Highly Conductive Ink Based on Self-Aligned Single-Walled Carbon Nanotubes through Inter-Fiber Sliding in Cellulose Fibril Networks.

Carbon nanotubes (CNTs), owing to their superior electrical and mechanical properties, are a promising alternative to nonmetallic electrically conducting materials. In practice, cellulose as a low-cost sustainable matrix has been used to prepare the aqueous dispersion of cellulose-CNT (C-CNT) nanocomposites. However, the compatibility with conventional solution-processing and structural rearrangement for improving conductivity has yet to be determined. Herein, a straightforward route to prepare a conductive composite material from single-walled CNTs (SWCNTs) and natural pulp is reported. High-power shaking realizes the self-alignment of individual SWCNTs in a cellulose matrix, resulting from the structural change in molecular orientations owing to countless collisions of zirconia beads in the aqueous mixture. The structural analysis of the dried C-CNT films confirms that the entanglement and dispersion of C-CNT nanowires determine the mechanical and electrical properties. Moreover, the rheological behavior of C-CNT inks explains their coating and printing characteristics. By controlling shaking time, the electrical conductivity of the C-CNT films with only 9 wt.% of SWCNTs from 0.9 to 102.4 S cm-1 are adjusted. the optimized C-CNT ink is highly compatible with the conventional coating and printing processes on diverse substrates, thus finding potential applications in eco-friendly, highly flexible, and stretchable electrodes is also demonstrated.

Electrospun Polyvinylidene Fluoride Membranes: Waterproofing and Acoustic Performance for Air and Acoustic Vents in Electronics.

Advancements in electronic devices demand materials capable of exceptional performance in various challenging environments. This study presents polyvinylidene fluoride (PVDF) nonwoven membranes with controlled porosity, created using an air-guided electrospinning method, followed by a calendaring process. These membranes exhibit a combination of water-repellent properties and sound transmission capabilities, making them ideal candidates for use in air and acoustic vents in electronic systems. A key feature of our membrane is the three-dimensional nanostructured pores, ranging from 0.20 to 0.76 µm, with a mean pore size of 0.51 µm, achieved through the formation of randomly arranged long nanofibers. By employing both experimental and theoretical methods, we achieved impressive performance metrics: air permeability of 0.86 cm3/cm2/s, water contact angles up to 139.3°, and breakthrough pressure as low as 0.27 MPa. Our PVDF nonwoven membranes maintain an optimal balance of stiffness, density, and air permeability, leading to exceptionally low sound transmission loss values ranging between -10 and -40 dBV/Pa, all while preserving their structural integrity. These findings contribute to the development of next-generation waterproof and acoustically permeable membranes, offering enhanced performance capabilities in demanding operational scenarios. This work advances the field of nanomaterials, environmental engineering, and acoustic technologies, with the potential to influence the design of future electronic devices.

Acer tegmentosum extract-mediated silver nanoparticles loaded chitosan/alginic acid scaffolds enhance healing of E. coli-infected wounds.

This work developed Acer tegmentosum extract-mediated silver nanoparticles (AgNPs) loaded chitosan (CS)/alginic acid (AL) scaffolds (CS/AL-AgNPs) to enhance the healing of E. coli-infected wounds. The SEM-EDS and XRD results revealed the successful formation of the CS/AL-AgNPs. FTIR analysis evidenced that the anionic group of AL (-COO-) and cationic amine groups of CS (-NH3+) were ionically crosslinked to form scaffold (CS/AL). The CS/AL-AgNPs exhibited significant antimicrobial activity against both Gram-positive (G+) and Gram-negative (G-) bacterial pathogens, while being non-toxic to red blood cells (RBCs), the hen's egg chorioallantoic membrane (HET-CAM), and a non-cancerous cell line (NIH3T3). Treatment with CS/AL-AgNPs significantly accelerated the healing of E. coli-infected wounds by regulating the collagen deposition and blood parameters as evidenced by in vivo experiments. Overall, these findings suggest that CS/AL-AgNPs are promising for the treatment of infected wounds.

Decoupling and Cloaking of Rectangular and Circular Patch Antennas and Interleaved Antenna Arrays with Planar Coated Metasurfaces at C-Band Frequencies-Design and Simulation Study.

