Fabrication of Multifunctional Composite Nanofibers by Green Electrospinning

The present work takes advantage of green electrospinning to create novel composite multifunctional nanofibers (NFs) bearing inorganic nanoparticles (NPs), more specifically quantum dots (QDs), cerium oxide nanoparticles (CeO₂ NPs) and iron oxide nanoparticles (Fe₃O₄ NPs). This is achieved by first encapsulating the desired inorganic NPs into polymer particles by the use of miniemulsion polymerization, and second, spinning the hybrid polymer particles using polyvinyl alcohol (PVA) as template polymer. It is proved that using green electrospinning, it is not only possible to ensure an excellent distribution and encapsulation of the inorganic NPs along the NFs, but also allows to control and change the concentration, size, and type of the inorganic NPs without altering the NFs size, a fact that is not possible by conventional solution electrospinning. As proof of concept, NFs with up to three different types of inorganic NPs have been created in a single electrospinning step, but this technology allows to incorporate as much inorganic NPs as desired without altering the NFs morphology and ensuring a good distribution and encapsulation of the NPs. This paper demonstrates that green electrospinning is a powerful and attractive technology to create multifunctional NFs that are promising materials for sensing and biomedical applications.     

Recent Progress in Preparing Nonwoven Nanofibers via Needleless Electrospinning

Electrospinning has received a lot of attention in recent years because it can create nonwoven nanofiber webs with high surface area and porosity. However, the typical needle and syringe-based electrospinning systems feature poor productivity that has limited their usefulness in the industrial field. Here, current developments in the creation of nanofibers employing nonconventional electrospinning methods, such as needleless electrospinning and syringeless electrospinning, are examined. These alternate electrospinning techniques, which are dependent on numerous polymer droplets of varied shapes, have the potential to match the productivity required for industry-scale manufacturing of nanofibers. Additionally, they make it possible to produce nanofibers that are difficult to spin using traditional techniques, like electrospinning of colloidal suspensions.     

Electrospinning: A Novel Method to Incorporate POSS Into a Polymer Matrix

The effectiveness of electrospinning as a simple approach to disperse POSS into a polymer matrix at a nm‐level has been assessed. Electrospun and cast films were prepared by dissolving CA and epoxycyclohexylisobutyl POSS in the solvent mixture acetone/DMAc. The membranes were characterized by SEM, TEM and WAXD. Whereas films produced by casting showed µm‐sized POSS crystals, thus suggesting a small affinity between the polymer matrix and the POSS molecules, those prepared by electrospinning were characterized by a nanometric POSS distribution. This is explained by considering the peculiar solvent evaporation mechanism, occurring during the electrospinning process, which allows to produce nanofibers characterized by a silsesquioxane dispersion similar to that present in solution.

     

静电纺丝技术的研究及应用

介绍了静电纺丝的装置、静电纺丝基本原理及影响纤维成形与纤维形貌的各种因素,同时叙述了静电纺丝在过滤材料、生物医学工程、电学和光学、催化剂载体材料方面的应用。最后对静电纺丝发展方向进行了展望。     

Electrospinning of ultrafine non-hydrolyzed silk sericin/PEO fibers on PLA: A bilayer scaffold fabrication

We report the feasibility of electrospinning of protein-polymer multilayered scaffolds with selected materials such as non-hydrolyzed silk sericin (SS), polyethylene oxide (PEO), and polylactic acid (PLA), with tuned fiber size and properties for each layer. We present a new innovative way for the electrospinning (ES) of non-hydrolyzed SS mixed with PEO yielding fibers with an average diameter ranging between 120 and 150 nm. Different SS:PEO ratios have been electrospun to study the effect of the concentration of SS protein on the fibers size and shape, as well and their electrospinnability. Electrospun SS:PEO fibers display weak to no mechanical resistance (non-measurable) and their deposition onto a sturdier scaffold is necessary to allow their use in biomedical and/or pharmaceutical fields. Therefore, bilayer scaffolds have been fabricated consisting of a PLA support and SS:PEO fibers obtained from the optimized SS:PEO ratio (1.2:4). They are composed of a sturdy hydrophobic layer of PLA fibers and a layer of sticky hydrophilic SS:PEO fibers. The scaffolds have been characterized extensively by Fourier transforms infra-red (FTIR) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), and their resistance to mechanical stress. Finally, hydrophobicity of both layers has been determined by measuring the contact angle of water droplets on the scaffolds, further proving the bilayer nature of the scaffolds.     

