Self-Exfoliation of Flake Graphite for Bioinspired Compositing with Aramid Nanofiber toward Integration of Mechanical and Thermoconductive Properties

Biomimetic Intelligent Thermal Management Materials: From Nature-Inspired Design to Machine-Learning-Driven Discovery

The development of biomimetic intelligent thermal management materials (BITMs) is essential for tackling thermal management challenges in electronics and aerospace applications. These materials possess not only exceptional thermal conductivity but also environmental compatibility. However, developing such materials necessitates overcoming intricate challenges, such as precise control over the material structure and optimization of the material's properties and stability. This review comprehensively overviews the research progress of BITMs, emphasizing the synergy between biomimetic design principles and artificial-intelligence-driven methodologies to enhance their performance. The unique nature-inspired structures are explored and valuable insights are provided into adaptive thermal management strategies, which can be further enhanced through data analytics and machine learning (ML). This review offers insights into overcoming design challenges and outlines future prospects for advanced BITMs by integrating ML and biomimetic design principles.

Multi-Energy Conversion and Electromagnetic Shielding Enabled by Carbonized Polyimide/Kevlar/Graphene Oxide@ZIF-67 Bidirectional Complex Aerogel-Encapsulated Phase-Change Materials

To address the limitations of conventional energy systems and optimize the energy conversion pathways and efficiency, a type of "five-in-one" multifunctional phase-change composite with magnetothermal, electrothermal, solar-thermal, and thermoelectric energy conversion and electromagnetic shielding functions is developed for multipurpose applications. Such a novel phase-change composite is fabricated by an innovative combination of paraffin wax (PW) as a phase-change material and a carbonized polyimide/Kevlar/graphene oxide@ZIF-67 complex aerogel as a supporting material. The carbonized complex aerogel exhibits a unique bidirectional porous structure with high porosity and robust skeleton to support the loading of PW. The reduced graphene oxide and CoNC resulting from high-temperature carbonization are anchored on the aerogel skeleton to generate high thermal conduction and magnetic effect, enhancing the phonon and electron transfer of the aerogel and improving its energy conversion efficiency. The phase-change composite not only exhibits excellent solar-thermal, thermoelectric, electrothermal, and magnetothermal energy conversion performance, but also achieves high electromagnetic interference shielding effectiveness of 66.2 dB in the X-band. The introduction of PW significantly improves the thermal energy-storage capacity during multi-energy conversion. The developed composite exhibits great application potential for efficient solar energy utilization, sustainable power generation, outdoor deicing, human thermal therapy, and electronic device protection.

Multiscale Heat and Mass Transport Optimization for Solar-Driven Interfacial Evaporation: Opportunities and Challenges for Industrial Applications

Solar-driven interfacial evaporation (SDIE) offers an energy-friendly water treatment technique for underdeveloped areas due to its clean energy-driven, ease of deployment, and off-grid operation. However, extending SDIE to industrial application is still challenged by slow vapor transfer and low condensation efficiency. Addressing these bottlenecks requires a comprehensive framework that incorporates the optimization of multiscale heat and mass transport from evaporators to overall systems, enhancing the energy conversion efficiency in the real-world. This perspective identifies key factors affecting vapor transport and condensation dynamics within evaporators and evaporation systems. Based on the integration of functional materials and energy harvesting devices, viable routes to achieve rapid heat and mass transfer, vapor-liquid phase change, and improved energy conversion efficiency within the condensing chamber, condensing wall, and enthalpy cycle architecture are discussed. Next, multiple design guidelines for optimizing condensation based on different application scenarios and operating environments are provided, further enhancing the flexibility and reliability of the SDIE. This perspective follows the blueprint of the Sustainable Development Goals and aims to advance the industrial implementation of SDIE and global coverage of safely drinking water.

Ultra-high thermally conductive graphite microplatelet/aramid nanofiber composites with reduced interfacial thermal resistances by engineered interface π-π interactions

Polymer-based thermally conductive composites with ultrahigh in-plane thermal conductivity are ideal candidates for heat dissipation applications in electronics. However, the complex interfaces between the functional filler and polymer matrix limit the significant increase in thermal conductivity of the polymer composites. In this study, we developed a one-pot strategy to prepare highly thermally conductive composite films of freeze-expansion large-size graphite microplatelets (F-GMPs) and aramid nanofibers (ANFs) with π-π interactions. The obtained F-GMP/ANF nanocomposite films present salient in-plane thermal conductivity, considerable flexibility, and outstanding long-term stability. The π-π interactions between the F-GMPs and ANFs promote the freeze-expansion exfoliation of graphite, yielding stable F-GMP/ANF precursor pastes with high-quality graphite platelets. Moreover, the π-π interactions improve the filler-matrix interfacial compatibility and reduce the interfacial thermal resistance, while the large-size F-GMP particles are directly lapped to construct a thermal transfer pathway with a reduction in the filler-filler interfacial thermal resistance. Consequently, the F-GMP/ANF composite films with 30 wt% F-GMPs exhibit unprecedentedly high in-plane thermal conductivity (56.89 W m-1 K-1) and corresponding thermal conductivity enhancement efficiency, presenting great application potential for the effective thermal management of highly integrated electronics.

