Multifunctional Composites Research Articles

Stretchable Multifunctional Polydimethylsiloxane Composites with Cage‐Like Conductive Architecture for Integrated Thermosensitive and Electromagnetic Interference Shielding Performance

AbstractHigh‐performance sensors with outstanding sensitivity, wide working range, and multifunctional properties are highly desirable in modern integrated smart wearable electronics. Herein, polydimethylsiloxane (PDMS)‐based stretchable pyroresistive sensors composed of tightly‐assembled silver nanowires (Ag NWs)‐encapsulated PDMS microspheres (PM) and expandable microspheres (EM) are fabricated. The synergistic cage‐like conductive network and EM endow the temperature sensor with tunable sensitivity (Max TCR: 27.4% °C−1), broad sensing range (25–85 °C), low perception limit (0.1 °C), and excellent anti‐interference ability. Interestingly, at elevated temperature field (> 90 °C), a remarkable conduction‐insulation transition is observed, which is employed to facilitate an early fire alarm system. In addition, the selectively distributed Ag NWs constructs segregated conductive pathways at an ultralow content (Pc = 0.014 vol%), leading to efficient electromagnetic interference shielding (40.0 dB). The underlying mechanism responsible for the observed superior thermosensation and EMI shielding performance is elucidated, and possible applications are demonstrated. Consequently, this work offers a novel strategy for the design of flexible, multifunctional pyroresistive sensors toward artificial intelligence and emerging wearable electronics.

Highly efficient Cu(II) capture by salicylaldoxime functionalized magnetic polydopamine core-shell hybrids: Behavior and mechanism

Functionalized magnetic nanocomposites were considered as promising adsorbents owing to their abundant functional groups and ease of separation properties. Herein, we combined the solvothermal method with molecular copolymerization to synthesize a salicylaldoxime-grafted magnetic polydopamine (SMP) core-shell hybrid and exploited it for Cu(II) adsorption. The physicochemical properties of SMP were comprehensively studied by SEM, TEM, XRD, FT-IR, TGA, XPS, and VSM measurements. The results manifested that polydopamine acts as a bridge connecting magnetic iron oxide and salicylaldoxime to fabricated core-shell hybrids with rich functional groups. The batch experimental results showed that the Cu(II) adsorption was consumingly pH-reliant behavior, while adsorption data fitted the pseudo-second-order kinetic model and Langmuir isothermal model well, and the adsorption process achieved equilibrium within 60 min. Moreover, SMP exhibited remarkable anti-interference and can be recycled for 5 times with an inconspicuous decrease in adsorption performance. Importantly, salicylaldoxime functionalization endowed SMP with maximum Cu(II) adsorption capacity of 141.24 mg/g at pH 6.0 and 25 °C as compared with pure MP. Based on FT-IR and XPS study, the main adsorption mechanisms were proposed with a synergistic effect including a strong chemical chelation and partial Cu(II) reduction. Importantly, this strategy can be extended to multifunctional magnetic composites for Cu-contaminated wastewater cleanup.

Janus polyurethane composite film with highly aligned graphene fluoride and liquid metal: A versatile technique for thermal management and electromagnetic interference shielding

Flexible and multi-functional thermoconductive polymer composites have significant potential for application in advanced electronics. However, achieving a composite with necessary requirements such as flexibility, thermal conductivity, electromagnetic interference (EMI) shielding, and electrical insulation are challenging. The concept of Janus materials has provided the requirements of advanced electronics by forming a layered structure in polyurethane via sedimentation of liquid metal (LM) and graphene fluoride (GF). The fillers in the polyurethane were elongated and aligned along the draw direction using a stretching-induced filler alignment approach, which enhanced in-plane thermal conductivity and EMI shielding performance simultaneously. The Janus composite film exhibited electrical conductivity on one side and insulation on the other side, demonstrating the true nature of the Janus structure, while the film showed superior thermal conductivity (9.62 W·m−1·K−1) and EMI shielding effectiveness (55 dB) at a draw ratio of 2. These findings provide a novel approach to fabricating multifunctional composites for electronics applications.