Electrospinning fabrication and characterization of poly(vinyl alcohol)/layered double hydroxides composite fibers

Nanofibers of poly(vinyl alcohol) (PVA)/layered double hydroxide (Mg‐Al LDH) composites are prepared by the electrostatic fiber spinning using water as the solvent at a high voltage of 21 kV. Either inorganic LDH carbonate (LDH‐CO₃) or L ‐lactic acid‐modified LDH (Lact‐LDH) is used for incorporating with PVA. Scanning electron microscopy SEM investigations on the nanofibers suggest that the average diameters of PVA/LDH composite fibers are smaller than that of neat PVA. Transmission electron microscopy (TEM) investigations indicate that the dispersity of the LDH in PVA matrix is much improved after modification with L ‐lactic acid. The mechanical properties of the PVA/LDH fibers are obviously enhanced compared to that of neat PVA. For example, the tensile stress and elongation at break of the PVA/Lact‐LDH electrospun fibrous mat with 5 wt % Lact‐LDH are 31.7 MPa and 36.7%, respectively, which are significantly higher than those of neat PVA, and also higher than those of PVA/LDH‐CO₃ owing to the better dispersity of Lact‐LDH nanoparticles. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Electrospinning zwitterion-containing nanoscale acrylic fibers

Free radical copolymerization of n-butyl acrylate and a sulfobetaine methacrylamide derivative provided high molecular weight zwitterionic copolymers containing 6-13 mol% betaine functionality, and the electrospinning of low T_g zwitterionomers was explored for the first time. Copolymerizations were performed in dimethylsulfoxide (DMSO) rather than fluorinated solvents previously reported in the literature. Dynamic mechanical analysis of zwitterionomer films revealed biphasic morphology and featured a rubbery plateau and two distinct thermal transitions. Electrospinning from chloroform/ethanol (80/20 v/v) solutions at low concentrations between 2 and 7 wt% afforded nanoscale polymeric fibers with diameters near 100 nm. The presence of only 6 mol% zwitterion allowed the formation of low T_g, free-standing, non-woven mats, and we hypothesize that zwitterionic aggregation rather than chain entanglements facilitated electrospinning at these relatively low solution concentrations. To our knowledge, this is the first report of electrospun zwitterionic polymers and these non-woven membranes are expected to lead to new applications for sulfobetaine copolymers.     

A Review on the Impact of Humidity during Electrospinning: From the Nanofiber Structure Engineering to the Applications

Electrospinning is the process of choice for the elaboration of nanofibrous mats. During the process, a thin and continuous charged jet of a polymer solution is traveling from an emitter subjected to a high voltage toward a grounded collector. Although the duration of the jet travel is in the order of few tens of milliseconds, the physical interactions acting between the jet and the air play a key role on the resulting fiber morphology. These interactions mainly rely on the amount of water molecules in air. This review deals with the effect of humidity during electrospinning on solvent evaporation, the solidification rate of nanofibers and finally, on the morphology at length scales ranging from the non-woven mat, the nanofiber itself down to the polymer crystal. Original electrospinning processes operating under specific environmental conditions as well as specificities encountered in needleless and free-surface electrospinning dedicated to industrial-scale mass production are also discussed. Then, it is shown how the control of humidity during electrospinning and the understanding of its influence on the fibrous structure can be exploited to target various applications dedicated to energy, environment, and health. Finally, current challenges and ideas for future research and new developments are presented.     

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.     

In Situ Viscosity‐Controlled Electrospinning with a Low Threshold Voltage

In the present study, a novel electrospinning method is proposed,where jet formation is aided by shearing the solution in situ. With a generalpolymer solution, viscosity decreases by shearing, that is, the solution isshear‐thinning. Poly(ethylene‐oxide) is used as a model polymer andthe effects of rotation speed, solution concentration, and gap size (the widthof the annular orifice) on the process and the morphology of the obtainedfibers are investigated. It is found that the threshold voltage for generatingmultiple jets decreased from 35 to 12 kV when rotation speed is higher than60 rpm (or shear rate more than 310 s^?1). Additionally, the results show thatfiber diameter increases as the concentration of the solution increases. Thechi‐square two‐sample test is used to compare the distribution of fibersproduced by the capillary method and the novel electrospinning process. Inthe authors' method, the viscosity of the solution can be changed by applyingmechanical forces on it during the electrospinning process, which results inthe initiation of the electrospinning jet at a low threshold voltage. It is alsofound that gap size has a similar effect on fiber diameter as needle diameter in classical electrospinning.     