Biopolymer-Derived Carbon Materials for Wearable Electronics

Advanced carbon materials are widely utilized in wearable electronics. Nevertheless, the production of carbon materials from fossil-based sources raised concerns regarding their non-renewability, high energy consumption, and the consequent greenhouse gas emissions. Biopolymers, readily available in nature, offer a promising and eco-friendly alternative as a carbon source, enabling the sustainable production of carbon materials for wearable electronics. This review aims to discuss the carbonization mechanisms, carbonization techniques, and processes, as well as the diverse applications of biopolymer-derived carbon materials (BioCMs) in wearable electronics. First, the characteristics of four representative biopolymers, including cellulose, lignin, chitin, and silk fibroin, and their carbonization processes are discussed. Then, typical carbonization techniques, including pyrolysis carbonization, laser-induced carbonization, Joule heating carbonization, hydrothermal transformation, and salt encapsulation carbonization are discussed. The influence of the processes on the morphology and properties of the resultant BioCMs are summarized. Subsequently, applications of BioCMs in wearable devices, including physical sensors, chemical sensors, energy devices, and display devices are discussed. Finally, the challenges currently facing the field and the future opportunities are discussed.

Anisotropic Heat Transfer in a Fibrous Membrane with Hierarchically Assembled 2D Materials

Effective heat redistribution in specific directions is vital for advanced thermal management, significantly enhancing device performance by optimizing spatial heat configurations. We have designed and fabricated a hierarchical fibrous membrane that enables precise heat directing. By integrating hierarchical structure design with the anisotropic thermal conductivity of two-dimensional (2D) materials, we developed a fibrous membrane for anisotropic heat transfer. Such a structure is fabricated by aligning a 1D structured fiber in the 2D plane to achieve anisotropy at each scale level. The fiber units, where 2D nanosheets circumferentially and axially aligned, achieved a high axial thermal conductivity of 16.8 W·m-1·K-1 and advanced heat directing ability, confirmed by characterizations and simulations. The assembled membrane demonstrated an exceptional tensile strength (365 MPa) and high thermal conductivity (10.5 W·m-1·K-1) along the fiber axis. Our membranes are seen as a refined model for thermal management materials, combining the benefits of heat spreaders and thermal interface materials, thus being proficient in directing heat along programmed pathways. A practical wireless charging cooling demonstration illustrated this. Our methodology also proved versatile with different 2D fillers and various geometries. This research presents a method to achieve precise heat directing at the material's level, facilitating the systematic design of thermal management in electronics.

Hydrogel-embedded vertically aligned metal-organic framework nanosheet membrane for efficient water harvesting

Highly porous metal-organic framework (MOF) nanosheets have shown promising potential for efficient water sorption kinetics in atmospheric water harvesting (AWH) systems. However, the water uptake of single-component MOF absorbents remains limited due to their low water retention. To overcome this limitation, we present a strategy for fabricating vertically aligned MOF nanosheets on hydrogel membrane substrates (MOF-CT/PVA) to achieve ultrafast AWH with high water uptake. By employing directional growth of MOF nanosheets, we successfully create superhydrophilic MOF coating layer and pore channels for efficient water transportation to the crosslinked flexible hydrogel membrane. The designed composite water harvester exhibits ultrafast sorption kinetics, achieving 91.4% saturation within 15 min. Moreover, MOF-CT/PVA exhibits superior solar-driven water capture-release capacity even after 10 cycles of reuse. This construction approach significantly enhances the water vapor adsorption, offering a potential solution for the design of composite MOF-membrane harvesters to mitigate the freshwater crisis.

