A Predictive Model for the Elastic Properties of a Collagen-Hydroxyapatite Porous Scaffold for Multi-Layer Osteochondral Substitutes

2015 ◽  
Vol 07 (04) ◽  
pp. 1550063 ◽  
Author(s):  
Dario Gastaldi ◽  
Gianluca Parisi ◽  
Riccardo Lucchini ◽  
Roberto Contro ◽  
Simone Bignozzi ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Elastic Modulus ◽  
Elastic Properties ◽  
Porous Scaffold ◽  
Single Layer ◽  
Porous Scaffolds ◽  
Sufficient Information ◽  
Structure Property ◽  
Flat Punch ◽  
Dry Conditions

Damaged articular cartilage can be substituted by porous scaffolds exhibiting tailored mechanical properties and with a suited layer-based design. Reliable predictive models are able to provide a structure–property relationship in the design phase is still an open issue which is of prominent relevance. In this paper, a bottom-up homogenization approach is presented having the purpose to determine the elastic properties of each single layer of a osteochondral porous three-layers scaffold: a top cartilage chondral layer and two mineralized layers: an intermediate and a subchondral bone layer. For the cartilage top layer, dry and wet conditions are considered; while, for intermediate and bone layers only dry conditions are considered. The homogenization model is based on the porosity of each layer and on the elastic properties of the constituent materials, i.e., water, hydroxyapatite (HA) and collagen. The elastic moduli predicted for the mineralized layers are compared with available literature results. The model results obtained on the cartilage layers are validated through flat punch micro-indentation tests carried out on wet and dry samples. The results have shown that the elastic modulus of the mineralized layers is of the order of magnitude of few GPa; whereas, the elastic modulus of the cartilage layer which exhibits porosity higher than 90% is as low as 50 kPa and 300 kPa in wet and dry conditions, respectively. The above results show that the knowledge of the mechanical properties of the basic constituents which are universally known and the porosity of the layers are sufficient information to obtain a reliable prediction of the elastic properties of both mineralized layers and of cartilage layers.

scholarly journals Influence of HIP Treatment on Mechanical Properties of Ti6Al4V Scaffolds Prepared by L-PBF Process

Metals ◽  
2019 ◽  
Vol 9 (12) ◽  
pp. 1267 ◽  
Author(s):  
Lili Liu ◽  
Huade Zheng ◽  
Chunlin Deng
Keyword(s):  
Mechanical Properties ◽  
Electron Microscope ◽  
Oxide Layer ◽  
Critical Stress ◽  
Porous Scaffold ◽  
Optical Microscope ◽  
Post Treatment ◽  
Material Surface ◽  
Porous Scaffolds ◽  
Pressure Test

To improve biocompatibility and mechanical compatibility, post-treatment is necessary for porous scaffolds of bone tissue engineering. Hot isostatic pressing (HIP) is introduced into post-treatment of metal implants to enhance their mechanical properties by eliminating residual stress and pores. Additionally, oxide film formed on the material surface can be contributed to improve its biocompatibility. Ti6Al4V porous scaffolds fabricated by laser-powder bed fusion (L-PBF) process is studied in this paper, their mechanical properties are measured by pressure test, and the macroscopic surface morphology and microstructure are observed by optical microscope (OM), scanning electron microscope (SEM) and transmission electron microscope (TEM). After HIP treatment, an oxide layer of 0.8 μm thickness forms on the surface of Ti6Al4V porous scaffolds and the microstructure of Ti6Al4V transforms from α’ phase to α + β dual-phase, as expected. However, the pressure test results of Ti6Al4V porous scaffolds show a definitely different variation trend of mechanical properties from solid parts, unexpectedly. Concerning Ti6Al4V porous scaffolds, the compression stiffness and critical stress improves clearly using HIP treatment, and the fracture morphology shows obvious brittle fracture. Both the strengthening and brittleness transition of Ti6Al4V porous scaffolds result from the formation of an oxide layer and an oxygen atom diffusion layer. The critical stress of Ti6Al4V porous scaffolds can be calculated by fully considering these two strengthening layers. To obtain a porous scaffold with specific mechanical properties, the effect of post-treatment should be considered during structural design.

