69 research outputs found

    Multi-compartment centrifugal electrospinning based composite fibers

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    Multi-faceted technological advances in fiber science have proven to be invaluable in several emerging biomaterial and biomedical engineering applications. In the last decade, notable fiber engineering advances have been demonstrated ranging from co-axial flows (for micron and nano-scaled layering), non-concentric flows (for Janus composites) and even 3D printing (for controlled alignment). The ES process is however limited, both for commercial impact (low production rates) and also in its facile capability to deliver reliable mimicry of numerous biological tissues which comprise blended and aligned fibers (e.g. tendons and ligaments). In the technological advance demonstrated here, a combinatorial multi-compartment centrifugal electrospinning (CMCCE) system is developed and demonstrated. A proof-of-concept enabling multiple formulation solution hosting (including combinatorial grading) in a single centrifugal electrospinning system (CES) comprising one spinneret is shown. Using this process, controlled blending and tuning of resulting fibrous membrane properties (contact angle and active release behavior) via aligned and phased fiber mat composition is demonstrated. In addition, the CMCCE process is capable of replicating production rates of recently developed centrifugal electrospinning systems (โˆผ120 g/h), while potentially permitting better mimicry of naturally occurring fibrous tissue blends. It is envisaged the advance in technology will be ideally suited to engineer synthetic fibrous biomaterials with greater host surface replication and will fulfil production rate requirements for the industrial sector

    Recent developments in the use of centrifugal spinning and pressurized gyration for biomedical applications

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    Centrifugal spinning is a technology used to generate small diameter fibers and has been extensively studied for its vast applications in biomedical engineering. Centrifugal spinning is known for its rapid production rate and has inspired the creation of other technologies which leverage the high-speed rotation, namely Pressurized Gyration. Pressurized gyration incorporates a unique applied gas pressure which serves to provide additional control over the fiber production process. The resulting fibers are uniquely suitable for a range of healthcare-related applications that are thoroughly discussed in this work, which involve scaffolds for tissue engineering, solid dispersions for drug delivery, antimicrobial meshes for filtration and bandage-like fibrous coverings for wound healing. In this review, the notable recent developments in centrifugal spinning and pressurized gyration are presented and how these technologies are being used to further the range of uses of biomaterials engineering, for example the development of core-sheath fabrication techniques for multi-layered fibers and the combination with electrospinning to produce advanced fiber mats. The enormous potential of these technologies and their future advancements highlights how important they are in the biomedical discipline

    Suspension Near-Field Electrospinning: a Nanofabrication Method of Polymer Nanoarray Architectures for Tissue Engineering

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    Chapter 1. This chapter is divided into six sections. The first will discuss the issue of nerve tissue loss, and the strategies of therapy (1.1). The second describes the role of nanofabrication in tissue engineering (1.2). The third section details the theoretical background of electrospinning in terms of solution and process parameters (1.3). The fourth section introduces near-field electrospinning (NFES), recent advances in this field and the principles of NFES techniques (1.4). The fifth section details objectives for a tissue engineered construct for neural cell therapy, and presents possible viable solutions (1.5). The sixth summarizes the aims and structure of this thesis (1.6)..

    Experimental and Theoretical Analysis of Pressure Coupled Infusion Gyration for Fibre Production

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    In this work, we uncover the science of the combined application of external pressure, controlled infusion of polymer solution and gyration in the field of nanofiber preparation. This novel application takes gyration-based method into another new arena through enabling the mass production of exceedingly fine (few nanometres upwards) nanofibres in a single step. Polyethylene oxide (PEO) was used as a model polymer in the experimental study, which shows the use of this novel method to fabricate polymeric nanofibres and nanofibrous mats under different combinations of operating parameters, including working pressure, rotational speed, infusion rate and collection distance. The morphologies of the nanofibres were characterised using scanning electron microscopy, and the anisotropy of alignment of fibre was studied using two dimensional fast Fourier transform analysis. A correlation between the product morphology and the processing parameters is established. The response surface models of the experimental process were developed using the least squares fitting. A systematic description of the PCIG spinning was developed to help us obtain a clear understanding of the fibre formation process of this novel application. The input data we used are the conventional mean of fibre diameter measurements obtained from our experimental works. In this part, both linear and nonlinear fitting formats were applied, and the successes of the fitted models were mainly evaluated using Adjusted R2 and Akaike Information Criterion (AIC). The correlations and effects of individual parameters and their interactions were explicitly studied. The modelling results indicated the polymer concentration has the most significant impact on fibre diameters. A self-defined objective function was studied with the best-fitted model to optimise the experimental process for achieving the desired nanofibre diameters and narrow standard deviations. The experimental parameters were optimised by several algorithms, and the most favoured sets of parameters recommended by the non-linear interior point methods were further validated through a set of additional experiments. The results of validation indicated that pressure coupled infusion gyration offers a facile way for forming nanofibres and nanofibre assemblies, and the developed model has a good prediction power of experimental parameters that are possible to be useful for achieving the desirable PEO nanofibres