Efficient preparation of polydimethylsiloxane‐based phase change composites with sandwich structure

AbstractWith the rapid development of portable electronic devices, there is an urgent need for the multifunctional composites like excellent electromagnetic interference (EMI) shielding performance, mechanical property, and thermal management capabilities. Here, due to the low thermal conductivity of phase change materials (PCMs), a sandwich structure carbon nanotube/phase change microcapsule/carbon nanotube (CNT/PMC/CNT (CPC)) film was prepared by vacuum‐assisted filtration (VAF) method. CNT, PMC, and cellulose nanocrystal (CNC) were used as functional fillers. The addition of CNCs was used to improve the mechanical performance of CPC film. Compared with PMC‐CNC (PC) film, CPC film with sandwich structure prevented leakage phenomenon efficiently. Subsequently, the use of ultrasonic‐assisted forced infiltration (UAFI) successfully infiltrated polydimethylsiloxane (PDMS) matrix in the filler skeleton to obtain CNT/PMC/CNT/PDMS (CPCP) composites. When filler mass ratio (CNT: CNC and PMC: CNC) reached 10:1, the thermal conductivity of CPCP composites was 2.32 W/(m·K) and total EMI shielding effectiveness (EMI SET) of it with 0.38 mm thickness reached 37.46 dB at 12.4 GHz. Besides, these sandwich composites exhibited the good mechanical properties and heat storage capacity. And we systematically observed the impact of different addition amounts of PC homogeneous dispersing solution on phase change ability of CPCP10:1 composites. In summary, CPCP phase change composites with sandwich structure shows potential application prospect in thermal management materials with EMI shielding of electronic devices.Highlight The sandwich structure CPCP composites prepared by the combination of VAF and UAFI method, showing superior thermal conductivity and phase change ability. CPCP has excellent EMI shielding performance, which can meet the need of TMMs with EMI shielding performance. Compared with same thickness PC film, sandwich CPC film can prevent leakage phenomenon efficiently.

Experimental Investigation of the Three-Point Bending Property of a Sandwich Panel with a Metal Rubber Core

Sandwich structures and porous materials have been applied widely in various fields due to their excellent mechanical performance, and multifunctional composites will have a significant engineering demand in the future. Studying damped composites’ mechanical properties and failure forms has significant engineering value and significance. However, the current connecting processes for sandwich panels and porous materials must be improved. Therefore, to explore the ambiguity of the connection interface between the core material and panel in sandwich panels, as well as the mechanical properties of such structures, a sandwich panel with a metal rubber core material was prepared using vacuum brazing and cementing processes. Microscopic examinations using scanning electron microscopy and energy-dispersive spectroscopy were conducted to observe the physical bonding mechanism at the interface of the sandwich panel. The results indicate that the brazed sandwich panels exhibited a more uniform and continuous interface than the cemented sandwich panels. This work designs three-point bending compression experiments to investigate the effects of core material thickness, density, and preparation process on the bending mechanical properties of the sandwich panel. Failure modes of the sandwich panel during the experiments are analyzed. The experimental results show that the failures of the brazed sandwich panels are attributable to the bending deformation of the panel and the shear failure of the metal wire core material. The cemented sandwich panels exhibit separation failures in the area below the indenter and at both ends of the panel. The core material’s thickness and density significantly influence the bending performance of the sandwich panels. An increase in the core material’s thickness and density effectively enhances the sandwich panels’ peak load and energy absorption capacity.

A one step method to prepare polymer‐based flexible wires by continuous spatial‐confining network assembly technique

AbstractIn recent years, flexible electronics technology has been developing rapidly, and flexible electronic devices have been widely used in wearable gadgets and robotics. Flexible wires are the basic components of these devices, which usually consist of metallic materials with flexibility and ductility. However, the introduction of flexible conductive materials has broadened the application scope of flexible wires. In this paper, PDMS/SCF conductive composites exhibiting different conductivity properties on both sides are fabricated by adding meshes based on the continuous spatial‐confining network assembly method. The conductivity of PDMS/SCF (6 wt%) composites can be exhibited as 173.45 S/m in the conductive layer and 6.25 × 10−11 S/m in the insulating layer, which can be used as core and surface layers of conductors, respectively. A mathematical model is also developed to predict the electrical conductivity of the PDMS/SCF conductive composites, and the experimental data are in good agreement with the predicted results. This work provides a method for the continuous preparation of multifunctional composites that can be molded in one step with conductive layer and insulating layer, which can be used as the core and insulating layers of wires, thus simplifying the preparation process of composite‐based wires and expanding the range of conductive composites applications.