An electromagnetic cloaking approach is employed with the intention to curb the destructive effects of mutual interference for rectangular and circularly shaped patch antennas situated in a tight spacing. Primarily, we show that by coating the top surface of each patch with an appropriately designed metasurface, the mutual coupling is considerably reduced between the antennas. Furthermore, the cloak construct is extended to a tightly spaced, interleaved linear patch antenna array configuration and it is shown that the coated metasurfaces successfully enhance the performance of each array in terms of their matching characteristics, total efficiencies and far-field realized gain patterns for a broad range of beam-scan angles. For rectangular patches, the cloaked Array I and II achieve corresponding peak total efficiencies of 93% and 90%, in contrast to the total efficiencies of 57% and 21% for uncloaked Array I and II, respectively, at their operating frequencies. Moreover, cloaked rectangular Array I and II exhibit main lobe gains of 13.2 dB and 13.8 dB, whereas uncloaked Array I and II only accomplish main lobe gains of 10 dB and 5.5 dB, respectively. Likewise, for the cloaked circular patches, corresponding total efficiencies of 91% and 89% are recorded for Array I and II, at their operating frequencies (uncloaked Array I and II show peak efficiencies of 71% and 55%, respectively). The main lobe gain for each cloaked circular patch array is approximately 14.2 dB, whereas the uncloaked Array I and II only achieve maximum gains of 10.5 dB and 7.5 dB, respectively.

Dispersion Homogeneity of Silicon Anode Slurries with Various Binders for Li-Ion Battery Anode Coating.

We aimed to determine the relationship between surface chemistry and the rheological properties of silicon anode slurries in lithium-ion batteries. To accomplish this, we investigated the use of various binders such as PAA, CMC/SBR, and chitosan as a means to control particle aggregation and improve the flowability and homogeneity of the slurry. Additionally, we utilized zeta potential analysis to examine the electrostatic stability of the silicon particles in the presence of different binders, and the results indicated that the conformations of the binders on the silicon particles can be influenced by both neutralization and the pH conditions. Furthermore, we found that the zeta potential values served as a useful metric for evaluating binder adsorption and particle dispersion in the solution. We also conducted three-interval thixotropic tests (3ITTs) to examine the structural deformation and recovery characteristics of the slurry, and the results demonstrated that these properties vary depending on the strain intervals, pH conditions, and chosen binder. Overall, this study emphasized the importance of taking into account surface chemistry, neutralization, and pH conditions when assessing the rheological properties of the slurry and coating quality for lithium-ion batteries.

Probing metal-carboxylate interactions in cellulose nanofibrils-based hydrogels using nonlinear oscillatory rheology.

Cellulose nanofibrils (CNFs) have gained much attention as part of biocompatible soft hydrogels used in various biomedical applications such as biodegradable scaffolds, biomedicine, tissues, and regenerative medicine. The CNF hydrogels were mediated with metal cations for improved mechanical strength and structural reversibility. Intermolecular interactions in these CNF hydrogels are controlled by metal cation-carboxylate coordination bonding, leading to the creation of interconnected three-dimensional nanofibril structures that produce high structural reversibility. The nonlinear inter- and intra-cycle were investigated viscoelastic responses of these CNF hydrogels by quantitative nonlinear viscoelastic parameters and transient responses. The dynamic and transitional analyses conducted indicate that the structural deformation and recovery characteristics of the CNF hydrogels are affected by the valency number of the metal cations. This property can be carefully chosen to tune the intermolecular interactions between the cellulose nanofibrils to create an efficient interwoven network structure with high structural reversibility that can go through repeated cycles of reformation and yielding.

Unraveling the liquid gliding on vibrating solid liquid interfaces with dynamic nanoslip enactment.

