composites: Trends and Prospects

Epoxy resins are thermosets with interesting physicochemical properties for numerous engineering applications, and considerable efforts have been made to improve their performance by adding nanofillers to their formulations. MXenes are one of the most promising functional materials to use as nanofillers. They have attracted great interest due to their high electrical and thermal conductivity, hydrophilicity, high specific surface area and aspect ratio, and chemically active surface, compatible with a wide range of polymers. The use of MXenes as nanofillers in epoxy resins is incipient; nevertheless, the literature indicates a growing interest due to their good chemical compatibility and outstanding properties as composites, which widen the potential applications of epoxy resins. In this review, we report an overview of the recent progress in the development of MXene/epoxy nanocomposites and the contribution of nanofillers to the enhancement of properties. Particularly, their application for protective coatings (i.e., anticorrosive and friction and wear), electromagnetic-interference shielding, and composites is discussed. Finally, a discussion of the challenges in this topic is presented.

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.

Isolated Solid Wall-Assisted Thermal Conductive Performance of Three-Dimensional Anisotropic MXene/Graphene Polymeric Composites

The introduction of three-dimensional (3D) continuous conformations in polymer materials is a convincing proposal for acquiring the desirable multifunction to fulfill the urgent demands of highly integrated electronic devices. However, the limited functional design of the filled aligned network remains challenging. Herein, directional self-assembly 3D MXene/graphene aerogels are fabricated as conductive networks for polyethylene glycol (PEG) matrix. Based on the uniaxial and biaxial ice template method, the temperature gradient affects the aligned arrangement of the 3D microstructure. The biaxial PEG/MXene/GR composites exhibit an enhanced through-plane thermal conductivity of 1.64 W m^-1 K^-1 at 10.6 vol % content, which is 522% higher than that of pure PEG. The influence of the biaxial self-assembly strategy compared with that of the uniaxial one on the thermal conductivity reaches the highest 333% when the weight ratio equals 1:1. Meanwhile, the same difference also occurs in the electromagnetic shielding interference (EMI) property. The advanced EMI-shielding effectiveness of the biaxial PM1G1 composites reaches ∼36 dB at the 2.5 mm thickness. This research provides valuable guidance for designing high-performance applications of anisotropic thermal management and EMI shielding in 5G telecommunications and mobile electronic devices.

Epoxy composite with high thermal conductivity by constructing 3D-oriented carbon fiber and BN network structure

As electronic devices tend to be integrated and high-powered, thermal conductivity is regarded as the crucial parameter of electronic components, which has become the main factor that limits the operating speed and service lifetime of electronic devices. However, constructing continuous thermal conductive paths for low content particle fillers and reducing interface thermal resistance between fillers and matrix are still two challenging issues for the preparation of thermally conductive composites. In this study, 3D-oriented carbon fiber (CF) thermal network structures filled with boron nitride flakes (BN) as thermal conductive bridges were successfully constructed. The epoxy composite was fabricated by thermal conductive material with a 3D oriented structure by the vacuum liquid impregnation method. This special 3D-oriented structure modified by BN (BN/CF) could efficiently broaden the heat conduction pathway and connected adjacent fibers, which leads to the reduction of thermal resistance. The thermal conductivity of the boron nitride/carbon fiber/epoxy resin composite (BN/CF/EP) with 5 vol% 10 mm CF and 40 vol% BN reaches up to 3.1 W m⁻¹ K⁻¹, and its conductivity is only 2.5 × 10⁻⁴ S cm⁻¹. This facile and high-efficient method could provide some useful advice for the thermal management material in the microelectronic field and aerospace industry.

As electronic devices tend to be integrated and high-powered, thermal conductivity is regarded as the crucial parameter of electronic components, which is the main factor that limits the operating speed and service lifetime of electronic devices.

