Bulk Modulus Research Articles

Mechanical properties and macro–micro failure mechanisms of granite under thermal treatment and inclination

The coupling effects of inclination angle (θ) and high temperature (T) on rock degradation present significant construction challenges for underground engineering projects, such as underground coal gasification, inclined mining pillars, and nuclear waste repositories. This study is built on a novel combined compression and shear test system, investigating granite’s physical and mechanical properties and macroscopic failure characteristics under varying temperatures and inclination angles. Additionally, acoustic emission technology was used to analyze the impact of inclination and temperature on the micro-failure behavior of the specimens. The experimental results indicate that as the inclination angle increases, the specimens’ peak compressive strength and elastic modulus decrease linearly. In contrast, the shear stress increases non-linearly, suggesting that additional shear stress accelerates the initiation and propagation of cracks. Furthermore, these mechanical parameters initially increase with rising temperatures before decreasing, with a temperature threshold identified at 400 °C. The effect of inclination angle on the failure mode of the specimens is more pronounced than that of temperature; as the inclination angle increases, the failure mode transitions from splitting failure to shear failure at any given temperature. Acoustic emission results reveal that the specimens’ microcrack initiation (CI) and damage (CD) thresholds reduce with increasing inclination, while the corresponding shear stress increases. As temperature rises, the CI and CD thresholds exhibit an initial increase attended by a decrease. Finally, founded on the experimental findings, a multivariate equation was established to accurately predict the peak compressive strength and elastic modulus about θ and T. The results of this study provide valuable insights and references for the construction of underground thermal engineering under complex conditions.

T700 Carbon Fiber/Epoxy Resin Composite Material Hygrothermal Aging Model

The hygrothermal aging model, based on Fick’s second law of diffusion, characterizes the degradation of engineering constants in T700 carbon fiber/epoxy resin composites. It focuses on changes in the tensile modulus, shear modulus, and transverse Poisson’s ratio due to moisture absorption and temperature variations. The model validates through mass change observations before and after seawater immersion, along with surface morphology assessments and tensile experiments. The results reveal that the saturated moisture absorption rate for single-layer laminates in seawater immersion is 0.35%. Short-term seawater immersion at room temperature (≤60 days) does not induce cracks or defects (≥10 μm) on the composite’s surface. The composite’s modulus decreases as moisture absorption increases, with the longitudinal tensile modulus dropping by an order of 10−5%, while the other engineering constants decrease by an order of 10−3%. The modulus also decreases with rising temperature; the closer the temperature is to the matrix’s glass transition, the faster the modulus declines, with the longitudinal tensile modulus decreasing by 0.84%, and the other engineering constants decreasing by 100%. This research provides valuable insights for the engineering applications of composite materials in marine environments.

Role of A-Site Cation Hydrogen Bonds in Hybrid Organic-Inorganic Perovskites: A Theoretical Insight.

Hybrid organic-inorganic halide perovskites (HOIPs) have garnered a significant amount of attention due to their exceptional photoelectric conversion efficiency. However, they still face considerable challenges in large-scale applications, primarily due to their instability. One key factor influencing this instability is the lattice softness attributed to the A-site cations. In this study, we investigated the effects of four different A-site cations (MA, FA, EA, and GA) on the lattice softness of perovskites by using a combination of ab initio molecular dynamics and first-principles calculations. Our results demonstrate that an increase in the number of hydrogen bonds for A-site cations correlates with enhanced lattice and atomic fluctuations, resulting in a reduction in the bulk modulus and an increase in the lattice softness. The strength of hydrogen bonding of the A-site cation increases the rotational energy barrier of the cation, along with the formation energy and kinetic coupling between the A-site cation and the [PbI6]4- octahedron. Consequently, this increases the lifetime of hydrogen bonding and enhances the rigidity of the perovskite lattice. Notably, we found that EA cations, which exhibit stronger hydrogen bonding with fewer total hydrogen bonds, can limit the rotation of the A-site cation, inhibit the rocking motion of the [PbI6]4- octahedron, and thereby increase the rigidity of the inherently soft perovskite lattice, ultimately enhancing the stability of the material. Our findings elucidate the effect of hydrogen bonding in A-site cations on the lattice softness of perovskites, providing valuable theoretical insights for the design of more stable HOIPs.

