Mechanical Strain Research Articles

Engineering Symmetry Breaking Interfaces by Nanoscale Structural-Energetics in Orthorhombic Perovskite Thin Films.

The atomic configuration of phases and their interfaces is fundamental to materials design and engineering. Here, we unveil a transition metal oxide interface, whose formation is driven by energetic influences─epitaxial tensile strain versus oxygen octahedra connectivity─that compete in determining the orientation of an orthorhombic perovskite film. We study this phenomenon in layers of LaVO3 grown on (101) DyScO3, using atomic-resolution scanning transmission electron microscopy to measure intrinsic markers of orthorhombic symmetry. We identify that the film resolves this energetic conflict by switching its orientation by 90° at an atomically flat plane within its volume, not at the film-substrate interface. At either side of this "switching plane", characteristic orthorhombic distortions tend to zero to couple mismatched oxygen octahedra rotations. The resulting boundary is highly energetic, which makes it a priori unlikely; by using second-principles atomistic modeling, we show how its formation requires structural relaxation of an entire film grown beyond a critical thickness measuring tens of unit cells. The switching plane breaks the inversion symmetry of the Pnma orthorhombic structure, and sharply joins two regions, a thin intermediate layer and the film bulk, that are held under different mechanical strain states. By contacting two distinct phases of one compound that would never otherwise coexist, this alternative type of interface will enable nanoscale engineering of functional systems, such as creating a chemically uniform but magnetically inhomogeneous heterostructure.

Deconvoluting thermomechanical effects in X-ray diffraction data using machine learning.

X-ray diffraction is ideal for probing the sub-surface state during complex or rapid thermomechanical loading of crystalline materials. However, challenges arise as the size of diffraction volumes increases due to spatial broadening and because of the inability to deconvolute the effects of different lattice deformation mechanisms. Here, we present a novel approach that uses combinations of physics-based modeling and machine learning to deconvolve thermal and mechanical elastic strains for diffraction data analysis. The method builds on a previous effort to extract thermal strain distribution information from diffraction data. The new approach is applied to extract the evolution of the thermomechanical state during laser melting of an Inconel 625 wall specimen which produces significant residual stress upon cooling. A combination of heat transfer and fluid flow, elasto-plasticity and X-ray diffraction simulations is used to generate training data for machine-learning (Gaussian process regression, GPR) models that map diffracted intensity distributions to underlying thermomechanical strain fields. First-principles density functional theory is used to determine accurate temperature-dependent thermal expansion and elastic stiffness used for elasto-plasticity modeling. The trained GPR models are found to be capable of deconvoluting the effects of thermal and mechanical strains, in addition to providing information about underlying strain distributions, even from complex diffraction patterns with irregularly shaped peaks.

Exploring electronic and optical properties of MoSeS/WSeS heterojunction under mechanical strain and electric field

Exploring electronic and optical properties of MoSeS/WSeS heterojunction under mechanical strain and electric field

Deciphering respiratory viral infections by harnessing organ-on-chip technology to explore the gut-lung axis.

The lung microbiome has recently gained attention for potentially affecting respiratory viral infections, including influenza A virus, respiratory syncytial virus (RSV) and SARS-CoV-2. We will discuss the complexities of the lung microenvironment in the context of viral infections and the use of organ-on-chip (OoC) models in replicating the respiratory tract milieu to aid in understanding the role of temporary microbial colonization. Leveraging the innovative capabilities of OoC, particularly through integrating gut and lung models, opens new avenues to understand the mechanisms linking inter-organ crosstalk and respiratory infections. We will discuss technical aspects of OoC lung models, ranging from the selection of cell substrates for extracellular matrix mimicry, mechanical strain, breathing mechanisms and air-liquid interface to the integration of immune cells and use of microscopy tools for algorithm-based image analysis and systems biology to study viral infection in vitro. OoC offers exciting new options to study viral infections across host species and to investigate human cellular physiology at a personalized level. This review bridges the gap between complex biological phenomena and the technical prowess of OoC models, providing a comprehensive roadmap for researchers in the field.

