Needleless electrospinning of nanofibers with a conical wire coil

In this article, we have demonstrated a novel needleless electrospinning of PVA nanofibers by using a conical metal wire‐coil as spinneret. Multiple polymer jets were observed to generate on the coil surface. Up to 70 kV electric voltage can be applied to this needleless electrospinning nozzle without causing “corona discharge.” Compared with conventional needle electrospinning, this needleless electrospinning system produced finer nanofibers on a much larger scale, and the fiber processing ability showed a much greater dependence on the applied voltage. Finite element calculation indicates that the electric field intensity profiles for the two systems are also quite different. This novel concept of using wire coil as the electrospinning nozzle will contribute to the further development of new large‐scale needleless electrospinning system for nanofiber production. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers     

Influence of electric field interference on double nozzles electrospinning

The low production rate of electrospinning process may limit the industrial use of single needle system. To meet high yield requirement and uniform fibers, a bottom‐up multiple jets electrospinning nozzle was designed, each nozzle can emit 6–18 jets. The influence of electric field interference on jet path, membrane shape, and fiber morphology were investigated. Experiment finds that electrical field strength in the closer part of two nozzles is weakened because of electric field interference when the distance between two nozzles is 30 mm, making the jet hard to emit in this section, and closer part of electrospun fiber webs has fewer fibers. The spinning in far side part of two nozzles is similar to that of single nozzle. While in middle part of one nozzle, the jet path is short, elongation of jets smaller, the formed fibers thicker, solvent evaporation less sufficient. When the distance of two nozzles is increased to 50 mm, influence of electric field interference is weaker, the electrospun fiber web and average diameter of fibers are almost the same as that of single nozzle electrospinning. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Fabrication of nanofibers by a modified air-jet electrospinning method

A modified air-jet electrospinning (MAE) setup was demonstrated for contributing to the large-scale nanofibers production. With this single nozzle air-jet electrospinning device, the productivity of nanofibers can be increased more than forty times as compared with using the single-needle electrospinning (SNE) setup. When compared with other needle-less electrospinning setups, the benefits of this setup include ability to keep stable concentration of electrospun solution and to produce more uniform and thinner fibers, controlling of the jets formed speed and position, higher throughput, lower critical voltage, easier assembling, simpler operation, and so on. Four different parts of the fiber generator were, respectively, charged as electrospun electrodes to produce fibers. The distributions of the electric field with different electrodes were simulated and investigated for explaining the experimental results including the fibers productivity, the deposition area of nanofiber mats, as well as the surface morphology of the fibers. When the whole nozzle was charged, as compared with charging other electrodes, the MAE system produced thinner fibers with larger standard deviation on a much larger scale. By reduction of charged area, the received fibers presented lower productivity and thicker diameter with lower standard deviation. Especially, when a half of the nozzle was charged, the deposition area of nanofiber mats was larger than charging other electrodes. Besides, when a half of the nozzle was charged, the influences of electrospinning parameters such as applied voltage, collecting distance and the flow rate of air on nanofibers morphology were also investigated. Furthermore, based on this spinning unit, multi-nozzle air-jet electrospinning setup can be designed for larger production of nanofibers.     

Double‐nozzle air‐jet electrospinning for nanofiber fabrication

A novel double‐nozzle air‐jet electrospinning apparatus was developed to fabricate nanofibers on a large scale. The distribution of the electric field at different nozzle distances was simulated to analyze the jet path, productivity, and deposition area of nanofiber webs and the nanofiber morphology. Our experiments showed that the bubbles usually ruptured intermittently on the top surface of the two nozzles and the jets traveled in a straight path with a high initial velocity. A continuous and even thickness of the nanofiber webs were obtained when the nozzle distances was less than 55 mm. At nozzle distances of 55 mm, the received fibers were thin with the lowest standard deviation. Experimental parameters involving the applied voltage, collecting distance, and air flow rate were also investigated to analyze the nanofiber morphology at a nozzle distance of 55 mm. The results show that the nanofibers presented a finer and thinner diameter at an applied voltage of 36 kV, a collecting distance of 18 cm, and an air flow rate of 800 mL/min. The nanofiber production of this setup increased to nearly 70 times that with a single‐needle electrospinning setup. On the basis of the principle of this air‐jet electrospinning setup, various arrangements of multinozzle electrospinning setups could be designed for higher throughput of nanofibers. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2014 , 131, 40040.     