Study on the properties of the electrospun silk fibroin/gelatin blend nanofibers for scaffolds

Silk fibroin (SF)/gelatin blend nanofibers membranes as scaffolds were fabricated successfully via electrospinning with different composition ratios in formic acid. The formation of intermolecular hydrogen bonds and the conformational transition of SF provided scaffolds with excellent mechanical properties. FTIR and DTA analysis showed the SF/gelatin nanofibers had more β‐sheet structures than the pure SF nanofibers. The former's breaking tenacity increased from 0.95 up to 1.60 MPa, strain at break was 7.6%, average fiber diameter was 89.2 nm, porosity was 87%, and pore diameter was 142 nm. MTT, H&E stain, and SEM results showed that the adhesion, spreading, and proliferation of human umbilic vein endothelium cells (HUVECs) and mouse fibroblasts on the SF/gelatin nanofibers scaffolds were definitely better than that on the SF nanofibers scaffolds. The scaffolds could replace the natural ECM proteins, support long‐term cell growth, form three‐dimensional networks of the nanofibrous structure, and grow in the direction of fiber orientation. Our results prove that the addition of gelatin improved the mechanical and biological properties of the pure SF nanofibers, these SF/gelatin blend nanofiber membranes are desirable for the scaffolds and may be a good candidate for blood vessel engineering scaffolds. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Electrospinning of cellulose‐based nanofibers

Cellulose derivatives of carboxymethyl cellulose sodium salt (CMC), hydroxypropyl methylcellulose (HPMC), methylcellulose (MC), and enzymatically treated cellulose have been electrospun, and the microstructure of the resulting nanofibers has been analyzed by scanning electron microscopy (SEM). Before electrospinning, the solutions were characterized by viscometry and surface tension measurements, and the results were correlated with spinnability. Four different CMC derivatives, varying in molecular weight (M_w), degree of substitution (DS), and substitution pattern, have been electrospun in mixtures with poly(ethylene oxide) (PEO), and nanofibers of various characteristics have formed. The CMC‐based nanostructures, i.e., the nonwoven sheet and individual nanofibers, proved to be independent of M_w and DS but largely dependent on the substitution pattern. The nonwoven sheets varied in homogeneity, and beads appeared on the individual fibers. Depending on the chemical nature of the CMC, the extraction of PEO resulted in pure CMC nanostructures of varying appearance, indicating that the distribution of PEO and CMC in the nanofibers also varied. Two different HPMC derivatives, varying in DS, were electrospun into nanofibers. Homogeneous nonwoven sheets based on nanofibers of similar appearance are formed, independent of the substitution content of the HPMC sample. Preliminary fibers were obtained from enzymatically treated cellulose in a solvent system based on lithium chloride dissolved in dimethyl acetamide (LiCl: DMAc). © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1473–1482, 2007     

Engineering of a Stable Collagen Nanofibrous Scaffold with Tunable Fiber Diameter,Alignment, and Mechanical Properties

The effect of varying electrospinning parameters is reported for the production of collagen nanofibers from acetic acid with controlled fiber diameter, orientation, and mechanical properties. Nanofibers with a range of diameters of 175–400 nm are obtained by varying either the voltage or the flow rate. An increase in nanofiber alignment is observed by increasing injection flow rate. Mechanical testing of these fibers reveals that the elasticity modulus can be tuned in the range of 2.7–4.1 MPa by the selection of the crosslinking method. Fourier transform infrared spectroscopy reveals that the secondary structure of collagen is preserved after electrospinning and crosslinking. Lastly, in vitro testing reveals that a high number of fibroblasts attach to the collagen matrices indicating, that they are suitable for mammalian cell culture.

