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Thermal management is ubiquitous in the modern world and indispensable for a sustainable future. Radiative heat management provides unique advantages because the heat transfer can be controlled by the surface. However, different object emissivities require different tuning strategies, which poses challenges to develop dynamic and universal radiative heat management devices. Here, we demonstrate a triple-mode midinfrared modulator that can switch between passive heating and cooling suitable for all types of object surface emissivities. The device comprises a surface-textured infrared-semiabsorbing elastomer coated with a metallic back reflector, which is biaxially strained to sequentially achieve three fundamental modes: emission, reflection, and transmission. By analyzing and optimizing the coupling between optical and mechanical properties, we achieve a performance as follows: emittance contrast Δε = 0.58, transmittance contrast Δτ = 0.49, and reflectance contrast Δρ = 0.39. The device can provide a new design paradigm of radiation heat regulation for wearable, robotics, and camouflage technologies.

Efficient thermal transportation in a preferred direction is highly favorable for thermal management issues. The combination of 3D printing and two-dimensional (2D) materials such as graphene, BN, and so on enables infinite possibilities for hierarchically aligned structure programming. In this work, we report the formation of the asymmetrically aligned structure of graphene filled thermoplastic polyurethane (TPU) composites during 3D printing process. The as-printed vertically aligned structure demonstrates a through-plane thermal conductivity (TC) up to 12 W m-1 K-1 at 45 wt % graphene content, which is ∼8 times of that of a horizontally printed structure and surpasses many of the traditional particle reinforced polymer composites. The superior TC is mainly attributed to the anisotropic structure design that benefited from the preferable degree of orientation of graphene and the multiscale dense structure realized by finely controlling the printing parameters. Finite element method (FEM) confirms the essential impact of anisotropic TC design for highly thermal conductive composites. This study provides an effective way to develop 3D printed graphene-based polymer composites for scalable thermal-related applications such as battery thermal management, electric packaging, and so on.

Graphene oxide is currently used in peripheral nerve engineering but has certain limitations, such as cytotoxicity and lack of electrical conductivity, both of which are crucial in regulating nerve-associated cell behaviors. In this work, we engineered reduced graphene oxide-GelMA-PCL nanofiber nerve guidance conduits via electrospinning. rGO incorporated into the GelMA/PCL matrix significantly enhanced the electrical conductivity and biocompatibility of the hybrid materials. In addition, hybrid nanofibers with low concentrations of rGO (0.25 and 0.5 wt%) could significantly improve the proliferation of Schwann cells (RSC96). More importantly, rGO/GelMA/PCL hybrid nanofibers could activate the epithelial-mesenchymal transition (EMT)-related gene expression of Schwann cells (RSC96). From the in vivo study, it was observed that rGO/GelMA/PCL nerve guidance conduits could promote both sensory/motor nerve regeneration and functional recovery in rats. Our composite strategy of combining rGO within a biocompatible nanofiber scaffold is simple but effective in improving tissue engineering outcomes. The rGO/GelMA/PCL hybrid nanofibers have great potential in peripheral nerve tissue engineering. They will also provide an experimental basis for the development of further electrical stimulation in peripheral nerve regeneration.

With the growing challenges of modern electronics in heat dissipation, developing thermal management materials with high thermal conductivity and electrical insulation property remains an important issue for electronics. In this work, a novel three-dimensional network (3D) of boron nitride/reduced graphene oxide (BN/rGO) with covalent bond connections were fabricated by using the surface modification and ice-templated methods. The as-prepared boron nitride/reduced graphene oxide/nature rubber composites (BN/rGO/NR) possessed an enhanced through-plane thermal conductivity of 1.28 W m−1 K−1 and satisfactory electrical insulation at a low filler loading of 4.9 vol%. The results demonstrated that the covalent bond connections and three-dimensional networks of fillers greatly reduced the interfacial thermal resistance as well as phonon scatterings at the filler/filler and filler/matrix interface simultaneously. More importantly, this strategy provided a creative insight to the design of advanced thermal management materials and also presented a bright application prospect for next-generation electronic packing.

Adaptive radiative heat management can switch between heating and cooling based on the cover material's mid-IR property. However, such modulation is dependent on the underlying object's emissivity, which limits the applicability of the modulation device. For instance, to achieve the best cooling performance, the human body requires a transmissive cover, and metallic motor vehicles require an emissive one. In this talk, I will introduce a mechanical switchable radiative heat modulator that can change among three different modes - transmission, reflection, and emission - to adapt for the underlying object property. This modulation principle can improve the design flexibility of future adaptive radiative heat management.