Facile Electrochemical Microbiosensor Based on In Situ Self-Assembly of Ag Nanoparticles Coated on Ti3C2Tx for In Vivo Measurements of Chloride Ions in the PD Mouse Brain

Chloride ion (Cl^-), one of the most important anions in the brain, has been confirmed to participate in the pathological process of Parkinson's disease (PD). As such, the development of a reliable method for in vivo measurements of Cl^- is extremely appealing, especially for understanding the pathogenesis of PD. We herein designed a facile electrochemical microbiosensor (ECMB), based on in situ self-assembly of Ag nanoparticles (Ag NPs) coated on Ti₃C₂T_x. The uniform nanosized Ag NPs were reduced by Ti₃C₂T_x by a simple dipping process, endowing the ECMB with excellent specificity toward Cl^- detection and remarkably reproducible preparation process. Meanwhile, electro-oxidized graphene oxide was introduced as an inner reference, thus avoiding the environmental interference of the complicated brain systems to increase the determination accuracy. An extensive in vitro study revealed that the proposed ECMB would be a robust candidate for real-time monitoring of Cl^- in the PD mouse brain with high selectivity, accuracy, and reproducibility. Moreover, the availability and reliability toward in vivo Cl^- monitoring of the designed ECMB were well confirmed by comparing with the standard Volhard's method. Finally, by virtue of the successful employment of the developed detecting platform in the in vivo measurement of Cl^- in the PD mouse brain, systematic analysis and comparison of the average levels of Cl^- in the three regions including cortex, striatum, and hippocampus of brains from normal and PD model mice have been achieved.

Wall Density-Controlled Thermal Conductive and Mechanical Properties of Three-Dimensional Vertically Aligned Boron Nitride Network-Based Polymeric Composites

Polymeric composites with good thermal conductive and improved mechanical properties are in high demand in the thermal management materials. Construction of a three-dimensional (3D) structure has been proved to be an effective method to obtain polymeric composites with improved through-plane thermal conductivity (TC) for efficient thermal management of electronics. However, the TC enhancement of the obtained polymeric composites is limited, mainly due to poor control of the 3D thermal conductive network. Additionally, achieving high thermal conductive properties and enhanced mechanical properties simultaneously is of great challenge for polymeric composites. In this work, a 3D boron nitride framework (BNF) with a well-defined vertically aligned open structure and designed wall density fabricated by a unidirectional freezing technique was applied. The as-prepared BNF/polyethylene glycol (PBNF) composites exhibit enhanced through-plane TC, excellent thermal transfer capability (ΔT_max = 34 °C), and improved mechanical properties (Young's modulus enhancement up to 356%) simultaneously, making it attractive to thermal management applications. Strong correlation between the TC and mechanical properties of the PBNF composites and the wall density of the BNF scaffolds was found, providing opportunities to tune the TC and mechanical properties through the controlling of wall density. Furthermore, the models between TC and Young's modulus of PBNF composites were established by using the data-driven method "sure independence screening and sparsifying operator", which enables us to predict TC and Young's modulus of the polymeric composites for designing promising composite materials. The design principles and fabrication strategies proposed in this work could be important for developing advanced composite materials.

Recent Advances in Preparation, Mechanisms, and Applications of Thermally Conductive Polymer Composites: A Review

At present, the rapid accumulation of heat and the heat dissipation of electronic equipment and related components are important reasons that restrict the miniaturization, high integration, and high power of electronic equipment. It seriously affects the performance and life of electronic devices. Hence, improving the thermal conductivity of polymer composites (TCPCs) is the key to solving this problem. Compared with manufacturing intrinsic thermally conductive polymer composites, the method of filling the polymer matrix with thermally conductive fillers can better-enhance the thermal conductivity (λ) of the composites. This review starts from the thermal conduction mechanism and describes the factors affecting the λ of polymer composites, including filler type, filler morphology and distribution, and the functional surface treatment of fillers. Next, we introduce the preparation methods of filled thermally conductive polymer composites with different filler types. In addition, some commonly used thermal-conductivity theoretical models have been introduced to better-analyze the thermophysical properties of polymer composites. We discuss the simulation of λ and the thermal conduction process of polymer composites based on molecular dynamics and finite element analysis methods. Meanwhile, we briefly introduce the application of polymer composites in thermal management. Finally, we outline the challenges and prospects of TCPCs.

