【作者】 张明；

【导师】 徐晓嵘； 司廷；

【作者基本信息】 中国科学技术大学 ， 仪器科学与技术， 2021， 博士

【摘要】 多功能微尺度纤维具有较高的比表面积、良好的可操作性以及灵活的组分和结构等特性,因而在组织工程、雾水收集、信息编码和药物释放等领域得到了广泛应用。而在这些实际应用中,微纤维材料的结构和组分特征往往决定了最终的性能表现。经过数十年的发展,研究人员已经建立了包括湿法纺丝、静电纺丝和微流体纺丝在内的多种技术平台,以用于微纤维材料的可控制备。作为一种新兴的技术平台,微流体纺丝技术能够在微尺度通道内实现对多相流体的精确操控,因而在制备结构复杂和组分多样的微纤维材料时具有显著优势。但是,传统微流体纺丝技术中复杂的纺丝装置和封闭的纺丝环境不利于通道构型的调整和外部激励的引入,使得微纤维结构的灵活性和可编程性受到限制,进而影响了微纤维材料在各类应用中的性能表现。针对传统微流体纺丝技术中存在的不足,本文开发了一种基于振动激励调控的动态界面纺丝(Dynamic Interfacial Spinning,DIS)技术,实现了微纤维材料在开放环境下的可控、灵活和可编程化制备,并探索了这些多功能微纤维在实际应用中的潜力,主要内容如下:1.开发了一种兼具简易性、可控性和灵活性的主动式微流体纺丝技术,即DIS技术。DIS过程中使用的纺丝针管由常见的不锈钢针头组装而成,无需进行表面处理即可使用,从而大大降低了装置制造难度。在外部激励控制下,纺丝针管会在凝固浴界面处竖直振动,因而能够在纤维成形过程中对其施加界面剪切作用,最终实现微纤维的可控制备。开放的纺丝环境则赋予了 DIS过程出色的灵活性,便于对纺丝针管的通道构型进行调整和拓展。利用单轴和同轴DIS过程,我们分别制备了单相水凝胶微纤维和载液滴微纤维。并且,微纤维的结构特征可通过调整振动参数和流体流量进行精确控制。通过进一步拓展针管构型,还可以构建具有复合结构的水凝胶微纤维和载液滴微纤维,从而扩充了微纤维材料的结构类型。2.通过对单轴DIS过程中制备的节点形水凝胶微纤维进行干燥脱水,成功构建了具有“纺锤形节点+连接段”结构的仿蛛丝微纤维。与天然蛛丝相似,该纤维具有雾水收集功能,可在模拟雾气环境下完成雾气的凝结、水滴的定向汇聚和相邻水滴的合并,从而捕获和富集雾气中的水分。并且,在雾水收集过程中,仿蛛丝微纤维表现出了出色的水运输和悬挂能力。在深入研究纤维集水机制的基础上,我们通过改变纤维的结构特征实现了对纤维集水性能的灵活调控,从而为高效集水纤维的优化设计提供了依据。更进一步,通过将具有复合结构的多轴节点形水凝胶微纤维进行干燥脱水,还可以构建结合了两种仿生集水结构的组合仿生微纤维。该纤维不仅具有类似天然蛛丝的节点形外观,同时其表面还与仙人掌针刺的表面相似,分布着多条轴向微沟槽。与仿蛛丝微纤维相比,组合仿生微纤维的集水效率得到了显著提升,从而证明了组合仿生策略在高效集水纤维设计方面的有效性。3.利用振动激励的连续性和灵活性,成功开发了可编程化DIS过程用于制备具有体积编码特征的载液滴微纤维。通过对振动信号波形的灵活编辑,可以实现对纤维内部液滴体积的连续和可编程化调控。而不同大小的液滴可以作为编码单元,从而在纤维内部形成液滴编码序列。和基于颜色差异的传统纤维编码策略相比,体积编码微纤维具有良好的稳定性和优异的信息容量,可实现完整文本信息的存储和读取,从而为微纤维材料在信息传输领域的应用奠定了基础。除此以外,通过整合不同的功能材料,体积编码微纤维还可以实现信息加密和精准化药物释放的功能,这证明了可编程化DIS过程在构建功能化微纤维方面的通用性和灵活性。更多还原