Probing the interplay among elevated-temperature mechanical properties, microstructural evolution, and dynamic strain aging in reduced activation ferritic/martensitic steels

Probing the interplay among elevated-temperature mechanical properties, microstructural evolution, and dynamic strain aging in reduced activation ferritic/martensitic steels

EVALUATION OF VISUAL ACUITY IN WORKERS OF TEXTILE INDUSTRY

Background: Workers in the textile industry are exposed to occupational hazards that can adversely affect visual functions. Prolonged exposure to bright light, mechanical strain, and hazardous chemicals may contribute to visual impairments, including refractive errors, glare sensitivity, and ocular injuries. Limited research has comprehensively assessed multiple visual functions among textile workers, particularly in Pakistan. This study aims to evaluate visual acuity, contrast sensitivity, glare sensitivity, color vision, and visual field integrity in textile industry workers, identifying potential occupational risks affecting their ocular health. Objective: To assess visual functions and determine the magnitude of work-related visual problems among textile industry workers in Lahore. Methods: A cross-sectional survey was conducted among 93 textile workers aged 15–45 years. Visual acuity was measured using the LogMAR chart, color vision using Ishihara plates, visual field by confrontation testing, contrast sensitivity using Lea number plates, and glare sensitivity by targeted light exposure. Participants provided informed consent before data collection, and a structured questionnaire recorded demographic details, ocular complaints, and work-related risk factors. Data were analyzed using SPSS 20.0, applying descriptive statistics and comparative analyses where appropriate. Results: Among 93 participants, 10% were male and 90% female. Normal visual acuity was recorded in 56 (61%) workers, while myopia was found in 43 (46.2%). Glare sensitivity was detected in 22 (24%), contrast sensitivity was deficient in 14 (15.2%), and color vision deficiency was observed in 4 (4.3%). Bright light exposure was reported by 88 (94.6%) workers. Five (5.4%) workers had vision-threatening ocular diseases, including cataract (3.2%) and diabetic retinopathy (2.2%). Protective devices were provided to all workers, contributing to a lower rate of ocular injuries. Conclusion: This study highlights that textile workers are at significant risk of refractive errors, with myopia being the most prevalent. While color vision and contrast sensitivity impairments were less frequent, glare sensitivity was notable. Cataract and diabetic retinopathy were detected in older workers. Protective eyewear contributed to a reduced incidence of ocular injuries, underscoring the importance of workplace safety measures and routine ophthalmic screening.

Impaired MC3T3-E1 osteoblast differentiation triggered by oncogenic HRAS is rescued by the farnesyltransferase inhibitor Tipifarnib

HRAS is a ubiquitously expressed protein and functions as a central regulator of cellular homeostasis. In somatic cells, mutations in this gene cause cancer, while germline mutations trigger a developmental disorder known as Costello syndrome (CS). Among numerous pathologies, adult CS patients develop osteoporosis. Previous studies revealed that HRAS is implicated in bone homeostasis by controlling osteoblast differentiation, adaptation to mechanical strain and repression of RANKL expression in mature osteoblasts, and by regulating osteoclast differentiation. However, the impact of HRAS on osteoblast differentiation is still debatable. In this study, we created stable doxycycline inducible cell lines overexpressing HRAS G12 mutants in MC3T3-E1 preosteoblast cell line and analyzed their impact on osteoblast differentiation. We demonstrated an inhibitory role of HRAS G12S and HRAS G12V mutants on osteogenic differentiation and identified an increased expression of Opn in an HRAS-dependent manner, which directly correlated with impaired osteogenesis, and was rescued by the farnesyl transferase inhibitor Tipifarnib. At the molecular level, Tipifarnib was not able to block HRAS activation, but impaired HRAS localization to the plasma membrane, and inhibited MAPK activation and Opn expression. Thus, HRAS abundance/activation and its potential crosstalk with OPN may be more critical for osteogenic differentiation than previously assumed.