熔体静电纺丝中电极结构对电场和纤维的影响

采用Ansys数值模拟方法,建立了电场分析的有限元模型,研究了电极结构不同时的电场分布及其对纤维直径的影响,以及电压大小对纤维直径的影响。并进行了实验对照分析,发现电极结构包括圆板电极和圆环电极影响熔体静电纺丝的电场分布,但场强最大都出现在喷嘴处,并随接收距离的增大成不同趋势减小,但中空电极能集聚电场,稳定场强,获得更细的纤维。     

Needleless Electrospinning from a Tube with an Embedded Wire Loop

Enhancing the production rate while maintaining control in electrospinning has been a challenge for years. This work proposes a novel spinneret from a tube with a single wire loop embedded in its one end. With the feeding of solution precisely controlled and the spinning process stablized, multiple polymer jets can be continuously generated from the wire loop. The as‐spun fibers show nanofibrous structure and its fiber diameter is greatly affected by the applied voltage and polymer concentration. As compared to needle electrospinning, the wire loop spinneret generates a stronger electric field with a larger spinnable area due to its special geometrical structure and a higher applied voltage it is connected to. Slightly coarser nanofibers are fabricated as compared to the nanofibers from needle electrospinning and the production rate is as high as 0.48 g h^?1.     

PVA／MC纳米纤维膜的制备与吸水性、保水性研究

采用水热工艺和电纺方法制备了PVA／MC纳米纤维膜;对PVA／MC混和溶液的粘度、PVA／MC纳米纤维膜的结构、吸水性能和保水性能进行了研究。结果表明,随着MC含量的增加,PVA／MC混和溶液的粘度逐渐增大;FESEM表明,本身不能电纺的MC在与PVA混和则可以电纺制得PVA／MC纳米纤维膜,但随着MC含量的增加,混和溶液的粘度会逐渐增大而无法电纺;在不改变电压的情况下增大电纺的接受距离,所得PVA／MC纤维膜连续、直径均匀、表面光滑平整;吸水性能和保水性能研究表明,随着MC含量的增加,PVA／MC纳米纤维膜的吸水速率和保水性能逐渐提高。     

气流辅助聚合物熔体微分电纺流道优化设计

为进一步降低熔体微分电纺的纤维直径,使其达到纳米尺度,在现有直线狭缝电纺喷头的基础上设计了可以使高速气流汇聚的“V”形风道,通过高速气流对熔体微分射流进行二次牵伸细化。采用实验研究和数值模拟相结合的方法,以射流间距和喷头端电场强度为指标,研究了“V”形风道结构、材质对电纺微分射流的影响。研究结果表明,风道结构会不可避免地削弱喷头端的电场强度、降低射流的效率。增加风刀与喷头尖端的头端凸出量以及采用不导电的聚醚醚酮作为风刀材质都可以有效地降低风刀对射流效率的影响,而风道的宽度对喷头端电场强度影响不大。在优化的风刀结构和材质的基础上,成功制备了平均直径为825 nm的熔体电纺超细纤维。研究证实在气流辅助牵伸的作用下,直线狭缝电纺能够实现熔体电纺超细纤维的批量制备。     

Preparation of atactic poly(vinyl alcohol)/silver composite nanofibers by electrospinning and their characterization

