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 our understanding of 2D material-based TIMs, in this review, we focus primarily on graphene and boron nitride-based TIMs, exploring their structures, properties, and applications. Building on this foundation, we emphasize the developmental history of these TIMs and provide a detailed analysis of critical challenges and potential solutions. Additionally, we briefly introduce the preparation and application of some other novel 2D materials-based TIMs, aiming to offer constructive guidance for the future development of high-performance TIMs. This article is protected by copyright. All rights reserved.
AD is the abbreviation for Alzheimer's Disease, which is a neurodegenerative disorder that features progressive dysfunction in cognition. Previous research has reported that mitophagy impairment and mitochondrial dysfunction have been crucial factors in the AD's pathogenesis. More recently, literature has emerged which offers findings suggesting that the nicotinamide adenine dinucleotide (short for NAD+) augmentation eliminates the defective mitochondria and restores mitophagy. Meanwhile, as an enzyme which is rate-limiting, the Nicotinamide phosphoribosyltransferase, or NAMPT, is part of the salvage pathway of NAD+ synthesis. Therefore, the aim of the research project has been to produce proof for how the NAMPT-NAD +-silent information-regulated transcription factors1/3 (short for SIRT1/3) axis function in mediating mitophagy in APP/PS1 mice aged six months. The results revealed that the NAMPT-NAD+-SIRT1/3 axis in the APP/PS1 mice's hippocampus was considerably declined. Surprisingly, P7C3 (an NAMPT activator) noticeably promoted the NAD+-SIRT1/3 axis, improved mitochondrial structure and function, enhanced mitophagy activity along with the ability of learning and memory. While FK866 (an NAMPT inhibitor) reversed the decreased NAD+-SIRT1/3 axis, and even exacerbated Aß plaque deposition level in the APP/PS1 mice's hippocampus. The findings observed in this study indicate two main points: avoiding downregulation of the NAMPT activity can prevent AD-related mitophagy impairment; on the other hand, NAMPT characterizes a potential therapeutic intervention regarding AD pathogenesis.
The rapid development of highly integrated microelectronic devices causes urgent demands for advanced thermally conductive adhesives (TCAs) to solve the interfacial heat-transfer issue. Due to their natural 2D structure and isotropic thermal conductivity, metal nanoflakes are promising fillers blended with polymer to develop high-performance TCAs. However, achieving corresponding TCAs with thermal conductivity over 10 W m-1 K-1 at filler content below 30 vol% remains challenging so far. This longstanding bottleneck is mainly attributed to the fact that most current metal nanoflakes are prepared by "bottom-up" processes (e.g., solution-based chemical synthesis) and inevitably contain lattice defects or impurities, resulting in lower intrinsic thermal conductivities, only 20-65% of the theoretical value. Here, a "top-down" strategy by splitting highly purified Ag foil with nanoscale thickness is adopted to prepare 2D Ag nanoflakes with an intrinsic thermal conductivity of 398.2 W m-1 K-1 , reaching 93% of the theoretical value. After directly blending with epoxy, the resultant Ag/epoxy exhibits a thermal conductivity of 15.1 W m-1 K-1 at low filler content of 18.6 vol%. Additionally, in practical microelectronic cooling performance evaluations, the interfacial heat-transfer efficiency of the Ag/epoxy achieves ≈1.4 times that of the state-of-the-art commercial TCA.
With the increase in heat power density in modern integrating electronics, thermal interface materials (TIM) that can efficiently fill the gaps between the heat source and heat sinks and enhance heat dissipation are urgently needed owing to their high thermal conductivity and excellent mechanical durability. Among all the emerged TIMs, graphene-based TIMs have attracted increasing attention because of the ultrahigh intrinsic thermal conductivity of graphene nanosheets. Despite extensive efforts, developing high-performance graphene-based papers with high through-plane thermal conductivity remains challenging despite their high in-plane thermal conductivity. In this study, a novel strategy for enhancing the through-plane thermal conductivity of graphene papers by in situ depositing AgNWs on graphene sheets (IGAP) was proposed, which could boost the through-plane thermal conductivity of the graphene paper up to 7.48 W m-1 K-1 under packaging conditions. In the TIM performance test under actual and simulated operating conditions, our IGAP exhibits strongly enhanced heat dissipation performance compared to the commercial thermal pads. We envision that our IGAP as a TIM has great potential for boosting the development of next-generation integrating circuit electronics.