    Gyration Spun Polymeric Fibres for Antibacterial Applications

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    Hybrid polymeric fibres and fibrous structures have widely been used to construct porous polymer scaffolds with excellent functionally, and are of great interest in biomedical applications. In this thesis, in contrast to electrospinning, a novel approach, gyration spinning with or without pressure is reported to achieve a high production rate for hybrid nanoparticle embedded polymer fibres in the micro to nanometre scale range using either polymer solutions or melts. Polyurethane (PU), nylon, and poly(ethylene oxide) (PEO) were used as the polymers not only because of their excellent biocompatibility, but also depends on good oxidative biostability, processability of PU, good mechanical strength, spinnability and stability for nylon, and non-toxicity of PEO. In the meantime, silver nanoparticles, copper oxide nanoparticles and zinc oxide nanoparticles were used to increase the antibacterial performance to produce hybrid nanofibres using pressurised solution gyration. A pressurised melt gyration process was used for the first time to generate poly(ฮต-caprolactone) (PCL) fibres and silver coated PCL fibres in the micrometre range (< 50 m) due to the low melting point (60ยฐC) of PCL pellets. The formation of fibres depends on the centrifugal force, pressure blowing and evaporation. Fibre diameter is significantly reduced with a decrease in the weight percentage of the polymer in solution, and an increase in the melting temperature, rotational speed and working pressure. Field emission scanning electron microscopy (FE-SEM) was used to study the characteristics and morphology of the fabricated polymer fibres. Incorporation of Ag nanoparticles into the polymer fibres was confirmed using a combination of advanced microscopical techniques and Raman spectrometry to study the bonding characteristics of the polymer and Ag nanoparticles. Inductively coupled plasma mass spectroscopy (ICP-MS) showed that the substantial concentration of Ag ions in the nylon fibre matrix was producing effective antibacterial properties. Ag nanoparticles and CuO nanoparticles were successfully incorporated into polymer fibres and proved to be of higher antibacterial efficacy than virgin polymer fibres, against the Gram-negative bacteria Escherichia coli and Pseudomonas aeruginosa

    MANUFACTURING OF ALIGNED ELECTROSPUN NANOFIBER YARNS FOR THEIR ENHANCED MECHANICAL AND PIEZOELECTRIC PROPERTIES

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    Electrospinning is a widely used technique for producing nanofibers with diverse applications. This method uses polymer solutions and strong electric fields to generate nano-sized fibers with unique properties. This study presents a novel manufacturing approach that enables the production of electrospun poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) nanofiber yarns using an automated parallel track system and an adjustable roll-to-roll collector. This research examines the impact of an automated post-drawing system on the polymer chain orientation, crystallinity, tensile strength, morphology, and piezoelectric properties of PVDF-HFP nanofiber yarn. The results reveal that the post-drawing process significantly improves molecular alignment, increases tensile strength, and enhances the piezoelectric outputs of the nanofiber yarn. The potential applications of these piezoelectric nanofiber yarns extend to the realm of smart textiles, where they can be integrated into various wearable devices and intelligent fabrics. It highlights a significant advancement in the field and emphasizes the importance of post-drawing processing in improving the tensile and piezoelectric properties of electrospun PVDF-HFP nanofiber yarn. Furthermore, it demonstrates the potential for manufacturing on a commercial scale, a feat not achieved by previous research efforts, increasing economic market opportunities in the smart textile industry

