| Near-field electrospinning(NFES)is one of the most potential techniques to fabricate the aligned microdevices efficiently and accurately.To meet the fabrication requirement of high efficiency and precision,the method of array multi-nozzle near-field electrospinning direct-writing has become the current research focus.However,the method has faced the science and technology problem,including deposit positioning accuracy affected by electric field interference,coupling effect of multiple technological parameters and so on.In this academic dissertation,the core problems of direct-writing process is proposed and studied during array multi-nozzle NFES,which including the adjusting and control mechanism of multi-nozzle NEFS direct-writing,electric field interference mechanism with multi-nozzle,direct-writing process programming,dynamics modeling of multi-jet deposition process and fabrication of alignedmicrodevices.The main research work and contributions of this dissertation are introduced as follows:Firstly,in view of fabricating aligned pattern with array multi-nozzle NFES direct-writing printing process,the experimental studies based on the injected and flight behavior of multi-jet,which have studied the influence law of technological parameterson charged multi-jet deposition behavior and fiber morphology,including substrate velocities,applied voltage and electrode-to-collector distance.Moreover,the synthetically action mechanism between the multi-jet and tractive force by substrate has revealed under inhomogeneous electric field environment.Then the deposition accuracy of aligned fiber with controllable morphology has been realized.Furthermore,a dual-nozzle cooperative NFES direct-writing aligned 3D microstructure method is proposed.The direct-writing printing method has achieved the consistent and respective stacking of multi-jet to fabricate large ratio of height to width(about 18:1)3D aligned microstructure efficiently.And the microstructure forming and morphology of microstructure influenced by process parameters has been studied.Secondly,the influence of geometry parameters on aligned fiber deposition process and surface morphology has been studied during multi-nozzle NFES process.According to analyze the interaction mechanism of charged multi-jet,the relationship of geometry parameters of array multi-nozzle and electrostatic field interference have been revealed.Furthermore,the quantitative evaluation of electrostatic field interference among array multi-nozzle has been established,which is used to analyze the influence of geometry parameters of array multi-nozzle on structure and morphology of aligned fibers.The results showed that the quantitative evaluation index of electrostatic field interference is satisfactory.In same geometry parameters of array multi-nozzle,the longer the multi-nozzle are,the bigger the electrostatic field interference is,but it is indistinctive.With increasing needle spacing,the quantity of electrostatic field interference is decreased.With increasing the numbers of multi-nozzle,the quantity of electrostatic field interference is increased.The average fiber diameter is increasing when the quantity of electrostatic field interference is increased.With different numbers of multi-nozzle,there is closed to a positive correlation between the average fiber diameter and average quantity of electrostatic field interference,besides the fiber diameters and homogeneity of deposition distance have almost showed a negative correlation relationship.Thirdly,the planning method of process parameter during dual-nozzle NFES direct-writing process is proposed.Based on electrospinning environment of multi-nozzle NFES system,the core factor is identified among multi-domain coupling factors.Moreover,a multi-quadratic regression model is established to analyze coupling effect between multi-domain factors and its sensitivity to deposition distance of aligned fibers based on the quadratic response surface method.And the planning method of process parameter has revealed the comprehensive influence of multi-domain factors on the deposition distance of aligned fiber,which has obtained the optimal parameter combination for the dual-nozzle NFES direct-writing process.Moreover,to direct-write higher density aligned pattern in difference path,which is used to provide process guidance for direct-writing high resolution and integration structured patterns.Fourthly,the behavior of flight and deposition with charged multi-jet is studied to analyze the effect of process parameters on deposition distance of aligned fibers under non-uniform electric field environment.The theoretical model is established to analyze deposition characteristics of dual-nozzle NFES process,which is driven by electrohydraulic coupling.Moreover,it has verified the influence of process parameters on deposition distance of aligned,and realized the charged multi-jet to deposit accurately.Through further deduction and verification,the adaptability of the improved theoretical model of multi-nozzle NFES direct-writing is confirmed and provided to guide to direct-write aligned pattern controllably in large quantities.Finally,based on multi-nozzle NFES direct-writing aligned microstructure process,the application researches are developed in transmission gratings,transparent electrodes and microfluidic channels.With multi-nozzle NFES,the high efficiency and simple preparation of transmission grating is proposed by direct-writing PEO aligned fiber array,which is fully verified the reliability of theoretical model on deposition characteristic and related processes.Through direct-writing aligned 3D microwall array by dual-nozzle cooperative NFES,the application research of high-performance and low-cost transparent electrode is carried.The influence of structure and morphology of aligned microwall array on performance of transparent electrode is studied.With increasing average diameter and Au thickness of fibers,the electrical conductivity increases but the transmittance decreases.And the photoelectric properties of transparent electrode is enhanced when the ratio of height to width with microwall increases.Moreover,the experiment has shown that the sheet resistance is 8 Ω/sq and the transmittance is 97%,which is superior to the performance of transparent electrode prepared than the conventional process.The PEO nanofibers have prepared as template by dual-nozzle cooperative NFES,which used to fabricate submicron microfluidic channel devices on PDMS.The connectivity of parallel aligned arrays and grid array microfluidic channels is verified,and whose size index is 931 nm in width and 2.41 μm in height. |
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