Papers by Author: Qing Xi Hu

Abstract: The clinical applications of tissue engineering are still limited by the lack of a functional vascular supply in tissue-engineered constructs. In order to improve the pre-vascularization of tissue-engineered scaffold during in vitro culture, in this study, based on three-dimensional (3D) printing technology, using the crosslinking effect of coaxial fluids (sodium alginate and CaCl₂) to prepare vessel-like hollow gel fibers, then layer by layer overlapping into 3D scaffold. The biological 3D printing platform was successfully developed and a coaxial nozzle module was introduced to generate a CaCl₂-in-Alginate coaxial microfluidic. The inner core diameters of the prepared hollow gel fibers were 220~380 micrometers. In addition, the influence of materials concentration and dispensing rates on hollow fiber dimension were investigated, the cell-encapsulated in the printed hollow fibers was realized and the viability of endothelial cells (ECs) was studied with Laser scanning confocal microscopy (LSCM) and Live-Dead cell staining. The 3D scaffold built by hollow fibers could improve the phenomenon of diffusion constrain and enhance the survival rate of those ECs growing at a greater depth in the construct. This study provides a new theoretical basis for the vascularization of bone scaffold.

Abstract: LDM process is used for preparing three-dimensional scaffolds for tissue engineering rapid prototyping technologies. Because of its forming process is complex, which influenced by a variety of factors, so the processing environment is not stable, the forming of scaffold pore size can not be guaranteed, therefore the forming precision is poor. However, the scaffold pore size accuracy is mainly decided by the wire filament width. Neural network theory and development provides a powerful tool for the study of nonlinear systems. This article analyzed the influence factors for forming bone scaffold filament width of LDM process, based on improved BP neural network, using MATLAB software programming, then predicted the filament width. The results show that model prediction error was less than 8%, it has high forecasting precision, and it can be used to guide the LDM process parameter selection and forming precision of prediction.

Abstract: To solve vacuum casting process exist two-component polyurethane difficult to uniform mixing problems. A non-symmetric eccentric large blade agitator was proposed and the speed was period changed to strengthen the mixed effects. A fluid dynamics of variable speed agitator tank was proposed to numerical simulation flow behacior with Euler - Euler two-fluid model and the dynamic mesh (SM) method. Though numerical simulate to study flow field characteristics of variable speed agitator tank.. The experiment results show that the proposed method can not only achieve high viscosity polyurethane resin with uniform mixing, and shorten the processing time. Effectively solve the polyurethane resin materials difficult to uniform mixing problems.

Abstract: An ideal scaffold should mimic the morphology of the natural extracellular matrix and have good mechanical properties and biologically functional. So, the key point of fabricating of scaffolds is to realize the composition of scaffolds by materials having different physical and biological properties and control porous structure accurately. In this study, we propose a novel technology combining a low-temperature deposition, electrospinning process and freeze-drying to produce a hierarchical 3D biomedical scaffold consisting of micro-sized highly porous chitosan-gelatin strands and nanosized PCL fibers network. Scanning electron microscopy analysis showed that the scaffold composed of parallel aligned micro-strands in a grid-like arrangement layer by layer, along the thickness direction intercalated by a network with randomly distributed nanofibers. The stand of macro-scaffold composed of natural-derived biomaterials and nanofibers composed of synthetic biomaterials were bonded together firmly to form a stable network structure.

Abstract: From the perspective of forming bone scaffold, the technologic parameters of LDM which have important influence on the shape of the deposition material are studied. Through building experimental platform and using chitosan solution as experimental material, the influence of the temperature and the layer height on the lap of every fiber layer are firstly discussed in detail. Besides, the effects of nozzle diameter, the velocity of receiving device, the pressure of feeding device are also discussed. Then the above mentioned process parameters are all optimized, which make the forming mechanism of LDM to be clear. Finally, based on the optimal parameters, the scaffold with self-designed pore size and a high degree of pore interconnectivity, which meeting the requirements of the structure of tissue engineering are fabricated.

Abstract: Low-temperature deposition manufacturing (LDM) has been proven as an effective bone scaffold preparation process, but its further application has been seriously hindered by the existing material over-accumulation problem. In view of the over-accumulation problem of the traditional pneumatic extrusion material feeding way, designed and developed a feeding system based on pneumatic-extrusion and valve-control, which can achieve rapid pressure/relief, Combined with the inflation / deflation time calculation method of fixed volume container for analysis and calculation. A unified data management method of the material feeding device and a regulation scheme of the controller are given. Experimental results show that, by adjusting parameters, the feeding system based on pneumatic-extrusion and valve-control can achieve rapid gas pressure/relief, the flux has been well controlled, the over-accumulation on deposition path at the end has been eliminated, which lead to effective guarantee of scaffold forming quality.

Abstract: Aiming at the problem that current vacuum casting method lack of the filling ability in filling large & thin-wall castings. Therefore, a regulated pressure vacuum casting method is proposed, which using regulated pressure to improve the filling ability. The process and mechanism for regulated pressure vacuum casting method is presented and proved it through the home-made V450N-VD vacuum casting prototype. The results show that the regulated pressure vacuum casting method has higher filling capacity and can provide higher negative pressure during the whole filling process. So regulated pressure vacuum casting method has profound development potential.

Abstract: Boolean operation is the key technology for modeling the bone scaffold. This paper proposes a Boolean operation algorithm based on triangle mesh model. It firstly voxelizes the mesh models based on project vector and octree, and classifies the vertices into inside, outside and surface type according to the position relationship between the vertex and the other mesh model’s voxel. Then the triangles can be easily classified based on the vertices class. Finally the Boolean model can be composed by the corresponding triangles of the Boolean operation. In order to obtain the intersection features well, it detects the intersection lines and gets the intersection polygons further, and then triangulates the polygon using the ear clipping method. This Boolean operation algorithm has been applied to the bone scaffold modeling and got good performance．

Abstract: To prevent the collision of tools and machine during the process of numerical control processing, reduce the number of cutting experiments and improve the production efficiency, it is a better way by using virtual simulation. This paper based on a mold cavity model of STL files, realized the numerical control programming based on Power Mill, researched the dynamic simulation process based on VERICUT, and at last verified the correctness and practicability of VERICUT simulation result by physical processing, which provided a reliable reference for physical machining.

Abstract: Electrospinning is an effective and versatile technology to fabricate ultrafine nanofiber,however further development is urgently limited due to the low uniformity distribution and unpredictable feature of the fiber deposited. For that sake, experiment has been done and analyzed to address these problems. Relation between process physics-Taylor cone and fiber diameter characters has been discovered. Furthermore, the feature parameters of the Taylor cone are extracted effectively by CCD detection and image processing. The above experiments results and processing data is analysis and examed by the steady jet theory. This paper offers significant theoretical guidance and technical support to the online control of electrospinning fiber diameter.