Effect of Hilbert Fractal Acoustic Metamaterials on Ventilation Noise Control

Abstract Ventilation noise control devices often involve a trade-off between their size and ventilating performance, which limits the ability to reduce low-frequency sound in high-ventilation conditions. To address this challenge, the present study explores the use of Hilbert fractal-based design in ventilated metamaterials for improved acoustic performance. The sound transmission loss (STL) of these metamaterials is compared to that of a simple expansion chamber, which serves as the base case. Various parameters, including Hilbert order (O), channel width (K), ventilated space (l), unit cell thickness (H), and the number of unit cells (N) are investigated. Initially, the transfer matrix method evaluates STL without considering thermoviscous effects, which are later incorporated in numerical simulations and impedance tube experiments. The parametric study reveals that increasing the Hilbert curve order decreases the fundamental frequency, while a higher K value increases it. Additionally, more unit cells enhance STL but reduce its broadband nature. Through the finite element method, band diagrams and eigenmodes of Hilbert and base configurations indicate that increased Hilbert orders result in more bands and correspondence between transmission loss spectra and band gaps. The study also identifies dipole resonance modes in the Hilbert structure, which induce a negative effective bulk modulus that contributes to STL. Real-time performance testing in a twin reverberation chamber demonstrates that the Hilbert structure achieves a 5-dB improvement in STL compared to the base configuration across the 700- to 1400-Hz range. These findings are essential for achieving broadband low-frequency noise reduction while allowing airflow.

Investigating slope stability of multiple stopes prone to instability in the Ziluoyi iron ore mining site

The ore mining sites commonly experience slope instability, which is causing concern for the workers’ safety and the operation’s stability. Considering the Ziluoyi iron ore mining site as a case study, uniaxial compression strength and shear tests are performed on the lower disk peripheral rock, ore body, and upper disk peripheral rock, leading to the extraction of compressive strength and elastic modulus (lower disk: 77.7 MPa–9.093 GPa; ore body: 19.6 MPa–4.619 GPa; upper disk: 55.47 MPa–5.573 GPa). Further, using the Hoek–Brown criterion in conjunction with the Moher–Columb criterion, the cohesion and internal friction angle of various samples are appropriately determined (lower disk: 21.124 MPa–35.614°; ore body: 21.66 MPa–26.5°; upper disk: 42.916 MPa–25.743°). By employing an appropriate rock mass reduction model, its constants (m and s) and RMR score for the consisting layers (schist layer and ore body) of the three understudy slopes (Slope#1–Slope#3) are evaluated. An effective algorithm based on the Morgenstern–Price method is employed and its effectiveness is also proved by comparing its factor of safety results with those of Geo-Slope for various slope structures subjected to different loads. Subsequently, the stability analyses of various slopes are methodically examined by predicting the factor of safety values under multiple types of loading (i.e., self-weight + groundwater, slope self-weight + groundwater + blasting vibration force, and self-weight + groundwater + seismic force). The factor of safety values of the slopes pertinent to Slope#1/Slope#2/Slope#3 subjected to the above loading conditions are obtained as 1.354/1.273/1.188, 1.326/1.239/1.169, and 1.321/1.232/1.162, respectively. Upon comparing these results with those of a valid homeland specification, it becomes clear that the results are able to meet safety standards and ensure efficient mine operation.

Improved Mesenchymal Stem Cell Viability in High-Stiffness, Translational Cartilage Matrix Hydrogels.

