Young's Modulus Values Research Articles

Changes in ultrasonic elastometry parameters of the liver parenchyma during its radiofrequency ablation (experimental study)

Objective. To determine in the experiment the changes in the elasticity of the liver parenchyma during its radiofrequency ablation at different distances from the electrode and their correspondence to the zones of irreversible thermal damage of the tissue. Materials and methods. The elasticity of the parenchyma of six samples of isolated porcine liver during radiofrequency ablation in automatic mode for 12 min with an initial applicator power of 50 W and its subsequent automatic increase by 10 W/min until critical impedance values were reached was evaluated by ultrasonic elastometry with the determination of the Young's modulus. The elasticity of the liver in kilopascals was determined before the start of radiofrequency ablation, during its implementation every minute for 12 minutes and 15, 30 and 60 minutes after the procedure in three zones located at a distance of 1.0, 1.8 and 3.0 cm from the applicator. Results. Before radiofrequency ablation, the elasticity of the liver parenchyma ranged from 4.1 to 9.3 kPa and averaged (6.64 ± 1.55) kPa. At the maximum power of the applicator – (109.67 ± 4.97) W – the transverse size of the hyperechogenic “cloud” at the 12th minute of the procedure was (18.0 ± 1.41) mm. The value of Young's modulus in the first zone of elastometry statistically significantly increased from the 1st minute of radiofrequency ablation and by the 11th minute reached the level of (46.38 ± 5.43) kPa and did not change significantly thereafter. In the second zone, a statistically significant increase in the value of Young's modulus to (44.22 ± 6.55) kPa was observed throughout the procedure, and after its termination it changed statistically insignificantly. In the third zone, changes in the value of Young's modulus occurred 3 minutes after the start of the procedure and continued until its completion, but its maximum value – (15.63 ± 1.57) kPa – exceeded the baseline level only about 2 times, and an hour after the completion of radiofrequency ablation, the value of Young's modulus decreased statistically significantly. Conclusions. The stiffness of the parenchyma of isolated porcine liver increases significantly during radiofrequency ablation under conditions of its sufficient duration, and depending on the distance to the electrode, these changes have different phase character. In loci corresponding to the zone of irreversible tissue necrosis, the initial slow approximately twofold increase in Young's modulus during the first 3 to 4 minutes is followed by a rapid exponential increase in the next 5 to 6 minutes and the formation of a plateau with 6 to 8 times the initial level, after which the index does not change significantly. To determine the edge of liver parenchyma ablation by elastometry, in addition to the absolute value of Young's modulus at the end of radiofrequency ablation and the multiplicity of its increase relative to the baseline value, such criteria as the three–phase nature of the increase in this indicator and the absence of its decrease within an hour after the procedure are equally important.

On demand thermal surface modification of carbon fiber for improved interfacial shear strength

A thermally triggered, on demand, surface modification method was exploited using carbon fibers (CFs). Bisdiazomethanes undergo thermal activation to generate extremely reactive carbene intermediates, able to react with the CF surface. Herein, the surface modification of continuous CFs is demonstrated by dipping the fibers in a solution of bisdiazomethane at three different concentrations of 1 mmol, 5 mmol, and 10 mmol, followed by air drying and heating at 120 °C. Tensile strength and Young's Modulus values were preserved in the treated fibers, while the interfacial shear strength (IFSS) values showed significant improvement. The highest IFSS improvement was found (189 %) for the fibers dipped in the 5 mmol solution, with significant increases noted for the 1 and 10 mmol modifications, of 54 % and 97 %, respectively. When the thermal modification was repeated with parameters analogous to a sizing application used in CF manufacture (30 s dip, 2-min heating), 74–79 % improvements in IFSS resulted. Hence, this approach can serve as a simple, scalable, and tunable surface modification method for discontinuous CFs that promotes their use in high value applications.

