Low thermal contact resistance boron nitride nanosheets composites enabled by interfacial arc-like phonon bridge.

Two-dimensional materials with ultrahigh in-plane thermal conductivity are ideal for heat spreader applications but cause significant thermal contact resistance in complex interfaces, limiting their use as thermal interface materials. In this study, we present an interfacial phonon bridge strategy to reduce the thermal contact resistance of boron nitride nanosheets-based composites. By using a low-molecular-weight polymer, we are able to manipulate the alignment of boron nitride nanosheets through sequential stacking and cutting, ultimately achieving flexible thin films with a layer of arc-like structure superimposed on perpendicularly aligned ones. Our results suggest that arc-like structure can act as a phonon bridge to lower the contact resistance by 70% through reducing phonon back-reflection and enhancing phonon coupling efficiency at the boundary. The resulting composites exhibit ultralow thermal contact resistance of 0.059 in2 KW-1, demonstrating effective cooling of fast-charging batteries at a thickness 2-5 times thinner than commercial products.

On-column capping of poly dT media-tethered mRNA accomplishes high capping efficiency, enhanced mRNA recovery, and improved stability against RNase.

The messenger RNA (mRNA) 5'-cap structure is indispensable for mRNA translation initiation and stability. Despite its importance, large-scale production of capped mRNA through in vitro transcription (IVT) synthesis using vaccinia capping enzyme (VCE) is challenging, due to the requirement of tedious and multiple pre-and-post separation steps causing mRNA loss and degradation. Here in the present study, we found that the VCE together with 2'-O-methyltransferase can efficiently catalyze the capping of poly dT media-tethered mRNA to produce mRNA with cap-1 structure under an optimized condition. We have therefore designed an integrated purification and solid-based capping protocol, which involved capturing the mRNA from the IVT system by using poly dT media through its affinity binding for 3'-end poly-A in mRNA, in situ capping of mRNA 5'-end by supplying the enzymes, and subsequent eluting of the capped mRNA from the poly dT media. Using mRNA encoding the enhanced green fluorescent protein as a model system, we have demonstrated that the new strategy greatly simplified the mRNA manufacturing process and improved its overall recovery without sacrificing the capping efficiency, as compared with the conventional process, which involved at least mRNA preseparation from IVT, solution-based capping, and post-separation and recovering steps. Specifically, the new process accomplished a 1.76-fold (84.21% over 47.79%) increase in mRNA overall recovery, a twofold decrease in operation time (70 vs. 140 min), and similar high capping efficiency (both close to 100%). Furthermore, the solid-based capping process greatly improved mRNA stability, such that the integrity of the mRNA could be well kept during the capping process even in the presence of exogenously added RNase; in contrast, mRNA in the solution-based capping process degraded almost completely. Meanwhile, we showed that such a strategy can be operated both in a batch mode and in an on-column continuous mode. The results presented in this work demonstrated that the new on-column capping process developed here can accomplish high capping efficiency, enhanced mRNA recovery, and improved stability against RNase; therefore, can act as a simple, efficient, and cost-effective platform technology suitable for large-scale production of capped mRNA.

Coaxial Wet Spinning of Boron Nitride Nanosheet-Based Composite Fibers with Enhanced Thermal Conductivity and Mechanical Strength.

Hexagonal boron nitride nanosheets (BNNSs) exhibit remarkable thermal and dielectric properties. However, their self-assembly and alignment in macroscopic forms remain challenging due to the chemical inertness of boron nitride, thereby limiting their performance in applications such as thermal management. In this study, we present a coaxial wet spinning approach for the fabrication of BNNSs/polymer composite fibers with high nanosheet orientation. The composite fibers were prepared using a superacid-based solvent system and showed a layered structure comprising an aramid core and an aramid/BNNSs sheath. Notably, the coaxial fibers exhibited significantly higher BNNSs alignment compared to uniaxial aramid/BNNSs fibers, primarily due to the additional compressive forces exerted at the core-sheath interface during the hot drawing process. With a BNNSs loading of 60 wt%, the resulting coaxial fibers showed exceptional properties, including an ultrahigh Herman orientation parameter of 0.81, thermal conductivity of 17.2 W m-1 K-1, and tensile strength of 192.5 MPa. These results surpassed those of uniaxial fibers and previously reported BNNSs composite fibers, making them highly suitable for applications such as wearable thermal management textiles. Our findings present a promising strategy for fabricating high-performance composite fibers based on BNNSs.

