Single Lamella Research Articles

Nano-scale modeling of energy dissipation in a single lamella reveals the significant contribution of collagen-mineral sliding to intrinsic bone toughness

Although collagen-mineral sliding is recognized as one of the intrinsic mechanisms that contribute to the bone toughness, its precise role in energy release at the nano-scale, as well as its relationship to other intrinsic toughness mechanisms, remains unclear. This lack of understanding stems from the challenges associated with quantifying the specific nature of contact at the mineral-collagen interface, and the energy dissipation capacity resulting from plastic deformation at this scale. To address this issue, we developed a three-dimensional model of mineralized collagen fibril using ABAQUS, incorporating hyperelastic isotropic collagen, elastic isotropic mineral, and a cohesive contact formulation to represent the collagen-mineral interface. Knowing the properties of collagen and mineral and using a parametric modeling approach, we estimated the properties of contact based on experimental measurements of the stress-strain behavior in a single bone lamella, considering the angle of the collagen fibril in relation to the loading axis. By comparing the experimental elastic modulus with the model predictions, we determined that the cohesive contact exhibited a maximum strength of 9 MPa and a fracture energy of 50 mJ/m2 within the bone. Further analysis indicated that fracture energy at the collagen-mineral interface is potentially closer to 5 mJ/m2. Using these findings, we concluded that the interfaces were responsible for 52% to 98% of the energy release in mineralized collagen fibrils, depending on collagen angle, both directly and indirectly by influencing stress and strain in adjacent collagen fibril. The results of this study demonstrated that plastic deformation at the collagen-mineral interface is the primary mechanism underlying bone toughness at the nano-scale. Importantly, we found that these conclusions held true regardless of the angle of the collagen fibril relative to the loading axis. The modeling framework presented in this study provides a valuable tool for investigating the elastic and post-yield behavior of bone across different mineral volume fractions at the nano-scale, and at the lamellar level.

Temporal dynamics of chloroplast biogenesis revealed initiation of photosynthesis-related gene expression and protein complexes during alfalfa seed germination

The chloroplast biogenesis occurs in cotyledon during alfalfa seed germination before true leaf formation, and is extremely important for the followed plant development and growth. In this study, we conducted a simulation of alfalfa seed germination in the soil by using tin foil and focused on 10 pivotal time points of chloroplast biogenesis in cotyledons before and after light exposure, which showed significant differences in multispectral images, and covered the whole process of chloroplast biogenesis from proplastid, etioplast to mature chloroplast. We revealed three phases that referred to the programmed involvements of photosynthesis promotion, ultrastructure maturity, transcriptomic expression, and protein complex construction, and observed distinct transcriptional expressions of genes from nuclear and chloroplast genomes. In phase I at dark germination before light exposure, chloroplast-encoded genes showed up-regulated expressions together with the importation of chloroplast proteins. In phase II for the first day after light exposure, nuclear-encoded genes’ expressions were initiated at 2 h after light exposure (E2h), followed by swift assembly of chloroplast thylakoid membrane protein complexes, and roaring Fv/Fm and contents of chlorophyll a, chlorophyll b and carotenoid. The initiation at E2h was pronounced by the observation of gradual accumulation of single lamella, and facilitated the formation of granum stacks (thylakoid) at E8h in phase II. In phase III from the second day after light exposure, chloroplast became gradually complete with the fully established photosynthetic capacity. Altogether, our results layed a theoretical foundation for enhancing potential photosynthetic efficiency in alfalfa and related species.

Hydrophilic 2D composite LDHs-MXene pervaporation membrane for highly efficient ethanol dehydration

Mixed matrix membranes (MMMs) demonstrate significant potential for pervaporation applications. Nevertheless, single lamella 2D materials are prone to stacking problems in membranes, resulting in unforeseen matrix inhomogeneity and defects. Here, we propose a wafer-like membrane structure designed for ethanol dehydration. This structure features a surface modification of transition metal carbides (MXenes) with layered dihydroxides (LDHs), which effectively enlarges the interlayer spacing and ameliorates the stacking issue. The LDHs-modified MXenes were then incorporated into the sodium alginate (SA) layer. The hydrophilicity, stability and morphology of the MMM were evaluated by water contact angle measurements, swelling tests and scanning electron microscopy. The experiment results indicated the hydrophilicity and stability of the MMM were effectively improved. The novel L-M@CS MMM exhibited outstanding dehydration performance for ethanol solution, with the membrane containing 0.4 wt % LDHs-modified MXenes achieving the highest permeation flux of 1377 g/(m2·h) and the optimal separation factor up to 1650.