Effects of γ-Ray Irradiation on the Properties of Nano-Hydroxyapatite/Polyurethane Composite Porous Scaffolds

2016 ◽  
Vol 852 ◽  
pp. 422-427 ◽  
Author(s):  
Jia Xing Jiang ◽  
Li Mei Li ◽  
Li Li Lin ◽  
Yi Zuo ◽  
Yu Bao Li ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Irradiation Dose ◽  
Porous Scaffold ◽  
Porous Scaffolds ◽  
Mechanical And Thermal Properties ◽  
Structure And Properties ◽  
Composite Scaffolds ◽  
Remarkable Effect ◽  
Polyurethane Composite ◽  
Γ Ray

To well understand the influence of the sterilization on the properties of biomaterials prior to application is pivotal. The effect of γ-ray irradiation on the mechanical and thermal properties of nanohydroxyapatite/polyurethane (n-HA/PU) porous scaffold for bone tissue engineering was studied in this paper. The mechanical testing, fourier transform infrared spectroscopy and thermal analysis were employed to determine the structure and properties change of these composite scaffolds after γ-ray irradiation with different doses.The results show that thermal stability, and mechanical properties of the composite scaffolds increase after γ-ray irradiation with doses of15 kGy to 25 kGy, especially the irradiation dose of 15kGy which imposed a remarkable effect on these properties. However, a reverse trend is found when the 50kGy irradiation dose was applied.In general, it can be concluded that sterilization using γ-ray irradiation with proper dose has no adverse effect on the properties of n-HA/PU composite scaffolds.

NANOINDENTATION AND ASH CONTENT STUDY OF AGE DEPENDENT CHANGES IN PORCINE CORTICAL BONE

2015 ◽  
Vol 15 (05) ◽  
pp. 1550074 ◽  
Author(s):  
MICHAEL CHITTENDEN ◽  
AHMAD RAEISI NAJAFI ◽  
JUN LI ◽  
IWONA JASIUK
Keyword(s):  
Mechanical Properties ◽  
Elastic Modulus ◽  
Cortical Bone ◽  
Age Groups ◽  
Structure Property ◽  
Micro Computed Tomography ◽  
Mineral Contents ◽  
Age Related ◽  
Age Dependent ◽  
Composition Structure

Composition-structure-property relations of bone provide fundamental understanding of bone quality. The objective of this paper was to investigate age dependent changes in the composition, structure and mechanical properties of porcine femoral cortical bone at mid-diaphysis region from six age groups (1, 3.5, 6, 12, 30, 48 months). This study was motivated by the fact that limited data is available in the literature on young porcine cortical bone. Nanoindentation technique with Berkovich fluid cell tip was employed to measure the elastic modulus and hardness. Individual lamellae were indented in the longitudinal direction of bone in different microstructural components (osteonal, interstitial and plexiform bone). A grid of indentations was also made on one bone sample to obtain spatial variations in the elastic modulus and hardness. Ash and water content tests were performed to measure water, organic and mineral contents of bone as a function of age. Finally, high resolution micro-computed tomography was used to measure porosity and visualize three-dimensional void structures. We found that the elastic modulus and hardness of bone increased with age but at different rates in each microstructural component. The mineral content increased correspondingly with age while the porosity decreased. The obtained structure, composition, and mechanical properties data give new insights on the age related changes in young cortical bone and can serve as inputs for and validation of multiscale models of bone.

Strain rate and temperature effects on elastic properties of polycaprolactone/starch composite

e-Polymers ◽  
2016 ◽  
Vol 16 (3) ◽  
pp. 217-223 ◽  
Author(s):  
Fethma M. Nor ◽  
Ho Yong Lee ◽  
Joong Yeon Lim ◽  
Denni Kurniawan
Keyword(s):  
Mechanical Properties ◽  
Strain Rate ◽  
Elastic Properties ◽  
Temperature Effects ◽  
Porous Scaffold ◽  
Element Model ◽  
Strain Rates ◽  
Body Temperatures ◽  
Tissue Engineering Scaffolds ◽  
Human Body Temperature