A Malleable Composite Dough with Well-Dispersed and High-Content Boron Nitride Nanosheets.

Aggregation of two-dimensional (2D) nanosheet fillers in a polymer matrix is a prevalent problem when the filler loading is high, leading to degradation of physical and mechanical properties of the composite. To avoid aggregation, a low-weight fraction of the 2D material (<5 wt %) is usually used to fabricate the composite, limiting performance improvement. Here, we develop a mechanical interlocking strategy where well-dispersed high filling content (up to 20 wt %) of boron nitride nanosheets (BNNSs) can be incorporated into a polytetrafluoroethylene (PTFE) matrix, resulting in a malleable, easy-to-process and reusable BNNS/PTFE composite dough. Importantly, the well-dispersed BNNS fillers can be rearranged into a highly oriented direction due to the malleable nature of the dough. The resultant composite film has a high thermal conductivity (4408% increase), low dielectric constant/loss, and excellent mechanical properties (334%, 69%, 266%, and 302% increases for tensile modulus, strength, toughness, and elongation, respectively), making it suitable for thermal management applications in the high-frequency areas. The technique is useful for the large-scale production of other 2D material/polymer composites with a high filler content for different applications.

Rapid electrophoretic deposition of biocompatible graphene coatings for high-performance recording neural electrodes.

The electrical and biological interfacial properties of invasive electrodes have a significant impact on the performance and longevity of neural recordings in the brain. In this study, we demonstrated rapid electrophoretic deposition and electrochemical reduction of graphene oxide (GO) on metal-based neural electrodes. Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and other characterizations confirmed the existence of a uniform and effectively reduced graphene oxide coating. Electrochemically reduced graphene oxide (ErGO) coated Pt/Ir neural electrodes exhibited 15.2-fold increase in charge storage capacity (CSC) and 90% decrease in impedance with only 3.8% increase in electrode diameter. Patch clamp electrophysiology and calcium imaging of primary rat hippocampus neurons cultured on ErGO demonstrated that there was no adverse impact on the functional development of neurons. Immunostaining showed a balanced growth of excitatory and inhibitory neurons, and astrocytes. Acute recordings from the auditory cortex and chronic recordings (19 days) from the somatosensory cortex found ErGO coating improved the performance of neural electrodes in signal-to-noise ratio (SNR) and amplitude of signals. The proposed approach not only provides an in-depth evaluation of the effect of ErGO coating on neural electrodes but also widens the coating methods of commercial neural electrodes.

Sweat-Resistant Silk Fibroin-Based Double Network Hydrogel Adhesives.

The adhesion between flexible epidermal sensors and human skin is essential for maintaining the stable functionality of the sensors. However, it is still challenging for epidermal electronic devices to achieve durable adhesion to the surface of the skin, especially under sweaty or humid conditions. Here, we report a silk fibroin-polyacrylamide (SF-PAAm) double network (DN) hydrogel adhesive with excellent biocompatibility, strong and durable adhesion on wet surfaces, and tunable adhesive properties. The hydrophilic PAAm network greatly improves the water retention capability of the DN hydrogel and reduces the ß-sheet crystalline content of SF, leading to excellent adhesive properties of the hydrogel across a wide range of humidity. The SF-PAAm DN hydrogel adhesive can be readily integrated with different epidermal sensor arrays and performs very well in real-time on-body sweat sensing. The SF-PAAm DN hydrogels have great potential for application in various epidermal healthcare sensors as well as medical adhesives for other medical applications.

Viscous Solvent-Assisted Planetary Ball Milling for the Scalable Production of Large Ultrathin Two-Dimensional Materials.

Ball milling is a widely used method to produce graphene and other two-dimensional (2D) materials for both industry and research. Conventional ball milling generates strong impact forces, producing small and thick nanosheets that limit their applications. In this study, a viscous solvent-assisted planetary ball milling method has been developed to produce large thin 2D nanosheets. The viscous solvent simultaneously increases the exfoliation energy (Ee) and lowers the impact energy (Ei). Simulations show a giant ratio of η = Ee/Ei, for the viscous solvent, 2 orders of magnitude larger than that of water. The method provides both a high exfoliation yield of 74%, a high aspect ratio of the generated nanosheets of 571, and a high quality for a representative 2D material of boron nitride nanosheets (BNNSs). The large thin BNNSs can be assembled into high-performance functional films, such as separation membranes and thermally conductive flexible films with some performance parameters better than those 2D nanosheets produced by chemical exfoliation methods.