Developing advanced thermal interface materials (TIMs) to bridge heat-generating chip and heat sink for constructing an efficient heat transfer interface is the key technology to solve the thermal management issue of high-power semiconductor devices. Based on the ultra-high basal-plane thermal conductivity, graphene is an ideal candidate for preparing high-performance TIMs, preferably to form a vertically aligned structure so that the basal-plane of graphene is consistent with the heat transfer direction of TIM. However, the actual interfacial heat transfer efficiency of currently reported vertically aligned graphene TIMs is far from satisfactory. In addition to the fact that the thermal conductivity of the vertically aligned TIMs can be further improved, another critical factor is the limited actual contact area leading to relatively high contact thermal resistance (20-30 K mm2 W-1) of the "solid-solid" mating interface formed by the vertical graphene and the rough chip/heat sink. To solve this common problem faced by vertically aligned graphene, in this work, we combined mechanical orientation and surface modification strategy to construct a three-tiered TIM composed of mainly vertically aligned graphene in the middle and micrometer-thick liquid metal as a cap layer on upper and lower surfaces. Based on rational graphene orientation regulation in the middle tier, the resultant graphene-based TIM exhibited an ultra-high thermal conductivity of 176 W m-1 K-1. Additionally, we demonstrated that the liquid metal cap layer in contact with the chip/heat sink forms a "liquid-solid" mating interface, significantly increasing the effective heat transfer area and giving a low contact thermal conductivity of 4-6 K mm2 W-1 under packaging conditions. This finding provides valuable guidance for the design of high-performance TIMs based on two-dimensional materials and improves the possibility of their practical application in electronic thermal management.
Sintering aid was very crucial to influence the microstructure and thus the optical property of the sintered optical ceramics. The purpose of this work was to explain the difference between the sintering aids of Li+ and Y3+ on Al23O27N5 (AlON) ceramic via reaction sintering method. The effects of LiAl5O8 (LA) and Y2O3 on the sintering of Al2O3-AlN system were carefully compared, in terms of X-ray diffraction (XRD), microstructure, density, X-ray photoelectron spectroscopy (XPS) and optical transmittance. According to the XPS and XRD lattice analysis, the chemical structure of the materials was not obviously affected by different dopants. We firstly reported that, there was obvious volume expansion in the Y3+ dopped AlON ceramics, which was responsible for the low transparency of the ceramics. Obvious enhancements were achieved using Li+ aids from the results that Li: AlONs showing a higher transparency and less optical defects. A higher LA content (20 wt%) was effective to remove pores and thus obtain a higher transmittance (~86.8% at ~3.5 µm). Thus, pores were the main contributions to the property difference between the dopant samples. The importance of sintering aids should be carefully realized for the reaction sintering fabrication of AlON based ceramics towards high transparency.
Combining the advantages of high thermal conductivities and low graphene contents to fabricate polymer composites for applications in thermal management is still a great challenge due to the high defect degree of exfoliated graphene, the poor orientation of graphene in polymer matrices, and the horrible phonon scattering between graphene/graphene and graphene/polymer interfaces. Herein, mesoplasma chemical vapor deposition (CVD) technology was successfully employed to synthesize vertically aligned graphene nanowalls (GNWs), which are covalently bonded by high-quality CVD graphene nanosheets. The unique architecture leads to an excellent thermal enhancement capacity of the GNWs, and a corresponding composite film with a matrix of polyvinylidene fluoride (PVDF) presented a high through-plane thermal conductivity of 12.8 ± 0.77 W m-1 K-1 at a low filler content of 4.0 wt%, resulting in a thermal conductivity enhancement per 1 wt% graphene loading of 1659, which is far superior to that using conventional graphene structures as thermally conductive pathways. In addition, this composite exhibited an excellent capability in cooling a high-power light-emitting diode (LED) device under real application conditions. Our finding provides a new route to prepare high-performance thermal management materials with low filler loadings via the rational design of the microstructures/interfaces of graphene skeletons.