AbstractComposite of polycaprolactone (PCL) and starch is a potential biomaterial for tissue engineering scaffolds. During implantation, its mechanical properties might be compromised considering the various strain rates it is subjected to and that human body temperature is close to polycaprolactone’s melting temperature. This study aims at revealing the effect of strain rate and temperature to the elastic properties of polycaprolactone-starch composite. Tensile test at strain rates of 5, 0.1, and 0.01 mm/min at ambient and body temperatures were performed. It was revealed that strain rate as well as temperature readily have significant effects on the composite’s elastic properties. Such effects have similar trends with that of PCL homopolymer which is used as the composite’s matrix. Further analysis on the consequence of the finding was performed by applying the behavior to a finite element model of a porous scaffold and it was found that the discrepancy in elastic properties throughout the construct is even greater.

scholarly journals Analysis of Mechanical Properties and Permeability of Trabecular-Like Porous Scaffold by Additive Manufacturing

2021 ◽  
Vol 9 ◽  
Author(s):  
Long Chao ◽  
Chen Jiao ◽  
Huixin Liang ◽  
Deqiao Xie ◽  
Lida Shen ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Bone Repair ◽  
Bone Cells ◽  
Porous Scaffold ◽  
Bone Ingrowth ◽  
Voronoi Tessellation ◽  
Stress Shielding ◽  
Porous Scaffolds ◽  
Porous Structures ◽  
Element Analysis

Human bone cells live in a complex environment, and the biomimetic design of porous structures attached to implants is in high demand. Porous structures based on Voronoi tessellation with biomimetic potential are gradually used in bone repair scaffolds. In this study, the mechanical properties and permeability of trabecular-like porous scaffolds with different porosity levels and average apertures were analyzed. The mechanical properties of bone-implant scaffolds were evaluated using finite element analysis and a mechanical compression experiment, and the permeability was studied by computational fluid dynamics. Finally, the attachment of cells was observed by confocal fluorescence microscope. The results show that the performance of porous structures can be controlled by the initial design of the microstructure and tissue morphology. A good structural design can accurately match the performance of the natural bone. The study of mechanical properties and permeability of the porous structure can help address several problems, including stress shielding and bone ingrowth in existing biomimetic bone structures, and will also promotes cell adhesion, migration, and eventual new bone attachment.

scholarly journals Additively Manufactured Continuous Cell-Size Gradient Porous Scaffolds: Pore Characteristics, Mechanical Properties and Biological Responses In Vitro

Materials ◽  
2020 ◽  
Vol 13 (11) ◽  
pp. 2589 ◽  
Author(s):  
Fei Liu ◽  
Qichun Ran ◽  
Miao Zhao ◽  
Tao Zhang ◽  
David Z. Zhang ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Elastic Modulus ◽  
Pore Size ◽  
Cell Size ◽  
Porous Scaffolds ◽  
Ct Reconstruction ◽  
Pore Characteristics ◽  
Growth Environment ◽  
Size Gradient

Porous scaffolds with graded open porosity combining a morphology similar to that of bone with mechanical and biological properties are becoming an attractive candidate for bone grafts. In this work, scaffolds with a continuous cell-size gradient were studied from the aspects of pore properties, mechanical properties and bio-functional properties. Using a mathematical method named triply periodic minimal surfaces (TPMS), uniform and graded scaffolds with Gyroid and Diamond units were manufactured by selective laser melting (SLM) with Ti-6Al-4V, followed by micro-computer tomography (CT) reconstruction, mechanical testing and in vitro evaluation. It was found that gradient scaffolds were preferably replicated by SLM with continuous graded changes in surface area and pore size, but their pore size should be designed to be ≥ 450 μm to ensure good interconnectivity. Both the Gyroid and Diamond structures have superior strength compared to cancellous bones, and their elastic modulus is comparable to the bones. In comparison, Gyroid exhibits better performances than Diamond in terms of the elastic modulus, ultimate strength and ductility. In vitro cell culture experiments show that the gradients provide an ideal growth environment for osteoblast growth in which cells survive well and distribute uniformly due to biocompatibility of the Ti-6Al-4V material, interconnectivity and suitable pore size.