Comparative Antibacterial Activity of Clay-Supported Silver Nanoparticles Prepared by Conventional Heating and Microwave Methods

The synthesis of multifunctional composites still relies on the use of conventional methods. However, these methods are expensive, time consuming and require high volumes of reducing agents which are often toxic. In this study, composites of bentonite-supported silver nanoparticles were prepared comparatively by the conventional heating method and the rapid microwave method; and their antibacterial activity was investigated against Escherichia coli and Staphylococcus aureus. The crystalline nature of the composites was evaluated by X-ray diffraction (XRD), while transmission electron microscope (TEM) coupled with energy-dispersive spectroscope was used for morphology and elemental analysis, respectively. Surface area and pore size analysis of the composites were conducted by the Brunauer, Emmett and Teller analyzer. TEM images revealed successful synthesis of the composites with a better dispersion of the nanoparticles achieved through microwave, where nanoparticle sizes were 6–38 nm and 9–56 nm by the conventional method. It is worth noting that the composites were prepared in less than 30 min using microwave as compared to 2 h of the conventional method. The XRD spectra confirmed the formation of silver and not any other impurities of the metal. These results revealed that, although the two methods are comparable, microwave method is efficient and time saving and can, therefore, synthesize composites with well-dispersed and narrow distributed nanoparticles. The antibacterial results demonstrated that the prepared composites are effective in the inactivation of various bacteria. These composites could be applied in water treatment, wound dressing, packaging, etc.

A sol-gel strategy for constructing a hydroxyapatite nanowire/aramid nanofiber electric insulating composite with excellent flame retardancy and mechanical property

With the increasing demand for high power and miniaturization of modern large-scale electrical equipment, preparing high-performance electrical insulation materials with high thermal stability and excellent mechanical properties has become an urgent problem. In this study, hydroxyapatite (HAP) nanowires and aramid nanofibers (ANF) multifunctional composites were prepared by sol-gel-membrane strategy. Aramid fibers containing an amide structure and HAP can form an ordered hydrogen bonding network and exhibit strong hydrogen bonding. The prepared HAP/ANF nanocomposite films with nanowire/nanofiber network skeleton and laminate structure have good tensile strength (69.6 MPa), dielectric breakdown strength (65.7 kV mm−1), and processing properties. Particularly emphasized is that the multifunctional HAP/ANF nanocomposite films are fireproof and high-temperature resistant, and the interfacial hydrogen-bonding enhancement between HAP nanowires and aramid fibers facilitates the construction of multifunctional insulating materials.

Achieving enhanced multifunctional performance for structural composite supercapacitors by reinforcing interfaces with polymer coating

Carbon fiber structural composite supercapacitors possess the multifunctionality of storing electrochemical energy and withstanding mechanical loads simultaneously, attracting increased attention in electric vehicles, drones, and aircraft sectors. A polymer-based coating was meticulously constructed at the electrode/electrolyte interface to enhance adhesion and stability between active materials and the carbon fiber fabric collector under diverse conditions, especially mechanical stress. Mechanical testing and corresponding physical characterization substantiated the superior performance of the polymer coating. With the protective polymer coating, the optimized structural composite Zn-ion supercapacitor (SZSC), consisting of carbon fiber@active carbon-P (CF@AC-P) cathode, ionogel electrolyte, and Zn anode, displayed a maximum energy density of 164.6 mWh kg−1, at power density of 563.3 mW kg−1. Moreover, the optimized SZSC demonstrated stable operation over more than 8000 cycles at 0.3 mA cm−2 without capacity degradation. The optimized SZSC exhibited a tensile strength of 399.7 MPa and Young's modulus of 11.5 GPa. Furthermore, employing vacuum infusion techniques, the fabricated three-dimensional (3D) wing skin model shell and tube shell curved-surface structural composite Zn-ion supercapacitor component composites showcased exceptional electrochemical performance. These achievements further validate the practicality of 3D multifunctional composites. Consequently, this research presented a practical and straightforward interface engineering approach to develop multifunctional structural devices with remarkable electrochemical and mechanical properties.