Slip length describes the classical no-slip boundary condition violation of Newtonian fluid mechanics, where fluids glide on the solid surfaces. Here, we propose a new analytical model validated by experiments for characterization of the liquid slip using vibrating solid surfaces. Essentially, we use a microfluidic system integrated with quartz crystal microbalance (QCM) to investigate the relationship between the slip and the mechanical response of a vibrating solid for a moving fluid. We discover a liquid slip that emerges especially at high flow rates, which is independent of the surface wetting condition, having significant contributions to the changes in resonant frequency of the vibrating solid and energy dissipation on its surface. Overall, our work will lead to consideration of 'missing slip' in the vibrating solid-liquid systems such as the QCM-based biosensing where traditionally frequency changes are interpreted exclusively with mass change on the sensor surface, irrespective of the flow conditions.

Revealing the enhanced structural recovery and gelation mechanisms of cation-induced cellulose nanofibrils composite hydrogels.

In this study, we fabricate physically dual-crosslinked cellulose-based hydrogels by varying coordination bonding effects with the addition of either divalent or trivalent metal cations. The first crosslinked network is created by metal-carboxylate coordination bonds between the cellulose nanofibrils that have abundant carboxyl groups and the metal cations. The second crosslinked network is formed by the reaction of tetra-functional borate ion complex and the hydroxyl groups in polyvinyl alcohol. These physically dual-crosslinked networks are strongly interwoven by non-sacrificial hydrogen bonds, this dual-crosslinked network leads to enhanced recovery characteristics in the resulting hydrogels. We use three interval thixotropic testing to investigate the deformation and recovery behaviors of the hydrogels and plot their structural deformation parameters in phase diagrams to understand the underlying complexity of energy dissipation and viscoelastic dynamics of the dual-crosslinked hydrogels.

Interfacial Tension Measurements in Microfluidic Quasi-Static Extensional Flows.

Droplet microfluidics provides a versatile tool for measuring interfacial tensions between two immiscible fluids owing to its abilities of fast response, enhanced throughput, portability and easy manipulations of fluid compositions, comparing to conventional techniques. Purely homogeneous extension in the microfluidic device is desirable to measure the interfacial tension because the flow field enables symmetric droplet deformation along the outflow direction. To do so, we designed a microfluidic device consisting of a droplet production region to first generate emulsion droplets at a flow-focusing area. The droplets are then trapped at a stagnation point in the cross junction area, subsequently being stretched along the outflow direction under the extensional flow. These droplets in the device are either confined or unconfined in the channel walls depending on the channel height, which yields different droplet deformations. To calculate the interfacial tension for confined and unconfined droplet cases, quasi-static 2D Darcy approximation model and quasi-static 3D small deformation model are used. For the confined droplet case under the extensional flow, an effective viscosity of the two immiscible fluids, accounting for the viscosity ratio of continuous and dispersed phases, captures the droplet deformation well. However, the 2D model is limited to the case where the droplet is confined in the channel walls and deforms two-dimensionally. For the unconfined droplet case, the 3D model provides more robust estimates than the 2D model. We demonstrate that both 2D and 3D models provide good interfacial tension measurements under quasi-static extensional flows in comparison with the conventional pendant drop method.

Revealing the flame retardancy mechanism of highly transparent cellulose nanopapers fabricated by vacuum filtration assisted layer-by-layer deposition.

We fabricate transparent cellulose nanopapers with significantly enhanced flame retardancy by a vacuum filtration assisted layer-by-layer deposition method. Flame retardancy is enhanced by increasing the layer-by-layer thickness while not hampering optical transparency of the nanopapers. Thermal degradation and combustion behaviors show that the nanopapers have been successfully functionalized by phosphorus and amine compounds that act effectively as intumescent and blowing agents. Based on the heat release rate of the various nanopapers herein, we propose that the area of the second peak in the heat release rate can serve as an indicator for coating efficiency of these flame retardant materials. We also suggest a possible mechanism behind the material's flame retardancy where by the phosphorus and blowing materials promote intumescent carbonaceous and porous char layers that prevent diffusion of oxygen and heat penetration into the underlying cellulose nanopapers.

Dewetting Metal Nanofilms-Effect of Substrate on Refractive Index Sensitivity of Nanoplasmonic Gold.