Study on the Effect of Nano Pour Point Depressant on Wax Oil Crystallization

The influence of nano pour point depressant (NPPD) on crude oil containing wax is primarily manifested through their interaction with the wax constituents. This study examines the depressant's effects using a polarizing microscope and an atomic force microscope (AFM) to assess morphological and structural changes in the wax crystals within the oil, both before and after the addtion of the NPPD. Additionally, a surface tensiometer measured surface tension, while a rheometer evaluated viscosity and modulus alterations. These methods facilitated insights into NPPD's mechanistic effects. The interaction process between crude oil wax crystal molecules and the main components of NPPD was simulated using JOCTA molecular dynamics simulation software, and the highest interaction strength between benzenesulfonic acid groups and crude oil wax crystal molecules was determined. The findings indicate that the addition of the NPPD alters the growth patterns and crystalline structure of the wax in the oil. Initially, the wax crystals present as flaky, predominantly single molecular layer lamellae with a thickness of approximately 100 nm. Post-treatment, the wax crystals adopt a flattened lamellar configuration, composed of multilayer lamellae, with a reduced thickness of within 10 nm and exhibiting short-range order. AFM height maps reveal an increase in the average roughness of the wax oil correlated with the addition of the NPPD across different sampling lengths. Surface tension measurements demonstrate that the wax oil doped with the NPPD exhibits lower surface tension than undoped oil, with the surface tension decreasing as the temperature increases.

Confinement-induced self-assembly of a diblock copolymer within a non-uniform cylindrical nanopore.

The self-assembly of a diblock copolymer melt confined within a non-uniform cylindrical nanopore is studied using the self-consistent field theory. The non-uniformity manifests in the form of a converging-diverging cylindrical nanopore. The axial variation in pore diameter presents a range of curvatures within the same confinement pore as opposed to a single curvature in a uniform-diameter cylindrical pore. The introduction of multiple curvatures leads to the formation of novel microstructures not accessible in uniform cylindrical confinement. The well-known equilibrium structures like a single helix, double helices, and concentric lamella under cylindrical confinement transition into new morphologies such as hyperboloidal phases, microstructures containing rings with a bead, rings with spheres, and a squeezed helical phase as the pore diameter varies axially. The converging-diverging geometry of the confining pore renders the helical phases seen in the cylindrical pore less favorable. A phase diagram in the parametric space of the block fraction and the ratio of the smallest and largest pore radii has been constructed to depict the order-order transition of various microstructures. The ratio of radii, a measure of the non-uniformity of the pore, along with the pore length brings out some interesting morphologies. The mechanism of these structural transitions is understood as the interplay between the variation in pore curvature attributed to the non-uniformity, the spontaneous curvature of the block copolymer interface, and the enthalpic interaction between the segregated blocks.

Evolution of the Deformation‐ and Flow‐Induced Crystallization and Characterization of the Microstructure of a Single Spherulite, Lamella, and Chain of Isotactic Polypropylene

AbstractIsotactic polypropylene (iPP) is a frequently used polymer in industrial processing and scientific research, used as a model material. This review highlights some current and forefront issues in polymer science and engineering. This review alludes to classical deformation schemes to interpret the complicated deformation in isotactic polypropylene as a semicrystalline polymer. Also, due to the complex hierarchical structures of crystallized polymers, the progress on the multiscale and multistage microstructural evolution covering each deformation stage from the initiation of plasticity until failure is mainly concerned, particularly in terms of crystalline morphology changes. Specifically, the characterization of the microstructure evolution of a single spherulite, lamella, and chain of isotactic polypropylene will be emphasized and mentioned. Here, the authors are most interested in the results obtained from stretching (strain‐induced) orientation and crystallization studies accompanied by the in situ scattering and spectroscopy techniques offering a detection window from nano to micrometer scale, which should be able to reflect the microstructural changes at different length scales of interest. During polymer processing, the melts are frequently subjected to shear or/and elongation flow fields, producing flow‐induced molecular chain orientation in the melt. The oriented molecular chains crystallize differently than those encountered under quiescent conditions. Thus, orientation‐induced crystallization has long been an object of intense interest. A vast body of research is reported about the effects of preorientation on the crystallization of various polymers. Among them, iPP is most frequently studied since its diversified structure and morphology are very sensitive to changes in processing conditions and molecular parameters.

