Elastic Behavior Research Articles

Computational investigation of the phase stability, electronic, optical, phonon spectrum, and elastic behavior of layered perovskites Ca2XO4 (X = Zr, Hf) for optoelectronic applications.

A significant class of solid-state materials, Ruddlesden-Popper (RP) perovskites are well-known for their rich chemical compositions that make them excellent electrocatalysts. Therefore, in this work, we conduct thorough analysis of RP perovskites, specifically Ca2XO4 (X = Zr, Hf). We delve into the structural, electronic, optical, and mechanical properties presenting their insights for the first time. Our investigations reveal that Ca2XO4 (X = Zr, Hf) exhibits stable tetragonal phase structures, with energies (E0) of - 10,522.93eV and - 33,520.14eV, respectively. The calculated in terms of the ground state determines to possess distinct values such as - 4.79 eV/atom for LiScTe2 and - 3.95 eV/atom for Ca2ZrO4 and Ca2HfO4. Notably, the semiconductor characteristics of Ca2ZrO4 and Ca2HfO4 are underscored by their respective wide direct band gap of 5.02eV and 5.30eV. Then, we discuss the optical parameters encompassing the dielectric function, absorption coefficient, optical conductivity, refractive index, and energy loss function. is described as ductile, whereas is defined as brittle. Our outcomes underscore remarkable ability of these materials to absorb ultraviolet radiation from the electromagnetic spectrum, positioning them as promising candidates for optoelectronic applications. We made these calculations by employing first-principles approach rooted in density functional theory (DFT) and utilizing the Perdew-Burke-Ernzerhof-Generalized Gradient Approximation (PBE-GGA) and Tran and Blaha-modified Becke-Johnson (TB-mBJ) functional within the WEIN2K framework. In this framework, Kramers-Kronig relations are used to obtain crucial optical parameters. Mechanical behavior is assessed by employing Voigt-Reuss-Hill approximation (VRH) fulfilling the Born's criteria which emphasizes that these materials are equally appropriate for a broad range of mechanical applications.

Static and dynamic responses of point-fixing laminated glass plates under out-of-plane loading

In canopy and façade panel applications where glass elements are utilized, support is typically provided through small point-fixed steel hinges, which can enhance transparency but introduce notable structural challenges. To ensure structural integrity over time, the design of these systems must be supported by experimental evidence or its response monitored during its lifetime. A common approach involves continuous structural monitoring via accelerometers, which theoretically enables the detection of stiffness variations, indicative of potential damage, within the monitored components.The paper examines the static and dynamic responses of point-fixed, two-ply laminated glass panels, both heat-strengthened and thermally toughened (tempered), to assess their elastic and post-breakage behavior. Experimental data are compared directly with results from numerical simulations. The findings demonstrate that: (i) conventional monitoring systems for damage detection in glass panels are effective only with thermally toughened glass; (ii) point-fixed boundary conditions represent the most structurally disadvantageous support configuration; (iii) simplified numerical models offer a preliminary but informative framework for understanding the post-breakage response of glass panels.

Interfacial structure modification and enhanced emulsification stability of microalgae protein through interaction with anionic polysaccharides

Microalgae protein (MP) have emerged as a focal point of research within food processing due to its nutritional value and foaming properties. However, its isoelectric point around pH 4 leads to it susceptible to collision, binding, and precipitation. Additionally, MP has poor emulsification properties and only shows stability under strongly alkaline conditions. This study investigated the effects of food-grade anionic polysaccharides (guar gum (GG), gum arabic (GA), low acyl gellan gum (LG), and pectin (PT)) on the molecular structure and emulsification properties of MP. Results indicated that these anionic polysaccharides enhanced the UV absorption of MP near 620 nm, especially at 14 % content, while fluorescence intensity decreased due to amino acid residues masking without structural changes. The addition of polysaccharides resulted in bimodal or multimodal particle size distributions, with LG and PT showing larger particle sizes. At pH 4, negatively charged polysaccharides formed stable complexes with near-neutral MP, improving solution stability via electrostatic repulsion and diminishing turbidity. The droplet distribution analysis indicated that higher anionic polysaccharide ratios (1:4, 1:2, and 1:1) correlated with smaller droplet sizes and increased emulsion stability. Zeta-potential measurements revealed negative charges for emulsions, with LG-MP and PT-MP complexes displaying higher absolute values (15.0 to 20.7 mV) compared to GG-MP and GA-MP complexes, indicating superior stability. Storage stability analysis showed that LG-MP and PT-MP complexes stabilized emulsions had minimal delamination over two weeks. Rheological assessments showed that increasing GG and GA contents from 14 % to 50 % had negligible effects on apparent viscosity, while LG-MP (1:1) complexes stabilized emulsion displayed higher viscosity compared to PT-MP emulsions. Frequency sweep results showed that GG-MP, GA-MP, and LG-MP emulsions had greater elastic moduli (G') than viscous moduli (G"), indicating elastic behavior, whereas PT-MP emulsions transitioned from liquid-like to solid-like behavior as frequency increased. This study illustrates the advantages of high LG and PT content in preventing particle aggregation and enhancing emulsion stability, providing a theoretical and practical foundation for MP applications in food processing.