Stabilized Solid Electrolyte Interphase Induced by Ultrathin Boron Nitride Membranes for Safe Lithium Metal Batteries.

Lithium-ion batteries (LIBs) are still facing safety problems, mainly due to dendrite growth on the anode that leads to combustion and explosion. Forming a stable solid electrolyte interface (SEI) layer is an effective way to suppress this. To induce the formation of stable SEI using simple methods at a low cost, we report an ultrathin and large-scale hexagonal boron nitride (h-BN)/polyimide (PI) layer that was coated on a commercial polypropylene (PP) separator. The formation of a stabilized SEI component induced by the h-BN coating layer is proposed, as suggested by theoretical calculations and confirmed by electrochemical analysis and spectroscopy. It effectively suppresses Li dendrite growth and reduces the consumption of active lithium. The separator also has good electrolyte wettability, excellent mechanical strength and thermal conductivity, and high thermal stability. When using the h-BN modified separator in a full cell, the capacity is extremely stable after long cycling and high temperature.

Sb nanosheet modified separator for Li-S batteries with excellent electrochemical performance.

An air-stable antimony (Sb) nanosheet modified separator (SbNs/separator) has been prepared by coating exfoliated Sb nanosheets (SbNs) successfully onto a pristine separator through a vacuum infiltration method. The as-prepared Li-S batteries using SbNs/separators exhibit much improved electrochemical performance compared to the ones using commercial separators. The coulombic efficiency (CE) of the Li-S battery using the SbNs/separator after the initial cycle is close to 100% at a current density of 0.1 A g-1, and 660 mA h g-1 capacity retained after 100 cycles. The rate capability of Li-S battery using SbNs/separator delivers a reversible capacity of 425 mA h g-1 when the current density increases to 1 A g-1. The improved electrochemical performance is mainly attributed to the following reasons. Firstly, the combination of physical adsorption and chemical bonding between SbNs and lithium polysulfides (LiPSs), which efficiently inhibits the shuttle phenomena of LiPSs. Secondly, the good electronic conductivity of SbNs improves the utilization of the adsorbed LiPSs, which benefits the capacity release of active materials. Lastly, the fast conversion kinetics of intermediate LiPSs caused by the catalytic effect from SbNs further suppresses the shuttle effect of LiPSs. The SbNs/separators exhibit a great potential for the future high-performance Li-S batteries.

Integrated Paper-Based Flexible Li-Ion Batteries Made by a Rod Coating Method.

Design and fabrication of flexible Li-ion batteries (FLIBs) with excellent electrochemical and structural stability via scalable fabrication techniques are important for their practical applications. A wide range of FLIBs with excellent flexibility have been reported. However, sophisticated designs and complex fabrication techniques are often used in fabricating FLIBS, making them difficult to be realized in industrial production. Here, we fabricate FLIBs with an integrated structure by assembling the LiFePO4 cathode, Li4Ti5O12 anode, graphene current collectors, and poly(vinylidene fluoride) (PVDF) electrolyte all together on commercial printing paper via conventional and scalable Meyer rod coating. In the design, the commercial paper serves as a flexible substrate to enable good flexibility of the device, and the paper is coated twice with PVDF to avoid the short-circuit problem and create a strong binding to integrate the device. The resultant integrated FLIBs exhibit excellent internal structural stability and good electrochemical performance under cycling bending for 100 times.

Electrodeposited Vanadium Dioxide Films with Unique Optical Property.

This study represents a facile but effective electrodeposition method to fabricate vanadium dioxide (VO2) thin films on fluorine doped tin oxide (FTO) glass at room temperature. The film microstructure (thickness, surface structure, particle size and composition) and relevant optical properties were investigated by several advanced techniques. The pertinent variables that can affect the thin film formation and structure, such as deposition potential, time and post-treatment annealing temperature were also studied. It was found that the film thickness could be tuned from 35 to 130 nm by adjusting the potential from -1.22 to -1.35 V, and consequently leading to optical transmittance decreasing from ∼60% to ∼38% in the wavelength of 500-1000 nm, further confirmed by computational simulations using three-dimension (3D) finite-difference time-domain method. The hysteresis loop of the generated VO2 film on FTO glass shows that the phase transition temperature from monoclinic to rutile is around 73 °C, a little higher than pure monoclinic VO2 (∼68 °C) in this study. This proposed electrodeposition method is possible to extend into obtaining metal oxide films with tuneable surface properties for thermochromic smart devices.