Mechanical model for a full fusion tokamak enabled by supercomputing

Abstract Determining stress and strain in a component of a fusion power plant involves defining boundary conditions for the mechanical equilibrium equations, which implies the availability of a full reactor model for defining those conditions. To address this fundamental challenge of reactor design, a finite element method model for the Mega-Ampere Spherical Tokamak Upgrade fusion tokamak, operating at the Culham Campus of UKAEA, has been developed and applied to assess mechanical deformations, strain, and stress in the full tokamak structure, taken as a proxy for a fusion power plant. The model, handling 127 million finite elements using about 800 processors in parallel, illustrates the level of fidelity of structural simulations of a complex nuclear device made possible by the modern supercomputing systems. The model predicts gravitational and atmospheric pressure-induced deformations in broad agreement with observations, and enables computing the spectrum of acoustic vibrations of a tokamak, arising from mechanical disturbances like an earthquake or a plasma disruption. We introduce the notion of the density of stress to characterise the distribution of stress in the entire tokamak structure, and to predict the magnitude and locations of stress concentrations. The model enables defining computational requirements for simulating a whole operating fusion power plant, and provides a digital foundation for the assessment of reactor performance as well as for specifying the relevant materials testing programme.

Strain Engineering of Magnetic Anisotropy in the Kagome Magnet Fe3Sn2.

The ability to control magnetism with strain offers innovative pathways for the modulation of magnetic domain configurations and for the manipulation of magnetic states in materials on the nanoscale. Although the effect of strain on magnetic domains has been recognized since the early work of C. Kittel, detailed local observations have been elusive. Here, we use mechanical strain to achieve reversible control of magnetic textures in a kagome-type Fe3Sn2 ferromagnet without the use of an external electric current or magnetic field in situ in a transmission electron microscope at room temperature. We use Fresnel defocus imaging, off-axis electron holography and micromagnetic simulations to show that tensile strain modifies the structures of dipolar skyrmions and switches the magnetization between out-of-plane and in-plane configurations. We also present quantitative measurements of magnetic domain wall structures and their transformations as a function of strain. Our results demonstrate the fundamental importance of anisotropy effects and their interplay with magnetoelastic and magnetocrystalline energies, providing opportunities for the development of strain-controlled devices for spintronic applications.

Investigations on mechanical and stress strain characteristics of geopolymer concrete reinforced with glass fibers

Geopolymer concrete (GPC) is an eco-friendly alternative to traditional cement concrete and has sparked widespread interest due to its potential to reduce CO2 emissions. However, its mechanical performance, notably stress–strain behaviour for plain concrete and fiber reinforced concrete, has been a significant topic for development over the last few decades. This study examines the mechanical and stress–strain parameters of geopolymer concrete reinforced with alkali-resistant glass fibers with varying aspect ratios (444, 963) and volume fractions (0%, 0.1%, 0.2%, 0.3% and 0.4% by vol. of concrete). A series of experimental tests were conducted on geopolymer concrete viz. split tensile strength, compressive strength, flexural strength, and stress vs strain behavior of GPC. To examine the influence of fibers, binder content, aggregate proportions, and alkaline activator solution dosage were all kept constant. The obtained results indicate that the addition of alkali resistant glass fibers improved the mechanical strengths significantly, with optimal performance at 0.3% of fiber volume. The stress vs strain curves of fiber-reinforced specimens revealed enhanced ductility. An equation was proposed to generate the stress vs strain curve. The Response Surface Methodology technique was applied to investigate the effect of fiber length and fiber volume on fresh and mechanical characteristics of geopolymer concrete.

Depth and Strain-Dependent Structural Responses of Mouse Lens Fiber Cells During Whole Lens Shape Changes.