On the identification of the ultra-structural organization of elastic fibers and their effects on the integrity of annulus fibrosus

Due to the complicated structure of the elastic fiber network in annulus fibrosus, existing in-silico studies either simplified or just overlooked its distribution pattern. Nonetheless, experimental and simulation results have proven that elastic fibers are of great importance to maintaining the structural integrity of annulus fibrosus and therefore to ensuring the load-bearing ability of intervertebral discs. Such needs call for a fine model. This work aims at developing a biphasic annulus fibrosus model by incorporating the accurate distribution pattern of collagen and elastic fibers. Both the structural parameters and intrinsic mechanical parameters were successfully identified using single lamella and inter-lamella microscopy anatomy and micromechanical testing data. The proposed model was then used to implement finite element simulations on various anterior and posterolateral multi-lamellae annulus fibrosus specimens. In general, simulation results agree well with available experimental and simulation data. On this basis, the effects of elastic fibers on the integrity of annulus fibrosus were further investigated. It was found that elastic fibers significantly influence the free swelling, radial stretching and circumferential shear performances of annulus fibrosus. Nonetheless, no significant effects were found for the circumferential stretching capability. The proposed biphasic model considers for the first time the distribution characteristics of elastic fibers at two scales, including both the principal orientations of all fiber families and the detailed distribution pattern within each family. Better understandings on the functions of collagen and elastic fibers can therefore be realized. To further enhance its prediction capability, the current model can be extended in the future by taking the fiber–matrix interaction as well as progressive damages into consideration.

Yield stress of foam flow in porous media: The effect of bubble trapping

Foam behaves as a yield-stress fluid as it flows in a porous medium. Quasi-static analysis suggests that the yield stress arises from the non-smooth motion of foam films, denoted as lamellae, in pores. In order to study the effect of trapped lamellae on the motion of a moving lamella and consequently on the yield stress of foam, we conduct numerical simulations in the quasi-static limit. We propose a new method utilizing the surface energy minimization algorithm, which explicitly considers the connectivity of pores in a porous medium. We consider two different shapes of pore and vary the number of nearby trapped lamellae to investigate the effects of bubble trapping on the non-smooth and the smooth motion of a single lamella passing through a pore, respectively. We find that the trapped lamellae lead to the increased volume-averaged pressure drop and thus the increased yield stress. Notably, the motion of a lamella through a pore with rounded corners in the pore body becomes non-smooth, due to the presence of trapped lamellae. The results contribute to a better understanding of the yield stress of foam in porous media.

The hierarchical internal structure of labradorite

Abstract. The different structural features of labradorite and its incommensurate atomic structure have long been in the eye of science. In this transmission electron microscopy (TEM) study, all of the structural properties of labradorite could be investigated on a single crystal with an anorthite–albite–orthoclase composition of An53.4Ab41.5Or5.1. The various properties of labradorite could thus be visualized and connected to form a hierarchical structure. Both albite and pericline twins occur in the labradorite. The size of alternating Ca-rich and Ca-poor lamellae could be measured and linked to the composition and the color of labradorescence. Furthermore, a modulation vector of 0.0580(15)a* + 0.0453(33)b* − 0.1888(28)c* with a period of 3.23 nm was determined. The results indicate an eα labradorite structure, which was achieved by forming Ca-rich and Ca-poor lamellae. The average structure and subsequently the incommensurate crystal structure were solved with a three-dimensional electron diffraction (3DED) data set acquired with automated diffraction tomography (ADT) from a single lamella. The results are in good agreement with the structure solved by X-ray diffraction and demonstrate that 3DED–ADT is suitable for solving even incommensurate structures.