Innovative spiral nerve conduits: Addressing nutrient transport and cellular activity for critical-sized nerve defects

Large-gap nerve defects require nerve guide conduits (NGCs) for complete regeneration and muscle innervation. Many NGCs have been developed using various scaffold designs and tissue engineering strategies to promote axon regeneration. Still, most are tubular with inadequate pore sizes and lack surface cues for nutrient transport, cell attachment, and tissue infiltration. This study developed a porous spiral NGC to address these issues using a 3D-printed thermoplastic polyurethane (TPU) fiber lattice. The lattice was functionalized with poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) electrospun aligned (aPHBV) and randomly (rPHBV) oriented nanofibers to enhance cellular activity. TPU lattices were made with 25 %, 35 %, and 50 % infill densities to create scaffolds with varied mechanical compliance. The fabricated TPU/PHBV spiral conduits had significantly higher surface areas (25 % TPU/PHBV: 698.97 mm2, 35 % TPU/PHBV: 500.06 mm2, 50 % TPU/PHBV: 327.61 mm2) compared to commercially available nerve conduits like Neurolac™ (205.26 mm2). Aligned PHBV nanofibers showed excellent Schwann cell (RSC96) adhesion, proliferation, and neurogenic gene expression for all infill densities. Spiral TPU/PHBV conduits with 25 % and 35 % infill densities exhibited Young's modulus values comparable to Neurotube® and ultimate tensile strength like acellular cadaveric human nerves. A 10 mm sciatic nerve defect in Wistar rats treated with TPU/aPHBV NGCs demonstrated muscle innervation and axon healing comparable to autografts over 4 months, as evaluated by gait analysis, functional recovery, and histology. The TPU/PHBV NGC developed in this study shows promise as a treatment for large-gap nerve defects.

PH-sensitive aminated chitosan/carboxymethyl cellulose/aminated graphene oxide coated composite microbeads for efficient encapsulation and sustained release of 5-fluorouracil

The application of smart pH-sensitive carriers has become an ideal choice for administering drugs with desired release profiles. Although pH-sensitive microbeads offer distinct benefits for delivering anticancer drugs orally, they encounter drawbacks, including low encapsulation efficiency, weak mechanical stability, biocompatibility concerns, and the risk of abrupt release. This study focuses on developing pH-sensitive coated composite microbeads for effective encapsulation and sustained release of 5-fluorouracil (5-FU). Aminated graphene oxide (AmGO) was integrated into carboxymethyl cellulose (CMC) microbeads, which were subsequently coated with an aminated chitosan (AmCs) derivative. Various analysis techniques, including Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), X-ray diffractometer (XRD), X-ray photoelectron spectroscopy (XPS), thermogravimetric analyzer (TGA), zeta potential (ZP), and mechanical testing, were utilized to characterize the microbeads. The AmCs@CMC@AmGO composite microbeads demonstrated a compact structure with enhanced mechanical properties, achieving a maximum Young's modulus value of 35.99 N/mm2 compared to 25.95 N/mm2 for pure CMC microbeads. Moreover, pH-sensitivity and water uptake studies (at pH 1.2 and pH 7.4) revealed significant tunability of the composite microbeads by altering the AmGO and AmCs ratios. The coated composite microbeads encapsulated approximately 86.4 % of 5-FU compared to 47 % for CMC microbeads. The burst release of 5-FU at pH 7.4 was significantly reduced, with sustained release reaching 51 % over 24 h. The predominant release mechanism was Fickian diffusion, which well-described by the Peppas-Sahlin kinetic model. The developed microbeads exposed improved biodegradability and non-toxicity toward normal colon cells, while exhibiting notable toxicity against cancerous cells, emphasizing its potential for anticancer drug delivery.

Granular Porous Nanofibrous Microspheres Enhance Cellular Infiltration for Diabetic Wound Healing.