Poly(vinyl alcohol) (PVA)/silver composite nanofibers were successfully prepared by the electrospinning method. Water‐based colloidal silver in a PVA solution was directly mixed without any chemical or structural modifications into PVA polymer fibers to form organic–inorganic composite nanofibers. The ratio of silver colloidal solution to PVA played an important role in the formation of the PVA/silver composite nanofibers. We prepared two different atactic PVA/silver nanocomposites with number‐average degrees of polymerization of 1700 and 4000 through electrospinning with various processing parameters, such as initial polymer concentration, amount of silver colloidal solution, applied voltage, and tip‐to‐collector distance. The PVA/silver composite nanofibers were characterized by field emission scanning electron microscopy and transmission electron microscopy (TEM). TEM images showed that silver nanoparticles with an average diameter of 30–50 nm were obtained and were well distributed in the PVA nanofibers. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Solution blow spinning: A new method to produce micro‐ and nanofibers from polymer solutions

A solution blow spinning technique was developed using elements of both electrospinning and melt blowing technologies as an alternative method for making non‐woven webs of micro‐ and nanofibers with diameters comparable with those made by the electrospinning process with the advantage of having a fiber production rate (measured by the polymer injection rate) several times higher. The diameters of fibers produced ranged from 40 nm for poly(lactic acid) to several micrometers for poly(methyl methacrylate). This solution blow spinning method uses a syringe pump to deliver a polymer solution to an apparatus consisting of concentric nozzles whereby the polymer solution is pumped through the inner nozzle while a constant, high velocity gas flow is sustained through the outer nozzle. Analysis of the process showed that pressure difference and shearing at the gas/solution interface jettisoned multiple strands of polymer solution towards a collector. During flight, the solvent component of the strands rapidly evaporates forming a web of micro and nanofibers. The effect of injection rate, gas flow pressure, polymer concentration, working distance, and protrusion distance of the inner nozzle was investigated. Polymer type and concentration had a greater effect on fiber diameter than the other parameters tested. Injection rate, gas flow pressure, and working distance affected fiber production rate and/or fiber morphology. Fibers were easily formed into yarns of micro‐ and nanofibers or non‐woven films that could be applied directly onto biological tissue or collected in sheets on a rotating drum. Indeed, virtually any type of target could be used for fiber collection. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Interjet distance in needleless melt differential electrospinning with umbellate nozzles

Melt electrospinning technique has shown great advantages in numerous areas where polymer dissolving, solvent accumulation, or toxicity is a concern in solution electrospinning. However, conventional capillary spinnerets in electrospinning are less productive. In this article, two needleless umbellate nozzles were used based on melt differential method, and the smallest interjet distance of 1.1 mm was observed. Experimental results indicated that the main factors affecting the interjet distance were the electric field strength and melts viscosity. The produced fiber diameter was related to interjet distance directly. Finite element modeling (FEM) showed that umbellate structure determines the intensity of maximum electric field around the rim of nozzles and the resultant interjet distance. This new method enabled the mass production of ultra‐fine fibers using needleless melt electrospinning method when relatively low voltage (less than 65 kV) was loaded on the receive plate. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40515.     

熔体直写电纺聚己内酯纤维有序沉积工艺

目前聚合物熔体电纺技术制备的纤维大多以杂乱无序的无纺布形式存在,限制了电纺技术在组织工程支架以及机器人等需要有序结构领域的应用。本文将熔体电纺技术与三维运动平台相结合,采用自主设计的熔体电纺可控成型实验装置,对聚己内酯（PCL）进行熔体直写静电纺丝,获得了有序纤维。研究了喷头移动速度、接收距离和纺丝电压对熔体直写电纺纤维沉积形貌的影响。结果表明,纤维直径随着喷头移速、接收距离和纺丝电压的增大而减小,其中接收距离的改变对直径的影响最为显著;接收距离的增大虽然有利于纤维的细化,但是距离过大会使纤维沉积的有序性变差;当射流下落速度与喷头移动速度相匹配时,射流才能实现有序沉积;增大接收距离和纺丝电压会引起射流鞭动,需要相应地增大喷头移动速度才能实现有序沉积。     

