1,097 research outputs found
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Transferring Unit Cell Based Tissue Scaffold Design to Solid Freeform Fabrication
Designing for the freeform fabrication of heterogeneous tissue scaffold is always a challenge in
Computer Aided Tissue Engineering. The difficulties stem from two major sources: 1)
limitations in current CAD systems to assembly unit cells as building blocks to form complex
tissue scaffolds, and 2) the inability to generate tool paths for freeform fabrication of unit cell
assemblies. To overcome these difficulties, we have developed an abstract model based on
skeletal representation and associated computational methods to assemble unit cells into an
optimized structure. Additionally we have developed a process planning technique based on
internal architecture pattern of unit cells to generate tool paths for freeform fabrication of tissue
scaffold. By modifying our optimization process, we are able to transfer an optimized design to
our fabrication system via our process planning technique.Mechanical Engineerin
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Automated Design of Tissue Engineering Scaffolds by Advanced CAD
The design of scaffolds with an intricate and controlled internal structure represents a
challenge for Tissue Engineering. Several scaffold manufacturing techniques allow the
creation of complex and random architectures, but have little or no control over geometrical
parameters such as pore size, shape and interconnectivity- things that are essential for tissue
regeneration. The combined use of CAD software and layer manufacturing techniques allow
a high degree of control over those parameters, resulting in reproducible geometrical
architectures. However, the design of the complex and intricate network of channels that are
required in conventional CAD, is extremely time consuming: manually setting thousands of
different geometrical parameters may require several days in which to design the individual
scaffold structures. This research proposes an automated design methodology in order to
overcome those limitations. The combined use of Object Oriented Programming and
advanced CAD software, allows the rapid generation of thousands of different geometrical
elements. Each has a different set of parameters that can be changed by the software, either
randomly or according to a given mathematical formula, so that they match the different
distribution of geometrical elements such as pore size and pore interconnectivity.
This work describes a methodology that has been used to design five cubic scaffolds with
pore size ranging from about 200 to 800 µm, each with an increased complexity of the
internal geometry.Mechanical Engineerin
Geometric Modeling of Cellular Materials for Additive Manufacturing in Biomedical Field: A Review
Advances in additive manufacturing technologies facilitate the fabrication of cellular materials that have tailored functional characteristics. The application of solid freeform fabrication techniques is especially exploited in designing scaffolds for tissue engineering. In this review, firstly, a classification of cellular materials from a geometric point of view is proposed; then, the main approaches on geometric modeling of cellular materials are discussed. Finally, an investigation on porous scaffolds fabricated by additive manufacturing technologies is pointed out. Perspectives in geometric modeling of scaffolds for tissue engineering are also proposed
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Accuracy and Mechanical Properties of Open-Cell Microstructures Fabricated by Selective Laser Sintering
This paper investigates the applicability of selective laser sintering (SLS) for the manufacture of
scaffold geometries for bone tissue engineering applications. Porous scaffold geometries with
open-cell structure and relative density of 10-60 v% were computationally designed and
fabricated by selective laser sintering using polyamide powder. Strut and pore sizes ranging from
0.4 - 1 mm and 1.2 -2 mm are explored. The effect of process parameters on compressive
properties and accuracy of scaffolds was examined and outline laser power and scan spacing
were identified as significant factors. In general, the designed scaffold geometry was not
accurately fabricated on the micron-scale. The smallest successfully fabricated strut and pore size
was 0.4 mm and 1.2 mm, respectively. It was found that selective laser sintering has the potential
to fabricate hard tissue engineering scaffolds. However the technology is not able to replicate
exact geometries on the micron-scale but by accounting for errors resulting from the diameter of
the laser and from the manufacturing induced geometrical deformations in different building
directions, the exact dimensions of the manufactured scaffolds can be predicted and controlled
indirectly, which corresponds favorably with its application in computer aided tissue engineering.Mechanical Engineerin
Recent advances in 3D printing of biomaterials.