Diabetic foot ulcers (DFUs) are a significant challenge in the clinical care of diabetic patients, often necessitating limb amputation and compromising the quality of life and life expectancy of this cohort. Minimally invasive therapies, such as modular scaffolds, are at the forefront of current DFU treatment, offering an efficient approach for administering therapeutics that accelerate tissue repair and regeneration. In this study, we report a facile method for fabricating granular nanofibrous microspheres (NMs) with predesigned structures and porosities. The proposed technology combines electrospinning and electrospraying to develop a therapeutic option for DFUs. Specifically, porous NMs were constructed using electrospun poly(lactic-co-glycolic acid) (PLGA):gelatin short nanofibers, followed by gelatin cross-linking. These NMs demonstrated enhanced cell adhesion to human dermal fibroblasts (HDF) during an in vitro cytocompatibility assessment. Notably, porous NMs displayed superior performance owing to their interconnected pores compared to nonporous NMs. Cell-laden NMs demonstrated higher Young's modulus values than NMs without loaded cells, suggesting improved material resiliency attributed to the reinforcement of cells and their secreted extracellular matrix. Dynamic injection studies on cell-laden NMs further elucidated their capacity to safeguard loaded cells under pressure. In addition, porous NMs promoted host cell infiltration, neovascularization, and re-epithelialization in a diabetic mouse wound model, signifying their effectiveness in healing diabetic wounds. Taken together, porous NMs hold significant potential as minimally invasive, injectable treatments that effectively promote tissue integration and regeneration.

Matrix Stiffness of GelMA Hydrogels Regulates Lymphatic Endothelial Cells toward Enhanced Lymphangiogenesis.

Lymphatic vessel regeneration is crucial for various tissue engineering strategies, particularly in resolving inflammation and restoring tissue homeostasis. In our study, we focused on investigating how hydrogel matrix stiffness influences lymphatic endothelial cells (LECs) in promoting lymphatic vessel regeneration. Gelatin methacrylate (GelMA) was chosen as our biomaterial due to its versatility in tissue engineering and biofabrication. We fabricated GelMA hydrogels at concentrations of 5, 7.5, and 15% (w/v) with corresponding Young's modulus values of 1.55 kPa (soft matrix), 12.02 kPa (medium matrix), and 48.50 kPa (stiff matrix). Among these, the 7.5% GelMA hydrogel exhibited optimal stiffness for promoting lymphangiogenesis. LECs seeded either on the hydrogel surface or within spontaneously formed a more stable lymphatic capillary network compared with other GelMA formulations. Furthermore, we investigated the enhancement of lymphangiogenesis by incorporating VEGF-C into the GelMA hydrogel, leveraging the synergistic effects of mechanical and chemical cues. Our results underscored the critical role of FAK-phosphorylation in this process; treatment with an FAK-specific inhibitor prevented the formation of tube-like structures by LECs and attenuated the expression of lymphatic markers. Overall, our findings highlight how the mechanical and chemical cues provided by GelMA hydrogels can effectively regulate LEC behavior toward enhanced lymphangiogenesis via the integrin/FAK mechanotransduction pathway. This study proposes a promising strategy for developing hydrogel-based scaffolds or bioinks tailored to promote lymphatic vessel regeneration in therapeutic applications.

Employing Young's modulus and Debye temperature to calculate the elastic, thermodynamic and thermophysical properties of titanium oxynitrides.

The values of the shear v s and longitudinal v l wave velocities were calculated for 14 selected titanium oxynitrides TiN x O y using the known values of Young's modulus and Debye temperature. The errors Δ of the calculations did not exceed ±0.01%. It turned out that some TiN x O y samples are able to compete with artificial diamonds in terms of v l values and can potentially be used in acoustic resonators for intelligent chemical and biochemical sensors. A number of elastic, thermodynamic and thermophysical quantities were calculated, and graphical dependencies between them were plotted. The established correlations were used to develop two algorithms for predicting the properties of TiN x O y alloys based on a single experimental parameter, namely the X-ray coefficient of thermal expansion or pycnometric density. The highest accuracy was shown by the method based on the experimental density, which allowed to estimate, with acceptable errors, the values of the shear v s and mean v m wave velocities (Δ = ±(1-5)%), the minimum thermal conductivity λ min within the framework of the Cahill‒Pohl model (Δ = ±(0-3)%), the isobaric C p and isochoric C V heat capacities (Δ < 1%); while the known experimental methods and alternative models for determining these quantities are characterized by wider error intervals: Δ(v s) = ±(1-10)%, Δ(λ) = ±(1-10)% and Δ(C p) = ±(1-3)%.

