| Polymer melt electrospinning direct writing technology is a new material forming processing technology,and is a new technology with good prospects in the field of scaffold technique of tissue engineering.At present,the particulate leaching and phase separation methods are used to prepare the tissue engineering scaffold by the polymers.Compared with these technologies,the melt electrospinning direct writing technology has good controllability,low production cost,good biocompatibility and biodegradability of materials.Meanwhile,the tissue engineering scaffold prepared by this technology has the advantages of high porosity and large surface area.In the essay,the development process and the research progress at home and abroad of the polymer melt electrospinning direct writing technology are reviewed and the shortcomings of the existing researches are pointed out.It elaborates the controllable modeling mechanism of the polymer melt electrospinning direct writing technology,and studies the variation of electric field in the electrospinning direct writing process as well as the effect of voltage,relative movement speed and spinning distance on deposition morphology of fibers.The controllable modeling device of the polymer melt electrospinning direct writing technology is designed and developed.And then,the fiber orientation and property of single fibers,parallel and cross-grid structures,and multi-level complex grid structures are studied.It proposes a method to eliminate the effect of the accumulated charge on the number of spinning layers during spinning process.Finally,the continuously and gradually changing multi-level complex grid structure is prepared.And the major work is as following:1.Elaborate the key mechanisms of polymer melt electrospinning direct writing technology by analyzing the basic principles of the electrospinning technology,charge accumulation in polymer and environmental factors.The variation of electric field in melt electrospinning direct writing process is stimulated by the finite element software and it is discovered that the relative movement of spinning nozzle and receiving plate had a great influence on the field strength.Therefore,to ensure a better deposition morphology of fibers,the spinning nozzle should be kept stationary and the receiving plate should be kept moving.In addition,it is discovered that the location of the electrode plate will have a great effect on the voltage and field strength in the spinning process.Thus,the electrode plate and receiving plate shall be connected together to promote the fiber diameter refinement and the increase of spinning layer numbers.2.A controllable modeling device of melt electrospinning direct writing technology is designed and then the CPU,the 3D control core of the receiving plate,is printed by 3D technology,which solves the control accuracy of the motion.By adopting the device as the experiment platform,it studies the speed matching mechanism in the melt electrospinning direct writing forming process and summarizes the influence of relative movement speed,spinning voltage,receiving distance parameters on the deposition morphology of jet fibers and the correlation mechanism of these three parameters.Meanwhile,a new outlook is designed for the device and the device operation experience is optimized,which has laid a foundation for the device industrialization.3 The electric field drive method is introduced to decrease fiber diameter,and a safe,green and precise 3D print method is put forward.The voltage will have great impact on the fiber diameter and the larger the voltage is,the smaller the fiber diameter is.During the fabrication process of the multi-level complex grid,the effect of charge accumulation on the fabrication process is decreased by the method of suspending print-air blowing and then restarting print,which promotes to obtain the structure of more printing layers.Through the experiment,it is found that under the voltage of 6KV,the method of "suspending print-restarting print" will increase the number of spinning layers and the accuracy of fiber deposition.And it is discovered that,the influence is most obvious when the suspend time is within 30s.In addition,the method of"suspending print-restarting print" can effectively help to prepare different structural features between layers in multilevel complex grid structures.4.Based on the above mentioned experiment,the application research on the preparation of the tissue engineering scaffold is conducted at the last time of the essay.Firstly,a multi-level complex grid structure with gradient characteristics is designed to adapt to the growth of cells.Secondly,a new mesh structure preparation method based on the offset print method is put forward,by which,the mesh structure with the aperture size of 1/2 or less of the spinning distance can be obtained.It is a effective way to avoid the influence of charge accumulation on the spinning process.In conclusion,in the essay,the controllable modeling mechanism and method of the polymer melt electrospinning direct writing technology are studied,and the important influence factors of the spinning process are stimulated.A kind of controllable modeling device of the polymer melt electrospinning direct writing technology is designed and developed and the industrial design of the device is conducted.Besides,the preparation experiment of the fiber grid is conducted by the device and the major technology parameters of the electrospinning direct writing process is summarized.A 3D topological structure print method that can effectively control the fiber diameter is proposed and the effect of charge accumulation on the electrospinning direct writing is verified.It points out that the method of "suspending print-restarting print" can increase the number of layers and the print accuracy of multi-level complex grid structure.In addition,a multi-level complex grid structure with gradient characteristics is designed and a kind of offset print method is put forward to avoid the effect of charge accumulation on spinning process.These studies have laid a good foundation for the preparation of the tissue engineering scaffold. |
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