Multifunctional Metal-Phenolic Composites Promote Efficient Periodontitis Treatment via Antibacterial and Osteogenic Properties.

Periodontitis, a complex inflammatory disease initiated by bacterial infections, presents a significant challenge in public health. The increased levels of reactive oxygen species and the subsequent exaggerated immune response associated with periodontitis often lead to alveolar bone resorption and tooth loss. Herein, we develop multifunctional metal-phenolic composites (i.e., Au@MPN-BMP2) to address the complex nature of periodontitis, where gold nanoparticles (AuNPs) are coated by metal-phenolic networks (MPNs) and bone morphogenetic protein 2 (BMP2). In this design, MPNs exhibit remarkable antibacterial and antioxidant properties, and AuNPs and BMP2 promote osteogenic differentiation of bone marrow mesenchymal stem cells under inflammatory conditions. In a rat model of periodontitis, treatment with Au@MPN-BMP2 leads to notable therapeutic outcomes, including mitigated oxidative stress, reduced progression of inflammation, and the significant prevention of inflammatory bone loss. These results highlight the multifunctionality of Au@MPN-BMP2 nanoparticles as a promising therapeutic approach for periodontitis, addressing both microbial causative factors and an overactivated immune response. We envision that the rational design of metal-phenolic composites will provide versatile nanoplatforms for tissue regeneration and potential clinical applications.

Multifunctional hybrid composite: Plasma sprayed Al and graphene reinforced alumina coating

Multifunctional composite coatings are essential and challenging to develop, for versatile applications in structural-mechanical components, wear-resistant surfaces, joining, etc. In this perspective, we developed a multifunctional, hybrid Al and exfoliated graphene-reinforced alumina composite coating using atmospheric plasma spraying. We observed the unique microstructural features such as uniform thickness (∼300 μm), phase retention, graphene sandwiching with splats, etc., which offered high-density (>90%) in alumina composite coating. The Alumina-Al-graphene composite coatings exhibited impressive mechanical properties, including high hardness (9–13 GPa), elastic modulus (100–150 GPa), and toughness (2–13 MPam0.5) along with exceptional adhesion (∼35 MPa). These coatings offered superior tribological behaviour, wear rate (0.1–1.5 × 10−4), COF:<0.5, etc., due to exfoliated graphene, its lubricating capability. Furthermore, the electrical conductivity of these hybrid coatings increased, enabling the metallization of alumina ceramics and facilitating ceramic surface joining. Therefore, our exfoliated graphene-reinforced ceramic-metal, a hybrid composite coating, makes itself an impressive approach for industrial applications.

Stretchable and translucent liquid-metal composite mesh for multifunctional electromagnetic shielding/sensing and Joule heating

Flexible liquid metal (LM)-based composite materials with strain-undiminished electromagnetic interference (EMI) shielding effectiveness (SE) and multifunctional integration are attracting great attention due to the urgent need for flexible electronic and wearable devices. Herein, stretchable and translucent polydimethylsiloxane/LM composite mesh (PLM) is developed by introducing highly deformable LM filler into elastomer and constructing conductive mesh structures by cast molding and mechanical sintering, which shows strain-enhanced EMI SE without a significant decrease in light transmittance due to the contribution of stretch-induced enhanced conductivity, mesh densification, and orientation. The linear response of relative SE change with tensile strain allows the PLM to exhibit ideal EM sensing characteristics, superior to most reported stretchable EMI shields. The oriented mesh structure endows the stretched PLM with anisotropic EMI SE under rotation, revealing a feasible means to realize tunable SE in a tensile state. More importantly, the high conductivity and deformability of the LM network further provide the PLM with excellent and relatively stable Joule-heating performance when served as a stretchable Joule heater. This work offers a new strategy for developing multifunctional stretchable LM-based composites that can achieve strain-enhanced EMI SE and ideal EM sensing capability without significantly sacrificing the light transmittance and Joule-heating performances under stretching.