Calcium Phosphate Open Porous Scaffold Bioceramics

2005 ◽  
Vol 284-286 ◽  
pp. 349-352 ◽  
Author(s):  
J.P. Gittings ◽  
I.G. Turner ◽  
A.W. Miles
Keyword(s):  
Calcium Phosphate ◽  
Pore Structure ◽  
Size Range ◽  
Porous Scaffold ◽  
Total Porosity ◽  
Porous Scaffolds ◽  
Structure Property ◽  
Wide Range ◽  
Microcrack Formation ◽  
Relationship Of

Calcium phosphate (CaP) ceramics possessing an interconnecting porosity network in the appropriate size range for vascularisation offer the possibility of providing a structural matrix for replacement of diseased or damaged bone. Such bioceramics must possess sufficient mechanical strength to avoid failure whilst offering a bioactive surface for bone regeneration. The objective of the current study was to produce a hydroxyapatite/tricalcium phosphate (HA/TCP) bioceramic that imitated the orientated trabecular structure found in cancellous bone. The structure-property relationship of these bioceramics was then analysed. It was hypothesised that the mechanical properties would be linked to the shape of the pore structure due to the orientation of the open porous scaffolds (OPS) produced. OPS bioceramics possessed an interconnected macroporosity network of 40-70% by volume with bending strengths of 0.30MPa ± 0.01MPa and apparent densities of 0.35g/cm3 ± 0.05g/cm3. Typically, pore sizes in the range of 150-300µm were produced. The fabrication of CaP OPS resulted in a wide range of macroporosity in the correct size range for osseointegration to occur. Elongating the pore structure did not affect the total porosity of the bioceramics. Strengths were low due to microcrack formation on sintering and not due to the shape of the pores present in the scaffold as initially hypothesised.

scholarly journals Characterization and in vitro assessment of three-dimensional extrusion Mg-Sr codoped SiO2-complexed porous microhydroxyapatite whisker scaffolds for biomedical engineering

2021 ◽  
Vol 20 (1) ◽  
Author(s):  
Chengyong Li ◽  
Tingting Yan ◽  
Zhenkai Lou ◽  
Zhimin Jiang ◽  
Zhi Shi ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Cell Proliferation ◽  
Pore Size ◽  
Osteogenic Differentiation ◽  
Bone Repair ◽  
Porous Scaffold ◽  
Porous Scaffolds ◽  
Sprague Dawley ◽  
Active Elements

Abstract Background Large bone defects have always been a great challenge for orthopedic surgeons. The use of a good bone substitute obtained by bone tissue engineering (BTE) may be an effective treatment method. Artificial hydroxyapatite, a commonly used bone defect filler, is the main inorganic component of bones. Because of its high brittleness, fragility, and lack of osteogenic active elements, its application is limited. Therefore, its fragility should be reduced, its osteogenic activity should be improved, and a more suitable scaffold should be constructed. Methods In this study, a microhydroxyapatite whisker (mHAw) was developed, which was doped with the essential trace active elements Mg2+ and Sr2+ through a low-temperature sintering technique. After being formulated into a slurry, a bionic porous scaffold was manufactured by extrusion molding and freeze drying, and then SiO2 was used to improve the mechanical properties of the scaffold. The hydrophilicity, pore size, surface morphology, surface roughness, mechanical properties, and release rate of the osteogenic elements of the prepared scaffold were detected and analyzed. In in vitro experiments, Sprague–Dawley (SD) rat bone marrow mesenchymal stem cells (rBMSCs) were cultured on the scaffold to evaluate cytotoxicity, cell proliferation, spreading, and osteogenic differentiation. Results Four types of scaffolds were obtained: mHAw-SiO2 (SHA), Mg-doped mHAw-SiO2 (SMHA), Sr-doped mHAw-SiO2 (SSHA), and Mg-Sr codoped mHAw-SiO2 (SMSHA). SHA was the most hydrophilic (WCA 5°), while SMHA was the least (WCA 8°); SMHA had the smallest pore size (247.40 ± 23.66 μm), while SSHA had the largest (286.20 ± 19.04 μm); SHA had the smallest Young's modulus (122.43 ± 28.79 MPa), while SSHA had the largest (188.44 ± 47.89 MPa); and SHA had the smallest compressive strength (1.72 ± 0.29 MPa), while SMHA had the largest (2.47 ± 0.25 MPa). The osteogenic active elements Si, Mg, and Sr were evenly distributed and could be sustainably released from the scaffolds. None of the scaffolds had cytotoxicity. SMSHA had the highest supporting cell proliferation and spreading rate, and its ability to promote osteogenic differentiation of rBMSCs was also the strongest. Conclusions These composite porous scaffolds not only have acceptable physical and chemical properties suitable for BTE but also have higher osteogenic bioactivity and can possibly serve as potential bone repair materials.