To study the relationship between whole lens shape changes and fiber cell responses to externally applied loads. Freshly dissected mouse lenses were compressed by applying glass coverslips to the lens anterior, followed by fixation to preserve lens shape, and preparation for scanning electron microscopy (SEM). SEM images were collected from the outer cortex to the nucleus, and fiber cell end-to-end curvature and membrane paddle dimensions were measured using ImageJ. At 23% and 29% axial strain, cortical fiber bundle curvature increased significantly compared to control uncompressed lenses, whereas nuclear fiber bundle curvature was unaffected. Outer cortical fiber cell membrane paddles and protrusions were dramatically distorted in a radial direction, with loss of paddle-associated small protrusions in compressed lenses compared to controls, but nuclear fiber cell morphologies were unchanged. The compression-induced increases in cortical fiber cell curvature and distortion of membrane paddles were reversible, with fiber cell morphologies returning to those of control lenses after the release of load. Whole lens shape changes due to an increase in axial strain result in increased fiber cell curvature and distorted membrane morphologies in cortical but not nuclear fiber cells, indicating that mechanical strain dissipates with depth. The recovery of normal cortical fiber cell curvature and membrane morphologies after the removal of load and lens rounding back to its original shape suggests elastic properties of the young and mature fiber cells and their membrane paddles.

Ultrathin carbon biphenylene network as an anisotropic thermoelectric material with high temperature stability under mechanical strain

Ultrathin carbon biphenylene network as an anisotropic thermoelectric material with high temperature stability under mechanical strain

Investigating the effect of perforation geometry on the residual stress and mechanical behavior of 3D-printed honeycomb structure

PurposeIn this research, experimental and numerical methods were used to study the effect of pore geometry on residual stress and mechanical behavior of 3D-printed parts. In this regard, samples with circular, rhombic and hexagonal pore geometries were printed using fused deposition modeling (FDM), and their residual stress was measured through the mechanical strain release method. The finite-element method (FEM) was utilized to study the strength and natural frequency of the samples.Design/methodology/approachAs a modern method of part manufacturing and repair, 3D printing has been highly regarded in industrial arenas for its ability to offer high precision without the need for different dies. Porosity has been studied as a solution for reducing weight in structures, and its effect on the mechanical behavior of a structure depends on the loading conditions and applications.FindingsThe results of the investigation showed that the rhombic pore geometry had the highest residual stress, while the sample with circular pores exhibited the lowest residual stress. Stress distribution and modal analyses indicated that the sample with rhombic pore geometry had the lowest displacement coupled with the highest strength and natural frequency. However, considering the total of external load-induced stress and residual stresses, the sample with hexagonal pore geometry outperformed the other samples and showed the longest fatigue life.Originality/valueAccording to the literature review, residual stress is one of the key factors influencing the performance of 3D-printed parts. However, the effects of pore geometry on residual stress and structural strength in 3D-printed components remain underexplored. Therefore, this study investigates the impact of hexagonal, rhombic and circular pore geometries on residual stress and structural strength through both experimental and numerical analyses.

Cyclic mechanical loading of photopolymerized methacrylated hydrogels for probing interdependent effects of strain, stiffness, and substrate composition in pulmonary fibrogenesis

Pulmonary fibrosis is characterized by excessive deposition of extracellular matrix (ECM), stiffening of the lung tissue, and impaired gas exchange. Our current understanding of fibrogenesis generally focuses on the individual roles of mechanical and biochemical stimuli in driving disease progression. However, many mechano-chemical pathways are interrelated, so dissecting the interactive effects of mechanical and biochemical signals is an important knowledge gap. To address this gap, we investigated lung fibroblast behavior on static and cyclically strained photopolymerizable hydrogels consisting of different ratios of methacrylated gelatin, methacrylated hyaluronan, and non-methacrylated gelatin to create substrates with tunable stiffness and chemistry, representative of both healthy and fibrotic lung ECM properties. We observed that higher stiffness gels amplified the impact of strain, resulting in distinct differences in expression of MMP1, CTGF, Rho/ROCK, and ECM deposition genes. Substrates with hyaluronan demonstrated a capacity to modulate strain-induced fibrogenic responses, suggesting a buffering effect of hyaluronan on fibrotic disease progression. Overall, our results highlight mechanotransductive changes in gene expression in response to substrate composition, stiffness, and cyclic mechanical strain. Through the controlled study of mechanical and biochemical cues, our findings contribute to a deeper understanding of the pathogenesis of pulmonary fibrosis.