The rapid increase of operation speed, transmission efficiency, and power density of miniaturized devices leads to a rising demand for electromagnetic interference (EMI) shielding and thermal management materials in the semiconductor industry. Therefore, it is essential to improve both the EMI shielding and thermal conductive properties of commonly used polyolefin components (such as polyethylene (PE)) in electronic systems. Currently, melt compounding is the most common method to fabricate polyolefin composites, but the difficulty of filler dispersion and high resistance at the filler/filler or filler/matrix interface limits their properties. Here, a fold fabrication strategy was proposed to prepare PE composites by incorporation of a well-aligned, seamless graphene framework premodified with MXene nanosheets into the matrix. We demonstrate that the physical properties of the composites can be further improved at the same filler loading by nanoscale interface engineering: the formation of hydrogen bonds at the graphene/MXene interface and the development of a seamlessly interconnected graphene framework. The obtained PE composites exhibit an EMI shielding property of â¼61.0 dB and a thermal conductivity of 9.26 W m-1 K-1 at a low filler content (â¼3 wt %, including â¼0.4 wt % MXene). Moreover, other thermoplastic composites with the same results can also be produced based on our method. Our study provides an idea toward rational design of the filler interface to prepare high-performance polymer composites for use in microelectronics and microsystems.
With the continuous progress in electronic devices, thermal interface materials (TIMs) are urgently needed for the fabrication of integrated circuits with high reliability and performance. Graphene as a wonderful additive is often added into polymer to build composite TIMs. However, owing to the lack of a specific design of the graphene skeleton, thermal conductivity of graphene-based composite TIMs is not significantly improved. Here a chloroform-assisted method for rapid growth of vertical graphene (VG) arrays in electric field-assisted plasma enhanced chemical vapor deposition (PECVD) system is reported. Under the optimum intensity and direction of electric field and by introducing the highly electronegative chlorine into the reactor, the record growth rate of 11.5 µm h-1 is achieved and VG with a height of 100 µm is successfully synthesized. The theoretical study for the first time reveals that the introduction of chlorine accelerates the decomposition of methanol and thus promotes the VG growth in PECVD. Finally, as an excellent filler framework in polymer matrix, VG arrays are used to construct a free-standing composite TIM, which yields a high vertical thermal conductivity of 34.2 W m-1 K-1 at the graphene loading of 8.6 wt% and shows excellent cooling effect in interfacial thermal dissipation of light emitting diode.
As the power density and integration level of electronic devices increase, there are growing demands to improve the thermal conductivity of polymers for addressing the thermal management issues. On the basis of the ultrahigh intrinsic thermal conductivity, graphene has exhibited great potential as reinforcing fillers to develop polymer composites, but the resultant thermal conductivity of reported graphene-based composites is still limited. Here, an interconnected and highly ordered graphene framework (HOGF) composed of high-quality and horizontally aligned graphene sheets was developed by a porous film-templated assembly strategy, followed by a stress-induced orientation process and graphitization post-treatment. After embedding into the epoxy (EP), the HOGF/EP composite (24.7 vol %) exhibits a record-high in-plane thermal conductivity of 117 W m-1 K-1, equivalent to ≈616 times higher than that of neat epoxy. This thermal conductivity enhancement is mainly because the HOGF as a filler concurrently has high intrinsic thermal conductivity, relatively high density, and a highly ordered structure, constructing superefficient phonon transport paths in the epoxy matrix. Additionally, the use of our HOGF/EP as a heat dissipation plate was demonstrated, and it achieved 75% enhancement in practical thermal management performance compared to that of conventional alumina for cooling the high-power LED.