Scaffolds made from cartilage extracellular matrix are promising materials for articular cartilage repair, attributed to their intrinsic bioactivity that may promote chondrogenesis. While several cartilage matrix-based scaffolds have supported chondrogenesis in vitro and/or invivo, it remains a challenge to balance the biological response (e.g., chondroinductivity) with structural (e.g., robust mechanical performance, >1 MPa in compressive stiffness) and translational (e.g., ease of surgical implantation) considerations. Few studies have evaluated encapsulated cell viability within high-stiffness (>1 MPa) hydrogels. We previously fabricated one formulation of a high-stiffness (>3 MPa) pentenoate-functionalized, solubilized, devitalized cartilage (PSDVC) hydrogel that possessed an injectable, paste-like precursor for easy surgical application. In the current study, the characterization of the PSDVC material was expanded by varying the degree of functionalization (i.e., 0.45-1.09 mmol/g) and amount of crosslinker, dithiothreitol (DTT), to improve the reproducibility of the high compressive moduli and evaluate the viability of encapsulated human bone marrow-derived mesenchymal stem cells (hBMSCs) in high-stiffness cartilage matrix hydrogels. Prior to crosslinking, specific formulations functionalized with 0.80 mmol/g or less of pentenoate groups retained a paste-like precursor rheology. After crosslinking, these formulations produced hydrogels with greater than 1 MPa compressive stiffness. However, hBMSCs encapsulated in PSDVC hydrogels with lower functionalization (i.e., 0.57 mmol/g, no crosslinker) had a higher stiffness (i.e., 1.4 MPa) but the lowest viability of encapsulated hBMSCs (i.e., 5%). The middle PSDVC functionalization (i.e., 0.70 mmol/g) with DTT (i.e., 0.50 mmol thiols/g) demonstrated high cell viability (77%), high mechanical performance (1.65 MPa, 31% failure strain), and translational features (i.e., paste-like precursor, 1.5 min crosslinking time). For future evaluations of PSDVC hydrogels in cartilage repair, a middle functionalization (i.e., 0.70-0.80 mmol/g) with the addition of a crosslinker (i.e., 0.50 mmol thiols/g) had a desirable balance of high mechanical performance (i.e., >1 MPa compressive stiffness), high viability, and paste-like precursor for surgical translation.

Salvadora persica nanoparticles effect on the specific properties of a bio-composite dental material

The aim of this study is to evaluate the antibacterial activity of dental material containing nanoparticles of the extract of S. persica against Streptococcus pneumonia, Streptococcus mutans and Haemophilus influenza, and to examine their triboligical and mechanical properties. The specific properties of flowable dental material containing different percentage of the extract are investigated using the below different kinds of tests: - Antibacterial activity (including agar diffusion test), - Tribological behavior (including a pin-on-disk tribometer, surface profilometer and scanning electron microscopy (SEM)), - Mechanical behavior (including compressive strength, bending strength and bending modulus). The agar diffusion test reveals significant difference between the samples, whereas the antibacterial one demonstrates that the bacterial growth is diminished by increasing the nanoparticle content. The bending strength and the bending modulus remain unchanged by a 10% incorporation of the nanoparticles while the compressive strength increases significantly. The extract containing resins show higher wear resistance. The production of dental material with antibacterial activity, with suitable wear resistance, and particularly without any significant sacrificing effect on the mechanical properties is practically desirable in dental material science.

Theoretical exploration of structural, electronic, elastic, mechanical, and thermodynamic properties of MgCu4Sn intermetallic compound for engineering applications: first-principle calculations

The structural, electronic, elastic, mechanical, and thermodynamic properties of the ternary MgCu4Sn intermetallic compound are investigated by means of first-principle calculations within density functional theory (DFT), in combination with the quasi-harmonic Debye model. Local density approximation (LDA) and generalized gradient approximation (GGA) are made for electronic exchange–correlation potential energy. The lattice constant is in good agreement with experimental data. We determine the elastic constant tensor of the compound from the calculated stress–strain relation in both approximations. Once the elastic constants are obtained, the bulk modulus B, shear modulus G, Young’s modulus E, Poisson’s ratio ν, anisotropy factor A, and the ratio B/G for MgCu4Sn compound were deduced using Voigt-Reuss-Hill (VRH) approximation. The ground-state structure of MgCu4Sn is predicted to be thermodynamically and mechanically stable. The obtained band structure and density of states reveal metallic character of MgCu4Sn. The calculation results show also that this intermetallic crystal is a stiff, elastically anisotropic and ductile material. The Debye temperature is also determined from elastic constants. The temperature dependence of the constant volume heat capacity Cv, the entropy S, and the volumetric thermal expansion coefficient α in a quasi-harmonic approximation have been obtained from calculated energy E as a function of the volume V of a MgCu4Sn crystal and discussed for the first report.