The capacity curve framework of EN 1993-1-6 (2025): Cylindrical shells under uniform meridional compression vs uniform bending

The capacity curve framework of the Eurocode EN 1993-1-6 on the strength and stability of metal shells offers a standardised algebraic relationship between the dimensionless buckling strength and the dimensionless slenderness of a shell. It is the basis of the buckling resistance assessment when used in conjunction with algebraic stress design, reference resistance design or the semi-computational LBA-MNA design. The capacity curve for a cylinder under uniform meridional compression has long been treated as the most conservative by default, recommended when no other curve can be justified. However, the most recent EN 1993-1-6, likely to be published in 2025, cautions that the most conservative choice for systems of intermediate slenderness may in fact be the curve for uniform bending. As this has come as a surprise to some in the community, this paper intends to justify the rationale behind this codified recommendation through a quantitative comparison of both systems’ computed capacity curves.This paper illustrates that the historical perception of uniform meridional compression as the ‘most conservative’ cylindrical shell system is based solely on its more severe imperfection-sensitive elastic buckling behaviour at high slendernesses. However, at intermediate slendernesses it is the uniform bending system that exhibits a more conservative dimensionless capacity curve, owing to the mechanics of local buckling under only partial plastification of the circumference. This, as well as other interesting properties of computationally generated capacity curves, is discussed in detail herein. This paper is intended to act as a background document to the recently evolved EN 1993-1-6 and will be of significant interest to practitioners and researchers aiming to apply this new state-of-the-art Eurocode to buckling assessments.

Evaluating the dynamic response and phase angle behavior of SBS-modified asphalt mixtures for enhanced pavement performance

Bitumen exhibits viscoelastic properties, showcasing both viscous and elastic behaviors, which are characterized by the phase angle and dynamic modulus. Issues like early fatigue fractures, rutting, and permanent deformations in bituminous asphalt pavements arise due to moisture susceptibility, high-temperature deformation, low-temperature cracking, and overloading. These distresses result in potholes, alligator cracks, and specific deformations that lead to early pavement failure, increasing rehabilitation and maintenance costs. To address these issues, this study examines the dynamic modulus and phase angle behavior of Styrene Butadiene Styrene (SBS) modified and unmodified asphalt mixtures. SBS was incorporated in various proportions, ranging from 2 to 7% by the weight of bitumen. The asphalt mixture performance tester (AMPT) was utilized to measure the dynamic modulus at temperatures of 4.4, 21.1, 37.8, and 54.4 °C, and frequencies of 0.1, 0.5, 1, 5, 10, and 25 Hz. The study found significant correlations between dynamic modulus, temperature, loading frequency, and SBS content. Additionally, Multi Expression Programming (MEPX) and regression modeling were employed to estimate the dynamic modulus of SBS-modified HMA. Results indicated that increasing SBS content up to 7% decreased penetration and ductility values by up to 46% and 56%, respectively, while raising the softening point by 63% due to increased stiffness. The blend with 6% SBS by weight of bitumen exhibited superior performance compared to other mixtures. Phase angle initially increased with rising temperature, peaking at 37.8 °C at lower frequencies, and continued to increase at higher frequencies. Isothermal and isochronal plots showed that the 0% SBS mix had a higher phase angle due to increased bitumen content. Overall, the HMA mix with 6% SBS provided the best outcomes.