    ARTIFICIAL SYNTHETIC SCAFFOLDS FOR TISSUE ENGINEERING APPLICATION EMPHASIZING THE ROLE OF BIOPHYSICAL CUES

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    The mechanotransduction of cells is the intrinsic ability of cells to convert the mechanical signals provided by the surrounding matrix and other cells into biochemical signals that affect several distinct processes such as tumorigenesis, wound healing, and organ formation. The use of biomaterials as an artificial scaffold for cell attachment, differentiation and proliferation provides a tool to modulate and understand the mechanotransduction pathways, develop better in vitro models and clinical remedies. The effect of topographical cues and stiffness was investigated in fibroblasts using polycaprolactone (PCL)- Polyaniline (PANI) based scaffolds that were fabricated using a self-assembly method and electrospinning. Through this method, scaffolds of different topography and stiffness were fabricated with similar surface chemistries. The effect of scaffold morphologies on the cells were investigated. PCL scaffolds of three distinct morphologies- honeycomb, aligned and mesh were used with similar surface chemistry to investigate the changes in cell behavior of breast, renal, lung and bladder cancer to the physical cues. Selective adhesion and localization of cells to specific morphologies were determined. In order to demonstrate the scaffold as a source of biochemical signals, ManCou-H, capable of targeting the fructose-specific glucose transporter GLUT5 was electrospun with the scaffolds of different morphologies. The PCL scaffolds were used as the backbone to release ManCou-H and changes in protein expression and metabolic activity was characterized. The findings made available through this research will help in the design of better cell-specific in vitro model systems to better understand cellular responses to clinical therapies, assess cell response to specific mechanical and chemical cues

    Tantalum nanoparticles enhance the osteoinductivity of multiscale composites based on poly(lactide-co-glycolide) electrospun fibers embedded in a gelatin hydrogel

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    Bioresorbable polymeric materials have risen great interest as implants for bone tissue regeneration, since they show substantial advantages with respect to conventional metal devices, including biodegradability, flexibility, and the possibility to be easily modified to introduce specific functionalities. In the present work, an innovative nanocomposite scaffold, properly designed to show biomimetic and osteoinductive properties for potential application in bone tissue engineering, was developed. The scaffold is characterized by a multi-layer structure, completely different with respect to the so far employed polymeric implants, consisting in a poly(D,L-lactide-co-glycolide)/polyethylene glycol electrospun nanofibrous mat sandwiched between two hydrogel gelatin layers enriched with tantalum nanoparticles (NPs). The composition of the electrospun fibers, containing 10 wt% of polyethylene glycol, was selected to ensure a proper integration of the fibers in the gel phase, essential to endow the composite with flexibility and to prevent delamination between the layers. The scaffold maintained its structural integrity after six weeks of soaking in physiological solutions, albeit the gelatin phase was partially released. The combined use of gelatin, bioresorbable electrospun fibers and tantalum NPs endows the final device with biomimetic and osteoinductive properties. Indeed, results of the in vitro tests demonstrate that the obtained scaffolds clearly represent a favorable milieu for normal human bone-marrow derived mesenchymal stem cells viability and osteoblastic differentiation; moreover, inclusion of tantalum NPs in the scaffold improves cell performance with particular regard to early and late markers of osteoblastic differentiation. (C) 2022 Elsevier Ltd. All rights reserved