Catalysis and crack resistance are essential for the combustion and structure performances of composite energetic materials. Currently, catalysis is dominated by toxic metals, and chemical coupling agents are always needful for fabricating the robust interface to resist cracks, without a feasible green alternative method. In this work, a recrystallization method was developed in pure water, by which graphene oxide (GO) was perfectly coated on NaNO3 particles without any coupling agent. The particle size of NaNO3/GO is much smaller than that of pure NaNO3, due to the inhibition of GO to the growth of NaNO3 crystals. The ultrathin GO coating on the NaNO3 presents effective catalytic activity on the thermal decomposition of NaNO3 and crack resistance capability in the NaNO3/GO/polyurethane composites. This green and effective approach may open up the opportunities to develop various high-performance composite energetic materials with great potential.

Thermal management is ubiquitous in the modern world and indispensable for a sustainable future. Radiative heat management provides unique advantages because the heat transfer can be controlled by the surface. However, different surface emissivities require different tuning strategies. Here, we demonstrate a triple-mode mid-infrared modulator that can switch between passive heating and cooling suitable for all types of object surface emissivities. The device is composed of a surface-textured infrared-semi-transparent elastomer coated with a metallic back reflector, which is biaxially strained to sequentially achieve three fundamental modes: emission, reflection, and transmission. By analyzing and optimizing the coupling between optical and mechanical properties, we achieve a performance of emittance contrast = 0.58, transmittance contrast = 0.49, and reflectance contrast = 0.39. The device can provide a new design paradigm of radiation heat regulation to develop the next generation wearable devices, robotics, and camouflage technology.

Nature always provides intelligent strategy for developing advanced materials with superior properties. In this study, by cloning the reinforcing mechanisms in nacre, a nacre-inspired Al2O3/graphene/polyurethane (PU) composite with hybrid hierarchical structure, was successfully fabricated. The structural interlocking interface, together with its excellent force bearing property, leads to exceptional mechanical performance. Compared with pure PU, the bio-inspired, Al2O3/graphene reinforced PU composite demonstrates a unique improvement in Young's modulus (211%), tensile strength (41%), and compressive modulus (145%). Moreover, the thermal conductivity of Al2O3/graphene/PU composite reaches to 0.502 W m−1 K−1, enhanced by 141% compared with pure matrix, showing very high enhancement efficiency, which is attributed to the multilevel aligned structure and multi-contact conductive pathway inside the composite. This design strategy offers a promising approach to handling high mechanical and thermal performance of solid propulsion fuel by synthesizing bio-inspired architecture.

Thermoplastic composites have aroused extensive academic and industrial concern because of their recyclability and versatility. In this work, polypropylene (PP) composites filled with multilayer graphene sheets (GSs) and graphite platelets (GPs) were successfully fabricated via a facile melt-mixing procedure. The hybrid fillers exhibit simultaneous enhancement on thermal and mechanical properties of composites. With the loading of 3 wt% GSs and 20 wt% GPs, the thermal conductivity (TC) of GSs/GPs/PP composites reaches 1.72 Wm−1 K−1, which is much higher than that of single filler composites with the same loading. Besides, this composite material displays enhanced mechanical properties. Usually, high filler content leads to high thermal conductivity, but decreases mechanical properties. However, this work shows a simultaneous enhancement effect which could be explained by the unique connected microstructure. It is found that the small GSs are filled into the interspaces of large GPs, which not only facilitates the heat transfer, but also enhances the resistance to fracture, thus leading to better thermal and mechanical performances. The excellent properties of the composites endow a promising potential in industrial application.

Heat management is more and more crucial challenge since the development of modern electronic devices towards miniaturization and high dense integrity. Highly thermal conductive composites based on graphene are ideal heat-dissipating materials for their excellent heat dissipation ability, outstanding mechanical properties as well as low coefficient of thermal expansion. Numerous efforts have been made towards the development of graphene-based polymeric composites with high performance. Furthermore, it has been demonstrated that microstructure engineering of graphene-based construction of three-dimensional networks and high orientation is extremely important to improve the properties of composites. In this review, the research progress on the latest strategies of microstructure engineering of graphene for highly thermal conductive composites is summarized. Both fabrication methods and theoretical simulations are discussed. Finally, development and perspectives of highly thermal conductive composites are presented.

Wet weather conditions have been associated with increased bacterial and viral counts in surface waters. Moreover, heavy rainfall and flooding were found to be the most common events preceding waterborne disease outbreaks associated with extreme weather conditions. This study aimed to examine the effect of rainfall on the quality of surface waters and to determine its suitability for primary contact recreation during wet weather conditions. A total of 228 catchment water samples were collected during wet and dry periods. Parameters that were found to increase with increasing rainfall were , enterococci, somatic coliphages, and turbidity, whereas total dissolved solids were found to decrease. Positive correlations ( < 0.05) were observed between cumulative rainfall and geometric mean concentrations of , enterococci, somatic coliphages, and turbidity ( = 0.69-0.95), whereas a negative correlation was observed between cumulative rainfall and total dissolved solids ( = -0.58). In addition, a rapid decline in water quality was observed during heavy rainfall that resulted in failure to meet recreational water quality guidelines. In view of public health and safety, primary recreational activities in the water catchment may not be advisable during or immediately after a rainfall event due to poor water quality.