MoS2 Lubricate-Toughened MXene/ANF Composites for Multifunctional Electromagnetic Interference Shielding

The design and fabrication of high toughness electromagnetic interference (EMI) shielding composite films with diminished reflection are an imperative task to solve electromagnetic pollution problem. Ternary MXene/ANF (aramid nanofibers)-MoS2 composite films with nacre-like layered structure here are fabricated after the introduction of MoS2 into binary MXene/ANF composite system. The introduction of MoS2 fulfills an impressive "kill three birds with one stone" improvement effect: lubrication toughening mechanical performance, reduction in secondary reflection pollution of electromagnetic wave, and improvement in the performance of photothermal conversion. After the introduction of MoS2 into binary MXene/ANF (mass ratio of 50:50), the strain to failure and tensile strength increase from 22.1 ± 1.7% and 105.7 ± 6.4 MPa and to 25.8 ± 0.7% and 167.3 ± 9.1 MPa, respectively. The toughness elevates from 13.0 ± 4.1 to 26.3 ± 0.8 MJ m-3 (~ 102.3%) simultaneously. And the reflection shielding effectiveness (SER) of MXene/ANF (mass ratio of 50:50) decreases ~ 10.8%. EMI shielding effectiveness (EMI SE) elevates to 41.0 dB (8.2-12.4 GHz); After the introduction of MoS2 into binary MXene/ANF (mass ratio of 60:40), the strain to failure increases from 18.3 ± 1.9% to 28.1 ± 0.7% (~ 53.5%), the SER decreases ~ 22.2%, and the corresponding EMI SE is 43.9 dB. The MoS2 also leads to a more efficient photothermal conversion performance (~ 45 to ~ 55 °C). Additionally, MXene/ANF-MoS2 composite films exhibit excellent electric heating performance, quick temperature elevation (15 s), excellent cycle stability (2, 2.5, and 3 V), and long-term stability (2520 s). Combining with excellent mechanical performance with high MXene content, electric heating performance, and photothermal conversion performance, EMI shielding ternary MXene/ANF-MoS2 composite films could be applied in many industrial areas. This work broadens how to achieve a balance between mechanical properties and versatility of composites in the case of high-function fillers.

Ultrastrong Nanopapers with Aramid Nanofibers and Silver Nanowires Reinforced by Cellulose Nanofibril-Assisted Dispersed Graphene Nanoplates for Superior Electromagnetic Interference Shielding

High-strength, lightweight, ultrathin, and flexible electromagnetic interference (EMI) shielding materials with a high shielding effectiveness (SE) are essential for modern integrated electronics. Herein, cellulose nanofibrils (CNFs) are employed to homogeneously disperse graphene nanoplates (GNPs) into an aramid nanofiber (ANF) network and silver nanowire (AgNW) network, respectively, producing high-performance nanopapers. These nanopapers, featuring nacre-mimetic microstructures and layered architectures, exhibited high tensile strength (601.11 MPa) and good toughness (103.56 MJ m-3) with a thickness of only 24.58 μm. Their specific tensile strength reaches 447.59 MPa·g-1·cm3, which is 1.74 times that of titanium alloys (257 MPa·g-1·cm3). The AgNW/GNP composite conductive layers exhibit an electrical conductivity of 12010.00 S cm-1, providing the nanopapers with great EMI shielding performance, achieving an EMI SE of 63.87 dB and an EMI SE/t of 25978.80 dB cm-1. The nanopapers also show reliable durability, retaining a tensile strength of 500.96 MPa and an EMI SE of 57.59 dB after 120,000 folding cycles. Additionally, they have a good electrical heating performance with a fast response time, low driving voltage, effective deicing capability, and reliable heating capacity in water. This work presents a strategy to develop a high-performance nanopaper, showing great potential for applications in electromagnetic compatibility, national defense, smart electronics, and human health.

Flexible solid-liquid bi-continuous electrically and thermally conductive nanocomposite for electromagnetic interference shielding and heat dissipation

In the era of 5 G, the rise in power density in miniaturized, flexible electronic devices has created an urgent need for thin, flexible, polymer-based electrically and thermally conductive nanocomposites to address challenges related to electromagnetic interference (EMI) and heat accumulation. However, the difficulties in establishing enduring and continuous transfer pathways for electrons and phonons using solid-rigid conductive fillers within insulative polymer matrices limit the development of such nanocomposites. Herein, we incorporate MXene-bridging-liquid metal (MBLM) solid-liquid bi-continuous electrical-thermal conductive networks within aramid nanofiber/polyvinyl alcohol (AP) matrices, resulting in the AP/MBLM nanocomposite with ultra-high electrical conductivity (3984 S/cm) and distinguished thermal conductivity of 13.17 W m-1 K-1. This nanocomposite exhibits excellent EMI shielding efficiency (SE) of 74.6 dB at a minimal thickness of 22 μm, and maintains high EMI shielding stability after enduring various harsh conditions. Meanwhile, the AP/MBLM nanocomposite also demonstrates promising heat dissipation behavior. This work expands the concept of creating thin films with high electrical and thermal conductivity.