    ์ „๊ธฐ๋ฐฉ์‚ฌ ๊ณต์ •์„ ํ†ตํ•œ ํ—ฌ๋ฆฌ์ปฌ ๊ตฌ์กฐ์˜ ์€๋‚˜๋…ธ ์„ฌ์œ ์˜ ์ œ์กฐ

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    ํ•™์œ„๋…ผ๋ฌธ (๋ฐ•์‚ฌ) -- ์„œ์šธ๋Œ€ํ•™๊ต ๋Œ€ํ•™์› : ๊ณต๊ณผ๋Œ€ํ•™ ์žฌ๋ฃŒ๊ณตํ•™๋ถ€(ํ•˜์ด๋ธŒ๋ฆฌ๋“œ ์žฌ๋ฃŒ), 2020. 8. ์œ ์›…์—ด.This study aimed to fabricate silver nanofibers using new process parameters of electrospinning and develop transparent and stretchable electrodes for stretchable electronics using them. A series of research was carried out to achieve goals as follows. A multi-physics model for the simulation of gas-assisted melt-electrospinning (GAME) process was developed to understand the roles of process parameters. By numerically calculating the stresses acting on the jet during a single-nozzle GAME process, the shear viscous stress was identified as the main factor of jet stretch. The jet stretch ratio increased sharply when shear viscous stress reached the level at which jet sharpening occurred, leading to stable jet formation. This stress was defined as the critical shear viscous stress to determine stable spinnability. In addition, a multi-nozzle GAME was simulated, proposing a spinnability diagram for stable spinning. A new process was designed to fabricate helical fibers. Here, the effect of solidification behavior of the jet on the formation of intrinsic curvature and on the final morphology of electrospun fibers was investigated. Fiber morphology during electrospinning was observed to dramatically change from straight to helical due to rapid solidification of the jet. Investigation of the resulting jet morphologies revealed that fiber structure changed from straight to helical as the vapor pressure increased. A similar effect was observed with conductive solutions prepared by adding large amounts of metal ion to the polymer solution. Simulations revealed that the jet near the nozzle tip was subject to a strong electrical field due to increased charge density. The thickness of the emerging fiber was rapidly reduced with fast and simultaneous solidification, resulting in helical nanofibers. A