This work describes the fabrication, characterization, and deformation behavior of graphene oxide (GO) filled dual cross-linked polyurethane (PU) nanocomposites serving as solid propellant binder. The composites were synthesized through attaching isophorone diisocyanate onto GO nanosheets and cross-linking the modified GO (MGO) with PU chains. This methodology leads to uniform dispersion of MGO and its strong interface adhesion with matrix. The coefficient of thermal expansion (CTE) of the composites is tuned to the value of 150 ppm/°C, and reduced by 38.8% compared to neat PU. Moreover, both coefficient of energy dissipation and residual strain are linearly reduced, and the deformation recovery capability is specifically increased. Loss tangent (tan δ) shows the low dynamic viscous behavior, suggesting strong dependence on MGO content. Besides, the composite with 1.0 wt% MGO exhibits a critical point, where the transition from solid-like to liquid-like behavior nearly disappears. This study provides an achievable and important way to prepare the high-performance polymeric composite with prominent deformation properties.

Polyurethane (PU) based composites were fabricated by cross-linking hydroxyl-terminated polybutadiene (HTPB) chains with modified graphene oxide (MGO). The MGO worked as both the reinforcing agent and the cross-linker and strong interface between MGO sheets and PU matrix was formed, which provide the MGO/PU composites with well improved properties. Compared to neat PU and traditional direct-mixing GO/PU composites, the elastic modulus and tensile strength of 1 wt% MGO/PU composites increase significantly by 195.3% and 63.8%, respectively. Other properties such as thermal stability, anti-creep property and dynamic shear moduli are also much improved. All the improvements come from the enhanced interface bonding between MGO and PU, as well as dense molecular chains network in the composites. It can be expected that cross-linking method would be an effective fabrication approach and interface controlling strategy for the development of high-performance composites.

In the present study, high thermally conductive and electrically insulated polymer composites containing modified dense graphene foam (MGF) and modified hexagonal boron nitride (M-h-BN) via polydopamine (PDA) coating and 3-aminopropyltriethoxysilane (APTS) grafting were manufactured and studied. Due to the double percolated networks built by MGF and M-h-BN, the polydimethylsiloxane (PDMS) matrix composite has high thermal conductivity of 23.45Wm−1K−1 and 2.11Wm−1K−1 in in-plane and out-of-plane directions, respectively. In addition, an insulated layer of M-h-BN/PDMS can be introduced onto both sides of composite sample with the help of infiltration technique, which results in a high breakdown strength of 4.5 kV/mm. Owing to the excellent comprehensive properties, the M-h-BN/MGF/PDMS composite has a promising application in heat management field of the microelectronic industry.

A series of novel flexible polymer composites consisted of boron nitride foam (BNF), boron nitride nanosheets (BNNS) and polydimethylsiloxane (PDMS) were designed and fabricated by vacuum-assisted infiltrating BNNS/PDMS mixtures into 3D BNF synthesized via chemical vapor deposition (CVD). Their microstructure, thermal, mechanical and dielectric properties were studied. Contributed to the interconnected networks of BNF and synergistic effect of BNNS with BNF, 10 wt% BNNS/BNF/PDMS composite shows a high thermal conductivity of 0.56 W m−1 K−1, high heat resistance index of 275.6 °C, 33% increment of Young’s modulus compared to PDMS, relative permittivity of 3, dissipation factor of 0.0051, EMI shielding effectiveness of 1.5 dB at X band and breakdown strength of 21.8 MV/m. Due to the outstanding comprehensive properties, BNNS/BNF/PDMS composites have a promising potential application in wide electronic packaging field.

To meet the increasing demands for effective heat management of electronic devices, a graphene-based polymeric composite is considered to be one of the candidate materials owing to the ultrahigh thermal conductivity (TC) of graphene. However, poor graphene dispersion, low quality of exfoliated graphene, and strong phonon scattering at the graphene/matrix interface restrict the heat dissipation ability of graphene-filled composites. Here, a facile and versatile approach to bond graphene foam (GF) with polydimethylsiloxane (PDMS) is proposed, and the corresponding composite with considerable improvement in TC and insulativity is fabricated. First, three-dimensional GF was coated with polydopamine (PDA) via π–π stack and functional groups from PDA reacted with 3-aminopropyltriethoxysilane (APTS). Then, the modified GF was compressed (c-GF) to enhance density and infiltrated with PDMS to get the c-GF/PDA/APTS/PDMS composite. As a result, these processes endow the composite with high TC of in-plane 28.77 W m–1...

