尖端辅助电极在静电纺多射流形成与调控中的作用机制及其应用研究

Traditional electrospinning technique takes important position and has special advantage for mass production of nanofibers in the world. Some shortcomings, such as a single jet and mutual electrostatic interference among the spinnerets in this process, is currently the "bottle-neck" problem causing a low product rate and non-uniform structure of nanofiber mat. In this proposal, we suggest a novel technique, introducing a tip auxiliary electrode in the spinning zone, to control the number of jets ejected simultaneously from Taylor cone during electrospinning process. Our previous results showed that this technique could produce 2-12 jets by changing the electrode paramenters in a traditional process and improve greatly the yield of electrospun nanofibers. Our aims are, firstly, to study the effect of the electrode on the electric field distribution, the deformation of Taylor cone and the property of charged fluid drop through experimental and theoritical study. The critical spinning conditions and the patterns of EHD fluid flow will be also investigated, and the relationship between the process parameters and the formation of multi-jets will be summarized as well. Then the law of mutual electrostatic interference among multiple jets and the flight path of jets will be studied in detail. Finally, this technique will be examined in multiple-needle electrospinning process and needleless electrospinning process. Our research would provide a deep understand of the formation mechanism of multiple jets, the jet path and the control of nanofiber orientation distribution in electrospinning. It would be also used to design new scale-up electrospinning technique and new electrospinning apparatus, and give a theoretical and experimental basis for mass production of nanofibers.

传统针式静电纺在纳米纤维制备及规模化生产方面仍具有重要地位和优势。但针式静电纺喷丝头射流单一、喷头间相互静电干扰等缺陷是导致其生产效率较低和产品结构不匀的重要瓶颈问题。本项目提出在传统针式静电纺中引入尖端辅助电极调控喷丝头多射流形成的方法，实现类似非针式静电纺的多射流喷射，可有效提高纳米纤维制备效率，并有望改善产品结构不匀的现象。本项目拟结合纺丝优化实验和有限元分析软件，探索辅助电极参数对纺丝区电场分布等的影响，建立电极参数、工艺参数、溶液性能参数与多射流形成之间的联系，从实验和理论上阐明多射流喷射的关键物理机制和普适性条件；建立射流的力学模型，明晰多射流间静电干扰本质和多射流运动轨迹；并尝试应用该技术到多喷头式静电纺丝技术和其它非针式静电纺丝技术的可行性。本项目的实施，对于揭示静电纺丝机理、促进静电纺丝技术进步具有重要作用，为纳米纤维工业化生产设备的设计和制造提供新的思路和途径。

首先，项目组在对有尖端辅助电极参与的静电纺丝区电场模拟优化的理论研究基础上，对影响多射流数量和效果的参数进行了系统研究，建立了工艺参数、溶液性能参数和电极参数与多射流形成的关系模型。项目组总结了辅助电极位置（平行、垂直、相对）、辅助电极数量以及辅助电极接地、带正电压和带负电压等对静电纺丝过程中射流数量的影响规律，阐明了各种位置关系参数下多射流产生的临界条件。为进一步明确多射流形成的影响规律与普适性条件，借助色散关系模型建立了多射流喷射模型，给出了针式辅助电极静电纺产生多射流的理论临界条件；同时阐明了液滴泰勒锥形变与多射流形成的关系，利用高速摄影机对液滴以及多射流的运动过程进行了拍摄，结合图片二值化处理并通过Mathematica数学软件拟合液滴表面曲线，建立了带电液滴表面形变与多射流生成临界条件的数学模型。在探明了多射流产生的临界条件的基础上，对射流数量变化趋势进行了理论预测与实验验证。为了研究辅助电极静电纺丝多射流的运动轨迹，利用变分原理推导出射流振动频率与射流流量的关系数学模型。项目组还首次发现存在多射流“临界产生电压”和“临界退出电压”，并提出尖端辅助电极静电纺丝双“开关”电压的概念，阐明了溶液粘度、溶液表面张力、对射流数量极大值和双“开关”电压的影响规律。在此基础上，项目组将辅助电极技术应用到多喷头静电纺丝技术、气泡静电纺丝技术、“火山口”状泰勒锥静电纺丝技术等，均取得了成功。最后，项目组尝试利用该技术增强纳米纤维产量及纳米纤维膜结构均匀性的特点，将获得的纳米纤维应用于油水分离膜材料、可穿戴柔性传感器、膜蒸馏材料和锂离子电容器隔膜材料等，均取得了成功。本项目的研究，对于阐明辅助电极在静电纺丝过程中多射流形成的作用机制、静电纺丝工艺及装备设计与改进、提高纳米制备效率与应用具有重要推动作用。