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The trend towards miniaturization of electronics and increasing transistor density in semiconductors requires more efficient cooling solutions. Vapor chambers are well established passive cooling devices that are used in a wide variety of electronics. Commercial vapor chambers are often made of high-density metals such as copper which can be a downside in lightweight applications such as laptops, smartphones, and tablets. In this study, different novel lightweight graphene-enhanced vapor chambers were built using graphene-assembled film with high thermal conductivity as envelope material. The thermal performance of the designed graphene-enhanced vapor chambers was characterized in a customized test rig and compared to a copper vapor chamber. One of the graphene-enhanced vapor chambers was shown to have 21.6% lower thermal resistance than that of a copper vapor chamber with the same design. A mass-based thermal resistance parameter was introduced as a figure of merit to account for the superior low density of the graphene-enhanced vapor chambers. The mass-based thermal resistance of the graphene-enhanced vapor chamber was seen to be 46.5% lower than that of the copper vapor chamber. The result of this study shows that replacing copper with graphene-assembled film as envelope in vapor chambers can both reduce thermal resistance and decrease the mass of the device. Hence, it is believed that graphene-enhanced vapor chambers have great potential for replacing conventional metal-based vapor chambers in lightweight and high-performance electronics and power module cooling applications in the future., (Creative Commons Attribution license.)

Graphene-based film attracts tremendous interest in many potential applications due to its excellent thermal, electrical, and mechanical properties. This review focused on a critical analysis of fabrication, processing methodology, the interfacial modification approach, and the applications of this novel and new class material. Strong attention was paid to the preparation strategy and interfacial modification approach to improve its mechanical and thermal properties. The overview also discussed the challenges and opportunities regarding its industrial production and the current status of the commercialization. This review showed that blade coating technology is an effective method for industrial mass-produced graphene film with controllable thickness. The synergistic effect of different interface interactions can effectively improve the mechanical properties of graphene-based film. At present, the application of graphene-based film on mobile phones has become an interesting example of the use of graphene. Looking for more application cases is of great significance for the development of graphene-based technology.

Carbon nanotube (CNT) array thermal interface materials (TIMs) are promising candidates for high-performance applications in terms of thermal performance. However, in order to be useful in commercial applications, the reliability of the interfaces is an equally important parameter, which so far has not been thoroughly investigated. In this study, the reliability of CNT array TIMs is investigated through accelerated aging. The roles of CNT array height and substrate configuration are studied for their relative impact on thermal resistance degradation. After aging, the CNT catalyst is analyzed using X-ray photoelectron spectroscopy to evaluate chemical changes. The CNT-catalyst bond appears to degrade during aging but not to the extent that the TIM performance is compromised. On the other hand, coefficient of thermal expansion mismatch between surfaces creates strain that needs to be absorbed, which requires CNT arrays with sufficient height. Transfer and bonding of both CNT roots and tips also create more reliable interfaces. Crucially, we find that the CNT array height of most previously reported CNT array TIMs is not enough to prevent significant reliability problems.

During the last decades, there has been growing interest in using therapeutic messager RNA (mRNA) together with drug delivery systems. Naked, unformulated mRNA is, however, unable to cross the cell membrane and is susceptible to degradation. Here we use graphene quantum dots (GQDs) functionalized with polyethyleneimine (PEI) as a novel mRNA delivery system. Our results show that these modified GQDs can be used to deliver intact and functional mRNA to Huh-7 hepatocarcinoma cells at low doses and, that the GQDs are not toxic, although cellular toxicity is a problem for these first-generation modified particles. Functionalized GQDs represent a potentially interesting delivery system that is easy to manufacture, stable and effective., (© 2021 The Authors. Published by Wiley-VCH GmbH.)

This review focuses on the recent advances in the synthesis of graphene quantum dots (GQDs) and their applications in drug delivery. To give a brief understanding about the preparation of GQDs, recent advances in methods of GQDs synthesis are first presented. Afterwards, various drug delivery-release modes of GQDs-based drug delivery systems such as EPR-pH delivery-release mode, ligand-pH delivery-release mode, EPR-Photothermal delivery-Release mode, and Core/Shell-photothermal/magnetic thermal delivery-release mode are reviewed. Finally, the current challenges and the prospective application of GQDs in drug delivery are discussed.