The localized surface plasmon resonance (LSPR) sensitivity of metal nanostructures is strongly dependent on the interaction between the supporting substrate and the metal nanostructure, which may cause a change in the local refractive index of the metal nanostructure. Among various techniques used for the development of LSPR chip preparation, solid-state dewetting of nanofilms offers fast and cost effective methods to fabricate large areas of nanostructures on a given substrate. Most of the previous studies have focused on the effect of the size, shape, and inter-particle distance of the metal nanostructures on the LSPR sensitivity. In this work, we reveal that the silicon-based supporting substrate influences the LSPR associated refractive index sensitivity of gold (Au) nanostructures designed for sensing applications. Specifically, we develop Au nanostructures on four different silicon-based ceramic substrates (Si, SiO2, Si3N4, SiC) by thermal dewetting process and demonstrate that the dielectric properties of these ceramic substrates play a key role in the LSPR-based refractive index (RI) sensitivity of the Au nanostructures. Among these Si-supported Au plasmonic refractive index (RI) sensors, the Au nanostructures on the SiC substrates display the highest average RI sensitivity of 247.80 nm/RIU, for hemispherical Au nanostructures of similar shapes and sizes. Apart from the significance of this work towards RI sensing applications, our results can be advantageous for a wide range of applications where sensitive plasmonic substrates need to be incorporated in silicon based optoelectronic devices.

Prediction of Defect Formation during Resin Impregnation Process through a Multi-Layered Fiber Preform in Resin Transfer Molding by a Proposed Analytical Model.

It is very important to predict any defects occurring by undesired fiber deformations to improve production yields of resin transfer molding, which has been widely used for mass production of carbon fiber reinforced composite parts. In this study, a simple and efficient analytic scheme was proposed to predict deformations of a multi-layered fiber preform by comparing the forces applied to the preform in a mold of resin transfer molding. Friction coefficient of dry and wet states, permeability, and compressive behavior of unidirectional (UD) and plain woven (PW) carbon fabrics were measured, which were used to predict deformations of the multi-layered fiber preforms with changing their constitution ratios. The model predicted the occurrence, type, and position of fiber deformation, which agreed with the experimental results of the multi-layered preforms.

Temperature controlled tensiometry using droplet microfluidics.

We develop a temperature controllable microfluidic device for the accurate measurement of temperature dependent interfacial tensions between two immiscible liquids. A localized temperature control system is integrated with the microfluidic platform to maintain an accurate temperature inside the device. The temperature uniformity and sensitivity are verified by both simulation and experimental results. Temperature dependent interfacial tensions are measured dynamically and rapidly, relying on quantitative analysis of the deformation and retraction dynamics of droplets under extensional flow. Our microfluidic tensiometry offers the capability of measuring temperature dependent interfacial tensions with precise and systematic temperature control in the range of room temperature to 70 °C, which is valuable for studying transient interfacial dynamics, interfacial reactions, and the surfactant adsorption process.

Antioxidant and Anti-Adipogenic Activities of Trapa japonica Shell Extract Cultivated in Korea.

Trapa japonica shell contains phenolic compounds such as tannins. Studies regarding the antioxidant and anti-adipogenic effects of Trapa japonica shell cultivated in Korea are still unclear. Antioxidant and anti-adipogenic activities were measured by in vitro assays such as 2,2-diphenyl-1-picrylhydrazy (DPPH) radical scavenging activity, 2,2'-azinobis( 3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) radical scavenging activity, ferric reducing ability of plasma assay, reducing power, superoxide dismutase-like activity, and iron chelating ability in 3T3-L1 cells. We also measured the total phenol and flavonoids contents (TPC and TFC, respectively) in Trapa japonica shell extract. Our results show that TPC and TFC of Trapa japonica shell extract were 157.7±0.70 mg gallic acid equivalents/g and 25.0±1.95 mg quercetin equivalents/g, respectively. Trapa japonica shell extract showed strong antioxidant activities in a dose-dependent manner in DPPH and ABTS radical scavenging activities and other methods. Especially, the whole antioxidant activity test of Trapa japonica shell extract exhibited higher levels than that of butylated hydroxytoluene as a positive control. Furthermore, Trapa japonica shell extract inhibited lipid accumulation and reactive oxygen species production during the differentiation of 3T3-L1 preadipocytes. Trapa japonica shell extract possessed a significant antioxidant and anti-adipogenic property, which suggests its potential as a natural functional food ingredient.