静电纺丝装置的关键部件研究进展

随着轻工业的快速发展,我国的静电纺丝技术取得了较大的进步。静电纺丝装置是获取纳米纤维最简单也是最经济的方法之一,但是产量低限制了静电纺纳米纤维产业化生产及应用的最大的技术瓶颈。静电纺丝装置主要由注射泵、高压电源、喷头和收集器组成,而喷头是静电纺丝装置的关键部件,因此研究喷头的技术发展对静电纺丝装置起到非常重要的作用。本文主要介绍了静电纺丝装置关键部件喷头的技术发展进程与面临的问题及静电纺丝应用领域,并对静电纺丝装置的发展前景进行展望。     

Concept of minimum electrospinning voltage in electrospinning of polyacrylonitrile N,N‐dimethylformamide system

Polyacrylonitrile solutions in N,N‐dimethylformamide (DMF) were electrospun into nanofibers by charging the polymer fluid in an electric field. Controlled experiments were performed using a needle type spinneret to investigate the effect of various electrospinning parameters on the percentage conversion of polymeric fluid into fibers and on fiber diameter obtained. It was found that when the polymeric fluid was continuously fed at a constant rate, application of a minimum electrospinning voltage (MEV) was necessary to “completely” convert the ejected fluid into nanojets to form nanofibers. Also, that the maximum amount of splitting or elongation that a polymeric fluid could undergo was primarily dependent on number of entanglements per chain in the fluid. This resulted in obtaining nanofibers with a particular diameter irrespective of the values of important electrospinning variables such as applied voltage, flow rates, and distance between the electrodes. On the other hand, MEV, necessary to obtain full conversion into nanofibers, was found to be strongly dependent on the spinning parameters and was unique for a given set of parameters. The significance of the MEV was evident from the fact that the square of the MEV, which is a measure of the electrical energy utilized by the system, was found to be directly proportional to the rate of formation of fiber surface area during the electrospinning process. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

丝素蛋白-聚乙烯醇共混改性电纺膜的制备

采用静电纺丝技术,以特殊设计的金属丝螺旋盘绕滚筒作为接收装置,制备了具有一定取向的丝素蛋白(SF)-聚乙烯醇(PVA)共混纳米纤维材料。利用扫描电子显微镜(SEM)对纤维形貌进行观察,并通过Image-Pro Plus软件对纤维细度进行测试,探讨了SF与PVA的配比以及纺丝电压、接收距离等静电纺丝参数对所得纳米纤维形貌、细度及其分布的影响。结果表明:将质量浓度为25 kg/L的SF与质量分数为8%的PVA以质量比15∶3.2共混,并采用20 kV的纺丝电压和13 cm的接收距离静电纺时,所得纳米纤维的平均直径约为238 nm,且直径分布较为均匀。采用该法制得的纳米纤维材料具有一定的纤维取向,有利于细胞生长,可应用于生物医药领域。     

Molecular orientation and mechanical property size effects in electrospun polyacrylonitrile nanofibers

Electrospinning of polymeric solutions entails high jet velocities which could orient the polymer molecules along the jet direction. Polarized Fourier Transform IR spectroscopy (FTIR), Wide angle X-ray diffraction (WAXD) and Microelectromechanical System (MEMS)-based single nanofiber mechanical property experiments were employed to investigate the molecular orientation and crystallinity in electrospun polyacrylonitrile (PAN) nanofibers produced under different electrospinning conditions with diameters mainly varying between 100 and 300 nm. FTIR measurements with nanofibers fabricated at three different electrospinning distances, but under the same electric field intensity, revealed an enhanced molecular orientation only for the longest electrospinning distance. At long electrospinning distances the fiber solvent content is substantially reduced resulting in high viscosity, and, therefore, sustained shear stresses, which, in turn, allows for permanent molecular orientation. The orientation factors from polarized FTIR were in good agreement with the mechanical property trends obtained from individual nanofibers, where high elastic moduli and yield strengths were recorded from nanofibers with diameters smaller than 300 nm, which were fabricated at the longest electrospinning distance. WAXD studies on bundles of aligned PAN nanofibers showed small crystallinity which did not follow the trends in the mechanical properties and varied rather non-monotonically from 7%, for fibers spun at the shortest distance, to 17% for fibers spun at the longest distance used in this study.     