Given the thermal management problem aroused by increasing power densities of electronic components in the system, graphene-based papers have raised considerable interest for applications as thermal interface materials (TIMs) to solve interfacial heat transfer issues. Significant research efforts have focused on enhancing the through-plane thermal conductivity of graphene paper; however, for practical thermal management applications, reducing the thermal contact resistance between graphene paper and the mating surface is also a challenge to be addressed. Here, a strategy aimed at reducing the thermal contact resistance between graphene paper and the mating surface to realize enhanced heat dissipation was demonstrated. For this, graphene paper was decorated with polydopamine EGaIn nanocapsules using a facile dip-coating process. In practical TIM application, there was a decrease in the thermal contact resistance between the TIMs and mating surface after decoration (from 46 to 15 K mm2 W-1), which enabled the decorated paper to realize a 26% enhancement of cooling efficiency compared with the case without decoration. This demonstrated that this method is a promising route to enhance the heat dissipation capacity of graphene-based TIMs for practical electronic cooling applications.
Graphene is usually embedded into polymer matrices for the development of thermally conductive composites, preferably forming an interconnected and anisotropic framework. Currently, the directional self-assembly of exfoliated graphene sheets is demonstrated to be the most effective way to synthesize anisotropic graphene frameworks. However, achieving a thermal conductivity enhancement (TCE) over 1500% with per 1 vol% graphene content in polymer matrices remains challenging, due to the high junction thermal resistance between the adjacent graphene sheets within the self-assembled graphene framework. Here, a multiscale structural modulation strategy for obtaining highly ordered structure of graphene framework and simultaneously reducing the junction thermal resistance is demonstrated. The resultant anisotropic framework contributes to the polymer composites with a record-high thermal conductivity of 56.8-62.4 W m-1 K-1 at the graphene loading of ≈13.3 vol%, giving an ultrahigh TCE per 1 vol% graphene over 2400%. Furthermore, thermal energy management applications of the composites as phase change materials for solar-thermal energy conversion and as thermal interface materials for electronic device cooling are demonstrated. The finding provides valuable guidance for designing high-performance thermally conductive composites and raises their possibility for practical use in thermal energy storage and thermal management of electronics.
The rapid development of integrated circuits and electronic devices creates a strong demand for highly thermally conductive yet electrically insulating composites to efficiently solve "hot spot" problems during device operation. On the basis of these considerations, hexagonal boron nitride nanosheets (BNNS) have been regarded as promising fillers to fabricate polymer matrix composites. However, so far an efficient approach to prepare ultrahigh-aspect-ratio BNNS with large lateral size while maintaining an atomically thin nature is still lacking, seriously restricting further improvement of the thermal conductivity for BNNS/polymer composites. Here, a rapid and high-yield method based on a microfluidization technique is developed to obtain exfoliated BNNS with a record high aspect ratio of ≈1500 and a low degree of defects. A foldable and electrically insulating film made of such a BNNS and poly(vinyl alcohol) (PVA) matrix through filtration exhibits an in-plane thermal conductivity of 67.6 W m-1 K-1 at a BNNS loading of 83 wt %, leading to a record high value of thermal conductivity enhancement (≈35â¯500). The composite film then acts as a heat spreader for heat dissipation of high-power LED modules and shows superior cooling efficiency compared to commercial flexible copper clad laminate. Our findings provide a practical route to produce electrically insulating polymer composites with high thermal conductivity for thermal management applications in modern electronic devices.
Cardiac lymphoma is extremely rare in patients with normal immune function and difficult to identify through routine examinations in patients with atypical clinical manifestations, making early diagnosis very difficult. We reported a 71-year-old male patient who was repeatedly diagnosed of pulmonary infection, suspected lung tumour, and Kimura disease in other hospital due to cough, expectoration, and dyspnoea. Later on, the patient visited our hospital due to heart failure and epistaxis. Transthoracic echocardiogram confirmed the presence of a space-occupying lesion in the right heart, cardiac magnetic resonance imaging preliminarily determined the nature of this lesion, finally, 18 F-fluorodeoxyglucose positron-emission tomography/computed tomography, and nasal mass biopsy confirmed the diagnosis of cardiac malignant lymphoma, and the pathological type was diffuse large B-cell lymphoma.