High‐Performance PLA Foam Blocks Prepared From Beads Modified by Chain Extension and Heterogeneous Nucleation

ABSTRACTSupercritical CO₂ foaming effectively forms a uniform cellular structure in polylactic acid (PLA) beads by utilizing the high diffusion rate and solubility of CO₂ in polymers. In this study, PLA beads are modified with a chain extender (CE) composed of ethylene and glycidyl methacrylate, while thermoplastic polyurethane (TPU) serves as a heterogeneous nucleating agent. After being foamed with supercritical CO, the modified PLA beads are compression molded into foam blocks. The volume expansion ratio of PLA/TPU/CE foams increases by 12.5‐fold, and the resulting foam blocks exhibit a high compressive modulus of 21 MPa. The enhanced compressive strength results from the synergistic effects of chain extension and heterogeneous nucleation, which enhance the material's cellular structure and internal crosslinking. This study offers an effective strategy to enhance the compressive properties of PLA foam blocks, expanding their applications in high‐performance industries. In addition, the use of eco‐friendly PLA and the potential for scalable production make this approach a promising alternative for sustainable materials.

Preparation and characterization of novel PMMA bone cement containing 3,4-dichloro-5-hydroxyfuran-2(5H)-one.

Introduction: to address the issue of burst drug release in antibiotic-loaded poly(methyl methacrylate) (PMMA) bone cement (ALBC), this study involved preparation of novel PMMA bone cement and determination of its antibacterial activity, biocompatibility, compressive properties, maximum temperature, and setting time. Methods: a novel acrylic monomer, which contains the 3,4-dichloro-5-hydroxyfuran-2(5H)-one (DHF), was synthesized and utilized to develop non-leaching antibacterial PMMA bone cement (NLBC), designated as DHF-methacrylic acid (DHF-MAA) bone cement. In the preparation of this bone cement, DHF-MAA served as a key component of the liquid phase. Its antibacterial activity was determined using a surface antibacterial assay. The biocompatibility of the cement was evaluated through a rabbit-suspended erythrocyte hemolysis test, assessment of the relative proliferation rate of mouse embryonic osteoblast precursor cells (MC3T3-E1) using the CCK-8 method, and an acute toxicity test in mice. The assessment of compressive properties includes both compressive strength and compressive modulus before and after aging. Results: DHF-MAA bone cement exhibited antibacterial activity, excellent biocompatibility, and acceptable compressive properties; in particular, the 10% DHF-MAA bone cement, achieved 100% antibacterial activity, excellent biocompatibility, and a compressive strength that met the compressive value, as stated in ISO 5833. Conclusions: in this study, novel antibacterial non-leaching DHF-MAA bone cement was synthesized and evaluated for its antibacterial activity, biocompatibility, and compressive properties. In particular, the 10% DHF-MAA bone cement exhibited excellent antibacterial activity, biocompatibility, and acceptable compressive properties. As such, this cement formulation warrants further characterization with a view to using it to anchor cemented arthroplasties.

In situ swelling of low-friction, high load-bearing self-bending bilayer hydrogels inspired by articular cartilage.