Study on band-gap characteristics and formation mechanism of four-ligament chiral elastic metamaterials

Abstract Chiral elastic metamaterials, owing to their exceptional properties distinct from conventional materials and their superior mechanical performance, exhibit significant potential for applications in vibration reduction, noise suppression, energy absorption, and cushioning. To address the challenge of low-frequency vibration control, this paper proposes a dual-component chiral elastic metamaterial structure with four ligament elements. The study explores the bandgap characteristics and elastic wave propagation behavior of this structure within the 1000 Hz frequency range. By analyzing the vibration modes of the unit cell and calculating the group and phase velocities of elastic waves, the physical mechanism underlying bandgap formation is elucidated. The results demonstrate that the proposed four-ligament chiral elastic metamaterial exhibits excellent bandgap properties, with the bandgap covering more than 80.4% of the frequency range below 1000 Hz. This highlights its capability for low-frequency elastic wave control and offers a theoretical reference for the design of novel vibration reduction and noise suppression structures, as well as for low-frequency elastic wave regulation.

Model reconstruction method of irregular columnar jointed rock masses and corresponding elastic parameter analysis

A local Lloyd iteration-based Voronoi tessellation (LLI-VT) algorithm is proposed to reconstruct models of columnar jointed rock masses (CJRMs) according to their geometrical characteristics. Uniaxial compression numerical analysis was performed on specimens to analyze the effects of specimen size, joint density, irregularity, and joint dip angle on the elastic modulus and Poisson’s ratio of the CJRM. The results show that the LLI-VT algorithm generates models with good control over column size and distortion, which align more closely with natural CJRMs. For research on elastic behavior, an RVE size of at least 2 m is sufficient. As the joint density increases, the elastic modulus decreases at a decreasing rate, while Poisson’s ratio shows the opposite linear trend. With increasing irregularity, the elastic modulus increases at a decreasing rate, and Poisson’s ratios exhibit opposite nonlinear patterns. The joint dip angle is the most important factor affecting elastic parameters. The effects of joint density and irregularity on elastic parameters are different for different joint dip angles. Finally, a method for estimating the elastic parameters of CJRMs is discussed and proven effective. This approach is important for accurately simulating and predicting the mechanical behavior of CJRMs in engineering.

Theoretical investigation of structural, elastic, mechanical, thermodynamic, electronic, and half-metallic ferromagnetic behavior of quaternary Ti2Fe-based full-Heusler alloys Ti2FeGe1-xSnx (x = 0, 0.25, 0.5, 0.75, and 1) for spintronic applications: DFT computation

Theoretical investigation of structural, elastic, mechanical, thermodynamic, electronic, and half-metallic ferromagnetic behavior of quaternary Ti2Fe-based full-Heusler alloys Ti2FeGe1-xSnx (x = 0, 0.25, 0.5, 0.75, and 1) for spintronic applications: DFT computation

A slope-based J-integral approach and advanced image processing for assessment of the cyclic fatigue delamination behavior of adhesive joints

A fatigue fracture mechanics methodology was developed and established, employing a slope-based J-integral approach combined with advanced image processing techniques. Adhesively bonded double cantilever beam (DCB) specimens were tested under constant displacement amplitude loading. The beam rotation was tracked by affixing a repetitive pattern on the DCB specimens and capturing images at the maximum displacement amplitude. Using a custom-developed image processing procedure, the beam rotation was deduced. To validate the methodology, DCB fatigue experiments were conducted at 23, 60 and 75 °C on aluminum adherends bonded with a structural 2-K epoxy adhesive. The J-based approach was compared with a conventional, compliance-based linear elastic fracture mechanics (LEFM) method. The epoxy was a rather brittle, high-modulus adhesive with a bond line thickness of 0.25 mm, resulting in predominantly linear elastic material behavior. By analyzing the images taken during fatigue testing, a stiffening effect of the steel load blocks was observed. Excluding pattern elements directly below the load block yielded the best agreement between J-integral and LEFM data. Both approaches were in excellent agreement within the investigated temperature range. The investigated adhesive exhibited a highly temperature-dependent behavior, which was associated with higher crack propagation rates and a lower fatigue threshold at 60 and 75 °C.

Elastic local buckling of double-skinned UHPC composite plates considering interfacial shear slip

This study explores the elastic local buckling behavior of double-skinned ultra-high-performance concrete (DS-UHPC) composite plates, focusing on the effects of interfacial shear slip. A theoretical model, based on the first-order shear deformation theory for sandwich plates, was developed to predict the elastic local buckling behavior of these composite plates. An analytical solution for the elastic buckling coefficient under uniform compression with a simply supported boundary condition was derived. The results reveal that interfacial shear stiffness and the proportion of cross-sectional steel content significantly affect the elastic buckling coefficient. Specifically, lower interfacial shear stiffness and higher steel content proportion result in a decreased buckling coefficient, while increasing interfacial shear stiffness reduces the sensitivity of the buckling coefficient to variations in steel content proportion. Finite element models were established and validated against previous studies on the buckling performance of single-layer steel-concrete composite plates and classical solutions of buckling coefficients without interfacial shear slip. Semi-analytical solutions for the elastic buckling coefficient under various boundary conditions were also developed through a comprehensive set of finite element results. Building on these findings, a design procedure for DS-UHPC composite plates is proposed, emphasizing the optimization of interfacial connectors to minimize shear slip effects on local buckling. This procedure ensures the prevention of local buckling in both the external steel plates and the entire composite plate, thereby enhancing structural stability.