Programmable and Shape-Color Synchronous Dual-Response Wood with Thermal Stimulus

Stimuli-responsive materials exhibit huge potential in sensors, actuators, and electronics; however, their further development for reinforcement, visualization, and biomass-incorporation remains challenging. Herein, based on the impregnation of thermochromic microcapsule (TCM)-doped dynamic covalent vitrimers, a programmable shape-color dual-responsive wood (SRW-TC) was demonstrated with robust anisotropic structures and exchangeable covalent adaptable networks. Under mild conditions, the resultant SRW-TC displays feasible shape memorability and programmability, resulting from the rigidity-flexibility shift induced by the glass-transition temperature (34.99 °C) and transesterification reaction triggered by the topology freezing transition temperature (149.62 °C). Furthermore, the obtained SRW-TC possesses satisfactory mechanical performance (tensile strength of 45.70 MPa), thermal insulation (thermal conductivity of 0.27 W/m K), anisotropic light management, and benign optical properties (transmittance of 51.73% and haze of 99.67% at 800 nm). Importantly, the incorporation of compatible TCM enables SRW-TC to visualize shape memory feasibility and rigidity/flexibility switching and respond to the external thermal stimulus through the thermal-induced shape-color synchronous dual-responsiveness, which successfully demonstrates the applications of sensing temperature, grasping objects, encrypting/decoding icon messages, and so on. The proposed facile and highly effective strategy could serve as a guideline for developing high-performance multifunctional wood composite with promising intelligent applications in performance visualization, environmental sensing, materials interactivity, information dual-encryption, local precision shape and color regulation, etc.

Application and Development of Smart Thermally Conductive Fiber Materials

In recent years, with the rapid advancement in various high-tech technologies, efficient heat dissipation has become a key issue restricting the further development of high-power-density electronic devices and components. Concurrently, the demand for thermal comfort has increased; making effective personal thermal management a current research hotspot. There is a growing demand for thermally conductive materials that are diversified and specific. Therefore, smart thermally conductive fiber materials characterized by their high thermal conductivity and smart response properties have gained increasing attention. This review provides a comprehensive overview of emerging materials and approaches in the development of smart thermally conductive fiber materials. It categorizes them into composite thermally conductive fibers filled with high thermal conductivity fillers, electrically heated thermally conductive fiber materials, thermally radiative thermally conductive fiber materials, and phase change thermally conductive fiber materials. Finally, the challenges and opportunities faced by smart thermally conductive fiber materials are discussed and prospects for their future development are presented.

Large-Scale Fabrication of Tunable Sandwich-Structured Silver Nanowires and Aramid Nanofiber Films for Exceptional Electromagnetic Interference (EMI) Shielding

The recent advancements in communication technology have facilitated the widespread deployment of electronic communication equipment globally, resulting in the pervasive presence of electromagnetic pollution. Consequently, there is an urgent necessity to develop a thin, lightweight, efficient, and durable electromagnetic interference (EMI) shielding material capable of withstanding severe environmental conditions. In this paper, we propose an innovative and scalable method for preparing EMI shielding films with a tunable sandwich structure. The film possesses a nylon mesh (NM) backbone, with AgNWs serving as the shielding coating and aramid nanofibers (ANFs) acting as the cladding layer. The prepared film was thin and flexible, with a thickness of only 0.13 mm. AgNWs can easily form a conductive network structure, and when the minimum addition amount was 0.2 mg/cm2, the EMI SE value reached 28.7 dB, effectively shielding 99.884% of electromagnetic waves and thereby meeting the commercial shielding requirement of 20 dB. With an increase in dosage up to 1.0 mg/cm2, the EMI SE value further improved to reach 50.6 dB. The NAAANF film demonstrated remarkable robustness in the face of complex usage environments as a result of the outstanding thermal, acid, and alkali resistance properties of aramid fibers. Such a thin, efficient, and environmentally resistant EMI shielding film provided new ideas for the broad EMI shielding market.