The articular cartilage is characterized by its gradient hierarchical structure, which exhibits excellent lubrication and robust load-bearing properties. However, its inherent difficulty in self-repair after damage presents numerous formidable challenges for cartilage repair. Inspired by the unique structure of articular cartilage, a biomimetic bilayer hydrogel composed of PAM (polyacrylamide) and PAM/SA (sodium alginate) is prepared using a two-step in-situ swelling method. The bilayer hydrogel demonstrates exceptional structural stability due to the interlayer in-situ chemical cross-linking. Compared to monolayer hydrogels, the PAM-PAM/SA bilayer hydrogel demonstrates superior mechanical attributes, exhibiting a compressive strength of 1 MPa and a compressive modulus of 0.22 MPa. Furthermore, exploration of the tribological performance of the PAM-PAM/SA bilayer hydrogel have revealed its low-friction performance under high loads, with a coefficient of friction as low as 0.032. Finally, leveraging the differential swelling properties between the distinct layers of the PAM-PAM/SA bilayer hydrogel, a self-bending biomimetic cartilage capable of conforming to complex joint surfaces is fabricated. This highly lubricating, mechanically robust, and conformal biomimetic cartilage provides an effective means for addressing cartilage defects and joint diseases.

Compressibility of dense nuclear matter in the ρ-meson variant of the Skyrme model

We show that coupling the SU(2)-valued Skyrme field to the ρ-meson solves the long-standing issue of (in)compressibility in the solitonic Skyrme model. Even by including only one ρπ interaction term, motivated by a holographic-like reduction of Yang-Mills action by Sutcliffe, reduces the compression modulus from K0 ≃ 1080 MeV, in the massive Skyrme model, to K0 ≃ 351 MeV.

Stem cell mechanoadaptation. II. Microtubule stabilization and substrate compliance effects on cytoskeletal remodeling.

Stem cells adapt to their local mechanical environment by rearranging their cytoskeleton, which underpins the evolution of their shape and fate as well as the emergence of tissue structure and function. Here, in the second part of a two-part experimental series, we aimed to elucidate spatiotemporal cytoskeletal remodeling and resulting changes in morphology and mechanical properties of cells and their nuclei. Akin to mechanical testing of the most basic living and adapting unit of life, i.e., the cell, in situ in model tissue templates, we probed native and microtubule-stabilized (via Paclitaxel, PAX, exposure) stem cells' cytoskeletal adaptation capacity on substrates of increasing compliance (exerting local tension on cells) and with increased target seeding densities (exerting local compression on cells). On 10 and 100 kPa gels, cells seeded at 5000 cells/cm2 and cells proliferated to 15 000 cells/cm2 exhibited bulk moduli that nearly matched those of their respective substrates; hence, they exhibited a greater increase in Young's Modulus after microtubule stabilization than cells cultured on glass. Culture on compliant substrates also reduced microtubule-stabilized cells' F-actin, and microtubule concentration increases compared to cells seeded on glass. On gels, F-actin alignment decreased as more randomly oriented, short actin crosslinks were observed, representing emergent adaptation to the compliant substrate, mediated through myosin II contractility. We conclude that stem cell adaptation to compliant substrates facilitates the accommodation of larger loads from the PAX-stabilized polymerizing microtubule, which, in turn, exerts a larger effect in determining cells' capacity to stiffen and remodel the cytoskeleton. Taken as a whole, these studies establish correlations between cytoskeleton and physical and mechanical parameters of stem cells. Hence, the studies progress our understanding of the dynamic cytoskeleton as well as shape changes in cells and their nuclei, culminating in emergent tissue development and healing.

Stem cell mechanoadaptation. I. Effect of microtubule stabilization and volume changing stresses on cytoskeletal remodeling.

Here, we report on the first part of a two-part experimental series to elucidate spatiotemporal cytoskeletal remodeling, which underpins the evolution of stem cell shape and fate, and the emergence of tissue structure and function. In Part I of these studies, we first develop protocols to stabilize microtubules exogenously using paclitaxel (PAX) in a standardized model murine embryonic stem cell line (C3H/10T1/2) to maximize comparability with previously published studies. We then probe native and microtubule-stabilized stem cells' capacity to adapt to volume changing stresses effected by seeding at increasing cell densities, which emulates local compression and tissue template formation during development. Within the concentration range of 1-100 nM, microtubule-stabilized stem cells maintain viability and reduce proliferation. PAX stabilization of microtubules is associated with increased cell volume as well as flattening of the cell and nucleus. Compared to control cells, microtubule-stabilized cells exhibit thick, bundled microtubules and highly aligned, thicker and longer F-actin fibers, corresponding to an increase in the Young's modulus of the cell. Both F-actin and microtubule concentration increase with increasing PAX concentration, whereby the increase in F-actin is more prominent in the basal region of the cell. The corresponding increase in microtubule is observed more globally across the apical and basal region of the cell. Seeding at increasing target densities induces local compression on cells. This increase in local compression modulates cell volume and concomitant increases in F-actin and microtubule concentration to a greater degree than microtubule stabilization via PAX. Cells seeded at high density exhibit higher bulk modulus than corresponding cells seeded at low density. These data demonstrate the capacity of stem cells to adapt to an interplay of mechanical and chemical cues, i.e., respective compression and exogenous microtubule stabilization; the resulting cytoskeletal remodeling manifests as evolution of mechanical properties relevant to development of multicellular tissue constructs.