Simple, low-cost fabrication of semi-circular channel using the surface tension of solder paste and its application to microfluidic valves.

This work presents a simple, low-cost method to fabricate semi-circular channels using solder paste, which can amalgamate the cooper surface to form a half-cylinder mold using the surface tension of Sn-Pd alloy (the main component in solder paste). This technique enables semi-circular channels to be manufactured with different dimensions. These semi-circular channels will then be integrated with a polymethylmethacrylate frame and machine screws to create miniaturized, portable microfluidic valves for sequential liquid delivery and particle synthesis. This approach avoids complicated fabrication processes and expensive facilities and thus has the potential to be a useful tool for lab-on-a-chip applications.

Dual-Phase Transformation: Spontaneous Self-Template Surface-Patterning Strategy for Ultra-transparent VO2 Solar Modulating Coatings.

Dual-phase transformation has been developed as a template-free surface patterning technique in this study. Ordered VO2 honeycomb structures with a complex hierarchy have been fabricated via this method, and the microstructures of the obtained VO2(M) coatings are tunable by tailoring the pertinent variables. The VO2(M) honeycomb-structured coatings have excellent visible light transmittance at 700 nm (Tvis) up to 95.4% with decent solar modulating ability (ΔTsol) of 5.5%, creating the potential as ultratransparent smart solar modulating coatings. Its excellent performance has been confirmed by a proof-of-principle demonstration. The dual-phase transformation technique has dramatically simplified the conventional colloidal lithography technique as a scalable surface patterning technique for achieving high-performance metal oxide coatings with diverse applications, such as catalysis, sensing, optics, electronics, and superwettable materials.

Superwettability Strategy: 1D Assembly of Binary Nanoparticles as Gas Sensors.

Binary 1D nanowires consisting of both SnO2 nanoparticles and Au nanorods are fabricated through a "substrate-particle solution template" assembling method, which shows highly enhanced gas sensitivity toward acetone under ambient conditions.

Carbon-Coated Gold Nanorods: A Facile Route to Biocompatible Materials for Photothermal Applications.

Gold nanorods and their core-shell nanocomposites have been widely studied because of their well-defined anisotropy and unique optical properties and applications. This study demonstrates a facile hydrothermal synthesis strategy for generating carbon coating on gold nanorods (AuNRs@C) under mild conditions (<200 °C), where the carbon shell is composed of polymerized sugar molecules (glucose). The structure and composition of the produced core-shell nanocomposites were characterized using advanced microscopic and spectroscopic techniques. The functional properties, particularly the photothermal and biocompatibility properties of the produced AuNRs@C, were quantified to assess their potential in photothermal hyperthermia. These AuNRs@C were tested in vitro (under representative treatment conditions) using near-infrared (NIR) light irradiation. It was found that the AuNRs produced here exhibit exemplary heat generation capability. Temperature changes of 10.5, 9, and 8 °C for AuNRs@C were observed with carbon shell thicknesses of 10, 17, and 25 nm, respectively, at a concentration of 50 µM, after 600 s of irradiation with a laser power of 0.17 W/cm(2). In addition, the synthesized AuNRs@C also exhibit good biocompatibility toward two soft tissue sarcoma cell lines (HT1080, a fibrosarcoma; and GCT, a fibrous histiocytoma). The cell viability study shows that AuNRs@C (at a concentration of <0.1 mg/mL) core-shell particles induce significantly lower cytotoxicity on both HT1080 and GCT cell lines, as compared with cetyltrimethylammonium bromide (CTAB)-capped AuNRs. Furthermore, similar to PEG-modified AuNRs, they are also safe to both HT1080 and GCT cell lines. This biocompatibility results from a surface full of -OH or -COH groups, which are suitable for linking and are nontoxic Therefore, the AuNRs@C represent a viable alternative to PEG-coated AuNRs for facile synthesis and improved photothermal conversion. Overall, these findings open up a new class of carbon-coated nanostructures that are biocompatible and could potentially be employed in a wide range of biomedical applications.