Development and approval of a mobile test bench for the study of the mechanical properties of biological tissues

The determination of the mechanical properties of vessel walls and atherosclerotic plaques is a recurring issue in the numerical modelling of vessel sections. Testing machines are usually located in specialised laboratories outside medical facilities, and transporting samples from the clinic is difficult. Therefore, the task of developing mobile testing devices that can be installed directly in the clinic to perform tests immediately after surgery is relevant. This paper presents the results of the development and validation of a mobile test bench for performing mechanical experiments on uniaxial compression and tension of biological tissues. The purpose of the work is to perform mechanical tests on tissues in the clinic, avoiding their transport to the laboratory and/or freezing. Arduino UNO hardware platform is used as the control element of the test bench, which controls the main elements (motor, load cell), records data on SD card and displays information about the experiment on the computer screen. Structurally, the test bench is an analogue of a two-column testing machine. All mechanisms are assembled in a portable case, the control module is in the form of a remote plastic box. Verification of the test bench was carried out using an Instron 3342 universal testing machine with a 500 N load cell. A total of 121 soft tissue tests (including arterial wall and atherosclerotic plaque) were performed on the bench. The Young's modulus and ultimate strength values obtained are summarised in a table. The mean Young's modulus for the wall of the internal carotid artery was 0.32 ± 0.24 MPa, for soft plaque 0.30 ± 0.17 MPa, and for hard plaque 0.85 ± 0.39 MPa; a tensile strength of 1.12 ± 0.67 MPa was also determined for hard plaques in carotid arteries. The result is a unique database of tissue Young's moduli obtained from freshly collected material. The methodology and its implementation on the mobile test bench show good agreement with literature data.

Synthesis Of Biofoam Based On Glucomannan Porang And Polyvinyl Alcohol (PVA) With The Addition of Seaweed Dregs

Biofoam (Biodegradable foam) is an alternative packaging to Styrofoam made from natural raw materials that can be biodegraded in the soil. Biofoam is generally made from 3 constituent materials in the form of main ingredients in the form of starch or other similar materials, plasticizers such as PVA and also fillers in the form of fibers containing cellulose. The purpose of this study was to determine the effect of the combination of porang glucomannan, PVA and seaweed pulp on biofoam and to determine the best formulation and characteristics of the biofoam samples made.. The technique of making biofoam was done using baking technique with 9 different treatments. Each treatment was repeated 3x and observations were made on biofoam structure, mechanical properties testing (tensile strength, elongation and young modulus), water absorption test, and biodegradation test. The results showed that Polyvinyl Alcohol plays a role in the formation of a hollow biofoam structure. The thickness parameter value for each treatment was 0.628-1.939 mm. The tensile strength value of each treatment has a value ranging from 15.989-35.265 N/mm². The elongation value for each treatment ranged from 25.719-76.427%. The young modulus value for each treatment ranged from 0.343-0.896 N/mm². The water absorption value of each treatment obtained values ranging from 35.81-77.12%. And the value of testing biodegradation parameters obtained values ranging from 8.68-32.18%. So that the best treatment obtained using the multiple attribute method is the A3B1 treatment (PVA 15% and the ratio of seaweed pulp concentration to glucomannan 1: 2).