Dual-mode refractive index and charge sensing to investigate complex surface chemistry on nanostructures.

This work presents a novel dual-mode charge and refractive index sensitive device integrated with nanoplasmonic islands, for the first time, on insulator-semiconductor junctions. The developed nano-metal-insulator semiconductor (nMIS) sensor facilitates simultaneous detection of charge and mass changes on the nanoislands due to the binding of biomolecules. The charging of the nanoislands is traced by using the capacitive field-effect electrolyte-metal-insulator-semiconductor structure and the refractive index changes are quantified by measuring the change in the localized surface plasmon resonances of the nanoislands. To demonstrate the performance of our dual-mode sensor we study the effect of oxygen plasma on immobilized biomolecules. As a case study biotinylated aptamers specific to interleukin 6 (IL-6) were chosen to conduct the immunoassay studies. We confirm that the adsorbed aptamers on the nanoislands do not lose their functionality after exposure to low energy oxygen plasma (<600 J). This finding is critical for the development of 'ready-to-use' microfluidic immunoassay platforms (glass-PDMS based) where immobilizing biomolecules on one of the substrates is often required prior to the bonding of glass and PDMS. Our results also open new opportunities for utilizing plasma to encapsulate biomolecules in polymers and hydrogels. More significantly, nMIS sensors can readily be adopted for multiplexed and high throughput label free immunoassay systems, further driving innovations in biomedical and healthcare research.

Shape-tunable wax microparticle synthesis via microfluidics and droplet impact.

Spherical and non-spherical wax microparticles are generated by employing a facile two-step droplet microfluidic process which consists of the formation of molten wax microdroplets in a flow-focusing microchannel and their subsequent off-chip crystallization and deformation via microdroplet impingement on an immiscible liquid interface. Key parameters on the formation of molten wax microdroplets in a microfluidic channel are the viscosity of the molten wax and the interfacial tension between the dispersed and continuous fluids. A cursory phase diagram of wax morphology transition is depicted depending on the Capillary number and the Stefan number during the impact process. A combination of numerical simulation and analytical modeling is carried out to understand the physics underlying the deformation and crystallization process of the molten wax. The deformation of wax microdroplets is dominated by the viscous and thermal effects rather than the gravitational and buoyancy effects. Non-isothermal crystallization kinetics of the wax illustrates the time dependent thermal effects on the droplet deformation and crystallization. The work presented here will benefit those interested in the design and production criteria of soft non-spherical particles (i.e., alginate gels, wax, and polymer particles) with the aid of time and temperature mediated solidification and off-chip crosslinking.

Relationship between solid retention time and phosphorus removal in anaerobic-intermittent aeration process.

Solid retention time (SRT) is one of the most important control parameters in biological phosphorus removal. In this study, lab-scale biological nutrient removal (BNR) reactors using anaerobic-intermittent aeration (AIA) were operated at various SRTs (i.e., 15, 20, and 30 d) to evaluate their phosphorus removal efficiencies. Sludge wasting load decreased as SRT increased; however, the phosphorus content in the biomass increased as SRT increased. The highest phosphorus removal efficiency was 93% at an SRT of 20 d and the phosphorus wasting load was also highest at that SRT, which indicates that the optimal SRT for the highest phosphorus removal is not proportional to the phosphorus content in the biomass. Aerobic digestion experiments were also carried out to determine the number of phosphate-accumulating organisms (PAOs) in the biomass produced in different reactors. All three activated sludges from BNR at SRTs of 15, 20, and 30 d showed a slower volatile suspended solid (VSS) destruction rate and a larger amount of phosphorus released than the conventional activated sludge (CAS), suggesting that the activated sludge from BNR has more PAOs than CAS. Also, the sludge at an SRT of 30 d showed a slower VSS destruction rate and a larger amount of phosphorus released than the sludge at an SRT of 15 d, suggesting that PAOs are more predominant at longer SRTs. Thus, to improve phosphorus removal efficiency, it is recommended that SRT be increased to maximize the number of PAOs in the system and that SRT be determined to maximize phosphorus wasting load.