mechanism was suggested that can describe the formation of helical fibers. Transparent and stretchable electrodes (TSEs) was fabricated using electrospun silver nanofibers. Here, a composite comprising shape memory polymerโ€“TSE (SMPโ€“TSE) using crosslinked polycyclooctene as a substrate was fabricated, which showed wrinkle-free deformation and switchable optical transparency. Because of its considerable elongation without residual strain and the shape memory behavior of polycyclooctene, in-plane buckled nanofibers were formed effectively. Due to these in-plane buckled nanofibers, the electrode maintained its resistance during 3,000 cycles of a bending test and 900 cycles of a tensile test. Furthermore, SMPโ€“TSE was able to electrically control its temperature, optical transparency, elastic modulus, and shape memory behavior. Finally, SMPโ€“TSE was demonstrated for a smart electrode that could control its optical and mechanical properties. Keywords: Electrospinning, Numerical simulation, Process parameters, Silver nanofibers, Transparent and stretchable electrode Student number: 2014-22539๋ณธ ์—ฐ๊ตฌ์˜ ๋ชฉ์ ์€ ์ „๊ธฐ๋ฐฉ์‚ฌ ๊ณต์ •์—์„œ์˜ ์ƒˆ๋กœ์šด ๊ณต์ • ๋ณ€์ˆ˜๋“ค์„ ์ด์šฉํ•˜์—ฌ ์€๋‚˜๋…ธ์„ฌ์œ ๋ฅผ ์ œ์ž‘ํ•˜๊ณ  ์ด๋ฅผ ํ™œ์šฉํ•˜์—ฌ ํˆฌ๋ช…ยท์‹ ์ถ• ์ „๊ทน์„ ์ œ์ž‘ํ•˜๋Š” ๊ฒƒ์ด๋‹ค. ์ด๋ฅผ ์œ„ํ•œ ์ผ๋ จ์˜ ์—ฐ๊ตฌ๋“ค์ด ๋‹ค์Œ์˜ ์ˆœ์„œ๋กœ ์ง„ํ–‰๋˜์—ˆ๋‹ค. Gas-assisted ์šฉ์œต ์ „๊ธฐ๋ฐฉ์‚ฌ ๊ณต์ •์— ๋Œ€ํ•œ multi-physics ๋ชจ๋ธ๋ง์„ ๊ฐœ๋ฐœํ•˜์˜€์œผ๋ฉฐ ์ด๋ฅผ ํ†ตํ•˜์—ฌ ๊ณต์ • ๋ณ€์ˆ˜๋“ค์˜ ์—ญํ• ์„ ํŒŒ์•…ํ•˜์˜€๋‹ค. ๋‹จ์ผ ๋…ธ์ฆ์„ ์ด์šฉํ•œ ๊ณต์ •์—์„œ ์ ฏ์˜ ํ‘œ๋ฉด์— ์ธ๊ฐ€๋˜๋Š” ์‘๋ ฅ์„ ์ˆ˜์น˜ํ•ด์„์„ ํ†ตํ•˜์—ฌ ๋ถ„์„ํ•จ์œผ๋กœ์จ ์ ฏ์˜ ์ธ์žฅ์— ์žˆ์–ด ์ ์„ฑ ์ „๋‹จ ์‘๋ ฅ์ด ์ฃผ์š”ํ•˜๊ฒŒ ์ž‘์šฉํ•จ์„ ๋ฐํ˜€๋ƒˆ๋‹ค. ์ ฏ์€ ์ ์„ฑ ์ „๋‹จ ์‘๋ ฅ์ด ํŠน์ • ๊ฐ’์— ๋„๋‹ฌํ•˜์˜€์„ ๋•Œ์— ์•ˆ์ •์ ์œผ๋กœ ํ˜•์„ฑ๋˜์—ˆ์œผ๋ฉฐ, ์ ฏ์˜ ์ธ์žฅ๋ฅ  ๋˜ํ•œ ๊ธ‰๊ฒฉํžˆ ์ฆ๊ฐ€ํ•˜์˜€๋‹ค. ์ด๋•Œ์˜ ์‘๋ ฅ์„ ์•ˆ์ •์ ์ธ ๋ฐฉ์‚ฌ์„ฑ์„ ํŒ๋‹จํ•˜๋Š” ์ž„๊ณ„ ์ ์„ฑ ์ „๋‹จ ์‘๋ ฅ์ด๋ผ ์ •์˜ ํ•˜์˜€๋‹ค. ๋‹จ์ผ ๋…ธ์ฆ ๊ณต์ •๋ฟ๋งŒ ์•„๋‹ˆ๋ผ ๋ฉ€ํ‹ฐ ๋…ธ์ฆ ๊ณต์ •์„ ๋ชจ๋ธ๋งํ•˜์˜€์œผ๋ฉฐ ์ด๋กœ๋ถ€ํ„ฐ ์•ˆ์ •์ ์ธ ๋ฐฉ์‚ฌ์„ฑ์„ ํŒ๋‹จํ•  ์ˆ˜ ์žˆ๋Š” ๋ฐฉ์‚ฌ์„ฑ ๋‹ค์ด์–ด๊ทธ๋žจ์„ ์ œ์‹œํ•˜์˜€๋‹ค. ๋‹ค์Œ์œผ๋กœ๋Š” ์„ฌ์œ ์˜ ๊ตฌ์กฐ๋ฅผ ํ—ฌ๋ฆฌ์ปฌ ๊ตฌ์กฐ๋กœ ์ œ์ž‘ํ•˜๋Š” ๊ณต์ •์„ ๋””์ž์ธ ํ•˜์˜€๋‹ค. ์šฐ์„ , ์ ฏ์˜ ์ดˆ๊ธฐ ๊ณก๋ฅ ๊ณผ ์ ฏ์˜ ์œ„์น˜์— ๋”ฐ๋ฅธ ๊ณ ํ™”๊ฐ€ ์„ฌ์œ ์˜ ๊ตฌ์กฐ์— ๋ฏธ์น˜๋Š” ์˜ํ–ฅ์„ ์กฐ์‚ฌํ•˜์˜€๋‹ค. ์ „๊ธฐ ๋ฐฉ์‚ฌ๋œ ์„ฌ์œ ์˜ ๊ตฌ์กฐ๋Š” ์šฉ๋งค์˜ ์ฆ๊ธฐ์••์ด ์ฆ๊ฐ€ํ•จ์— ๋”ฐ๋ผ ๋ฐœ์ƒํ•˜๋Š” ๋น ๋ฅธ ๊ณ ํ™”๋กœ ์ธํ•˜์—ฌ ์ง์„ ํ˜•ํƒœ์—์„œ ํ—ฌ๋ฆฌ์ปฌ ๊ตฌ์กฐ๋กœ ๋ณ€ํ™”ํ•˜์˜€๋‹ค. ์ด๋Š” ๊ธˆ์† ์ด์˜จ์ด ๊ณผ๋Ÿ‰์œผ๋กœ ์ฒจ๊ฐ€๋œ ์ „๋„์„ฑ ์šฉ์•ก์— ๋Œ€ํ•ด์„œ๋„ ์œ ์‚ฌํ•œ ๊ฒฐ๊ณผ๋ฅผ ๋ณด์˜€๋‹ค. ์ด์— ๋Œ€ํ•œ ์‹œ๋ฎฌ๋ ˆ์ด์…˜ ๊ฒฐ๊ณผ๋Š” ์ „ํ•˜ ๋ฐ€๋„์˜ ์ฆ๊ฐ€๊ฐ€ ๊ฐ•ํ•œ ์ „๊ธฐ์žฅ์„ ๋ฐœ์ƒ์‹œ์ผฐ์œผ๋ฉฐ, ์ด๋กœ ์ธํ•˜์—ฌ ์ ฏ์˜ ๊ธ‰๊ฒฉํ•œ ์ธ์žฅ ๋ฐ ๊ณ ํ™”๊ฐ€ ๋ฐœ์ƒํ•˜์˜€์Œ์„ ๋ณด์—ฌ์ฃผ๋ฉฐ, ๊ทธ๋Ÿฌํ•œ ์ด์œ ๋กœ ํ—ฌ๋ฆฌ์ปฌ ๊ตฌ์กฐ๊ฐ€ ํ˜•์„ฑ๋˜์—ˆ์Œ ๋‚˜ํƒ€๋ƒˆ๋‹ค. ์ด๋ฅผ ์ด์šฉํ•˜์—ฌ ํ—ฌ๋ฆฌ์ปฌ ๊ตฌ์กฐ์˜ ์„ฌ์œ ๊ฐ€ ํ˜•์„ฑ๋˜๋Š” ๋ฉ”์ปค๋‹ˆ์ฆ˜์„ ์ œ์‹œํ•˜์˜€๋‹ค. ๋งˆ์ง€๋ง‰์œผ๋กœ ์ „๊ธฐ๋ฐฉ์‚ฌ๋ฅผ ์ด์šฉํ•ด ์ œ์ž‘ํ•œ ์€๋‚˜๋…ธ์„ฌ์œ ๋ฅผ ์ด์šฉํ•˜์—ฌ ํˆฌ๋ช…ยท์‹ ์ถ• ์ „๊ทน์„ ์ œ์ž‘ํ•˜์˜€๋‹ค. ์ „๊ทน์€ ํ˜•์ƒ๊ธฐ์–ต ๊ณ ๋ถ„์ž์ธ crosslinked polycyclooctene์„ ๊ธฐํŒ์œผ๋กœ ํ™œ์šฉํ•˜์˜€๋‹ค. ์ œ์ž‘ํ•œ ์ „๊ทน์€ ์ž”๋ฅ˜ ๋ณ€ํ˜•์ด ์—†๊ณ  ํˆฌ๋ช…๋„๋ฅผ ์ œ์–ดํ•  ์ˆ˜ ์žˆ๋Š” ํŠน์„ฑ์„ ๋ณด์˜€๋‹ค. ํฐ ์ธ์žฅ์—๋„ ์ž”๋ฅ˜ ๋ณ€ํ˜•์„ ๋ณด์ด์ง€ ์•Š๋Š” ํ˜•์ƒ๊ธฐ์–ต๊ณ ๋ถ„์ž ๊ธฐํŒ์˜ ํŠน์„ฑ์œผ๋กœ ์ธํ•ด ๋ฉด๋‚ด ๊ตฝํž˜ ๊ตฌ์กฐ์˜ ์€๋‚˜๋…ธ์„ฌ์œ ๊ฐ€ ํšจ์œจ์ ์œผ๋กœ ์ œ์ž‘๋˜์—ˆ๋‹ค. ์ด๋Ÿฌํ•œ ํŠน์„ฑ์œผ๋กœ ์ œ์ž‘ํ•œ ์ „๊ทน์€ 3,000ํšŒ์˜ ๊ตฝํž˜ ํ‰๊ฐ€์™€ 900ํšŒ์˜ ์ธ์žฅํ‰๊ฐ€์—๋„ ์ „๋„์„ฑ์„ ์œ ์ง€ํ•  ์ˆ˜ ์žˆ์—ˆ๋‹ค. ๋˜ํ•œ ์ œ์ž‘ํ•œ ์ „๊ทน์€ ์ „๊ธฐ์  ์ž๊ทน์„ ํ†ตํ•˜์—ฌ ์˜จ๋„, ํˆฌ๋ช…๋„, ๊ฐ•์„ฑ ๋ฐ ํ˜•์ƒ๊ธฐ์–ต ํŠน์„ฑ์„ ์ œ์–ดํ•  ์ˆ˜ ์žˆ๋‹ค๋Š” ํŠน์ง•์„ ๋ณด์˜€๋‹ค. ์ œ์ž‘ํ•œ ์ „๊ทน์„ ํ™œ์šฉํ•˜์—ฌ ๊ด‘ํ•™์  ๊ทธ๋ฆฌ๊ณ  ๊ธฐ๊ณ„์  ํŠน์„ฑ์„ ์ œ์–ดํ•  ์ˆ˜ ์žˆ๋Š” ์ƒˆ๋กœ์šด ํ˜•ํƒœ์˜ ์Šค๋งˆํŠธ ์ „๊ทน์„ ์‹œ์—ฐ ํ•˜์˜€๋‹ค. ํ•ต์‹ฌ์–ด: ์ „๊ธฐ๋ฐฉ์‚ฌ๊ณต์ •, ์ „์‚ฐ๋ชจ์‚ฌ, ๊ณต์ •๋ณ€์ˆ˜, ์€๋‚˜๋…ธ์„ฌ์œ , ํˆฌ๋ช…ยท์‹ ์ถ• ์ „๊ทน ํ•™๋ฒˆ: 2014-22539Chapter 1. Introduction 1 1.1. Electrospinning 1 1.1.1. Introduction of electrospinning 1 1.1.2. Types of electrospinning 3 1.1.3. Parameters in electrospinning 6 1.1.4. Structures of electrospun