Multilayer Sheets Research Articles

General Theory of Nano Trilayer Film Bending

Multilayer sheets or films have many potential applications in micro-nanoelectromechanical systems. When surface and scale effects are not considered, the bending of multilayer film systems can theoretically be discussed by the classical Stoney formula or Timoshenko formula. When the system has anisotropic surface stress or mismatch strain, the four-parameter bending model proposed by Narsu et al. can be used. However, if the thickness of the film is several nanometers and the bending radius of curvature is less than 1micron, the existing theoretical model is no longer applicable. For this reason, a bending formulation for the nanomulti-layer film system is derived and the structure of the multilayer film is optimized in this paper.

Contractility-induced self-organization of smooth muscle cells: from multilayer cell sheets to dynamic three-dimensional clusters

Smooth muscle cells (SMCs) are mural cells that play a vital contractile function in many tissues. Abnormalities in SMC organization are associated with many diseases including atherosclerosis, asthma, and uterine fibroids. Various studies have reported that SMCs cultured on flat surfaces can spontaneously form three-dimensional clusters whose organization resembles that encountered in some of these pathological settings. Remarkably, how these structures form remains unknown. Here we combine in vitro experiments and physical modeling to show that three-dimensional clusters initiate when cellular contractile forces induce a hole in a flat SMC sheet, a process that can be modeled as the brittle fracture of a viscoelastic material. The subsequent evolution of the nascent cluster can be modeled as an active dewetting process with cluster shape evolution driven by a balance between cluster surface tension, arising from both cell contractility and adhesion, and cluster viscous dissipation. The description of the physical mechanisms governing the spontaneous emergence of these intriguing three-dimensional clusters may offer insight into SMC-related disorders.

Charge Carrier Dynamics in Colloidally Synthesized Monolayer MoX2 Nanosheets

Transition metal dichalcogenides (TMDs) are nanostructured semiconductors with prospects in optoelectronics and photocatalysis. Several bottom-up procedures to synthesize such materials have been developed yielding colloidal transition metal dichalcogenides (c-TMDs). Where such methods initially yielded multilayered sheets with indirect band gaps, recently, also the formation of monolayered c-TMDs became possible. Despite these advances, no clear picture on the charge carrier dynamics in monolayer c-TMDs exists to date. Here, we show through broadband and multiresonant pump-probe spectroscopy, that the carrier dynamics in monolayer c-TMDs are dominated by a fast electron trapping mechanism, universal to both MoS2 and MoSe2, contrasting hole-dominated trapping in their multilayered counterparts. Through a detailed hyperspectral fitting procedure, sizable exciton red shifts are found and assigned to static shifts originating from both interactions with the trapped electron population and lattice heating. Our results pave the way to optimizing monolayer c-TMDs via passivation of predominantly the electron-trap sites.

First-principles study of electronic properties of multilayer palgraphyne and BN palgraphyne-like sheets

Palgraphyne is a new two-dimensional carbon allotrope with orthorhombic symmetry. The study of structural and electronic properties of bi- and tri-layer C and BN palgraphyne is the main purpose of the present work. The effect of the number of layers on the electronic properties is investigated by density functional theory calculations. The thermal stability of multilayer palgraphyne is evident from the calculation of the formation energy and ab-initio molecular dynamics simulations. The layers are attached via weak van der Waals interactions. Electronically, bi- and tri-layer C palgraphyne are semimetals as well as monolayer. The number of Dirac points increases with increasing the number of layers. The considered BN palgraphyne sheets show insulating properties. The band gap of BN palgraphyne is influenced by the number of layers. The multilayers have an energy gap smaller than monolayer BN palgraphyne. These results promise practical applications of C and BN palgraphyne in nanoelectronic devices.

Post-Ammonia-Treated V2CTx MXene at Different Pressures: Effects on Morphology, Electronic, and Optical Properties

In the present work, vanadium carbide (V2CTx) MXene was synthesized successfully and then treated with an ammonia solution (NH4OH) under different pressures using a hydrothermal process. The sample morphology reveals that the V2CTx MXene gradually changed from uneven multilayered micrometre-size sheets to uniform few-layered nanometer-size sheets as the pressure increased. The optical emission spectra show broad emission and a blue shift due to nitrogen-related defects and quantum confinement. X-ray photoelectron spectroscopy shows the presence of nitrogen in all of the samples. The ultraviolet photoelectron spectroscopy study shows a modified density of states near the Fermi level and a maximum of ∼0.6 eV valence band edge shift towards a higher binding energy side after post-treatment with ammonia. More interestingly, the E1g Raman band becomes degenerate and the E1g band upshifts (∼15 cm–1) with increasing pressure treatment. The Raman results suggest that the induced lattice strain due to post-ammonia treatment plays a crucial role in deciding the optical and electronic properties.