Organic reinforcement of an ethylene propylene diene monomer with the in situ synthesis of a polyimide dispersed phase by reactive extrusion

AbstractEthylene‐propylene‐diene monomer rubber, grafted with maleic anhydride functions (EPDM‐g‐MA) was organically reinforced by reactive extrusion from the in situ synthesis of a polyimide (PI) phase. The blends were reactively processed at 200°C in a twin‐screw extruder, with the PI content varying from 5 to 40 wt%. Transmission Electron Microscopy (TEM) revealed a very fine nodular dispersion of the PI phase with diameters ranging from 130 to 240 nm depending on the PI concentration. The reinforcement of the elastomer was evidenced with a sharp increase of the Young's modulus and the tensile strength, and the stiffness of the material was further increased with the PI content. The linear viscoelastic regime, as measured by the variation in storage modulus as a function of strain, was unaffected by this organic reinforcement, thus opening up an original way of controlling the Payne effect. Additionally, the cross‐linking of the blend with 20 wt% of PI with dicumyl peroxide (DCP) showed that the PI phase did not impact the creation of the cross‐linked network. The decrease of the swelling ratio and the improvement of the elastic recovery suggested that EPDM‐g‐PI copolymers can create a second network in the material, resulting in a higher apparent cross‐linking density. The mechanical properties of the cured blend showed a doubling of the Young's modulus and maximal stress values compared to those obtained for the pure matrix as well as a constant strain at break.Highlights Ethylene‐propylene‐diene monomer rubber, grafted with maleic anhydride functions (EPDM‐g‐MA) was organically reinforced by reactive extrusion. The reinforcement was obtained from the in situ synthesis of a polyimide (PI) phase. The Young's modulus of cross‐linked EPDM containing 20 wt% PI was doubled. The linear viscoelastic regime was unaffected by this organic reinforcement. This original way of reinforcement opens the control of the Payne effect.

A Review of the Development of Titanium-Based and Magnesium-Based Metallic Glasses in the Field of Biomedical Materials.

This article reviews the research and development focus of metallic glasses in the field of biomedical applications. Metallic glasses exhibit a short-range ordered and long-range disordered glassy structure at the microscopic level, devoid of structural defects such as dislocations and grain boundaries. Therefore, they possess advantages such as high strength, toughness, and corrosion resistance, combining characteristics of both metals and glasses. This novel alloy system has found applications in the field of biomedical materials due to its excellent comprehensive performance. This review discusses the applications of Ti-based bulk metallic glasses in load-bearing implants such as bone plates and screws for long-term implantation. On the other hand, Mg-based metallic glasses, owing to their degradability, are primarily used in degradable bone nails, plates, and vascular stents. However, metallic glasses as biomaterials still face certain challenges. The Young's modulus value of Ti-based metallic glasses is higher than that of human bones, leading to stress-shielding effects. Meanwhile, Mg-based metallic glasses degrade too quickly, resulting in the premature loss of mechanical properties and the formation of numerous bubbles, which hinder tissue healing. To address these issues, we propose the following development directions: (1) Introducing porous structures into titanium-based metallic glasses is an important research direction for reducing Young's modulus; (2) To enhance the bioactivity of implant material surfaces, the surface modification of titanium-based metallic glasses is essential. (3) Developing antibacterial coatings and incorporating antibacterial metal elements into the alloys is essential to maintain the long-term effective antibacterial properties of metallic biomaterials. (4) Corrosion resistance must be further improved through the preparation of composite materials, while ensuring biocompatibility and safety, to achieve controllable degradation rates and degradation modes.

Recyclable fully biobased high-performance epoxy thermosets

Thermosetting polymeric materials play a pivotal role in numerous sectors due to their versatility in tailoring physicochemical and mechanical properties and their exceptional performances. The aim of this study is to design 100 % bio-based high performant and recyclable thermosets. To achieve this goal, a natural and renewable-based epoxy monomer, triglycidyl ether of phloroglucinol (TGPh), was crosslinked with biobased anhydrides to create novel polymeric resins. Through detailed investigations, it was found that the designed materials have storage moduli values at room temperature ranging from 2.1 to 3.4 GPa, with damping factors spanning from 86 °C to 163 °C depending on the nature of the anhydride. Tensile tests corroborated the performant mechanical properties of the designed bio-resins, showing Young's modulus values ranging from 1.2 to 1.5 GPa. Furthermore, the water absorption values are very low, ranging from 0.25 % to 0.35 %. Besides, the designed bio-resins exhibited rapid dissolution in TBD/EG solution, as well as thermo-mechanical reprocessability.