Synthesis, Crystal Structure, and Antibacterial Properties of Silver-Functionalized Low-Dimensional Layered Zirconium Phosphonates.

New insoluble layered zirconium phosphate carboxyaminophosphonates (ZPs), with the general formula Zr2(PO4)H5[(O3PCH2)2N(CH2)nCOO]2·mH2O (n = 3, 4, and 5), have been prepared and characterized. The crystal structure for n = 3 and 4 samples was determined ab initio from X-ray powder diffraction data. The structure for n = 3 was monoclinic in space group C2/c with the following unit cell parameters: a = 34.346(1) Å, b = 8.4930(2) Å, c = 9.0401(2) Å, and β = 97.15(1)°. The structure for n = 4 was triclinic in space group P1̅ with the following unit cell parameters: a = 17.9803(9) Å, b = 8.6066(4) Å, c = 9.0478(3) Å, α = 90.466(3)°, β = 94.910(4)°, and γ = 99.552(4)°. The two structures had the same connectivity as Zr phosphate glycine diphosphonate (n = 1), as previously reported. By intercalation of short amines, these layered compounds were exfoliated in single lamella or packets of a few lamellae, which formed colloidal dispersions in water. After a thorough characterization, the dispersed lamellae were functionalized with Ag nanoparticles, which were grown in situ on the surface of exfoliated lamellae. Finally, their antimicrobial activity was tested on several Gram-positive and Gram-negative bacteria. All of these systems were found to be active against the four pathogens most frequently isolated from orthopedic prosthetic infections and often causative of nosocomial infections. Interestingly, they were found to express powerful inhibitory activity even against bacterial strains exhibiting a relevant profile of antibiotic resistance such as Staphylococcus aureus ATCC 700699.

Modeling multiaxial damage regional variation in human annulus fibrosus

In the present article, a fully three-dimensional human annulus fibrosus model is developed by considering the regional variation of the complex structural organization of collagen network at different scales to predict the regional anisotropic multiaxial damage of the intervertebral disc. The model parameters are identified using experimental data considering as elementary structural unit, the single annulus lamellae stretched till failure along the micro-sized collagen fibers. The multi-layered lamellar/inter-lamellar annulus model is constructed by considering the effective interactions between adjacent layers and the chemical-induced volumetric strain. The regional dependent model predictions are analyzed under various loading modes and compared to experimental data when available. The stretching along the circumferential and radial directions till failure serves to check the predictive capacities of the annulus model. Model results under simple shear, biaxial stretching and plane-strain compression are further presented and discussed. Finally, a full disc model is constructed using the regional annulus model and simulations are presented to assess the most likely failed areas under disc axial compression. Statement of significanceThe damage in annulus soft tissues is a complex multiscale phenomenon due to a complex structural arrangement of collagen network at different scales of hierarchical organization. A fully three-dimensional constitutive representation that considers the regional variation of the structural complexity to estimate annulus multiaxial mechanics till failure has not yet been developed. Here, a model is developed to predict deformation-induced damage and failure of annulus under multiaxial loading histories considering as time-dependent physical process both chemical-induced volumetric effects and damage accumulation. After model identification using single lamellae extracted from different disc regions, the model predictability is verified for various multiaxial elementary loading modes representative of the spine movement. The heterogeneous mechanics of a full human disc model is finally presented.

Microbeam bending of hydrated human cortical bone lamellae from the central region of the body of femur shows viscoelastic behaviour

Bone is a biological tissue with unique mechanical properties, owing to a complex hierarchical structure ranging from the nanoscale up to the macroscale. To better understand bone mechanics, investigation of mechanical properties of all structural elements at every hierarchical level and how they interact is necessary. Testing of bone structures at the lower microscale, e.g. bone lamellae, has been least performed and remains a challenge. Focused ion beam (FIB) milling is an attractive technique for machining microscopic samples from bone material and performing mechanical testing at the microscale using atomic force microscopy (AFM) and nanoindentation setups. So far, reported studies at this length scale have been performed on bone samples of animal origin, mostly in a dehydrated state, except for one study. Here we present an AFM-based microbeam bending method for performing bending measurements in both dehydrated and rehydrated conditions at the microscale. Single lamella bone microbeams of four human donors, aged 65–94 yrs, were machined via FIB and tested both in air and fully submerged in Hank's Balanced Salt Solution (HBSS) to investigate the effect of (de)hydration and to a certain extent, of age, on bone mechanics. Bending moduli were found to reduce up to 5 times after 2 h of rehydration and no trend of change in bending moduli with respect to age could be observed. Mechanical behavior changed from almost purely elastic to viscoelastic upon rehydration and a trend of lower dissipated energy in samples from older donors could be observed in the rehydrated state. These results confirm directly the importance of water for the mechanical properties of bone tissue at the microscale. Moreover, the trend of lowered capability of energy dissipation in older donors may contribute to a decrease of fracture toughness and thus an increase in bone fragility with age.

