面向电纺直写的流体包轴输运行为与调控研究

Electrohydrodynamic Direct-Writing (EDW) has become one of the great potiential micro/nano fabrication technologies. The requirement of fast response, precise controlled picoliter-level solution with high viscousity transport is the biggest obstracle for the industrial application of EDW technology. In the proposal, a picoliter-level solution tranport method based on Weissenberg Effect (Axel-Enwrapped Effect) has been proposed to satisfy the EDW solution supply requirements. With the typical characteristics of multi-scale geometry of the inkjet tip, strong electrical field, jetting and fast response behavior existed in EDW, some unconfronted problems, e.g. the static status and dynamic responses of solution enwraping on axel process under micro scale, the influx and jetting phenomena will be studied. The mechanisms of of micro-scale Axel-Enwrapping solution under the coupled field of strong electric and shear stress are to be disclosed. And also, the competing behaviors between wetting, surface tension, and electrical force will be investigated, so that the effects of the inkjet nozzel geometry, solid-liquid interface, shear stress on the Axel-Enwrapping, and the laws of influx and jetting etc, can be mastered. The local enviroment conditions and it's design rules are to be set up to realize the picolitre-level viscous solution transport continuously, based on which the stable jetting, the written long uniform fiber (structure) with diameter of sub-micron can be realized. As one of the examples, nano optical-fiber will be direct-written to evaluate fisibility of EDW technology based on the Axel-Enwrapping solution transport process. The results would provide a strong scientific and technological foundation for EDW technology industrilization, as well as useful approaches to improve the solution-processed micro-nano structures quality. Specially, the research will enlarge the area and enrich the contents of the traditional Axel-Enwrapping effect.

电纺直写技术以其独特的原理性优势被认为是最具发展潜力的微纳制造技术之一，响应快速、精密、微量高粘度流体可控供液是制约电纺直写获得产业化应用的关键技术问题。项目提出利用高粘度流体的包轴效应实现微量流体输运原理方案；针对电纺直写中喷嘴针尖的跨尺度、强电场、射流、快速响应等典型特征，研究微纳尺度、强电场作用下的包轴流体稳态和动力学响应、尖端汇流、射流等新问题，揭示电场、剪切耦合作用的微纳尺度流体包轴物理机制；阐明界面浸润-表面张力-电场力的竞争行为；掌握喷嘴结构、界面、剪切的静态与动态作用规律；探明流体输运的汇流、射流行为规律。构建微量高粘度流体的连续输运的微环境和调控策略及其设计规则，实现出射点稳定、直径可控的亚微米射流的连续直写，以纳米光纤为例加以验证与评价。为推进电纺直写技术实用化奠定理论和技术基础，为提升微纳压印这类高粘度溶液法微纳制造的品质提供新途径，也将拓宽包轴效应的内涵。

现有的静电纺丝供液技术存在压阻幅度较大、控制源距离喷嘴较远等问题，无法实现电纺直写技术所需的连续、稳定、响应快速的液体输运，制约了其在微纳制造技术上的应用和发展。针对电纺直写技术的供液需求，展开了对微尺度包轴效应、微纳流体包轴输运以及强电场作用下的包轴效应的研究，探索了基于液体包轴输运的电纺直写技术在微纳制造、柔性电子领域中的应用。. 研究了微尺度的包轴效应，考察了剪切运动形式、表面张力、表界面特性等单独或联合作用下的液面形貌，揭示了微纳尺度包轴效应的机制，建立了微纳尺度包轴效应的理论模型。构建了包轴自由液面与针芯直径、溶液浓度、剪切速度等参数的关系，掌握了包轴效应的液面形貌变化规律。. 探究了管芯结构包轴效应和包轴输运中表面张力的作用。考察了不同管道内径、针芯形貌、溶液属性等条件下的液面形貌，掌握了包轴自由液面与轴径、管道内径、转轴转速、溶液浓度等参数的相互关系，揭示了表面张力对包轴效应的影响机制。分析了管芯结构中表面张力对基于包轴效应的流体输运的作用规律，提出了喷嘴结构的设计依据。. 分析了剪切流变作用下管芯结构中的自由曲面形貌的变化，建立了微管道中包轴效应理论模型；以自行设计的喷嘴为基础，考察了电场作用下的包轴效应、射流源点位置及射流直径等，揭示了剪切力、表面张力和电场力的竞争机制与行为，获得了产生射流的条件和射流摆动幅度的变化规律，研究了剪切流变作用与射流的相互关系。并设计开发了基于包轴供液的直写实验系统，探究了基于包轴效应的供液规律以及工艺参数对电纺直写的影响规律。. 探究了基于包轴供液的电纺直写在石墨烯复合材料的柔性电子器件、微纳光纤以及电子皮肤压力传感器等制备方面的应用，验证了包轴输运供液系统在电纺直写方面微量、连续、快速的优势，为推动电纺直写在微纳制造领域的实际化应用奠定了一定的理论和技术基础。