Biomass-derived carbons have been extensively researched as electrode material for energy storage and conversion recently. However, most of the previous works convert crude biomass directly into carbon and the electrochemical capacitances for the resultant carbons are quite often underestimated as well as large variations in capacitances exist in literatures due to the complex nature of biomass, which practically hinder their applications. In this work, polysaccharide nanofibers were extracted from an inexpensive natural fungus using a hydrothermal method and were converted to porous carbon nanofibers (CNFs) by potassium hydroxide activation. The porous carbons were assembled into symmetric supercapacitors using both potassium hydroxide and an ionic liquid (IL) as electrolytes. Solid state nuclear magnetic resonance characterization showed that the micropores of the as-prepared carbons are accessible to the IL electrolyte when uncharged and thus high capacitance is expected. It is found in both electrolytes the electrochemical capacitances of CNFs are significantly higher than those of the porous carbon derived directly from the crude fungus. Furthermore, the CNFs delivered an extraordinary energy density of 92.3 Wh kg −1 in the IL electrolyte, making it a promising candidate for electrode materials for supercapacitors.

Thermal management is more and more crucial in advanced electronic devices with increasing power density. So, the demand for the materials with high thermal conductivity is rising. Hexagonal boron nitride (h-BN), called as “white graphene”, has high thermal conductivity of ~2000 W m −1 K −1 (by theoretical calculation) and is an electrical insulator, so h-BN filled polymer composite becomes a good candidate for potential employment in heat management of microelectronic devices. This paper gives a brief review on the development of h-BN based polymeric composites, including thermal transfer mechanism, fundamental design principle and application, as well as perspectives.

With the increasing packaging density and multi-functionality, thermal management and electromagnetic pollution in electronic devices are crucial. In this work, we propose a novel method to in-situ grow hollow Fe3O4 sphere (h-Fe3O4, inner and outer diameter of 870 nm and 975 nm, respectively) onto three-dimensional graphene foam (GF) surface and then filled it with polydimethylsiloxane (PDMS) to fabricate nanocomposites with high electromagnetic interference shielding effectiveness (70.37 dB from 8.2 to 12.4 GHz) and thermal conductivity (28.12 ± 1.212 W m−1 K−1) at room temperature. Moreover, conductive networks inside composites show super-flexible performance with high electrical conductivity (84.02 ± 8.385 S cm−1). The effect of in-situ growth hollow Fe3O4 spheres in the enhancement of EMI SE has been demonstrated via comparing with different contents, morphologies and preparation processing. Besides, the mechanism of thermal conductivity has been investigated by FEM simulation and theoretical modeling. Finally, the usage of GF/h-Fe3O4/PDMS composites as thermal interface materials (TIMs) for chip cooling is proved to be successful, and the corresponding temperature under usage power density is accurately predicted. These comprehensive properties of GF/h-Fe3O4/PDMS composite open a potential application for next-generation TIMs in chip packaging.

Fecal indicator bacteria, such as Escherichia coli (E.coli) and Enterococcus, have been widely used to indicate the presence of pathogens. However, the suitability of fecal indicator bacteria to represent health risks is still being challenged, particularly in tropical aquatic environments. The objective of this study is to understand the occurrence and prevalence of indicators and pathogens in areas with contrasting land use, as well as to identify the major correlations between indicators, pathogens and environmental parameters. The spatial and temporal variation of indicators and pathogens was studied to examine the distribution patterns for areas with different land use, and the impact of seasonal changes on microbial populations. A total of 234 water samples were sampled for two years from reservoirs and their tributaries, and tested for fecal indicator bacteria, coliphages, human specific markers, pathogenic bacteria and viruses. The prevalence of indicators and pathogens in reservoirs were generally low, while relatively high concentrations were observed in tributaries to varying degrees. Of the enteric viruses, norovirus GII was among the most prevalent and had the highest concentration. Although strong correlations were found between indicators, only relatively weak correlations were found between indicators and pathogens. The results in this study showed that none of the bacteria/phage indicators were universal predictors for pathogens. Inclusion of the alternative indicators, Methanobrevibacter smithii, Bacteroides and human polyomaviruses (HPyVs) to monitoring programs could help to determine whether the fecal source was human. The microbial distribution patterns allow the classification of sampling sites to different clusters and thus, help to identify sites which have poor water quality. This approach will be useful for water quality management to pinpoint factors that influence water quality and help to prioritize sites for restoration of water quality., Graphical abstract Image 1, Highlights • Norovirus GII was the most prevalent enteric viruses. • Land use classification was correlated to the distribution of pathogens/indicators. • Alternative indicators helped to improve the prediction of enteric viruses. • Cluster analysis identified sites with poor water quality.