Silica infiltration as a strategy to overcome zirconia degradation

The excellent clinical performance of yttria-partially stabilized zirconias (Y-SZs) makes them promising materials for indirect restorations. However, the Y-SZ phase stability is a concern, and infiltrating Y-SZs with a silica nanofilm may delay their degradation processes. In this study, we analyzed stabilities of silica-infiltrated zirconia surfaces after exposure to artificial aging (AA).Four zirconia materials with different translucencies (n = 40) were used, including low translucency 3 mol% Y-SZ (3Y-LT, Ceramill ZI, Amann Girrbach); high translucency 4 mol% Y-SZ (4Y-HT, Ceramill Zolid); and two high translucency 5 mol% Y-SZs (5Y-HT, Lava Esthetic, 3M and 5Y-SHT, Ceramill Zolid, FX white). Sintered specimens were exposed to 40 cycles of silica (SiO2) through room temperature atomic layer deposition (RT-ALD) using tetramethoxysilane (TMOS) and ammonium hydroxide (NH4OH). AA was applied for 15 h in an autoclave (134°C, 2 bar pressure). Stabilities of zirconia-silica surfaces were characterized in terms of hardness and Young's modulus using nanoindentation techniques and crystalline contents using x-ray diffraction (XRD) analyses. Silica deposition was also characterized by X-ray photoelectron spectroscopy (XPS).There was a significant effect of the interaction of materials and surface treatments on the hardness and Young's modulus values of zirconia-silica surfaces (p < 0.001). Silica deposition on zirconia surfaces improved the material resistance to degradation by AA.

Composite cellulose/bismuth/PVA nanocrystal for high-performance X-ray radiation shielding

The strong penetrating power of X-rays causes serious health problems. Longer exposure to radiation that penetrates normal cells can result in gene mutations, cancer, and even death. Protection against radiation exposure is necessary to prevent negative impacts from occurring. This research aims to make apron samples using a simple method based on cellulose as a matrix, bismuth as a filler with concentrations of 1 g, 0.75 g, 0.25 g and PVA acts as a binder that helps bind cellulose and bismuth particles into an effective X-ray radiation shield. The characterization carried out includes Fourier transform infrared (FTIR) to determine the functional groups and chemical composition of the sample, x-ray diffraction (XRD) to analyze the crystal size of the sample, and mobile x-ray with energies of 60, 70, and 80 keV to determine the radiation shielding performance. The findings of this study highlight that the optimal shielding properties were attained by employing a sample with the highest concentration of bismuth filler, specifically at 1 g. This material exhibits outstanding characteristics, including a high linear attenuation coefficient and mass attenuation coefficient of 0.68 cm−1 and 2.24 cm2/g respectively for an energy of 60 keV and especially low HVL (1.01 cm) and TVL (3.36 cm) values. These findings have significant implications for developing high-performance X-ray radiation shielding materials, particularly in industries where radiation exposure is a concern, such as the medical industry, research, and laboratories. The high tensile strength (2.83 N/mm2) and elongation (12.09 %) values as well as the low Young's modulus (0.108 N/mm2) values also indicate the flexibility of the resulting material, which could be beneficial for applications that require flexible shielding materials. The practicality of this research makes the audience feel that the findings are applicable and useful in real-world scenarios.

Effect of Tetrapropylammonium Chloride Quaternary Ammonium Salt on Characterization, Cytotoxicity, and Antibacterial Properties of PLA/PEG Electrospun Mat.