Efficient preparation of polymer nanofibers by needle roller electrospinning with low threshold voltage

A novel electrospinning system with needle roller as spinneret for efficient preparation of nanofibers was proposed. The results of finite element simulation indicate that the electric field is more concentrated at the tip of needle piece compared with that for disc and coil spinnerets, which can effectively reduce the threshold voltage of electrospinning. Using polyvinyl alcohol (PVA) as model polymer, the effects of spacing between needle pieces and concentration of spinning solution on fiber diameter and productivity of nanofibers were investigated. The results indicate that the average diameter decreases and the uniformity of diameter increases when increasing the spacing between needle pieces. When the spacing between the needle pieces is 14 mm, the average and standard deviation (SD) of fiber diameter is as small as 190 and 72 nm, respectively. The productivity of nanofibers slightly increases with the concentration of spinning solution, and it is as high as 12.8 g/h when the PVA concentration was 11 wt% for a needle piece spacing of 10 mm, which is much higher than the productivities of reported electrospinning systems. The proposed system has the potential for the preparation of uniform nanofibers with increased throughput and reduced cost. POLYM. ENG. SCI., 59:745–751, 2019. © 2018 Society of Plastics Engineers     

聚乳酸纤维的静电纺丝及其形态结构研究

采用二氯甲烷为溶剂,以滚筒为收集装置,利用静电纺丝法制备了聚乳酸纳米纤维。分析了溶液体系和滚筒转速对纤维形态结构的影响。结果表明:在质量分数相同的条件下,采用相对分子质量较大的聚乳酸切片所纺纤维直径细而均匀;质量分数增加时,电纺丝产品由一些高分子微/纳米液滴渐变为成形较好、珠状较少的平滑纤维,其平均纤维直径先增加后减小;控制收集滚筒的转速在一定范围内,可以获得排列取向较好的纤维。     

Electrospinning of polycarbonate urethane biomaterials

Polycarbonate urethane (PCU) nano-fibers were fabricated via electrospinning using N,N- dimethylformamide (DMF) and tetrahydrofuran (THF) as the mixed solvent. The effect of volume ratios of DMF and THF in the mixed solvent on the fiber structures was investigated. The results show that nano-fibers with a narrow diameter distribution and a few defects were obtained when mixed solvent with the appropriate volume ratio of DMF and THF as 1∶1. When the proportion of DMF was more than 75% in the mixed solvent, it was easy to form many beaded fibers. The applied voltage in the electrospinning process has a significant influence on the morphology of fibers. When the electric voltage was set between 22 and 32 kV, the average diameters of the fibers were found between 420 and 570 nm. Scanning electron microscopy (SEM) images showed that fiber diameter and structural morphology of the electrospun PCU membranes are a function of the polymer solution concentration. When the concentration of PCU solution was 6.0 wt-%, a beaded-fiber microstructure was obtained. With increasing the concentration of PCU solutions above 6.0 wt-%, beaded fiber decreased and finally disappeared. However, when the PCU concentration was over 14.0 wt-%, the average diameter of fibers became large, closed to 2 μm, because of the high solution viscosity. The average diameter of nanofibers increased linearly with increasing the volume flow rate of the PCU solution (10.0 wt-%) when the applied voltage was 24 kV. The results show that the morphology of PCU fibers could be controlled by electrospinning parameters, such as solution concentration, electric voltage and flow rate.     

A new approach for optimization of electrospun nanofiber formation process

Precise control of fiber diameter during electrospinning is very crucial for many applications. A systematic and quantitative study on the effects of processing variables enables us to control the properties of electrospun nanofibers. In this contribution, response surface methodology (RSM) was employed to quantitatively investigate the simultaneous effects of four of the most important parameters, namely solution concentration (C), spinning distance (d), applied voltage (V) and volume flow rate (Q), on mean fiber diameter (MFD) as well as standard deviation of fiber diameter (StdFD) in electrospinning of polyvinyl alcohol (PVA) nanofibers.