Poor bonding strength between nanomaterials and cement composites inevitably lead to the failure of reinforcement. Herein, a novel functionalization method for the fabrication of functionalized graphene oxide (FGO), which is capable of forming highly reliable covalent bonds with cement hydration products, and therefore, suitable for use as an efficient reinforcing agent for cement composites, is discussed. The bonding strength between cement and aggregates was improved more than 21 times with the reinforcement of FGO. The fabricated FGO also demonstrated many important features, including high reliability in cement pastes, good dispersibility, and efficient structural refinement of cement hydration products. With the incorporation of FGO, cement mortar samples demonstrated up to 40 % increased early and ultimate strength. Such results make the fast demolding and manufacture of light constructions become highly possible, and show strong advantages on improving productivity, saving cost, and reducing CO 2 emissions in practical applications., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Functional fillers, such as Ag, are commonly employed for effectively improving the thermal or electrical conductivity in polymer composites. However, a disadvantage of such a strategy is that the cost and performance cannot be balanced simultaneously. Therefore, the drive to find a material with both a cost efficient fabrication process and excellent performance attracts intense research interest. In this work, inspired by the core-shell structure, we developed a facile manufacturing method to prepare graphene-encapsulated Cu nanoparticles (GCPs) through utilizing an improved chemical vapor deposition (CVD) system with a cold wall reactor. The obtained GCPs could retain their spherical shape and exhibited an outstanding thermal stability up to 179 °C. Owing to the superior thermal conductivity of graphene and excellent oxidation resistance of GCPs, the produced GCPs are practically used in a thermally conductive adhesive (TCA), which commonly consists of Ag as the functional filler. Measurement shows a substantial 74.6 % improvement by partial replacement of Ag with GCPs., Competing Interests: A patent application has been filed.

Due to substantial phonon scattering induced by various structural defects, the in-plane thermal conductivity (K) of graphene films (GFs) is still inferior to the commercial pyrolytic graphite sheet (PGS). Here, the problem is solved by engineering the structures of GFs in the aspects of grain size, film alignment, and thickness, and interlayer binding energy. The maximum K of GFs reaches to 3200 W m -1 K -1 and outperforms PGS by 60%. The superior K of GFs is strongly related to its large and intact grains, which are over four times larger than the best PGS. The large smooth features about 11 µm and good layer alignment of GFs also benefit on reducing phonon scattering induced by wrinkles/defects. In addition, the presence of substantial turbostratic-stacking graphene is found up to 37% in thin GFs. The lacking of order in turbostratic-stacking graphene leads to very weak interlayer binding energy, which can significantly decrease the phonon interfacial scattering. The GFs also demonstrate excellent flexibility and high tensile strength, which is about three times higher than PGS. Therefore, GFs with optimized structures and properties show great potentials in thermal management of form-factor-driven electronics and other high-power-driven systems., (© 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The high thermal conductivity of graphene and few-layer graphene undergoes severe degradations through contact with the substrate. Here we show experimentally that the thermal management of a micro heater is substantially improved by introducing alternative heat-escaping channels into a graphene-based film bonded to functionalized graphene oxide through amino-silane molecules. Using a resistance temperature probe for in situ monitoring we demonstrate that the hotspot temperature was lowered by ∼28 °C for a chip operating at 1,300 W cm(-2). Thermal resistance probed by pulsed photothermal reflectance measurements demonstrated an improved thermal coupling due to functionalization on the graphene-graphene oxide interface. Three functionalization molecules manifest distinct interfacial thermal transport behaviour, corroborating our atomistic calculations in unveiling the role of molecular chain length and functional groups. Molecular dynamics simulations reveal that the functionalization constrains the cross-plane phonon scattering, which in turn enhances in-plane heat conduction of the bonded graphene film by recovering the long flexural phonon lifetime.

In this paper, an embedded fin-like metal-coated carbon nanotube (Fin-M/CNT) structure is demonstrated for flexible and transparent conductor wire applications. Embedded in a polydimethylsiloxane polymeric substrate, Fin-M/CNT wires with a minimum width of 5 μm and a minimum pitch of 10 μm have been achieved. Direct current resistances of single Fin-M/CNT wires, where the supporting CNT structures have been covered by Ti/Al/Au metal coatings of different thicknesses, have been measured. The high aspect ratio of the fin-like structures not only improves the adhesion between the wires and the polymeric substrate, but also yields a low resistance at a small surface footprint. In addition, transparent Fin-M/CNT grid lines with hexagonal patterns, with a sheet resistance of as low as 45 Ω sq(-1) , have been achieved at an optical transmittance of 88%. The robustness of the Fin-M/CNT structures has been demonstrated in bending tests up to 500 cycles and no significant changes in wire resistances are observed., (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)