In this study, poly(lactic acid) (PLA)-tetrapropylammonium chloride (TCL)-poly(ethylene glycol) (PEG) nonwoven networks were produced using PLA, PEG with different concentrations (3, 5, 7, and 9 wt%), and TCL. PEG is included as a plasticizer in PLA polymer, which has high biocompatibility but a brittle structure. The importance of this study is to investigate the effect of TCL salt on the characterization of PLA-PEG nanofibers. For this research, the cytotoxicity test system responsible for the fibroblast cell line (L929) was evaluated with the liquid absorption capacity (LAC) and drying time tests for its use in wound dressings. The addition of TCL salt reduced bead formation in PLA-PEG nanofibers and increased the homogeneity of fiber dispersion. The smoothest and most homogeneous nonwoven networks were obtained as PLA-5TCL-PEG. It was also reported that this nonwoven network exhibited liquid absorption behavior with a maximum increase of 150% compared to the PLA-PEG nonwoven network and had the highest Young's modulus value of 12.97 MPa. In addition to these tests, evaluations were made with Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), drying time test, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and mechanical tests. In addition, high cell viability was observed in L292 mouse fibroblast cells at the end of the 24th hour, again with the effect of TCL salt. In addition, antibacterial activity was tested against gram-negative E. coli and gram-positive S. aureus bacteria, and it was observed that there was no antibacterial activity. Since PLA-TCL-PEG nonwoven webs have a maximum cell viability of 133.27%, they are recommended as a potential dermal wound dressing.

Mechanical response of LPBFed TI64 thickness graded Voronoi lattice structures

The possibility to realize Additively Manufactured functionally graded lattice structure based on Voronoi tessellation enormously increases the possibility in tailoring the stiffness, mechanical properties and energy absorption capacity of the samples. The work presents the design and mechanical characterization of functionally thickness graded Voronoi lattice structures in comparison with constant thickness lattice structures for the evaluation of mechanical performance and energy absorption capacity. Firstly, the design and laser power bed fusion process are detailed. The dimensional deviation between designed models and Ti6Al4V specimens is quantified to assess the samples’ quality. Their mechanical performance is analyzed by quasi-static compression experimental tests, supported by numerical analysis for the evaluation of local stress distributions and deformation modes. The average dimensional deviation between CAD models and fabricated samples is 0.09 mm, likeminded with the literature optimum. The structures exhibit Young Modulus values ranging between 10 MPa and 21 MPa, compatible with biomedical applications. The compressive force for thickness graded structures tends to increase up to densification, while uniform thickness structures present an almost constant value of force in the platform stage. Additionally, the energy storage changes according to the presence of thickness gradient: the larger the thickness gradient, the larger the energy absorption capacity.

Characterization of Limbus Biomechanical Properties Using Optical Coherence Elastography.

The elasticity of the limbus is crucial for ocular health, yet it remains inadequately explored. This study employs acoustic radiation force optical coherence elastography (ARF-OCE) to evaluate the biomechanical properties of the limbus under varying intraocular pressures. The method was validated using a heterogeneous phantom and subsequently applied to ex vivo porcine limbus samples. Elastic wave velocity at specific locations within the limbus was calculated, and the corresponding Young's modulus values were obtained. Spatial elasticity distribution maps were generated by correlating Young's modulus values with their respective locations in the two-dimensional structural images. The results indicate that ARF-OCE enhances the understanding of limbus biomechanical behavior and holds potential for diagnosing regional variations caused by ocular diseases.

Preparation, mechanical analysis and investigation of swelling behavior of boron nitride reinforced hydrogel polymer composite films

AbstractThis study presents the preparation, hydrogel kinetics, and mechanical analysis of Boron Nitride (BN) reinforced PVA/PVP/PEO‐BN hydrogel composite films using Polyvinyl alcohol (PVA), Polyvinyl pyrrolidone (PVP), and Polyethylene oxide (PEO) commercial polymers. Dynamic mechanical analysis tests reveal that PVA90PEO5PVP5‐BN composite films exhibit plastic‐viscoelastic behavior under a maximum force of 18 N. The Young's Modulus values for PVA90PEO5PVP5, PVA90PEO5PVP5‐BN%10, and PVA90PEO5PVP5‐BN%20 are 0.22, 0.32, and 0.44 MPa, respectively. The highest % Strain value is observed in PVA90PEO5PVP5‐BN%20, reaching 279.80%. In the hydrogel kinetics study, Schott's and Fickian models are utilized. The regression from the Fickian model is quite low, with exponential diffusion index, n, values lower than 0.5, indicating a classical Fickian water diffusion mechanism. Schott's model provides graphs with significantly higher regression compared to the Fickian model. The results indicate compatibility with the other model and confirm the presence of water‐based diffusion. Equilibrium swelling values (Se, g H2O/g gel) are 6.71, 7.03, and 7.91 for PVA90PEO5PVP5, PVA90PEO5PVP5, PVA90PEO5PVP5‐BN%10, and PVA90PEO5PVP5‐BN%20, respectively. Differential Scanning Calorimetry (DSC) analysis results show that the glass transition temperatures, Tg, are 52.37, 60.20, and 63.05°C for PVA90PEO5PVP5, PVA90PEO5PVP5‐BN%10, and PVA90PEO5PVP5‐BN%20, respectively.