Effect of NaCl concentration on the interfacial and foaming properties of wheat aqueous phase protein

In this study, the structure, foaming properties, and air-water interfacial behavior of wheat aqueous phase protein (WAP) with different NaCl concentrations were investigated. With the addition of NaCl, the particle size and the β-sheet content increased, indicating the formation of larger aggregates. In the FT-IR spectrum NaCl also increased the peak intensity for WAP, this peak often associated with C-O and C-N stretching vibrations, indicating that NaCl may induce conformational changes, such as protein unfolding. As NaCl concentration increased, the foam capacity of WAP increased from 106.25 ± 1.41% to 142.38 ± 15.73%, while native WAP exhibited higher foam stability. Interfacial adsorption kinetics revealed that NaCl favored WAP adsorption at the air-water interface. The interfacial viscoelasticity modulus of all samples increased over time, forming an interfacial layer primarily characterized by elastic behavior. Native WAP exhibited a stronger viscoelasticity modulus, forming a stable adsorption layer at the air-water interface, which contributed to enhanced foam stability. This study provides valuable insights into the regulation of WAP structure and foaming properties by salt ions, which may offer a new strategy for improving the interfacial properties of wheat-based food products.

Preparation and characterization of sago/iota-carrageenan microgels as food thickener in texture modified food

An increasing number of older populations with swallowing difficulties need specialized diets with easy-to-chew and safe swallowing characteristics. Texture modification using a thickener is usually used to obtain the desired texture, which helps in lowering the risk of aspiration. Microgels usage to modify the texture and rheology of liquid and pureed foods has been an area of interest in the food industry for many years. Therefore, this study aimed to produce sago starch and ι-carrageenan based microgels with functionality as food thickeners. Different concentrations of ι-carrageenan (25%, 50% and 75%) were added into sago starch dispersion and then fabricated using ultrasound treatment followed by spray drying process. A commercial dysphagia thickener that is normally used at medical institutions and nursing homes was also included as a reference. Microgels with increasing ι-carrageenan concentration showed variation in behaviours during rheological and textural measurements. Rheological tests revealed that sago/ι-carrageenan microgels exhibited a predominant elastic behaviour, with G′>G″ within the frequency range. Texture profile analysis (TPA) suggested that the sample with 2.0 g of sago starch and 2.0 g ι-carrageenan, MS50, produced samples with similar hardness, springiness, and cohesiveness to the reference sample. Overall, sago/ι-carrageenan microgels have shown a potential to be used as an alternative thickener as it provides low adhesiveness and more elastic behaviour which is considered safe-to-swallow food, especially for elderly with swallowing difficulties.

Skin‐Like Soft Thermoelectric Composites with a “J‐Shaped” Stress–Strain Behavior for Self‐Powered Strain Sensing

AbstractPolymer thermoelectric (TE) materials present a promising alternative to actuating low‐power wearable electronics without an additional power source, among which poly(3,4‐ethylenedioxythiophene) (PEDOT):poly(styrenesulfonate) (PSS) is a promising candidate. However, it is too hard and brittle to integrate into wearables seamlessly and comfortably. Herein, PEDOT:PSS‐based TE composites with simultaneous softness and stretchability are fabricated by a water‐borne polyurethane (WPU) and PEDOT:PSS mixture containing the judiciously chosen ionic liquid (IL) and subsequent drop casting. The obtained composites show a stable TE voltage, high stretchability (>500%), ultra‐flexibility, and excellent sensitivity (gauge factor = 1251). More importantly, it exhibited “J‐shaped” stress–strain curves resembling human skins after a loading/releasing treatment. The skin‐like nonlinear elastic behavior combines enough softness in the “toe” region, high stretchability, and a strong strain hardening at the late deformation stage, enabling its seamless and comfortable integration with the human body. Given the desired mechanical performance and strain‐sensing capability, the composite is designed to serve as a self‐powered sensor with high sensitivity and accuracy, suggesting a high potential in human motion detection. This work demonstrates the versatility of the developed skin‐like PEDOT:PSS‐based composites in wearable electronics.