Comparing the Effects of Two Cryoprotectant Protocols, Dimethyl-Sulfoxide (DMSO) and Glycerol, on the Recovery Rate of Cultured Keratinocytes on Amniotic Membrane.

Background: Off-the-shelf supply of viable engineered tissue is critical for effective and fast treatment of life-threatening injuries such as deep burns. An expanded keratinocyte sheet on the human amniotic membrane (KC sheet-HAM) is a beneficial tissue-engineering product for wound healing. To access an on-hand supply for the widespread application and overcome the time-consuming process, it is necessary to develop a cryopreservation protocol that guarantees the higher recovery of viable keratinocyte sheets after freeze-thawing. This research aimed to compare the recovery rate of KC sheet-HAM after cryopreservation by dimethyl-sulfoxide (DMSO) and glycerol. Methods: Amniotic membrane was decellularized with trypsin, and keratinocytes were cultured on it to form a multilayer, flexible, easy-to-handle KC sheet-HAM. The effects of 2 different cryoprotectants were investigated by histological analysis, live-dead staining, and proliferative capacity assessments before and after cryopreservation. Results: KCs well adhered and proliferated on the decellularized amniotic membrane and successfully represented 3 to 4 stratified layers of epithelialization after 2 to 3 weeks culture period; making it easy to cut, transfer, and cryopreserve. However, viability and proliferation assay indicated that both DMSO and glycerol cryosolutions have detrimental effects on KCs, and KCs-sheet HAM could not recover to the control level after 8 days of culture post-cryo. The KC sheet lost its stratified multilayer nature on AM, and sheet layers were reduced in both cryo-groups compared to the control. Conclusion: Expanding keratinocytes on the decellularized amniotic membrane as a multilayer sheet made a viable easy-to-handle sheet, nonetheless cryopreservation reduced viability and affected histological structure after thawing. Although some viable cells were detectable, our research highlighted the need for a better cryoprotectant protocol other than DMSO and glycerol, specific for the successful banking of viable tissue constructs.

Roles of Two F-Box Proteins: FBXL14 in the Periosteum and FBXW2 at Elastic Fibers

I previously reported that F-box/leucine-rich repeat protein 14 (FBXL14) expressed in periosteum-derived cells, and F-box and WD-40 domain-containing protein 2 (FBXW2) in the periosteum form a fiber-like structure. Here, two culture medium conditions, that is, media with and without ascorbic acid, were compared during explant culture. In the absence of ascorbic acid, the expression patterns of osteocalcin, FBXW2, and elastin were compared using fluorescent immunostaining during weeks 3–5. By observing the periosteum, cambium layer and bone, I demonstrated FBXL14 expression in micro-vessels and bone lacuna. Fluorescent immunostaining revealed that, without ascorbic acid, the FBXL14 layer was thin. Conversely, in the presence of ascorbic acid, FBXL14 formed a thick membrane-like structure inside the periosteum, and the multilayer of periosteum-derived cells (PDCs) was strong. The expression patterns of osteocalcin and FBXW2 were similar. Elastin retained its fiber structure for up to five weeks. Although osteocalcin and FBXW2 were expressed in regions similar to elastin, they could not retain their fiber structures. In conclusion, FBXL14 appears to play a role in preparing a native scaffold for forming a multilayered sheet of PDCs inside the periosteum. FBXW2 and osteocalcin appear to separate from elastic fibers during calcification.

Gradient multi-layered aluminum sheet with excellent corrosion resistance

Diffusion is a very important phenomenon in the thermal processing, including Cu diffusion, Si diffusion and Zn diffusion in the sheet during brazing. Specifically, the migration of Si affects the amount of liquid metal that can be used to form joint, and further affects the solubility of solid substrate at the liquid–solid interface between the clad alloy and core alloy. In addition, Cu accumulates on Al(Fe,Mn)Si precipitates and in Al–Si eutectic at the grain boundaries. Compared with Al matrix, the formation of Al(Fe,Mn,Cu)Si enhances the potential difference between these materials. These events greatly damaged the corrosion resistance of the sheets. Due to the existence of the interlayer, Zn in the interlayer diffuses to the core layer, and the concentration of dissolved zinc decreases with the increase of depth, resulting in an increasing potential of the Al matrix towards the core layer. With depth from the surface to the core layer, the Al matrix is more cathodic, which promoting lateral corrosion within the interlayer region, prevents through failure and which protects the core alloy. Diffusion during brazing leads to microstructure evolution and local electrochemical characteristics of different layers. The optimized potential gradient of the clad layer-interlayer-core layer can greatly improve the corrosion resistance of the alloy.