3D Printing promises to produce complex biomedical devices according to computer design using patient-specific anatomical data. Since its initial use as pre-surgical visualization models and tooling molds, 3D Printing has slowly evolved to create one-of-a-kind devices, implants, scaffolds for tissue engineering, diagnostic platforms, and drug delivery systems. Fueled by the recent explosion in public interest and access to affordable printers, there is renewed interest to combine stem cells with custom 3D scaffolds for personalized regenerative medicine. Before 3D Printing can be used routinely for the regeneration of complex tissues (e.g. bone, cartilage, muscles, vessels, nerves in the craniomaxillofacial complex), and complex organs with intricate 3D microarchitecture (e.g. liver, lymphoid organs), several technological limitations must be addressed. In this review, the major materials and technology advances within the last five years for each of the common 3D Printing technologies (Three Dimensional Printing, Fused Deposition Modeling, Selective Laser Sintering, Stereolithography, and 3D Plotting/Direct-Write/Bioprinting) are described. Examples are highlighted to illustrate progress of each technology in tissue engineering, and key limitations are identified to motivate future research and advance this fascinating field of advanced manufacturing
Layer manufacturing for in vivo devices
Traditional in vivo devices fabricated to be used as implantation devices included sutures, plates, pins, screws, and joint replacement implants. Also, akin to developments in regenerative medicine and drug delivery, there has been the pursuit of less conventional in vivo devices that demand complex architecture and composition, such as tissue scaffolds. Commercial means of fabricating traditional devices include machining and moulding processes. Such manufacturing techniques impose considerable lead times and geometrical limitations, and restrict the economic production of customized products. Attempts at the production of non-conventional devices have included particulate leaching, solvent casting, and phase transition. These techniques cannot provide the desired total control over internal architecture and compositional variation, which subsequently restricts the application of these products. Consequently, several parties are investigating the use of freeform layer manufacturing techniques to overcome these difficulties and provide viable in vivo devices of greater functionality. This paper identifies the concepts of rapid manufacturing (RM) and the development of biomanufacturing based on layer manufacturing techniques. Particular emphasis is placed on the development and experimentation of new materials for bio-RM, production techniques based on the layer manufacturing concept, and computer modelling of in vivo devices for RM techniques
Internal Structure Evaluation of Three-Dimensional Calcium Phosphate Bone Scaffolds: A Micro-Computed Tomographic Study
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66317/1/j.1551-2916.2006.01143.x.pd
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Precision Extrusion Deposition of Polycaprolactone/Hydroxyapatite Tissue Scaffolds
Freeform fabrication provides an effective process tool to manufacture advanced tissue scaffolds
with specific designed properties. Our research focuses on using a novel Precision Extrusion
Deposition (PED) process technique to directly fabricate Polycaprolactone (PCL) and composite
PCL/ Hydroxyapatite (HA) tissue scaffolds. The scaffold morphology and the mechanical
properties were evaluated using SEM and mechanical testing. In vitro biological studies were
conducted to investigate the cellular responses of the composite scaffolds. Results and
characterizations demonstrate the viability of the PED process as well as the good mechanical
property, structural integrity, controlled pore size, pore interconnectivity, and the biological
compatibility of the fabricated scaffolds.Mechanical Engineerin
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Mechanical Properties and Biological Responses of Bioactive Glass Ceramics Processed using Indirect SLS
This paper will report on research which aims to generate bone replacement components by
processing bioactive glass-ceramic powders using indirect selective laser sintering. The indirect
SLS route has been chosen as it offers the ability to tailor the shape of the implant to the
implantation site, and two bioactive glass ceramic materials have been processed through this
route: apatite-mullite and apatite-wollostanite. The results of bend tests, to investigate
mechanical properties, and in vitro and in vivo experiments to investigate biological responses of
the materials will be reported, and the suitability of completed components for implant will be
assessed.Mechanical Engineerin
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