Ab initio calculations of second-, third-, and fourth-order partial and inner elastic constants of diamond

By means of ab initio calculations, a unified framework is presented to investigate the effect of internal displacement on the linear and nonlinear elasticity of single diamond crystals. The calculated linear and nonlinear elastic constants, internal strain tensor and internal displacement in single diamond crystals are compatible with the available experimental data and other theoretical calculations. The complete set of second-, third- and fourth-order elastic constants and internal strain tensor not only offer a better insight into the nonlinear and anisotropic elasticity behaviors, but also shows us the basic internal mechanical response of diamond. This study provides a route to calculate the nonlinear internal and external elasticity response in a nonprimitive lattice.

Free vibration and stability analyses of functionally graded plates resting on elastic foundations based on 2D and quasi-3D shear deformation theories using the finite strip method

This paper explores the elastic buckling and free vibration behavior of thick functionally graded material (FGM) plates placed on elastic foundations, using two-dimensional (2D) and quasi-three-dimensional (quasi-3D) shear deformation theories. The material properties of the FGM plates are assumed to vary continuously through the thickness based on a power-law distribution. By minimizing the total potential energy and solving the associated eigenvalue problem, the classical finite strip method is applied to determine the critical buckling loads and natural frequencies of the FGM plates. A key novelty of this work lies in the development of a quasi-3D shear deformation theory, which incorporates thickness stretching effects, providing a more accurate distribution of transverse shear strains across the plate thickness. Additionally, the FSM is utilized to efficiently discretize the in-plane geometry, offering a computationally cost-effective solution for analyzing free vibration and mechanical buckling characteristics. The elastic foundation is modeled using Winkler and two-parameter Pasternak models. The complexity of the governing equations is reduced by decomposing the transverse displacement into bending, shear, and thickness stretching components. Numerical results for FGM plates with various boundary conditions are validated by comparing them with analytical solutions from existing literature. Additionally, the effects of parameters such as plate thickness-to-length ratio, length-to-width ratio, boundary conditions, and the power-law index are analyzed and discussed.

A Visco-Elasto-Plastic Constitutive Law for Deformation Prediction of High Concrete Face Rockfill Dams

Deformation predictions in high Concrete Face Rockfill Dams tend to underestimate observed settlements due to scale effect and breakage phenomena that cannot be adequately captured by laboratory tests. This paper presents a Visco-Elasto-Perfectly Plastic (VEPP) model for predicting deformations in high Concrete Face Rockfill Dams (CFRDs) that addresses these challenges incorporating explicitly key rockfill parameters like grain size and post-compaction porosity, which influence both the non-linear elastic and plastic behaviors of rockfill. The VEPP model enables deformation prediction while using standard laboratory test results. The model’s effectiveness was demonstrated through its application to the 233 m high Shuibuya Dam, the tallest CFRD in the world. The VEPP model predictions closely align with observed deformations throughout the dam’s construction, impoundment, and early operational stages. By using physically meaningful parameters, the model reduces the uncertainty associated with the empirical assessment of model parameters using back-analysis from similar projects. While the VEPP model offers improved predictive accuracy, particularly during early design phases, further advancements could be achieved by refining the creep formulation and accounting for grain size evolution during construction. This approach has the potential to optimize the design and construction of future high CFRD construction.

Mechanical properties of hcp Fe at high pressures and temperatures from large-scale molecular dynamics simulations

We study the elastic behavior of hexagonal close-packed (hcp) Fe at the high temperature and pressure conditions of the Earth Core, using an embedded-atom method interatomic potential adjusted to those conditions. We calculate diffusivity, elastic constants, density, bulk modulus, shear modulus, and sound velocities vs temperature. We obtain reasonable agreement with ab initio simulations and with other empirical potential simulations. Our densities and shear modulus are slightly higher than those in the preliminary reference earth model for the core. Phase stability is discussed in terms of the Born criteria and free energies, finding that hcp is mechanically stable and that the free energy difference between hcp and body-centered cubic (bcc) is very small compared to the thermal energy. We compare our simulated shear modulus G to several analytical models, obtaining excellent agreement with the Atom in Jelium model by Swift and co-workers. Assuming that the yield strength Y is equal to the shear modulus G, Y=G/30, we find reasonable agreement with a recent parametrization of the Steinberg–Guinan model. These results can lead to future large-scale, multi-million simulations of Fe under core conditions for samples with microstructure like grain boundaries and twins, which might be present under those conditions.