Heart Neoplasms , Lymphoma, Large B-Cell, Diffuse , Aged , Fluorodeoxyglucose F18 , Heart Neoplasms/diagnosis , Heart Ventricles/diagnostic imaging , Humans , Lymphoma, Large B-Cell, Diffuse/diagnosis , Male , Positron Emission Tomography Computed Tomography
Background: The increasing prevalence of obesity among children and adolescents is a major public health challenge worldwide. This study examined the relationship between physical fitness and BMI spanning the range from underweight to obese among Chinese mainland children and adolescents. Methods: Participants were 22,681 children and adolescents (11,300 boys and 11,381 girls) aged 10-18 years from the Chinese mainland. Weight status was classified as underweight, normal weight, overweight, and obese using WHO 2007 standards. Physical fitness parameters such as cardiorespiratory fitness (VO2max), lower body explosive strength (standing broad jump), upper body explosive strength (handgrip strength), abdominal muscular endurance (sit-ups in 30 s), flexibility (sit-and-reach), and agility (repeat bestride (20 s)) were assessed. Results: There was a significant association between weight status categories and physical fitness in all age groups and sex (plinear < 0.001, pquadratic < 0.001). Underweight adolescents performed better in lower limb strength, flexibility, agility, and cardiorespiratory fitness than their obese peers, but worse in upper limb strength. Underweight boys aged 10-11 and 12-13 years and girls aged 10-11 years showed significantly (p < 0.05) high odds of meeting a low physical fitness index. Obese adolescents have high odds of meeting a low physical fitness index with age. Conclusion: The present study showed a nonlinear relationship between weight status and physical fitness. Children and adolescents who were classified as underweight or obese had poorer physical fitness than their normal-weight peers.
Body Weight , Hand Strength , Physical Fitness , Adolescent , Body Mass Index , Child , Cross-Sectional Studies , Female , Humans , Male , Overweight
Mitochondrial dysfunction is a hallmark of Alzheimer's disease (AD), which may be related to mitophagy failure. Previous reports suggest that treadmill exercise protects against mitochondrial dysfunction in AD. However, few studies have investigated the relationship between mitophagy and mitochondrial adaptation caused by treadmill exercise in AD. The current study aimed to investigate whether exercise-ameliorated AD is associated with changes in mitophagy activity. Both Wild-type and APP/PS1 transgenic mice were divided into sedentary (WTC and ADC) and exercise (WTE and ADE) groups (n = 9 for each group). WTE and ADE mice were subjected to treadmill exercise for 12 weeks, followed by evaluating the effect of treadmill exercise on learning and memory ability, Aß plaques, mitochondrial Aß peptide level, synaptic activity and mitochondrial function. Meanwhile, mitophagy-related proteins PINK1, Parkin, LC3II and P62 were measured in the hippocampal mitochondrial fractions. The results indicated that exercise not only restored learning and memory ability, but also reduced Aß plaque area, mitochondrial Aß peptide level, and increased levels of synaptic markers SYN and GAP43, as well as reversed mitochondrial dysfunction (defective mitochondrial ultrastructure, decreased PGC-1α, TFAM and ATP levels) in APP/PS1 transgenic mice. Moreover, exercise increased mitophagy activity as evidenced by a significant decrease in levels of P62 and PINK1 as well as an increase in levels of LC3II and Parkin in ADE mice. These findings suggest that treadmill exercise can enhance mitophagy activity in the hippocampus, which is efficient in ameliorating pathological phenotypes of APP/PS1 transgenic mice.
