[Show abstract][Hide abstract] ABSTRACT: The rapid prototyping and manufacturing technology (RPM), is an integration of many different disciplines. It is based on an advanced dispersed-accumulated forming principle and originated from 1980s. It generates an entity by first forming a series of layers according to the dispersed section information of the digital model, and then piling the formed layers sequentially together. It is capable of forming parts with complicated structures and non-homogeneous materials. Traditional RPM techniques are mainly used as prototypes in product invention process, such as stereolithography, three-dimensional printing, laminated object manufacturing, and fused deposition modeling. Later, with the progress of material and enabling technology, many new RPM techniques emerged out and have been already applied in the fields such as rapid tooling/moulding, direct formed usable part, nano-/micro-RPM, and biomanufacturing. This high flexible digital manufacturing method has a likely ability to become an almighty forming technology.
[Show abstract][Hide abstract] ABSTRACT: Small-diameter vascular grafts are potential substitutes for damaged vessels in patients, but most biodegradable grafts available now are not strong enough. The present study examined the burst strength, radial compliance, suture retention strength for a novel biodegradable tubular scaffold and investigated its behavior in vivo. The tubular scaffold (6-mm i.d., 4 cm long) has three layers including porous polylacticglycolic- acid in both inner and outer layers, a compact polyurethanes layer in midst. Bone marrow stromal cells (bMSCs) were seeded on the scaffolds and cultured for 7 days in vitro to construct tissue engineered vascular grafts which were then implanted in canine abdominal aorta. After 1, 3, 6, 12 and 24 weeks, the grafts were retrieved and evaluated histologically, angiographically and immunohistochemically. The biodegradable tubular scaffolds showed wall thickness of 0.295 mm to 0.432 mm; radial compliance of 3.80%/100 mmHg approximately 0.57%/100 mmHg, burst strength of 160 kPa approximately 183 kPa, and suture retention strength of 1959 N/cm(2) approximately 3228N/cm(2). The implanted grafts were fully patent without any signs of dilation or obstruction after 3 months' implantation. Scanning electron microscopy revealed a confluence endothelial cell layer spreading on the inner surface of the grafts. Immunohistochemistry of the retrieved grafts showed that vWF-stainin, alphaSMA-staining were positive in the inner and medium layer respectively. Masson's trichrome staining showed that amount of collagen fibers existed in the grafts wall. Overall, these novel three-layered scaffolds exhibited favourable mechanical strength, long term patency and good remodeling in vivo.
Full-text · Article · Mar 2008 · Biotechnology and Bioengineering
[Show abstract][Hide abstract] ABSTRACT: Using rapid prototyping technology, three-dimensional (3D) structures composed of hepatocytes and gelatin hydrogel have been formed. This technique employs a highly accurate 3D micropositioning system with a pressure-controlled syringe to deposit cell/biomaterial structures with a lateral resolution of 10 microm. The pressure-activated micro-syringe is equipped with a fine-bore exit needle for which a wide variety of 3D patterns with different arrays of channels (through-holes) were created. More than 30 layers of a hepatocyte/gelatin mixture were laminated into a high spacial structure using this method. The laminated hepatocytes remained viable and performed biological functions in the construct for more than 2 months. The rapid prototyping technology offers potential for eventual high-throughout production of artificial human tissues or organs.
No preview · Article · Feb 2006 · Tissue Engineering
[Show abstract][Hide abstract] ABSTRACT: We have recently developed an organ manufacturing technique that enables us to form cell/biomaterial complex three-dimensional (3D) architectures in designed patterns. This technique employs a highly accurate 3D micropositioning system with a pressue-controlled syringe to deposit cell/biomaterial structures with a lateral resolution of 10 microm. The pressure-activated micro-syringe is equipped with a fine-bore exit needle using which a wide variety of 3D patterns with different arrays of channels (through-holes) were created. The channels can supply living cells with nutrients and allow removing the cell metabolites. The embedded cells remain viable and perform biological functions as long as the 3D structures are retained. The new technology has the potential for eventual high-throughput production of artificial human tissues and organs.
[Show abstract][Hide abstract] ABSTRACT: To further enhance the properties of existing collagen/chitosan scaffolds for liver tissue engineering, a very simple method was developed to form noncovalently linked mimic of the liver extracellular matrices. Collagen/chitosan mixtures in various proportions (i.e., 1:0, 3:2, 1:1, 2:3, and 0:1 v/v) were lyophilized or evaporated to form sponges or flat films before they were gelled using an aqueous 25% ammonia solution. The porosities of the obtained sponges were above 90% with various pore sizes. The highest mechanical strength (1.9+/-0.7 MPa) and the lowest degradation time (65+/-1.7 days) were achieved by the collagen/chitosan (1:1) matrices. Hepatocytes cultured on the collagen/chitosan (1:1) matrices exhibited relatively high glutamate-oxaloacetate transaminase and glucose secretion functions 25 days post-seeding. Nuclues of the hepatocytes were more elongated and arranged in certain directions on the 1:1 matrices. The cytocompatibility and enhanced biostability of our new ammonia-treated collagen/chitosan matrices suggest that they could be used as scaffolds for liver tissue engineering.
