1,721,029 research outputs found
Hybrid multi-layered scaffolds produced via grain extrusion and electrospinning for 3D cell culture tests
Full text linkPurpose: The purpose of this paper is to focus on the production of scaffolds with specific morphology and mechanical behavior to satisfy specific requirements regarding their stiffness, biological interactions and surface structure that can promote cell-cell and cell-matrix interactions though proper porosity, pore size and interconnectivity. Design/methodology/approach: This case study was focused on the production of multi-layered hybrid scaffolds made of polycaprolactone and consisting in supporting grids obtained by Material Extrusion (ME) alternated with electrospun layers. An open source 3D printer was utilized, with a grain extrusion head that allows the production and distribution of strands on the plate according to the designed geometry. Square grid samples were observed under optical microscope showing a good interconnectivity and spatial distribution of the pores, while scanning electron microscope analysis was used to study the electrospun mats morphology. Findings: A good adhesion between the ME and electrospinning layers was achieved by compression under specific thermomechanical conditions obtaining a hybrid three-dimensional scaffold. The mechanical performances of the scaffolds have been analyzed by compression tests, and the biological characterization was carried out by seeding two different cells phenotypes on each side of the substrates. Originality/value: The structure of the multi-layered scaffolds demonstrated to play an important role in promoting cell attachment and proliferation in a 3D culture formation. It is expected that this design will improve the performances of osteochondral scaffolds with a strong influence on the required formation of an interface tissue and structure that need to be rebuilt
Hybrid scaffolds with a 3D-printed polymer lattice core and a bioactive hydrogel shell for bone regeneration
No full textRecent research in the field of tissue engineering is focusing on the realization of hybrid scaffolds as multi-material systems which allow to successfully combine the advantages of different biomaterials. In addition, additive manufacturing technologies are currently explored for their production, as means to control and personalize the scaffold structure. In this paper, composite scaffolds with a core–shell structure are studied, the core consisting of a rigid poly-l-lactic acid lattice realized by fused deposition modeling, and the shell consisting of a bioactive hydrogel, grafted upon the core and freeze-dried to develop porous microstructure. Different lattice structures are designed and realized as repetition of unit cells having different size and strut arrangement. Compression tests reveal the suitability of the mechanical properties of the scaffolds for bone tissue regeneration, and the possibility to modulate their stiffness and strength upon the lattice parameters. Moreover, the interconnected porous structure of the shell, assessed by morphological analysis at the microscope, may promote cell colonization and proliferation, while its composition may support osteogenic differentiation
Influence of long and short glass fiber on the mechanical behaviour of a single cell metamaterial
No full textAdditive manufacturing is presenting new challenges in various aspects of part production. Among these, the potential benefits derived from material complexity have been growing in recent years, especially when using polymeric materials. In fact, mixing polymers with long/short fibres lead to moderate to significant improvements in the mechanical properties of the parts. The degree of improvement strongly depends on the part geometry and can become critical in the case of a workpiece with a repeating pattern, such as metamaterials. In this preliminary research, the authors investigate the mechanical performance of a single-hourglass cell which is a common auxetic geometry used to achieve a negative Poisson ratio in metamaterials. Nylon was used as the matrix, and glass as the fibre. FFF additive process was used to produce samples with different cell designs (in width, size, inclination) and the nature of the fibres (long and short). The results were analysed using statistical methods
Hierarchical motion of 4D-printed structures using the temperature memory effect
No full textThe temperature memory effect (TME) refers to the ability of a shape memory polymer to display recovery around the temperature at which its predeformation occurred so that the material expresses its shape memory response not only in terms of shape but also for what concerns the deformation temperature. This peculiar effect, displayed only by certain classes of polymers, allows to control of the triggering temperature for the shape memory effect as well as to provide multiple shape memory responses for specific, properly designed predeformation histories. Moreover, when combined with 3D printing, such an effect opens new powerful perspectives for designing autonomous structures with customized architectures and programmable/controllable shape changes. However, the design of such structures and of their active response is not trivial and requires careful attention at different levels, i.e., during printing, experimental characterization, modeling, and simulation. The topic of the present chapter concerns 4D-printed structures exhibiting the TME, and it aims at providing the reader with both an analysis and discussion, helpful in guiding toward the design of functional structures capable of controlled motions, also in a hierarchical manner. Particularly, a methodological approach is proposed and includes three main stages: evaluation of material properties, experimental characterization of 3D-printed structures, and modeling/simulation. A discussion about the steps of each stage is provided, together with an overview of the current state of the art, and a case study is presented. Potential application fields and future perspectives are also explored and discussed
A versatile cell-friendly approach to produce PLA-based 3D micro-macro-porous blends for tissue engineering scaffolds