Aggravated stress fluctuation and mechanical size effects of nanoscale lamellar bone pillars

The size effects of mechanical properties influence the microdeformation behaviors and failure mechanisms of hierarchical lamellar bones. Investigations of the continuous deformation behaviors and structure–behavior–property relationships of nanoscale lamellar bones provide essential data for reducing the risk of fracture. Here, five pillars with diameters ranging from 640 to 4971 nm inside a single lamella were fabricated. In situ pillar compressive tests inside a scanning electron microscope directly revealed the diameter-dependent enhanced strength, ductility, and stress fluctuation amplitude. Real-time observations also revealed the segmented deformation and morphological anisotropy of pillars with smaller diameters and the slight elastic recovery of pillars with larger diameters. The critical diameter leading to the brittle-to-ductile transition was confirmed. The “analogous to serrated flow” stress fluctuation behaviors at the nanoscale exhibited a significant size effect, with coincident fluctuation cycles independent of diameter, and each cycle of the fluctuation manifested as a slow stress increase and a rapid stress release. The discontinuous fracture of collagen fibrils, embedded enhancement of hydroxyapatite crystals, and layered dislocation movement on the basis of strain gradient plasticity theory were expected to induce cyclical stress fluctuations with different amplitudes.

Oxidation-induced rhenium evaporation in Ni-based single crystal superalloy thin lamella

Rhenium is the key element for improving the mechanical properties in γ/γ' structure single-crystal Ni-based superalloys, but its oxidation-induced evaporation results in a detrimental decrease in corrosion resistance. The in situ Re evaporation process of a single lamella of a high Re-containing Ni-based superalloy is recorded in an environmental transmission electron microscope. The local aggregation of Re in the inner border of the γ phase and subsequent evaporation forms channels for the accelerated oxidation of the base and other elements. The real oxidation process of Re evaporation provides detailed and essential information on corrosive gas resistance properties at the nanoscale.

Oxidation-Induced Rhenium Evaporation in Ni-Based Single Crystal Superalloy Thin Lamella

Rhenium is the key element for improving the mechanical properties in γ/γ'-structured single-crystal Ni-based superalloys, but its oxidation-induced evaporation results in a detrimental decrease in corrosion resistance. The in situ Re evaporation process of a single lamella of a high Re-containing Ni-based superalloy is recorded with an environmental transmission electron microscope, and volatilization is observed. The local aggregation of Re in the inner border of the γ phase and subsequent evaporation forms channels for the accelerated oxidation of the base and other elements. The real oxidation process of Re evaporation provides detailed and essential information on corrosive gas resistance properties at the nanoscale.

Rolling shear properties of cross-laminated timber (CLT) made from Australian Radiata Pine – An experimental study

Cross-laminated timber (CLT) is produced from renewable bio-composite material and has been gaining popularity in building industry largely due to easily customised panellised construction technique, which is fast, efficient, minimises construction risk and waste. CLT is often considered as a sustainable alternative to traditional construction materials, and can be used to complement steel and concrete to build a sustainable future. CLT is reported to provide excellent resistance against both out-of-plane and in-plane loading but rolling shear properties have been recognized as one of the critical parameters that often controls the design resistance when CLTs are subjected to out-of-plane loading scenario. Rolling shear characteristics are highly dependent on wood species, sawing patterns and width-to-thickness ratio (wl/tl) of a single lamella. This paper presents a thorough investigation on rolling shear properties of two types three-layer CLT panels (CL3/105 and CL3/135) produced by XLam from Australian Radiata Pine. Rolling shear properties were measured using two test methods i.e. short-span four-point bending test and planar shear test. Typical rolling shear failures were observed in samples tested using short-span bending method and rolling shear stresses were evaluated by using various analytical methods. Planar shear samples also failed in rolling shear, as expected, and showed comparable results. Existing theoretical approaches were used to evaluate the rolling shear properties with a characteristic rolling shear strength of 2.0 MPa and shear modulus of 65.5 MPa for the considered Radiata Pine CLT panels. In addition, an empirical equation has been proposed based on the rolling shear results for other similar species published in literature and the current observations were compared against the proposed equation.