Electromechanical hysteresis and relaxation processes in relaxor piezoceramics

This paper studies the relaxation processes and electromechanical hysteresis in relaxor piezoceramics based on the PZT system. Measurements and analysis of the electric displacement and mechanical strain hysteresis loops recorded in bipolar AC electric fields in the frequency range 0.001–5[Formula: see text]Hz were performed by means of the electromechanical response characterization system (STEPHV) and program (STEP). It was found that the coercive field, remnant and saturation electric displacement, area of hysteresis loops and relative mechanical strain values are strongly dependent on frequency. As a result of this study, complete sets of parameters characterizing the switching and ferroelectric hysteresis processes in relaxor piezoceramics were obtained.

High‐Performance Stretchable Gallium Battery for Wearable Electronics, Through Synthesis of Foam Electrodes

The demand for sustainable and stretchable thin‐film printed batteries for bioelectronics, wearables, and e‐textiles is rapidly increasing. Recently, we developed a fully 3D‐printed soft‐matter thin‐film Ga‐Ag2O battery with 3R characteristics: resilient to mechanical strain, repairable after damage, and recyclable. This battery achieved a record‐breaking areal capacity of 26.37 mAh cm−2, increasing to 30.32 mAh cm−2 after 10 cycles under 100% strain. This performance stems from the synergistic effects of gallium's liquid metal properties and the styrene‐isoprene‐styrene polymer in the anode. Gallium's high specific capacity (1153.2 mAh g−1), deformability, and self‐healing abilities, supported by its supercooled liquid phase, significantly enhance the battery's resilience and efficiency. However, the cathode's lower theoretical capacity, due to Ag2O (231.31 mAh g−1), remains a limitation. Traditional Ag2O‐carbon black‐styrene‐isoprene‐styrene cathodes experience rapid capacity decay as only the surface area of the active materials interacts with the electrolyte. To overcome this, we designed a carbon‐filled Ag2O foam electrode using a sacrificial sugar template, increasing the effective surface area. This optimization enhanced ion‐exchange efficiency, specific capacity, and cyclability, achieving a specific capacity of 221.16 mAh g−1. Consequently, the Ga‐Ag2O stretchable battery attained a record areal capacity of 40.91 mAh cm−2—double that of nonfoam electrodes—and exhibited fivefold improved charge–discharge cycles. Using ultrastretchable Ag‐EGaIn‐styrene‐isoprene‐styrene and carbon black‐styrene‐isoprene‐styrene current collectors, the battery's specific capacity increased by 33% under 50% strain. Integrated into a soft‐matter smart wristband for temperature monitoring, the battery demonstrated its promise for wearable electronics.

Mechanical strain focusing at topological defect sites in regenerating Hydra.

The formation of a new head during Hydra regeneration involves the establishment of a head organizer that functions as a signaling center and contains an aster-shaped topological defect in the organization of the supracellular actomyosin fibers. Here, we show that the future head region in regenerating tissue fragments undergoes multiple instances of extensive stretching and rupture events from the onset of regeneration. These recurring localized tissue deformations arise due to transient contractions of the supracellular ectodermal actomyosin fibers that focus mechanical strain at defect sites. We further show that stabilization of aster-shaped defects is disrupted by perturbations of the Wnt signaling pathway. We propose a closed-loop feedback mechanism promoting head organizer formation, and develop a biophysical model of regenerating Hydra tissues that incorporates a morphogen source activated by mechanical strain and an alignment interaction directing fibers along morphogen gradients. We suggest that this positive-feedback loop leads to mechanical strain focusing at defect sites, enhancing local morphogen production and promoting robust organizer formation.