【Abstract】 Multifunctional microscale fibers with high specific surface area,excellent flexibility,and controllable composition and structure have been widely used in the fields of tissue engineering,fog harvesting,encoding,and drug release.In this respect,the structural and compositional features of microfibers have decisive impact on the actual performance.Until now,a variety of technical platforms,including wet spinning,electrospinning and microfluidic spinning technology(MST),have been established for the controllable construction of structured microfibers.As an emerging platform,MST features precise manipulation of multiphase fluids in microscale channels,thus enabling the controllable generation of microfibers with complex structures and diverse components.However,the complex spinning devices and confined spinning condition in the traditional MST processes are not conducive to the adjustment of the channel configuration and the introduction of external excitation,which limits the structural flexibility and programmability of resultant microfibers,and thus restricts their actual performance in various applications.To overcome those limitations,we develop a dynamic interfacial spinning(DIS)technology through introducing tunable vibrational excitation in an unconfined spinning condition,thereby facilitating the controllable,flexible,and programmable generation of multifunctional microfibers.The main contents are as follows:1.A novel active microfluidic spinning technology,namely DIS technology,is developed,which is characterized with simplicity,controllability and flexibility.The spinning nozzles applied in DIS process are facilely assembled using commonly used stainless steel needles,and then directly utilized without the need for surface treatment,thus simplifying the design and manufacture of the spinning device in a DIS process.Under the external excitation,the spinning nozzle will undergo tunable vertical vibration at the air-liquid interface of the coagulation bath,thereby enabling precise structural control of the resultant fibers through introducing an interfacial shearing effect in the fiber gelatinization process.The freeform spinning condition endows the DIS process with superior flexibility,which facilitates the adjustment and extension of the configuration of the spinning nozzle.Through uniaxial and coaxial DIS processes,single-component hydrogel microfibers and droplet-embedded microfibers are controllably constructed,respectively.In addition,the structural features of those microfibers can be precisely controlled by adjusting the vibration parameters and the fluidic flow rates.Through the further extension of nozzle configuration,hydrogel and droplet-embedded microfibers with compound structural features can be flexibly constructed,thereby expanding the design space of functional microfibers.2.Through the dehydration of knotted hydrogel microfibers produced in the uniaxial DIS process,the spider-silk-like microfibers with the microstructure of periodic spindle knots and joints are controllably constructed.Similar to natural spider silk,those bioinspired microfibers can capture and enrich water from the simulated fog environment through fog condensation,directional water transport and coalescence of adjacent droplets,and demonstrate ultrafast water transport and superior water hanging ability in the fog harvesting process.Based on the experimental and theoretical investigation of fog harvesting process,the water collection efficiency of the spider-silk-like microfibers can be controlled by adjusting the structural features,which lays the foundation for the engineering of bioinspired microfibers with optimized water collection ability.Furthermore,combinational bionic microfibers with both cactus-spine-like surface grooves and spider-silk-like microstructure can be constructed through the dehydration of the multiaxial knotted hydrogel microfibers.Compared with the spider-silk-like microfibers,the water collection efficiency of the combinational bionic microfibers is significantly improved,which proves the effectiveness of the combinational bionic strategy in the design of efficient fog harvesting microfibers.3.Taking advantage of the continuity and flexibility of vibrational excitation,the programmable DIS process is successfully developed to generate droplet-embedded microfibers with volume encoding feature.Through the flexible modulation of the vibration signal waveform,continuous and programmable control of the droplet volume inside the microfibers can be realized.The embedded droplets of different volumes can be utilized as encoding units to form a volume encoding sequence.Compared with the traditional fiber encoding strategy based on color difference,volume-encoded microfibers possess good stability and superior information capacity,thus enabling the storage and reading of complete text information,which paves the way for the application of encoded microfibers in the field of information transmission.In addition,through the integration of various functional materials,the functionalized volume-encoded microfibers reveal great application potential in the fields of information encryption and precise drug release,which also proves the versatility and flexibility of programmable DIS process for the construction of functionalized microfibers.更多还原