Da Li Liu

Study on Low-Temperature Deposition Manufacturing Process Parameters of Three-Dimensional Chitosan Scaffold

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.

Study on Processing and Model Building of Composite Structure Forming for 3-D Regenerative Bone Scaffold

Based on the analyzing for strengths and weaknesses of the rapid prototyping (RP) and electrospinning technique in the manufacturing of three-dimensional bone scaffold, the defects including RP’s low precision and electrospinning’ low intensity has been found. Accordingly, composite structure forming (CSF) has been proposed. This approach integrates the advantage of rapid prototyping and electrospinning. Furthermore, the modeling method of Scaffold for composition forming has been proposed .At the end, the method of controlling process has been given.

On-Line Control for the Pore Size of Bone Scaffold Based on LDM

The scaffold is a key part of the artificial regeneration osseous tissues. The ideal scaffold will have the ability to mimic the fully functional tissue, which can afford the fibrous form and complex function of the native ECM. Although Low-temperature deposition manufacturing is a promising method for fabricate tissue scaffold because scaffold can maintain a good performance of biomaterials in low temperature, the scaffold pore size can not be controlled according to demands. Therefore, the key factors that affect the pore size of bone scaffolds are firstly analyzed. Then the mechanism for on-line control is given. Finally, an automatic control system is proposed and some experimental results are given, which have demonstrated the effects of processing parameters on the Shaping of scaffold material.

The Research on a New Feeding Device of Low-Temperature Deposition for Fabricating Tissue Engineering Scaffolds

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.

Studying on Auxiliary Gradient Rings for the Collecting Area of Electrospinning

When electrospinning has been used as a special technology of regenerative bone scaffold, for raising the efficiency of electrospinning and decreasing collecting area, the mechanism of bending instability was analyzed and concluded that the force of electric field is a key factor. Auxiliary gradient rings have been added to electric field, which changed the environment of electric filed. Then, it was verified that additive gradient rings could reduce the collecting area. On the other hand, Maxwell was used to analyze the strength and structure of electric field. The maximum intensity of electric field existed in the position of nozzle. The farther apart from nozzle, the rapidly intensity decreased. When auxiliary gradient rings had been added, the intensity of instability stage showed increased trend. Mechanism analysis and experimental result were confirmed by the simulation effectively.

A New Feeding Device of Electrospinning Design for the Micro-Structure of Bone Scaffold Prototyping

In order to solve the problem that bone cells can not adhere to the pore wall, the paper introduces a new method that combines RP method with electrostatic spinning method is used for the preparation of a comprehensive new bone scaffold technology, and pays close attention on the automatic control of process parameters, the feeding speed. According to the model of feed speed and the diameter of nano-fibers, a theoretical guidance is given to the real-time control of feed speed, and a new feeding device, including the configuration software iFIX, a microcontroller, a sensor and stepping motor, is presented. It can give a real-time effective control of the feed speed, which provides a theoretical and technological basis for the quality of scaffolds prototyping.

Algorithm Research of Pattern Recognition for Process Control of Electrospinning

Electrospinning is kind of unique craft to fabricate nanoscale fiber in the condition of high-voltage electric field. However, due to the nanoscale diameter manufacturing, it is a challenge to get the whole manufacturing process stable at certain level. For that sake, this paper figures out the monitor method for the electrospinning equipment, which solves the former matter as well as makes the fiber generating process in control. According to the method, CCD camera is put forward to make the detection of the Taylor cone image continuously, while pattern recognition algorithm is used to real-time monitor the shape and size of Taylor cone which indicate the stable process of electrospinning. In order to get the stable Taylor cone shape, the processing result is used as feedback signal for control system of the electrospinning equipment to coordinate the feeding module or power supply module. As a result, the problem of nonuniformity and uncontrollable about electrospinning has been solved effectively; whats more, experiments testify that this method is reliable and effective.

Bone Scaffold Forming Filament Width Prediction of LDM Based on the Improved BP Neural Network

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.

Design and Implementation Full Automatic Intelligent Control System Oriented to Vacuum Casting

Based on craft features analysis of vacuum casting, this paper concluded that the automation level and control precision of control system are key influencing factors for products quality of vacuum casting. So the purpose of this paper is to resolve these disadvantages of existing control system of vacuum casting equipments. This paper designed a new full automatic intelligent control system which adopts two-level distributed structure. The system is consisted of motor control subsystem, vacuum monitoring and control subsystem, and bubbles detecting and eliminating subsystem. According to the function requirement of control system, this paper described selection and configuration of hardware and function implement of software in detail. Finally, this paper designed and realized a new automatic detecting and eliminating method of bubbles based on vision sensor technology, and presented an intelligent controller model based on Wavelet Neural Network (WNN) for motors. The experimental prototype of vacuum casting has been developed and a large number of experiments have been carrying on. These new controlling algorithms have being tested. The control system integrates vision sensor, intelligent control, microcomputer interface and imaging processing technologies, so it possess high precision, efficiency and flexibility and has a good market application prospect and high economic value. It will be breakthrough for precise rapid tooling.

The Pneumatic Feeding System of Electrospinning Based on Numerical Simulation and System Identification

Electrospinning, which is a technology to make nano fiber, has quite high requirements of the speed of feeding. In order to solve the unstable phenomenon, salivation, and achieve the stability of quality, numerical simulation is used to compute the nozzle exit pressure and exit velocity, while recursive least squares is used to identify of the results of the simulation. At last, PID algorithm and recursive least squares methods are combined together to form a model for the feeding system controller. And the pneumatic device and pressure sensor are used to build electrospinning feeding system. Finally, experimental verification PEO solution is used to verify this method, no drooling electrospinning phenomenon happens