Polydopamine-Coated Paraffin Microcapsules as a Multifunctional Filler Enhancing Thermal and Mechanical Performance of a Flexible Epoxy Resin

This work focuses on flexible epoxy (EP) composites containing various amounts of neat and polydopamine (PDA)-coated paraffin microcapsules as a phase change material (PCM), which have potential applications as adhesives or flexible interfaces with thermal management capability for electronics or other high-value-added fields. After PDA modification, the surface of PDA-coated capsules (MC-PDA) becomes rough with a globular appearance, and the PDA layer enhances the adhesion with the surrounding epoxy matrix, as shown by scanning electron microscopy. PDA deposition parameters have been successfully tuned to obtain a PDA layer with a thickness of 53 ± 8 nm, and the total PDA mass in MC-PDA is only 2.2 wt %, considerably lower than previous results. This accounts for the fact that the phase change enthalpy of MC-PDA is only marginally lower than that of neat microcapsules (MC), being 221.1 J/g and 227.7 J/g, respectively. Differential scanning calorimetry shows that the phase change enthalpy of the prepared composites increases with the capsule content (up to 87.8 J/g) and that the enthalpy of the composites containing MC-PDA is comparable to that of the composites with MC. Dynamic mechanical analysis evidences a decreasing step in the storage modulus of all composites at the glass transition of the EP phase, but no additional signals are detected at the PCM melting. PCM addition positively contributes to the storage modulus both at room temperature and above Tg of the EP phase, and this effect is more evident for composites containing MC-PDA. As the capsule content increases, the mechanical properties of the host EP matrix also increase in terms of elastic modulus (up to +195%), tensile strength (up to +42%), Shore D hardness (up to +36%), and creep compliance (down to −54% at 60 min). These effects are more evident for composites containing MC-PDA due to the enhanced interfacial adhesion.

Artificial Nacre Epoxy Nanomaterials Based on Janus Graphene Oxide for Thermal Management Applications

Owing to the development of microelectronics, demands for excellent thermal dissipation materials have substantially increased. Learning from natural nacre, thermally conductive epoxy nanocomposites were prepared based on asymmetrically polydopamine-functionalized Janus graphene oxide (JPGO) scaffolds. The required highly oriented JPGO scaffolds were prepared via the bidirectional freeze-casting method. With the addition of epoxy resin, the resulting nanocomposite reveals anisotropic thermal properties. With the total content of the JPGO scaffold being 0.93 wt %, almost 35 times enhancement of in-plane thermal conductivity (perpendicular to the lamellar structure) (∼5.6 W m^-1 K^-1) has been obtained. The single-side-functionalized JPGO scaffolds play an important role in forming thermal conductive networks for the epoxy nanocomposites. Importantly, the nanocomposites present electrically insulating properties (>10¹⁴ Ω cm). Such high-performance nanocomposites have promising applications for thermal management in electronic devices.

Strengthened, Antibacterial, and Conductive Flexible Film for Humidity and Strain Sensors

With the development of artificial intelligence, people are not satisfied with the traditional conductive materials and tend to focus on stretchable and flexible electronic systems. Flexible conductive rubbers have great potential applications in wearable strain sensors. However, the rapid propagation of bacteria during the use of wearable sensors may be an ineluctable threat to humans' health. Herein, a conductive rubber film is fabricated based on carboxylic styrene-butadiene rubber (XSBR), citric acid (CA), and silver nitrate (AgNO₃) via a convenient approach, where Ag nanoparticles (Ag NPs) are in situ reduced without sintering at elevated temperatures. The resultant films exhibit many desirable and impressive features, such as strengthened mechanical properties, flexibility, and conductivity. More importantly, the Ag NP flexible conductive films exhibit excellent antibacterial activity against Escherichia coli (Gram-negative bacteria) and Staphylococcus aureus (Gram-positive bacteria), which have potential applications as flexible antibacterial materials to monitor movements of the human body in real time. Also, because of the hygroscopicity of CA, the resistance of our conductive film is sensitive to various humidities, which can be applied in the humidity sensor.