A FEM-based model for failure initiation in the microstructure of gray cast iron under uniaxial compression

PurposeThe purpose of this study was to validate the feasibility of the proposed microstructure-based model by comparing the simulation results with experimental data. The study also aimed to investigate the relationship between the orientation of graphite flakes and the failure behavior of the material under compressive loads as well as the effect of image size on the accuracy of stress–strain behavior predictions.Design/methodology/approachThis paper presents a microstructure-based model that utilizes the finite element method (FEM) combined with representative volume elements (RVE) to simulate the hardening and failure behavior of ferrite-pearlite matrix gray cast iron under uniaxial loading conditions. The material was first analyzed using optical microscopy, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) to identify the different phases and their characteristics. High-resolution SEM images of the undeformed material microstructure were then converted into finite element meshes using OOF2 software. The Johnson–Cook (J–C) model, along with a damage model, was employed in Abaqus FEA software to estimate the elastic and elastoplastic behavior under assumed plane stress conditions.FindingsThe findings indicate that crack initiation and propagation in gray cast iron begin at the interface between graphite particles and the pearlitic matrix, with microcrack networks extending into the metal matrix, eventually coalescing to cause material failure. The ferritic phase within the material contributes some ductility, thereby delaying crack initiation.Originality/valueThis study introduces a novel approach by integrating microstructural analysis with FEM and RVE techniques to accurately model the hardening and failure behavior of gray cast iron under uniaxial loading. The incorporation of high-resolution SEM images into finite element meshes, combined with the J–C model and damage assessment in Abaqus, provides a comprehensive method for predicting material performance. This approach enhances the understanding of the microstructural influences on crack initiation and propagation, offering valuable insights for improving the design and durability of gray cast iron components.

Three dimensional thermally frictional adhesive contact problem of quasicrystals materials

It is difficult to analytically solve the contact problem of one-dimensional hexagonal quasicrystal (1DHQ) coating considering the coupling effects of adhesion, friction force and frictional heat in the contact region, especially considering both the frictional heat and adhesion simultaneously. The thermally frictional adhesive contact problem of 1DHQ coating is investigated using a discrete convolution-fast Fourier transform-based (DC-FFT-based) semi-analytical method. The adhesive behavior is described based on the Maugis-Dugdale model, which was used to investigate the influence of adhesive force on the thermoelastic field. It is a continuum-mechanics model with all microscopic features subsumed in the elastic constants, covers only elastic behavior, omitting all other physical characteristics of quasicrystals. By developing an adhesion-driven conjugate gradient method (AD-CGM), the contact process is numerically implemented, and the DC-FFT method is applied to solve the contact displacement. The numerical results indicate that the contact area under the consideration of adhesive force is much larger than that without. For a given external force, the contact radius and adhesive radius increase with increasing parameters. And each physical quantity exhibits different changing trends with the variation of adhesive parameters, with 0.5 as the dividing line. The research results may provide theoretical guidance for the practical application of quasicrystals as thermal barrier coating materials, nanodevice materials, and intelligent robot coating materials.

Macroscopic creep behavior of spheroids derived from mesenchymal stem cells under compression

Spheroid culture, where cells are aggregated three-dimensionally, is expected to have applications as a model that better recapitulates invivo environment beyond two-dimensional environments. When human mesenchymal stem cells are subjected to spheroid culture in the presence of osteogenesis supplements, the gene expression of osteocyte differentiation marker is greatly increased within a short period compared to two-dimensional culture. However, how such alterations may be reflected to mechanical properties of the spheroid remains unknown. In this study, using a uniaxial compression system, we evaluated the macroscopic mechanical properties of human mesenchymal stem cell-derived spheroids including viscoelastic behavior. The Young's modulus of spheroids cultured for 2 days was about 18 kPa, whereas that of individual cells is around 1–10 kPa. We also found that creep behavior of the spheroid was greater in 50% strain compression beyond 10 or 30% strain, indicating that they are viscoelastic materials. Upon release from compression, the spheroids tended to revert to their original shape through elastic deformation. However, spheroids in which actin filament formation was inhibited exhibited a remarkably greater plastic deformation, suggesting that the actin filaments play a crucial role in the elastic behavior of spheroids. By understanding the mechanical properties and behavior of spheroids, it provides a framework for predicting and manipulating the development of tissues and organs in the field of morphogenesis.