From natural leather to intelligent wearable nanocomposite: design and application

As a natural material, leather has been widely used in daily life due to its high biocompatibility, wearing comfort, and excellent mechanical strength. However, with the increasing demand for a better life among people, the single function of leather has difficulty in meeting the requirements, which limits its application prospects. It is particularly important to develop multifunctional leather composites with diverse characteristics. Therefore, leather can be modified and functionally designed through physical and chemical methods towards intelligent wearable devices. From this perspective, we review the research progress of intelligent leather-based wearable composites, mainly focusing on the preparation methods and application directions in recent years. Finally, we emphasize the challenges that leather composites will face in practical applications and propose future research directions.

Highly selective detection and removal of mercury ions in the aquatic environment based on magnetic ZIF-71 multifunctional composites with sufficient chlorine functional groups

The development of both detection and removal technologies for heavy metal ions is of great importance. Most of the existing adsorbents that contain oxygen, nitrogen or sulfur functional groups can remove heavy metals, but achieving both selective detection and removal of a single metal ion is difficult because they bind to a wide range of heavy metal ions. Herein, we selected zeolite imidazolium hydrochloride framework-71 (ZIF-71) with sufficient chlorine functional groups to fabricate magnetic ZIF-71 multifunctional composites (M-ZIF-71). M-ZIF-71 had a large specific surface area, excellent water stability, and good magnetic properties, which made M-ZIF-71 conducive to the separation and recovery of adsorbents and the assembly of electrodes. M-ZIF-71 exhibited high selectivity, wide linear range (1–500 μg/L), and low detection limit (0.32 μg/L) for electrochemical detection of mercury ions (Hg2+). Meanwhile, M-ZIF-71 demonstrated rapid Hg2+ adsorption with a high capacity of 571.2 mg/g and excellent recyclability. The high selectivity for Hg2+ was attributed to the powerful affinity of highly electronegative chlorine and Hg2+. Moreover, XPS spectra demonstrated the interaction between chlorine and Hg2+. This work provides a new inspiration for applications in the targeted monitoring and removal of heavy metal pollution.

Multifunctional green composites based on plasma-activated and GO-coated dwarf palm fibers

In this work, we propose a green method for decorating natural fibers derived from dwarf palm waste with graphene oxide (GO) sheets. In detail, plasma-treatment was used to activate fiber surface for the subsequent GO-coating, which was performed in water. Poly(butylene adipate-co-terephthalate) (PBAT)-based composites incorporating 50 % of either raw, plasma-modified or hybrid fibers were prepared by compression moulding and thoroughly analysed to investigate the processing-structure-properties relationships of these systems. The outcomes reveal that combining plasma treatment and GO coating enables fabricating green composites with significantly improved mechanical performance (stiffness and tensile strength increments of up to 500 % and 300 %, respectively) and electrical conductivity on the order of 10-6 S/m.

Elastic porous microspheres/extracellular matrix hydrogel injectable composites releasing dual bio-factors enable tissue regeneration

Injectable biomaterials have garnered increasing attention for their potential and beneficial applications in minimally invasive surgical procedures and tissue regeneration. Extracellular matrix (ECM) hydrogels and porous synthetic polymer microspheres can be prepared for injectable administration to achieve in situ tissue regeneration. However, the rapid degradation of ECM hydrogels and the poor injectability and biological inertness of most polymeric microspheres limit their pro-regenerative capabilities. Here, we develop a biomaterial system consisting of elastic porous poly(l-lactide-co-ε-caprolactone) (PLCL) microspheres mixed with ECM hydrogels as injectable composites with interleukin-4 (IL-4) and insulin-like growth factor-1 (IGF-1) dual-release functionality. The developed multifunctional composites have favorable injectability and biocompatibility, and regulate the behavior of macrophages and myogenic cells following injection into muscle tissue. The elicited promotive effects on tissue regeneration are evidenced by enhanced neomusle formation, vascularization, and neuralization at 2-months post-implantation in a male rat model of volumetric muscle loss. Our developed system provides a promising strategy for engineering bioactive injectable composites that demonstrates desirable properties for clinical use and holds translational potential for application as a minimally invasive and pro-regenerative implant material in multiple types of surgical procedures.