Multilayer Sheets Based on Double Coatings of Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) on Paper Substrate for Sustainable Food Packaging Applications

This work reports on the development and performance evaluation of newly developed paper sheets coated, on both sides, with thin films of biodegradable poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) for applications of food packaging. For this, PHBV/paper/PHBV multilayers were first prepared by the thermo-sealing technique, optimizing the process variables of temperature and time. Thereafter, the multilayer sheets were characterized in terms of their morphological, optical, thermal, mechanical, and barrier properties and compared with equivalent paper structures double coated with high-barrier multilayer films of petrochemical polymers. The results indicated that the double coatings of PHBV successfully improved the mechanical resistance and ductility, protected from moisture, and also reduced the aroma and oxygen permeances of paper, having a minimal effect on its optical and thermal properties. Finally, the compostability of the resultant multilayer sheets was analyzed, confirming that the presence of the PHBV coatings slightly delayed the aerobic biodegradation and disintegration of paper.

Macromolecular crowding facilitates rapid fabrication of intact, robust cell sheets.

To develop a rapid and simple method to fabricate intact, robust cell sheets from common cell culture dishes by combination of a macromolecular crowding (MMC) reagent and vitamin C. It was found that 3T3 fibroblasts or human bone marrow mesenchymal stem cells (hBMSCs) and their secreted cell derived extracellular matrices could be easily detached as intact cell sheets under gently pipetting after treated by MMC and vitamin C for 4days. This method also allowed fabrication of functional multi-layered hepatic cell sheets by culturing 10 × 104 cells/cm2 HepG2 cells on top of confluent 3T3 fibroblast layers. What's more, MMC induced hBMSC cell sheets demonstrated 1.9 times larger area and 1.6 times greater cell number than that of cell sheets harvested from temperature-responsive cell culture dishes. MMC based method make it possible to fabricate various types of cell sheets more conveniently, economically, and thus may facilitate wide application of cell sheet technology.

Investigation of Adsorption of Heavy Metal Ions on C3N4 Nanosheets by Batch and Microscopic Methods

This paper mainly studies the adsorption of C3N4 on a series of heavy metals and focuses on the adsorption performance of C3N4 on Nd and Th. The main conclusions are as follows: Through the use of the thermal stripping method and melamine as the raw material, C3N4 was obtained at a lower cost, with superior adsorption performance. Through SEM-EDS, TEM, and other characterization analyses, the results show that C3N4 has a clear multilayer sheet structure, and the surface of the material is more uniformly dispersed. The maximum adsorption capacity of C3N4 for Th is 86.6 mg.g-1, and the maximum adsorption capacity for Nd is 60.1 mg.g-1. The kinetic model is also used for fitting, and the results showed that the kinetic of the adsorption was in line with the pseudo-second-order model, indicating that the adsorption was chemical interaction. After C3N4 adsorbed heavy metal elements, it was characterized by SEM-EDS, TEM, UHRTEM, and AFM. The results showed that a variety of heavy metal ions can be adsorbed by C3N4, which proved that C3N4 has good adsorption performance. Due to factors such as metal particle size, the adsorption of C3N4 on heavy metal elements is different.

The Effect of Preheating Temperature on the Forming Limit Diagram of AA1050/AA7050 Al Multilayered Sheets Produced by Accumulative Roll Bonding (ARB)

Multilayered sheets of AA1050 and AA7050 Al alloys produced by hot accumulative roll bonding (ARB) are tested to estimate their forming limit diagrams (FLDs). Sheets processed with preheating at 450 and 500 °C for up to six ARB cycles are submitted to Nakazima tests with an in situ digital image correlation system and tensile tests to analyze the mechanical behavior. X‐ray measurements and electron backscatter diffraction are performed to obtain the crystallographic texture and the mesotexture, respectively, and thus characterize the heterogeneous microstructure. A bimodal grain size distribution is observed in these sheets since AA7050 layers present elongated and fine grain size with nanometric precipitates and AA1050 layers present coarser and equiaxed grains. In addition, texture analysis indicates both rolling and shear components in the sheets. The FLDs show that the forming properties did not follow the expected rule of mixtures when compared with monolithic alloy sheets. Overall, the multilayered AA1050/AA7050 processed by means of ARB at 500 °C presents better formability than that at 450 °C, due to the combination of lower anisotropy measured by the Lankford coefficients values close to 1 and low normal anisotropy Δr values.