No full textIn this study we instituted an innovative, cost-effective, green and versatile methodology to produce a series of PLA-based open-pore porous blends with high porosity and interconnectivity as well physico-mechanical properties suitable for tissue engineering application. Parent poly-L-lactic acid (PLA) blend was prepared by melt-blending using crosslinked sodium polyacrylate particles as a porogen, commonly used as superabsorbent polymer (SAP). The obtained biphasic systems showed a regular distribution of SAP particles with diameters up to about 50 μm and, most importantly, retained their superabsorbent ability within the thermoplastic PLA based matrices that facilitated swelling followed by leaching out from PLA based matrices in aqueous environment generating very high porosity. Very importantly, versatility of this developed methodology was judged by accommodating different polymers, such as, poly (3-hydroxybutyrate) (PHB) poly (ɛ-caprolactone) (PCL) or poly (ethylene glycol) (PEG) or wood-cellulose microfiber (SP) to generate monophasic, biphasic, plasticized or reinforced blends, respectively, under identical benign condition. These blends were analyzed morphologically, thermally and mechanically to evaluate the degree of miscibility, thermal stability and mechanical property to apply as scaffolds in tissue engineering. Finally, all these scaffolds allowed good cell adhesion and proliferation during culture of mouse embryo fibroblasts cell line. Hence, this methodology of producing PLA-based polymeric system stunned with processability to accommodate other biocompatible polymers allows selectively modifying biomaterial properties for target application and appears very promising platform for several applications, particularly for scaffold production in tissue engineering
Microsegregating blends of ethyl cellulose and poly(vinyl pyrrolidone): a combined thermo-mechanical and positron annihilation spectroscopy study
No full textPolymer blends are a versatile playground for studying phase separation and its effect on the development of morphology and mechanical properties of the resulting materials. Blends obtained from two immiscible polymers, ethyl cellulose (EC) and poly(vinyl pyrrolidone) (PVP), are especially relevant for their practical applications as coatings for pharmaceutical preparations and controlled drug release. Here, films of EC-PVP blends are studied by means of thermal analysis, dynamic-mechanical analysis as well as positron annihilation lifetime spectroscopy. The morphology of the microstructures generated by phase separation is investigated by means of scanning electron microscopy. The effect of both components' ratio and of molecular mass of PVP on the final properties of the blends is determined in a systematical way. The results obtained are not only of theoretical interest but will prove useful for the optimization of industrial formulations based on these polymers
Tailoring the properties of composite scaffolds with a 3D-Printed lattice core and a bioactive hydrogel shell for tissue engineering
No full textThe optimal performance of scaffolds for tissue engineering relies on a proper combination of their constituent biomaterials and on the design of their structure. In this work, composite scaffolds with a core-shell architecture are realized by grafting a gelatin-chitosan hydrogel onto a 3D-printed polylactic acid (PLA) core, aiming in particular at bone regeneration. This hydrogel was recently found to sustain osteogenic differentiation of mesenchymal stromal cells, leading to new bone tissue formation. Here, the integration with rigid PLA lattice structures provides improved mechanical support and finer control of strength and stiffness. The core is prepared by fused deposition modeling with the specific aim to study several lattice structures and thereby better tune the scaffold mechanical properties. In fact, the core architecture dictates the scaffold strength and stiffness, which are seen to match those of different types of bone tissue. For all lattice types, the hydrogel is found to penetrate throughout the entire core and to present highly interconnected pores for cell colonization. By varying the void volume fraction in the core it is possible to significantly change the bioactive shell content, as well as the mechanical properties, over a wide range of values. Looking for design guidelines, relationships between stiffness/ strength and density are here outlined for scaffolds featuring different lattice parameters. Moreover, by acting on the core strut arrangement, scaffolds are reinforced along specific directions, as evaluated under compressive and bending loading conditions
Development and Comparison of Model-Based and Data-Driven Approaches for the Prediction of the Mechanical Properties of Lattice Structures
Full text linkLattice structures have great potential for several application fields ranging from medical and tissue engineering to aeronautical one. Their development is further speeded up by the continuing advances in additive manufacturing technologies that allow to overcome issues typical of standard processes and to propose tailored designs. However, the design of lattice structures is still challenging since their properties are considerably affected by numerous factors. The present paper aims to propose, discuss, and compare various modeling approaches to describe, understand, and predict the correlations between the mechanical properties and the void volume fraction of different types of lattice structures fabricated by fused deposition modeling 3D printing. Particularly, four approaches are proposed: (i) a simplified analytical model; (ii) a semi-empirical model combining analytical equations with experimental correction factors; (iii) an artificial neural network trained on experimental data; (iv) numerical simulations by finite element analyses. The comparison among the various approaches, and with experimental data, allows to identify the performances, advantages, and disadvantages of each approach, thus giving important guidelines for choosing the right design methodology based on the needs and available data
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