Amyloid beta-Peptides/metabolism , Amyloid beta-Protein Precursor , Mitochondria/metabolism , Mitophagy/physiology , Physical Conditioning, Animal/physiology , Presenilin-1 , Amyloid beta-Peptides/antagonists & inhibitors , Amyloid beta-Protein Precursor/genetics , Animals , Exercise Test/methods , Male , Maze Learning/physiology , Mice , Mice, Inbred C57BL , Mice, Transgenic , Mitochondria/pathology , Physical Conditioning, Animal/methods , Presenilin-1/genetics
Along with the technology evolution for dense integration of high-power, high-frequency devices in electronics, the accompanying interfacial heat transfer problem leads to urgent demands for advanced thermal interface materials (TIMs) with both high through-plane thermal conductivity and good compressibility. Most metals have satisfactory thermal conductivity but relatively high compressive modulus, and soft silicones are typically thermal insulators (0.3 W m-1 K-1). Currently, it is a great challenge to develop a soft material with the thermal conductivity up to metal level for TIM application. This study solves this problem by constructing a graphene-based microstructure composed of mainly vertical graphene and a thin cap of horizontal graphene layers on both the top and bottom sides through a mechanical machining process to manipulate the stacked architecture of conventional graphene paper. The resultant graphene monolith has an ultrahigh through-plane thermal conductivity of 143 W m-1 K-1, exceeding that of many metals, and a low compressive modulus of 0.87 MPa, comparable to that of silicones. In the actual TIM performance measurement, the system cooling efficiency with our graphene monolith as TIM is 3 times as high as that of the state-of-the-art commercial TIM, demonstrating the superior ability to solve the interfacial heat transfer issues in electronic systems.
Exercise is a non-pharmacological strategy that may help to protect against cognitive decline and reduce the risk of Alzheimer's disease. However, the optimal exercise modes for cognitive benefits are controversial. Mitochondrial function has been related to both exercise and cognition. The present study aimed to investigate the effects of two exercise modes on cognitive function and mitochondrial dynamics in APP/PS1 transgenic mice. The results showed that 12-week high-intensity interval training (HIIT) and moderate-intensity continuous training (MICT) could improve exploratory behavior, spatial learning and memory ability of APP/PS1 transgenic mice. Both HIIT and MICT interventions significantly alleviated the hippocampal ß-Amyloid (Aß) burden and mitochondrial fragmentation and improved mitochondrial morphology in hippocampus. Furthermore, both HIIT and MICT interventions down-regulated dynamin-related protein 1 (DRP1) and fission 1 (FIS1), whereas mitofusin 1 (MFN1), mitofusin 2 (MFN2) and optic atrophy 1 (OPA1) were up-regulated. Hippocampal levels of total reactive oxygen species (ROS), malondialdehyde (MDA) and hydrogen peroxide (H2O2) were decreased, whereas activities of superoxide dismutase (SOD) and catalase (CAT) were elevated by HIIT and MICT. The study suggests that both HIIT and MICT alleviate cognitive decline and down-regulat Aß level in the hippocampus in APP/PS1 transgenic mice, which may be mediated by improvements in mitochondrial morphology and dynamics.
Alzheimer Disease/therapy , Amyloid beta-Peptides/metabolism , Exercise Therapy , Memory Disorders/therapy , Mitochondrial Dynamics , Alzheimer Disease/metabolism , Amyloid beta-Protein Precursor/genetics , Amyloid beta-Protein Precursor/metabolism , Animals , Disease Models, Animal , Hippocampus/metabolism , Humans , Memory Disorders/metabolism , Mice, Inbred C57BL , Mice, Transgenic , Motor Activity/physiology , Oxidative Stress , Presenilin-1/genetics , Presenilin-1/metabolism , Random Allocation
High thermal conductivity polymer composites at low filler loading are of considerable interest because of their wide range of applications. The construction of three-dimensional (3D) interconnected networks can offer a high-efficiency increase for the thermal conductivity of polymer composites. In this work, a facile and scalable method to prepare graphene foam (GF) via sacrificial commercial polyurethane (PU) sponge templates was developed. Highly thermally conductive composites were then prepared by impregnating epoxy resin into the GF structure. An ultrahigh thermal conductivity of 8.04 W m-1 K-1 was obtained at a low graphene loading of 6.8 wt%, which corresponds to a thermal conductivity enhancement of about 4473% compared to neat epoxy. This strategy provides a facile, low-cost and scalable method to construct a 3D filler network for high-performance composites with potential to be used in advanced electronic packaging.