Multifunctional bamboo-based composites in-situ coated with graphene via continuous steam explosion

Biomass materials like bamboo have received much attention in studies of triboelectric nanogenerators (TENGs) electrode materials because its sustainability, however, it is a major challenge to construct high-quality conductive networks, originating from the agglomeration of conductive fillers and inferior interfacial properties. In this work, the continuous steam explosion in-situ coating technique (CSEICT) was innovatively adopted to fabricate bamboo/graphene/PVA composites (BGP) with an advanced structure of graphene in-situ coated on the surface of bamboo fibers. The BGP-based triboelectric nanogenerator (BGP-TENG) possessed a high output charge density of 155.86 μC/m2, 1.57 times higher compared with that of natural wood. The BGP-TENG was proven to be used as smart floors to harvest human walking energy. Notably, the BGP had extremely high electromagnetic interference (EMI) shielding effectiveness of 51.51 dB, electrical conductivity of 101.86 S/m with ultra-low percolation threshold of 0.06 vol%, and outstanding and stable electro-thermal management capabilities. On this basis, this work can provide a novel strategy for preparing bio-based composites and further expand the multiple functions of bio-based TENGs.

Multifunctionality Analysis of Structural Supercapacitors— A Review

Structural supercapacitors (SSCs) are multifunctional energy storage composites (MESCs) that combine the mechanical properties of fiber-reinforced polymers and the electrochemical performance of supercapacitors to reduce the overall mass in lightweight applications with electrical energy consumption. These novel MESCs have huge potentials, and their properties have improved dramatically since their introduction in the early 2000’s. However, the current properties of SSCs are not sufficient for complete energy supply of electrically driven devices. To overcome this drawback, the aim of the current study is to identify key areas for enhancement of the multifunctional performance of SSCs. Critical modification paths for the SSC constituents are systematically analyzed. Special focus is given to the improvement of carbon fiber-based electrodes, the selection of structural electrolytes and the implementation of separators for the development of more efficient SSCs. Finally, current SSCs are compared in terms of their multifunctionality including material combinations and modifications.

Increasing the Lifetime of Water Transportation Vehicles by Using Multifunctional Composites with a Polymer Matrix, Ultradisperse Diamond, and Discrete Fibrous Filler

Increasing the Lifetime of Water Transportation Vehicles by Using Multifunctional Composites with a Polymer Matrix, Ultradisperse Diamond, and Discrete Fibrous Filler

Use of Artificial Intelligence in Design, Development, Additive Manufacturing, and Certification of Multifunctional Composites for Aircraft, Drones, and Spacecraft

Multifunctional composites provide more than one function from the same part. The anisotropy, material, and process characterization challenges and the lack of standardization on the 3D-printed multifunctional carbon composites make it difficult for application into aerospace. The current solutions for additive manufacturing (AM) technologies and additively manufactured monofunctional and multifunctional composites are not mature enough for safety-critical applications. A new approach is proposed to explore the use of machine learning (ML) in the design, development, AM, testing, and certification of multifunctional composites for aircraft, unmanned aircraft systems (UAS), and spacecraft. In this work, an artificial neural network (ANN) architecture is proposed. An AM-embedded building block approach integrates the complete lifecycle of aircraft, UAS, and spacecraft using ANN to support the continued operational safety (COS) of aircraft, spacecraft, and UAS. The proposed method exploits the power of ANN on the metadata for the characterization of multifunctional material properties and processes and the mapping of the failure modes compared with the predicted models and history. This paper provides an in-depth analysis and explanation of the new methods needed to overcome the existing barriers, problems, and situations.