COMBINED ATOMIC FORCE AND FLUORESCENCE MICROSCOPIES TO MEASURE SUBCELLULAR MECHANICAL PROPERTIES OF LIVE CELLS

2013 ◽  
Vol 13 (04) ◽  
pp. 1350057 ◽  
Author(s):  
CHENG-TAO CHANG ◽  
CHOU-CHING K. LIN ◽  
MING-SHAUNG JU
Keyword(s):  
Mechanical Properties ◽  
Elastic Modulus ◽  
Elastic Properties ◽  
Previous Method ◽  
Live Cell ◽  
Live Cells ◽  
Cellular Functions ◽  
Atomic Force ◽  
Force Volume ◽  
The Relationship

Atomic force microscopy (AFM) has been widely applied to study cellular functions;however, the relationship between cellular elasticity and ultrastructure density of a live cell remains to be discovered. The objective of this study was thus to extend our previous method of integrating AFM and immunofluorescence imaging to measure the ultrastructure distribution-related local mechanical properties of live cells. First, the morphology of a live cell was obtained by AFM. Second, the indentation sites were selected and flexible force volume indentation was performed. Third, the immunofluorescence image of the cell was obtained. The last was the mapping of the indentation site to the immunofluorescence image and obtaining the relationship between the local elastic properties and cytoskeleton density. The results on differentiated rat Schwann cells (RSCs) showed that the elastic modulus of stress fibers is higher than those of the nucleus and cytosol. The local elastic modulus of the live RSCs is correlated to the actin density, and the stress fiber that behaves like a pretension beam can give RSCs enough strength to envelop axons during myelination. In particular, the elastic properties of the live RSCs were twofold lower than those of the fixed. The results demonstrated the integrated method's applicability for a live cell.

Experimental Study of Mechanical Properties of Additively Manufactured ABS Plastic as a Function of Layer Parameters

2015 ◽  
Author(s):  
Todd Letcher ◽  
Behzad Rankouhi ◽  
Sina Javadpour
Keyword(s):  
Mechanical Properties ◽  
Elastic Modulus ◽  
Layer Thickness ◽  
Maximum Stress ◽  
Testing Machine ◽  
Single Layer ◽  
Maximum Force ◽  
Fused Filament Fabrication ◽  
Individual Layer ◽  
Number Of Layers

In this study, a preliminary effort was undertaken to represent the mechanical properties of a 3D printed specimen as a function of layer number, thickness and raster orientation by investigating the correlation between the mechanical properties of parts manufactured out of ABS using Fused Filament Fabrication (FFF) with a commercially available 3D printer, Makerbot Replicator 2x, and the printing parameters, such as layer thickness and raster orientation, were considered. Specimen were printed at raster orientation angles of 0°, 45° and 90°. Layer thickness of 0.2 mm was chosen to print specimens from a single layer to 35 layers. Samples were tested using an MTS Universal Testing Machine with extensometer to determine mechanical strength characteristics such as modulus of elasticity, ultimate tensile strength, maximum force and maximum elongation as the number of layers increased. Results showed that 0° raster orientation yields the highest mechanical properties compared to 45° and 90° at each individual layer. A linear relationship was found between the number of layers and the maximum force for all three orientations, in other words, maximum force required to break specimens linearly increased as the number of layers increased. The results also found the elastic modulus and maximum stress to increase as the number of layers increased up to almost 12 layers. For samples with more than 12 layers, the elastic modulus and maximum stress still increased, but at a much slower rate. These results can help software developers, mechanical designers and engineers reduce manufacturing time, material usage and cost by eliminating unnecessary layers that do not increase the ultimate stress of the material by improving material properties due to the addition of layers.

Sign in / Sign up

Export Citation Format

Share Document