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新型静电纺丝技术制备功能微纳米纤维及其应用
【作者】 孙彬；
【导师】 龙云泽；
【作者基本信息】 青岛大学 ， 材料学， 2014， 博士
【摘要】 静电纺丝法是一种简单、快捷,且可以较大规模制备均匀、连续的一维纳米结构材料的方法,其制备的纤维直径可从几十个纳米到几微米。研究和开发静电纺丝技术及其制备的一维纳米结构材料的应用已经成为各国科研人员广泛关注的课题。到目前为止,通过电纺技术已经实现了近百种不同聚合物纳米纤维、各种类型聚合物/无机物复合纳米纤维及无机纳米纤维的制备。由于静电纺丝微纳米纤维独特的物理化学性质,因此在组织工程、纳米传感器、太阳能电池、药物缓释、催化、柔性器件等领域具有广泛的潜在应用。传统静电纺丝最常见的产物是二维无纺布纤维结构,这在某种程度上限制了其更进一步的应用,因此,对于形貌可控电纺微纳米纤维结构及其应用的需求也日益增加。本文基于电纺基本原理,尝试利用新型静电纺丝法制备形貌可控的微纳米纤维结构。在对其形成机理进行详细探讨的同时,还对其部分结构的应用进行了深入的探索和研究。首先,通过对电纺过程中部分工艺参数的控制,我们利用传统静电纺丝装置在很短的时间以内,制备了三维自组装堆垛纤维结构。该堆垛结构可在很短时间内达到超过10cm的高度。在详细研究该三维自组装纤维结构形成机理之后,我们实现了三维堆垛结构与传统二维纤维膜之间的成功转换。其次,考虑到扭曲结构在预应变控制方面得天独厚的优势,我们分别制备了基于无序和有序结构的电纺纤维扭曲结构：先是利用带有尖端收集极的静电纺丝装置制备了无序的螺旋扭曲结构。通过将常规静电纺丝中的铝箔变成一个具有很小面积的尖端收集极,可以改变正负极之间的电场分布,从而改变电纺纤维内部力学分布,增加纤维的力学不稳定性,因此更容易形成扭曲螺旋结构的微纳米纤维。然后,我们利用结合了静电纺丝与简谐运动的新型静电纺丝装置—纺丝喷头往复式静电纺丝装置,使得有序排列扭曲结构的导电聚合物纤维阵列得以制备。由于存储于扭曲结构中的预应变得以控制,因此基于该阵列制备的柔性可拉伸应变传感器,具有优良的抗拉伸性,并且具有很好的可重复性和耐久性。再次,我们以电纺PMMA纤维作为模板,通过原位聚合的方法在其表面生长了一层纳米枝状结构聚苯胺,从而制备出新型同轴纤维结构,PMMA纤维外包裹的纳米枝状结构聚苯胺使得材料具有较高的比表面积。此外,我们对该同轴结构纤维的电学性能以及对氨气的气体敏感性能进行了测试。结果表明,基于无序排列的同轴纤维结构具有较低的电导率,但对氨气的气体敏感性更高；而基于有序排列的同轴结构纤维则表现出更良好的电学性能。最后,我们通过双框架收集装置和离心电纺装置制备了纳米纤维绞线结构,通过对电纺参数的控制,这两种方法制备的绞线结构表面干净光滑,没有毛刺,且后者构成绞线的纤维数目可控,这对于研究单根电纺微纳米纤维的力学性能有着积极的意义。该绞线结构可望用于制备光学器件、电子器件,以及用于微机电系统的微纳米绳索/人工肌肉等。
【Abstract】 Electrospinning has drawn much interest nowadays as a simple and versatile technique for fabricating uniform ultrafine fibers with diameters ranging from several micrometres down to a few nanometers. Besides polymeric materials, nano/microfibers based on organic/inorganic composites, and organic materials have also been fabricated via electrospinning. The electrospun fibers have been developed as a good potential candidate in many fields, such as tissue engineering, nano-sensors, energy applications, drug release, catalyst supports, and flexible/stretchable devices. However, the random orientation of fibrous mats fabricated by the conventional electrospinning may limit the potential applications of as-spun fibers, especially in some fields such as electronics, photonics, photovoltaics and actuators which need direct, fast charge transfer or regular, uniform structures. Thus it is of significance to designing and fabricating structure-controlled electrospun micro-/nanofibers, as well as their further applications in many areas.In this thesis, mainly based on the theory of electrospinning, we not only fabricated some structure-control led fibrous architecture, but also studied the forming mechanism of them in detail. Moreover, some potential applications of the aforementioned fibrous constructs have been explored.First of all, by controlling experimental conditions precisely, we have fabricated self-assembled cone-like polystyrene fiber stacks with a height of more than10cm on an aluminum foil within30min. Moreover, conversion between the3D fiber stacking and2D thin film can be controlled. The formation mechanism of the self-assembled fiber stacks and the influence of experimental conditions have also been explored.Secondly, in consideration the advantage of curled fibers in controlling the prestrain, we report disordered curled microfibers fabricated by a modified electrospinning with a tip collector. Our results indicated that the formation mechanism for the curled fibrous structure can be ascribed to the more intense electrical driven bending instability and/or mechanical jet buckling when hitting the modified collector surface compared with the flat A1foil. Besides, stretchable strain sensors based on aligned micro fibrous arrays of PEDOT:PSS-PVP with curled architectures have been fabricated by a novel reciprocating-type electrospinning setup which combing the straightforward simple harmonic motion with electrospinning. Owing to the curled architectures of the as-spun fibrous polymer arrays, the sensors can be stretched reversibly with a linear elastic response to large strain which is three times higher than that from electrospun nonwoven mats. In addition, the stretchable strain sensor with a high repeatability and durability. These results may be helpful for the fabrication of stretchable devices which have potential applications in some fields such as soft robotics, elastic semiconductors, and elastic solar cells. Furthermore, we have fabricated nano-branched coaxial PANI fibers that grown on electrospun PMMA nanofibers by an in situ chemical oxidative polymerization method. The nonwoven PANI/PMMA fibers mat behaves much better than aligned samples in ammonia sensing ability and can response significantly to ultra-low concentration of ammonia, while the aligned sample exhibited better conductivity and easy approach of resistance.Finally, we utilized a two-frame collector and a centrifugal electrospinning technique to fabricate fibrous nano/microropes, respectively. By controlling the processing parameters during electrospinning, the nano/microrope structures generated by these two methods both demonstrated smooth surfaces without any beads. In addition, it is easy to count and control the number of the fibers consisted in the microropes from the umbrella-like structures in the latter technique, which is of importance for the mechanical properties measurement of an individual electrospun fiber.