Evaluation of the Forming Limit Diagram (FLD) for St-Mg-St Multilayer Sheet Manufactured by Transient Liquid Phase (TLP) Bonding

Evaluation of the Forming Limit Diagram (FLD) for St-Mg-St Multilayer Sheet Manufactured by Transient Liquid Phase (TLP) Bonding

Abstract 14632: Enhanced Therapeutic Effect on Myocardial Infarction by Using Thick and Viable iPSC Derived Cardiac Tissue

Introduction: Human iPSC derived cardiomyocytes (iPSC-CMs) have been proved to be a promising method to treat the heart failure. Multiple clinical studies including one in our group are ongoing around the world. Due to the diffusion limit, so far it is difficult to prepare viable cardiac tissue with high thickness. We hypothesized that by using multilayer fiber sheets and enhanced perfusion system, viable and thick cardiac tissue could be obtained for improved therapeutic effect for treating myocardial infarction. Method and Results: PLGA fiber sheet with multilayer and high porosity (30.61% ± 1.85%, n = 4) was fabricated for iPSC-CMs penetration and organization. A low-shear stress perfusion system was developed to promote the oxygen diffusion in the thick tissue. At day 5, multilayer cardiac tissue showed compact structure with thickness of 878.64 ± 193.45 μm (n = 4) and viability of 85.32 % ± 6.75 % (n = 4). Compared with the single layer tissues, the multilayer cardiac tissues demonstrated improved contractile properties and secretion of angiogenesis factors: VEGF, HGF and TGF-β1. When used for treating rat with myocardial infarction, multilayer group showed significantly improved left ventricular ejection fraction (0 vs. 4 week: 39.1 ± 4.6 % vs. 52.3 ± 7.8 %, n=8, p = 0.0029), whereas the control group showed no significant change (0 vs. 4 week: 40.6 ± 5.4 % vs. 44.9 ± 4.1 %, n=8, p = 0.37). The staining on sliced heart confirmed the survival of transplanted cells in large area. Moreover, the multilayer group showed significantly lower fibrosis at the border zone than the control group (10.8 % ± 3.1 % vs. 16.4 % ± 5.9 %, n=7, p=0.024). There are no significant differences in cell diameter and capillary density in border zone between two groups. Both groups showed no significant inflammatory reactions (CD68). Conclusion: By using multilayers fiber sheet and enhanced perfusion system, viable and thick iPSC-cardiac tissue could be obtained with enhanced features over the single layer cardiac tissue such as contractility and secretion. While used for transplantation, the multilayers cardiac tissue demonstrated improved therapeutic effect for treating myocardial infarction, holding high potential for future clinical applications.

Liquid Heterostructures: Generation of Liquid–Liquid Interfaces in Free-Flowing Liquid Sheets

Chemical reactions and biological processes are frequently governed by the structure and dynamics of the interface between two liquid phases, but these interfaces are often difficult to study due to the relative abundance of the bulk liquids. Here, we demonstrate a method for generating multilayer thin film stacks of liquids, which we call liquid heterostructures. These free-flowing layered liquid sheets are produced with a microfluidic nozzle that impinges two converging jets of one liquid onto opposite sides of a third jet of another liquid. The resulting sheet consists of two layers of the first liquid enveloping an inner layer of the second liquid. Infrared microscopy, white light reflectivity, and imaging ellipsometry measurements demonstrate that the buried liquid layer has a tunable thickness and displays well-defined liquid–liquid interfaces and that this inner layer can be only tens of nanometers thick. The demonstrated multilayer liquid sheets minimize the amount of bulk liquid relative to their buried interfaces, which makes them ideal targets for spectroscopy and scattering experiments.

Nanodiamonds as a knife for cutting graphene multilayers into ultrafine pieces under microwave irradiation

Graphene (Gr) has proved its potential as a successful material for various types of applications. However, poor dispersion due to the strong π–π stacking interactions between their layers limits its properties and potential as an effective material in some practical applications. In this work nanodiamonds (NDs) were successfully used under microwave irradiation for exfoliation/cutting Gr multi-layered sheets into ultrafine pieces of nanocomposite Gr-NDs of sizes less than 50 nm with a high yield of ∼ 93 %. A micro-mixing of xylene solution of NDs with a few Gr layers colloidal in dimethylformamide (DMF) were used without surfactant catalysts or other auxiliary substances. The nanocomposite hybrid material was prepared using the microwave-assisted chemical route at 1000 W for 30 mins. The new Gr-NDs nanocomposite was characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). Hence, we successfully fabricated 48.8 mg of Gr-NDs nanocomposite from 40 mL of the two solutions in the microwave digester, which might be useful for several applications including energy storage, electronics, sensors, etc.