nanofibers 16 1.1.5. Application of electrospun nanofibers 26 1.1.6. Limitation and perspective of electrospinning 44 1.2. Research objectives 47 Chapter 2. Numerical simulation of gas-assisted melt electrospinning 50 2.1. Needs for modeling of gas-assisted melt electrospinning 50 2.2. Methods 53 2.2.1. Gas-assisted melt-electrospinning process 53 2.2.2. Numerical simulation of single-nozzle GAME process 56 2.2.3. Calculation of electric field in multi-nozzle configuration 60 2.2.4. Numerical simulation of multi-nozzle GAME process 61 2.3. Results and discussion 62 2.3.1. Simulation of single-nozzle GAME process 62 2.3.2. Simulation of multi-nozzle GAME process 73 2.4. Summary 81 Chapter 3. Fabrication of inherently helical structure nanofibers 83 3.1. Needs for fabrication of helical nanofibers 83 3.2. Experimental 85 3.2.1. Preparation of dielectric solution for helical nanofibers 84 3.2.2. Preparation of conductive solution for helical nanofibers 86 3.2.3. Electrospinning and spinneret geometry 86 3.2.4. Characterization of Electrospun Fibers 87 3.3. Results and discussion 88 3.3.1. Effect of solvent vapor pressure on structure 88 3.3.2. Effects of solidification on structure 94 3.3.3. Numerical simulations of jet near nozzle 99 3.3.4. Further enhanced helical structrues 105 3.4. Summary 111 Chapter 4. Fabrication of a stretchable, wrinkle-free electrode with switchable transparency 113 4.1. Transparent and stretchable electrode 113 4.2. Experimental 116 4.2.1. Materials 116 4.2.2. Preparation of shape memory polymer substrate 117 4.2.3. Fabrication of free-standing silver nanofiber 117 4.2.4. Characterization of SMPโ€“TSE 118 4.3. Results and discussion 119 4.3.1. Fabrication of free-standing silver nanofibers 119 4.3.2. Optoelectrical properties of silver nanofibers 128 4.3.3. Shape memory substrate 129 4.3.4. Shape memory polymerโ€“transparent and stretchable electrode 137 4.4. Summary 143 Chapter 5. Conclusions 145 Chapter 6. Appendix 147 Reference 161 Korean abstract 189Docto
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