     

静电纺丝法制备碳纳米纤维及其应用

碳纳米纤维由于因其比表面积大、导电和导热性好,被广泛用于催化剂载体、吸附和储能材料。静电纺丝是制备一维纳米纤维直接、有效的方法,在介绍静电纺丝的基本原理和工艺影响因素的基础上,综述了电纺碳纳米纤维的特性及其应用。     

Bipolymer nanofibers: Engineering nanoscale interface via bubble electrospinning

Modern applications in biomedicine, drug delivery, and tissue engineering demand versatile materials capable of meeting multifaceted requirements. Conventional mono-functional materials fall short of addressing these complex demands. To tackle this challenge, this study introduces an innovative approach utilizing bubble electrospinning for the fabrication of bipolymeric side-by-side nanofibers. These nanofibers incorporate distinct hydrophilic and hydrophobic domains aligned parallel to their axis, achieved through the electrospinning of polyvinyl alcohol (PVA) as the hydrophilic component, alongside either poly(ε-caprolactone) (PCL) or Nylon6 as the hydrophobic component. The optimal diameter of the bubble electrospinning reservoir was theoretically determined via simulation of electric field using Maxwell 3D software and experimentally validated. Successful electrospinning resulted in nanofibers with hydrophilic and hydrophobic domains derived from PVA/Nylon6 and PVA/PCL polymer combinations. This innovative process yielded nanofibers with diameters as fine as 101 nm in the PVA/Nylon6 bipolymeric nanofibers. Transmission electron microscopy images provide compelling insights into the distinct interfaces formed during polymer-polymer interactions within the nanofibers, manifesting the Janus structure. Furthermore, Fourier-transform infrared spectroscopy confirms the presence of both polymers within the nanofiber matrix. This research represents a significant advancement in the efficient production of bipolymer nanofibers, holding promise for a wide range of applications.     

Electrospinning of type I collagen and PCL nanofibers using acetic acid

Fabrication of nanofibrous biomaterials based on natural materials (collagen, gelatin, etc.) through various techniques is an important research topic. Electrospinning, a well-established technique for nanofiber production has also been extended for producing nanofibrous structures of natural materials. Collagen nanofiber production utilizes hexafluoro isopropanol (HFIP) as a solvent for electrospinning. Research efforts are now focused on replacing HFIP with an environmentally benign solvent. In this study, electrospinning of Type I collagen of bovine skin with polycaprolactone (PCL) as a blend and an environmentally benign solvent, acetic acid, was carried out. The samples produced were subjected to contact angle measurements, porosity estimation, SEM, FTIR, TGA, and DSC. Nanofibers in the range of 100–200 nm were produced with an optimum porosity of 60%. The instrumental analyses confirm the physical interaction between collagen and PCL. Electrospinning of collagen in an environmentally benign solvent has been carried out and its usage in tissue engineering is being investigated by our research group. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

静电纺丝法制备BaO微/纳米纤维及其表征

以聚乙烯吡咯烷酮(PVP)为络合剂,与醋酸钡[Ba(CH3COO)2]反应制得前驱体溶液;以36%乙酸为钡盐的相容剂,和乙醇组成了混合溶剂体系,用静电纺丝法制备了PVP/Ba(CH3COO)2纤维,经煅烧得到BaO微/纳米纤维。对所制备纳米纤维的结晶度、纯度和表面形貌,分别采用差热-热重分析、红外光谱、X-射线衍射、扫描电镜等进行了表征。结果表明:煅烧前后,纤维的结晶度和形貌有很大变化。     

氮化镓纳米纤维的静电纺制备及光催化性能研究

以聚乙烯吡咯烷酮(PVP)和Ga(NO3)3为前驱体,利用静电纺丝和热处理技术制备了直径在100～300 nm左右的单斜结构的Ga2O3纳米纤维,并通过氨气氮化技术制备了GaN纳米纤维。XRD结果表明GaN样品为六方纤锌矿结构,且最佳氮化温度为850℃,氮化时间为2 h。Raman光谱发生了红移,并再次确定了GaN样品的结构,TGA结果表明GaN纤维在700℃以下在空气和氮气气氛下具有较好的稳定性,SEM和TEM表明纤维直径大约在100～200 nm之间,光催化测试表明GaN纤维对罗丹明6G有很好的降解效果。