Evolution of Low‐Frequency Vibrational Modes in Ultrathin GeSbTe Films

In article number 2000434, Eugenio Zallo and co-workers report a methodology based on the Raman technique for the measurement of the layer number in ultrathin GeSbTe films obtained by molecular beam epitaxy. The experimental and theoretical evolution of the in-plane low-frequency vibrational modes of Ge2Sb2Te5 from bulk down to a single lamella is demonstrated. The energy shift is mainly related to the weak van der Waals interactions between the layers.

Evolution of Low‐Frequency Vibrational Modes in Ultrathin GeSbTe Films

GeSbTe (GST) phase‐change alloys feature layered crystalline structures made of lamellae separated by van der Waals (vdW) gaps. This work sheds light on the dependence of interlamellae interactions at the vdW gap on film thickness of GST alloys as probed by vibrational spectroscopy. Molecular beam epitaxy is used for designing GST layers down to a single lamella. By combining density‐functional theory and Raman spectroscopy, a direct and simple method is demonstrated to identify the thickness of the GST film. The shift of the vibrational modes is studied as a function of the layer size, and the low‐frequency range opens up a new route to probe the number of lamellae for different GST compositions. Comparison between experimental and theoretical Raman spectra highlights the precision growth control obtained by the epitaxial technique.

Molecular to Macroscale Energy Absorption Mechanisms in Biological Body Armour Illuminated by Scanning X-ray Diffraction with In Situ Compression.

Determining multiscale, concurrent strain, and deformation mechanisms in hierarchical biological materials is a crucial engineering goal, to understand structural optimization strategies in Nature. However, experimentally characterizing complex strain and displacement fields within a 3D hierarchical composite, in a multiscale full-field manner, is challenging. Here, we determined the in situ strains at the macro-, meso-, and molecular-levels in stomatopod cuticle simultaneously, by exploiting the anisotropy of the 3D fiber diffraction coupled with sample rotation. The results demonstrate the method, using the mineralized 3D α-chitin fiber networks as strain sensors, can capture submicrometer deformation of a single lamella (mesoscale), can extract strain information on multiple constituents concurrently, and shows that α-chitin fiber networks deform elastically while the surrounding matrix deforms plastically before systematic failure under compression. Further, the results demonstrate a molecular-level prestrain gradient in chitin fibers, resulting from different mineralization degrees in the exo- and endo cuticle.

Fuel effects on aqueous film formation and foam degradation and their impact on fire suppression by foams containing fluorosurfactants

SummarySpreading coefficient, foam degradation, fuel transport through a foam layer, foam spread, and fire extinction time were collected by varying fuels for a given fluorosurfactant formulation. Varying fuel structure systematically enabled variation of foam‐fuel interactions, and spreading coefficients, which affected aqueous film formation. A wide range of spreading coefficients were studied using two foam formulations. Surfactant formulations with near‐zero or negative spreading coefficients (−1.2, −0.12 mN/m) suppressed the fires within the same time or faster than those with positive spreading coefficients (1.77, 3.28 mN/m). Both foams extinguished an iso‐octane and methylcyclohexane pool fire despite negative spreading coefficients on iso‐octane and positive spreading coefficients on methylcyclohexane. The fire extinction times collected relate more closely to foam degradation than to film formation. Foam degradation results showed a roughly 20% variation in lifetime between the two foams and the three fuels, consistent with fire extinction times. To understand the relationship between foam degradation and solution properties, a single lamella experiment was designed that monitors lamella thickness and lifetime. This experiment, relating solution to foam properties, will aid in the development of environmentally friendly surfactant replacements in firefighting foams.