Scalable Manufacturing of Low-Symmetry Plasmonic Nanospindle Arrays with Tunable Surface Lattice Resonance.

Geometry-dependent plasmonic surface lattice resonances (SLRs) have garnered great interest across a range of applications, including nanolasers, sensors, photocatalysis, and nonlinear optics. However, the rational fabrication of high-quality, low-symmetry, plasmonic nanoparticle arrays over large areas remains challenging. Herein, we report a versatile strategy for the scalable fabrication of centimeter-scale plasmonic nanospindle (NS) arrays with high positional and orientational precision. Our approach combines solvent-assisted soft lithography with in situ reduction of metal precursors, enabling the cost-effective production of large-area and well-ordered NS arrays without the need of specialized equipment. The Au NS arrays exhibit superior SLRs with a ultranarrow line width of 3.9 nm and a quality factor (Q-factor) of 309. The aspect ratio and lattice geometry of the NSs can be precisely tuned by applying mechanical strain to the stretchable elastomeric template, thus, allowing us to customize the SLR performance across the near-infrared spectrum. This technique enables the precise engineering of anisotropic nanoparticle arrays in a standard chemistry laboratory, opening new possibilities for advanced plasmonic devices.

Responsive Photonic Filaments from Confined Self-Assembly of Cellulose Nanocrystals.

Cellulose nanocrystals (CNCs) hold transformative potential for sustainable photonics, particularly in applications such as polarization-selective devices and chiroptical sensors. However, conventional CNC derivatives are primarily limited to dense flat films, restricting their functionalization in soft fibers and wearable textiles. Advancing CNCs into infinitely extending cylindrical filaments presents an opportunity to unlock fascinating applications, yet this transformation is often hindered by the Plateau-Rayleigh instability, leading to the breakup of CNC suspensions into droplets. Here, we propose an innovation strategy for the continuous and scalable production of chiral photonic filaments by confining the photo-cross-linking of CNC/poly(ethylene glycol) diacrylate precursors within cylindrical microtubules. The resulting filaments, driven by both shear flow and chiral self-assembly, exhibit a high degree of orientation along their central axis while preserving the nanohierarchical structure of the uniaxial nematic phase. Notably, these filaments achieve an orientation order parameter of 0.91, coupled with exceptional mechanical performances (14 MJ·m-3), as well as dynamic interference color-change capabilities in response to variations in hygroscopicity or applied mechanical strain. We present a proof-of-concept for optical fabrics using these photonic filaments, which supports the development of smart textiles and fashionable clothing, thereby significantly enriching the diversity and design possibilities of CNC-based materials.

Numerical Homogenization Method Applied to Evaluate Effective Converse Flexoelectric Coefficients

This paper presents a numerical homogenization method for estimating the effective converse flexoelectric coefficients. A 2D model made of two-phase composite is developed at the microscale in consideration of a representative volume element that includes a continuous flexoelectric fiber embedded in a pure elastic matrix. In the implementation, the constitutive equations are derived from the electromechanical enthalpy accounting for higher-order coupling terms. Electric boundary conditions associated with an inhomogeneous electric field are imposed, allowing the approximation of the generated mechanical strains and stresses. Accordingly, the numerical simulations yield the overall equivalent converse flexoelectricity tensor for the longitudinal, transversal, and shear couplings. The results showed that the composite undergoes an obvious straining, which creates actuation due to the converse effect. The components of the homogenized longitudinal and transverse coefficients were found to be dependent on the volume fraction and elastic properties of the constituents.