No preview · Article · Oct 2005 · Journal of Biomedical Materials Research Part B Applied Biomaterials
[Show abstract][Hide abstract] ABSTRACT: An organ manufacturing technique was developed that enables the formation of cell/extracellular matrix (ECM) complexes for in vitro or in vivo growth. In this study, a three-dimensional (3D) structure composed of hepatocytes and gelatin/alginate hydrogel was made using a cell assembler-I apparatus to thoroughly control cell assembling. Hepatocytes and ECM were constructed into 10 X 10 X 3mm3 structures according to a designed pattern. The embedded hepatocytes remained viable and performed biological functions in the construct for more than 12 days. This D structure has the potential to be used as a precursor for tissue or organ regeneration. This technology offers the potential for high-throughput production of artificial human tissues and organs.
Full-text · Article · May 2005 · Journal of Bioactive and Compatible Polymers
[Show abstract][Hide abstract] ABSTRACT: A new type of collagen/chitosan/heparin matrix, fabricated by gelation of collagen/ chitosan with heparin sodium containing ammonia, was produced to construct livers by tissue engineering and regenerative engineering. The obtained collagen/chitosan/heparin matrix was found to be highly porous, swelled rapidly in PBS solution and was stable in vitro for at least 60 days in collagenase/lysozyme containing buffered aqueous solution (PBS, pH 7.4) at 37 degrees C. The collagen/chitosan/heparin matrix resulted in a superior blood compatibility compared to the ammonia-treated collagen and collagen/chitosan matrices. The morphology and behavior of the cells on the collagen/chitosan/heparin membrane were found to be similar to those on the collagen membrane but different from those on the collagen/chitosan membrane. Hepatocytes cultured on the collagen/chitosan/heparin matrices exhibited highest urea and triglyceride secretion functions 25 days post seeding. These results suggest that this collagen/chitosan/heparin matrix is a potential candidate for liver tissue engineering.
No preview · Article · Feb 2005 · Journal of Biomaterials Science Polymer Edition
[Show abstract][Hide abstract] ABSTRACT: To make an implantable bioartificial liver (IBL), a new biocompatible collagen/chitosan/heparin complex was prepared using a crosslinking agent. The X-ray photoelectron spectroscopy (XPS), mechanical strength and biocompatibility with whole blood and hepatocytes were measured. The collagen/chitosan/heparin complex resulted in a superior blood compatibility compared to 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide (EDC) crosslinked collagen matrix. The morphology and behavior of the cells on the collagen/chitosan/heparin membrane were found to be different from those on the collagen and collagen/chitosan membranes. Cells on the collagen membrane formed smaller three-dimensional aggregates than those on the collagen/chitosan membrane, while on the collagen/chitosan/heparin membrane, a round shape with no junctions were manifested. No adverse effects were found on the viability and function of the hepatocytes on the collagen/chitosan/heparin membrane compared to the collagen and collagen/chitosan membranes. These results suggest that this collagen/chitosan/heparin matrix is a potential candidate for hepatic tissue engineering.
No preview · Article · Jan 2005 · Journal of Bioactive and Compatible Polymers
[Show abstract][Hide abstract] ABSTRACT: In Rapid Tooling (RT), all of the forming stages influence the dimensional accuracy of the die. The forming stages include slicing the CAD model to the STL file, making the prototype using an RP machine, obtaining the ceramic mold and transforming the ceramic mold to a metal die. In RT, the precise casting that is to transform the ceramic mold to a metal die plays a very important role in the dimensional accuracy of the die. The dimensional accuracy of the casting die during the solidification process is analyzed using a three dimensional (3-D) non-linear coupled thermo-mechanical model in this paper. The material non-linearity, geometry non-linearity and boundary non-linearity during the solidification process are considered. Guaranteeing the dimensional accuracy of the casting die is a key technical problem for RT technology. The coupled thermo-mechanical analysis is used to simulate a typical cylinder part and the die of an automobile deck part. In addition, the contact model for the boundary between the casting and the matrix during the coupled thermo-mechanical analysis is analyzed using the method of contacting mechanics with the casting and the matrix treated as elastic–plastic deformable bodies. The convergence criterion and time step are selected while solving the non-linear FEM equations with the material properties changing with temperature. The numerical result for the dimensional accuracy of the automobile deck part die matches well with the experimental result. The results demonstrate that an accurate 3-D non-linear coupled thermo-mechanical FEM model can be developed to analyze the dimensional accuracy for casting dies in RT. Accurately analyzing the dimensional accuracy of the casting die has important significance for modifying the CAD model to produce a die with high dimensional accuracy.
No preview · Article · Dec 2001 · Finite Elements in Analysis and Design
[Show abstract][Hide abstract] ABSTRACT: Multi-functional rapid prototyping manufacturing system (M-RPMS) is an important potential developing field and tendency of RP technique. Application area of the M-RPMS has been discussed in this paper. It is believed that the M-RPMS has to be developed both for industrial and academic purposes. The openness of software and hardware, the diversity of RP processes and the highest function/cost ratio are the outstanding speciality of the M-RPMS. This paper also introduces the design principle of the M-RPMS, the calculation method for function integration degree (FID), the running of SLS in the M-RPMS and the key of early stage rapid feedback design system.
Preview · Article · Jul 1998 · Integrated Manufacturing Systems