A First-Principle Study Investigating the Half-Metallic and Mechanical Properties of Double Halide Perovskites Rb2OsX6 (X = cl, Br, and I) for Spintronic Applications.

In this work, we present a density functional calculation of the structural, electronic, and mechanical properties of cubic double halide perovskites Rb2OsX6 (X = Cl, Br, and I). Our results show that these compounds are stable in the ferromagnetic phase with lattice parameters, bulk modulus, and their first-pressure derivatives in good agreement with other available theoretical data. The negative values of cohesive energy and formation energy, along with the absence of negative or imaginary frequencies in the phonon spectrum, confirm the mechanical stability of all the compounds. The Curie temperature (Tc) is determined using a Heisenberg model in the mean-field approximation. We obtained a half-metallic character for all compounds, making them promising materials for spintronic applications. The magnetic properties indicate that the Os atoms in all compounds are responsible for the magnetism, while the positive exchange constants suggest a strong preference for ferromagnetic alignment. This indicates a stable ferromagnetic phase and potential applications in spintronics. The mechanical properties demonstrate that the compounds studied are isotropic and ductile.

Effects of Post-Fire Rehydration on the Mechanical Properties of Slag-Modified Concrete

Although previous research has examined the mechanical properties of concrete exposed to high temperatures, further investigation is needed into the effects of post-fire curing on the recovery of strength and stiffness of sustainable concretes produced with slag-modified cement. This study conducted an experimental analysis of the residual compressive strength and modulus of elasticity of different types of concrete (20 MPa or 30 MPa) exposed to varying maximum temperature levels (200 °C, 400 °C, 600 °C, 800 °C) and post-fire treatments (with or without rehydration). The concrete specimens were produced using Portland cement CP II-E-32. The rehydration method involved one day of water curing, followed by 14 days of air curing. Statistical analyses revealed potential improvements in the mechanical properties of concretes produced with slag-modified cement due to rehydration processes after exposure to different temperatures levels. The highest values of the relative residual strength factor (Φc) were observed in specimens exposed to a maximum temperature of 600 °C, ranging from 0.862 to 0.905. The highest values of the relative residual elastic modulus factor (ψc) were verified for a maximum temperature of 200 °C, ranging from 0.720 to 0.778. The experimental results were compared with strength and stiffness predictions of design codes. The inclusion of slag in concrete reduced microcracking during the rehydration process due to the reduced amount of calcium hydroxide in the cementitious matrix, increasing the concrete’s relative residual strength and stiffness after post-fire curing.

Effect of pressure-induced lattice distortion on physical properties of L10-FeNi ordered alloy

The ground-state properties of tetragonal L10 type FeNi alloy have been thoroughly studied, while its physical properties under high pressure are poorly understood. Here, the effect of pressure on the structural, magnetic, mechanical and dynamical properties of L10-FeNi are systematically investigated from the first principles calculations. The critical pressure of ferromagnetic collapse is detected to be 250 GPa, and the system is mechanically and dynamically stable below the critical pressure. The pressure-induced lattice distortion is identified in the pressure range of 80-150 GPa. Within this pressure range, the magnetic moments of the system decrease dramatically, the elastic constants C12, C13, C33 and bulk modulus B show softening behavior, and consequently the ductility, longitudinal sound velocity, and acoustic Grüneisen constant exhibit softening behavior, while the elastic anisotropy increase sharply. Furthermore, there are significant variations in magnetocrystalline anisotropy, coercivity, maximum magnetic energy product and magnetic hardness parameters within the pressure range of lattice distortion. More interesting is the discovery that the pressure-induced lattice distortion triggers a transition from semi-hard to hard magnet near 130 GPa.