Highly Thermoconductive, Strong Graphene-Based Composite Films by Eliminating Nanosheets Wrinkles

Graphene-based thermally conductive composites have been proposed as effective thermal management materials for cooling high-power electronic devices. However, when flexible graphene nanosheets are assembled into macroscopic thermally conductive composites, capillary forces induce shrinkage of graphene nanosheets to form wrinkles during solution-based spontaneous drying, which greatly reduces the thermal conductivity of the composites. Herein, graphene nanosheets/aramid nanofiber (GNS/ANF) composite films with high thermal conductivity were prepared by in-plane stretching of GNS/ANF composite hydrogel networks with hydrogen bonds and π-π interactions. The in-plane mechanical stretching eliminates graphene nanosheets wrinkles by suppressing inward shrinkage due to capillary forces during drying and achieves a high in-plane orientation of graphene nanosheets, thereby creating a fast in-plane heat transfer channel. The composite films (GNS/ANF-60 wt%) with eliminated graphene nanosheets wrinkles showed a significant increase in thermal conductivity (146 W m-1 K-1) and tensile strength (207 MPa). The combination of these excellent properties enables the GNS/ANF composite films to be effectively used for cooling flexible LED chips and smartphones, showing promising applications in the thermal management of high-power electronic devices.

Functional Materials and Innovative Strategies for Wearable Thermal Management Applications

Highlights

This article systematically reviews the thermal management wearables with a specific emphasis on materials and strategies to regulate the human body temperature. Thermal management wearables are subdivided into the active and passive thermal managing methods. The strength and weakness of each thermal regulatory wearables are discussed in details from the view point of practical usage in real-life.

Abstract

Thermal management is essential in our body as it affects various bodily functions, ranging from thermal discomfort to serious organ failures, as an example of the worst-case scenario. There have been extensive studies about wearable materials and devices that augment thermoregulatory functionalities in our body, employing diverse materials and systematic approaches to attaining thermal homeostasis. This paper reviews the recent progress of functional materials and devices that contribute to thermoregulatory wearables, particularly emphasizing the strategic methodology to regulate body temperature. There exist several methods to promote personal thermal management in a wearable form. For instance, we can impede heat transfer using a thermally insulating material with extremely low thermal conductivity or directly cool and heat the skin surface. Thus, we classify many studies into two branches, passive and active thermal management modes, which are further subdivided into specific strategies. Apart from discussing the strategies and their mechanisms, we also identify the weaknesses of each strategy and scrutinize its potential direction that studies should follow to make substantial contributions to future thermal regulatory wearable industries.

Enhanced thermal properties of epoxy composites by constructing thermal conduction networks with low content of three-dimensional graphene

Micro/nano electronic devices heat dissipation depends heavily on the thermal interface materials (TIMs). Despite notable progress, it is hard to efficaciously enhance the thermal properties of the hybrid TIMs with high-load additives due to an absence of effective heat transfer routes. Herein, the low content of three-dimensional (3D) graphene with interconnected networks is adopted as the additive to improve the thermal properties of epoxy composite TIMs. The thermal diffusivity and thermal conductivity of the as-prepared hybrids were dramatically improved by constructing thermal conduction networks after adding 3D graphene as fillers. The 3D graphene/epoxy hybrid's optimal thermal characteristics were observed at 1.5 wt% of 3D graphene content, corresponding to a maximum enhancement of 683%. Besides, heat transfer experiments were further performed to determine the superb heat dissipation potential of the 3D graphene/epoxy hybrids. Moreover, the 3D graphene/epoxy composite TIM was also applied to high-power LED to improve heat dissipation. It effectively reduced the maximum temperature from 79.8 °C to 74.3 °C. These results are beneficial for the better cooling performance of electronic devices and provide useful guidelines for advancing the next-generation TIMs.

Flexible, Highly Thermally Conductive and Electrically Insulating Phase Change Materials for Advanced Thermal Management of 5G Base Stations and Thermoelectric Generators

Thermal management has become a crucial problem for high-power-density equipment and devices. Phase change materials (PCMs) have great prospects in thermal management applications because of their large capacity of heat storage and isothermal behavior during phase transition. However, low intrinsic thermal conductivity, ease of leakage, and lack of flexibility severely limit their applications. Solving one of these problems often comes at the expense of other performance of the PCMs. In this work, we report core-sheath structured phase change nanocomposites (PCNs) with an aligned and interconnected boron nitride nanosheet network by combining coaxial electrospinning, electrostatic spraying, and hot-pressing. The advanced PCN films exhibit an ultrahigh thermal conductivity of 28.3 W m-1 K-1 at a low BNNS loading (i.e., 32 wt%), which thereby endows the PCNs with high enthalpy (> 101 J g-1), outstanding ductility (> 40%) and improved fire retardancy. Therefore, our core-sheath strategies successfully balance the trade-off between thermal conductivity, flexibility, and phase change enthalpy of PCMs. Further, the PCNs provide powerful cooling solutions on 5G base station chips and thermoelectric generators, displaying promising thermal management applications on high-power-density equipment and thermoelectric conversion devices.