New Electrospinning Technique For Preparing Functional Micro And Nano Fiber And Its Application

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.