Crowding effects on the structure and rheology of ultrasoft PNIPAM-PEGMA copolymer microgels.

We investigate the link between the internal microstructure of poly(N-isopropylacrylamide)-poly(ethylene glycol) methyl ether methacrylate (PNIPAM-PEGMA) microgels, their bulk moduli and the rheological response and structural arrangement in dense suspensions. The low degree of crosslinking combined with the increased hydrophilicity induced by the presence of PEGMA results in a diffuse, star-like density profile of the particle and very low values of the bulk modulus in dilute conditions, as determined by small angle neutron scattering (SANS). The ultrasoft nature of the particle is reflected in the changes of the structural arrangement in dense suspensions, which evidence a strong deswelling and a sharp rise of the bulk modulus at moderate packing fractions. At larger packings the single particle morphology and softness saturate, and we observe a structural transition from a dispersion-like to a hydrogel-like behavior. The transition is also reflected in the rheological response in the form of a two-step yielding at large packing fractions, characteristic of systems in which a network structure is present. Our results demonstrate that a knowledge of the internal structure and mechanics of individual microgels is needed to determine and tune the properties of dense suspensions, and optimize their response for applications in biomedicine and as filtration systems.

Effects of cellulose nanofibrils on the mechanical and thermal properties of phase change foams based on polyethylene glycol/cellulose nanofibrils/waterborne polyurethane.

Incorporating phase change materials (PCM) into three-dimensional porous network structures could effectively address the leakage problem. In this study, by investigating the effects of different cellulose nanofibrils (CNF) contents on the mechanical and thermal properties of polyethylene glycol (PEG)/CNF/waterborne polyurethane (WPU) phase change foams, a series of leak-proof, lightweight, and stable PEG/CNF/WPU phase change foams were synthesized. Utilizing CNFs as porous support materials could effectively mitigate the leakage of PCMs. Meanwhile, the incorporation of WPU dispersions leads to the formation of CNFs/WPU composite network structure, which enhances the mechanical strength of the phase change foams and further reduces the leakage of PEG. The morphological, crystallographic, chemical, mechanical, and thermal characteristics of PEG/CNF/WPU phase change foams with varying CNF concentrations were comprehensively assessed using field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), mechanical testing, and differential Scanning calorimetry (DSC). The research results indicate that phase change latent heat of PEG/CNF/WPU phase change foam containing 0.8 wt% CNF reached 150.54 J·g-1 and demonstrated superior compressive strength, compressive yield stress, and compressive modulus with a remarkably low leakage rate of just 8.57 % after enduring a 30-day leakage test.

Synthesis and Characterization of a Nanoclay Reinforced Gelatin-Based Hybrid Hydrogel.

Bentonite clay nanoparticles assume a pivotal role in 3D bioprinting and tissue engineering by augmenting the mechanical rigidity and biological efficacy of hydrogels. In this investigation, Span80 was employed as a surfactant to facilitate the synthesis of uniformly sized bentonite nanoparticles measuring approximately 700 nm in diameter. The resultant hybrid hydrogel displaced a marked increase in compressive modulus, achieving a peak value of 17.5 kPa, including 1% bentonite twice that of the unmodified gelatin methacryloyl (GelMA). The discernible enhancements in the physical and biological characteristics of the hydrogel underscore its considerable potential for applications in tissue engineering. This includes heightened mechanical rigidity, robust cell viability, and a meticulously regulated degradation rate. While further examinations are imperative to evaluate the viability of the developed hydrogel comprehensively, its auspicious physical and biological attributes strongly suggest its potential utility in the domain of tissue engineering and bioprinting.