Fabrication of Oxide-Based All-Solid-State Batteries by a Sintering Process Based on Function Sharing of Solid Electrolytes.

Garnet-type Li7La3Zr2O12 (LLZ) has advantages of stability with Li metal and high Li+ ionic conductivity, achieving 1 × 10-3 S cm-1, but it is prone to react with electrode active materials during the sintering process. LISICON-type Li3.5Ge0.5V0.5O4 (LGVO) has the advantage of less reactivity with the electrode active material during the sintering process, but its ionic conductivity is on the order of 10-5 S cm-1. In this study, these two solid electrolytes are combined as a multilayer solid electrolyte sheet, where 2 μm thick LGVO films are coated on LLZ sheets to utilize the advantages of these two solid electrolytes. These two solid electrolytes adhere well through Ge diffusion without significant interfacial resistance. The LLZ-LGVO multilayer is combined with a LiCoO2 positive electrode and a lithium metal anode through annealing at 700 °C. The resultant all-solid-state battery can undergo repeated charge-discharge reactions for over 100 cycles at 25 or 60 °C. The LGVO coating suppresses the increases in the resistance from the solid electrolyte and interfacial resistance induced by annealing by ca. 1/40. As with sulfide-based all-solid-state batteries, function sharing of solid electrolytes will be a promising method for developing advanced oxide-based all-solid-state batteries through a sintering process.

Surface modification of high-Mn steel via laser-DED: Microstructural characterization and hot crack susceptibility of clad layer

High-Mn steels have been intensively developed in steel industries due to their excellent mechanical properties and low density. However, the weak surface properties of these steels significantly limited the production and application scope. Various surface modification solutions were proposed, but they were not suitable for mass production or degraded the physical properties of base materials. Here, a new solution is proposed for mass-producing an ultra-thin multilayer clad steel sheet using an additive manufacturing process without changing the superior mechanical property of the high-Mn steel. Functionally graded multilayers from high-Mn steel to high-strength low-alloy steel have been deposited onto a high-Mn steel slab by a powder-fed type additive manufacturing process to improve its surface properties. During the deposition at high laser intensities, solidification cracks appeared in the first and second layers. The hot crack susceptibility of the functionally graded multilayers was elucidated by employing thermodynamic solidification calculation and thermo-mechanical analysis.

Oxygen transmission rate through thermoformed trays: Modeling and influence of processing variables

AbstractThe oxygen transmission rate (OTR) is a key parameter when selecting a sheet to make a thermoformed tray, as it influences the shelf life of packaged food. The OTR of a thermoformed tray depends on the distribution of the material's thickness over its walls. The goal of this study is to model the evolution of oxygen in the headspace of a thermoformed plastic tray considering the thickness distribution of its walls. PET/PE films with different thicknesses and a PET/PE/EVOH/PE structure with EVOH acting as a barrier layer were used for the thermoformed trays. The thickness of the thermoformed trays was measured at different points to determine the average thickness of the tray subsections. A model was built to predict the variation in the oxygen content inside the headspace over time. The results of the model were correlated with experimental data by regression analysis. The model can be used to perform a straightforward comparison of both different structures as well as the effect of the thickness of the layers that constitute the multilayer sheet. The model can also support decisions about the best multilayer for a particular tray design so as to achieve a specific product shelf‐life.

Liquid exfoliated Bi2S3 nanosheets as photocatalysts for degradation of azo dyes and detoxification of hexavalent chromium

Layered materials represent a diverse source of two-dimensional crystals with exotic electronic properties and high specific surface areas essential for sensing, catalysis, and energy storage applications. Herein, bismuth sulfide (Bi2S3) crystals were ultrasonically exfoliated into nanosheets using N, N-dimethylformamide solvent. It was found that the as-prepared nanosheets with the atomic ratio of 2:3 for Bi (bismuth):S (sulphur) are rock-like structures consisting of multilayer sheets, orthorhombic phase, single-crystalline (d = 5.041 nm) in nature with 1.11 eV optical bandgap. The photocatalytic experiments showed excellent efficiency of up to 76.5 % in 240 min and 86.9 % in 50 min of visible light irradiation for methyl orange (MO) and Cr(VI), respectively. Both reactions follow a pseudo-kinetic first-order with kinetics constant (k) values of 0.0048 min−1 and 0.023 min−1 in terms of MO and Cr(VI), respectively. The probable mechanism strongly supports that Bi2S3 nanosheets are effective photocatalysts for water decontamination.