Repetitive recycling effects on mechanical characteristics of poly‐lactic acid and PLA/spent coffee grounds composite used for 3D printing filament

AbstractDue to its biodegradability, biocompatibility, and mechanical properties, poly‐lactic acid (PLA) is a leading biomaterial for numerous applications, especially for fused deposition modeling and fused filament fabrication. Nonetheless, the absence of a comprehensive recycling strategy may emerge as a significant source of plastic pollution in the future. Indeed, the polymer undergoes deterioration during melt recycling, resulting in a decrease in some mechanical properties that can compromise recyclability. To improve the properties of recycled PLA, the utilization of organic fillers coming from renewable materials can be considered as a sustainable solution. The objective of this work is then to evaluate the effect of recycling (reprocessing) on a virgin raw material as well as on biocomposites based on spent coffee grounds (incorporating 5% of spend coffee grounds in weight). The different types of filaments are extruded and re‐extruded and characterized under tensile, melt flow index, and hardness tests. The results show that the increase in the number of extrusions whether for virgin PLA or the composite contributes to the diameter fluctuation. Regarding the tensile properties, the rise in the frequency of recycling shows a weakness in the tensile strength and the elongation at break. On the other hand, Young's modulus values exhibit fluctuations. Concerning the addition of the spent coffee grounds filler, no major enhancement is observed in the tensile strength and the elongation at break, which is attributed to the poor adhesion between the matrix and the filler. The recycling process affects the hardness values of PLA, leading to an increase in these values, as well as those of the composite, which can be associated with the increased crystallinity caused by the recycling process and the SCG incorporation.Highlights Recycling and reusability strategy for poly‐lactic acid (PLA) and PLA/spent coffee grounds (SCG) filaments. Assessment of recycling effects on PLA and PLA/SCG. Mechanical characterization through tensile and hardness testing.

Comparative Study of the Dehydrothermal Crosslinking of Electrospun Collagen Nanofibers: The Effects of Vacuum Conditions and Subsequent Chemical Crosslinking.

Collagen nanofibrous materials have become integral to tissue engineering due to their exceptional properties and biocompatibility. Dehydrothermal crosslinking (DHT) enhances stability and maintains structural integrity without the formation of toxic residues. The study involved the crosslinking of electrospun collagen, applying DHT with access to air and under vacuum conditions. Various DHT exposure times of up to 72 h were applied to examine the time dependance of the DHT process. The DHT crosslinked collagen was subsequently chemically crosslinked using carbodiimides. The material crosslinked in this way evinced elevated Young's modulus values and ultimate tensile strength values, a lower swelling rate and lower shrinkage ratio during crosslinking, and a higher degree of resistance to degradation than the material crosslinked solely with DHT or carbodiimides. It was shown that the crosslinking mechanism using DHT occupies different binding sites than those using chemical crosslinking. Access to air for 12 h or less did not exert a significant impact on the material properties compared to DHT under vacuum conditions. However, concerning longer exposure times, it was determined that access to air results in the deterioration of the properties of the material and that reactions take place that occupy the free bonding sites, which subsequently reduces the effectiveness of chemical crosslinking using carbodiimides.