Keywords : electrospinning

Are the Electrospun Polymers Polymeric Fibers?

S. Fakirov

Advanced Materials Letters, 2020, Volume 11, Issue 1, Pages 1-3
DOI: 10.5185/amlett.2020.011456

In this short communication, an attempt is undertaken to demonstrate that the widely used practice to call the electrospun polymers from their solutions and melts “polymer nanofibers” is hardly correct for the following reasons. The polymer fibers prepared by means of the common melt-spinning are characterized by perfect molecular orientation of the parallel aligned macromolecules leading to superior mechanical performance. The electrospun polymers are also flexible cylindrical formations but with macromolecules in isotropic, non-oriented state and distinguished by poor mechanical properties, frequently inferior than those of the same polymer in isotropic state. For this reason, it is suggested to call these materials “fiber-like nanomaterials” instead of “polymer nanofiber”. The real target of the communication is to challenge the electrospinning community to modify the manufacturing process in such a way that the final nanomaterial is characterized by perfect molecular orientation resulting in excellent, typical for polymer fibers mechanical properties, which will offer wide real applications of these nanofibers. 

Study of TiO2 nanofibers prepared by electrospinning technique

Victor Jaya Nesamony; Namagal Selvan

Advanced Materials Letters, 2019, Volume 10, Issue 4, Pages 294-297
DOI: 10.5185/amlett.2019.2213

The nanostructured material properties are different from the bulk materials. Nanofibers are widely studied for many applications like tissue engineering, wound dressings, electronics, storage, catalysts, protective clothing, sensors, and cosmetics. In this study, pure form of one-dimensional TiO2 nanofibers have been successfully obtained by electrospinning technique and TiO2 nanopowders are synthesized by a conventional Sol-Gel method followed by high-temperature calcinations. The as-obtained products are characterized by X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Energy-Dispersive X-Ray (EDX) spectroscopy. The XRD results reveal the crystallite size of the synthesized material. SEM images depict the formation of nanopowders and nanofibers. EDX studies confirmed the presence of Ti and O in the prepared samples.

Effect of electrode material on piezoelectric output of PVDF sensor with electrospun nanofiber web

Hu Jiyong; Gu Yuanyuan; Zhang Hele; Zhu Yinda; Yang Xudong

Advanced Materials Letters, 2018, Volume 9, Issue 5, Pages 363-368
DOI: 10.5185/amlett.2018.1958

The electrospun PVDF (Polyvinylidene Fluoride) nanofiber web is commonly agreed on a kind of new sensitive materials for the sensor testing the dynamic pressure and energy harvesting, and has the characteristics of fast response and high sensitivity of pressure. As a result of the nanofiber web, it must be packaged to collect piezoelectric charge and bear strong mechanical behavior before industrial practice. The packaging of PVDF nanofiber web is usually sandwiched by incorporating a pair of flexible electrode. However, the effects of the surface and mechanical properties of electrodes such as morphology, roughness and compressibility have not been well investigated yet. This work will introduce three common types of packaging electrode materials (adhesive copper foil tape, indium tin oxide (ITO) thin film, adhesive conductive cloth.) in previously published literatures, compares the piezoelectric output of their sensor prototypes under a periodic impact, and discusses the effect of surface morphology, electrical resistance, and compressibility. The results showed that it has higher output of PVDF piezoelectric sensor packaged by electrode materials with the smooth surface and low mechanical compressibility. This result provides a guideline for designing the textile electrode material for the PVDF nanofiber web.

Effect of static charges on mechanical-to-electrical energy conversion of electrospun PVDF nanofiber mats

Hao Shao; Jian Fang; Hongxia Wang; Tong Lin

Advanced Materials Letters, 2017, Volume 8, Issue 4, Pages 418-422
DOI: 10.5185/amlett.2017.1461

Polyvinylidene fluoride (PVDF) nanofiber mats prepared using electrospinning technique have been used for making mechanical-to-electrical energy conversion devices. However, the effect of residual charges on this energy conversion process has never been seriously considered yet. In this study, by removing residual charges from electrospun PVDF nanofiber mats using a solvent treatment method, the contribution of the charges to device energy harvesting performance was carefully examined. It has been found that isopropanol treatment could effectively remove most of residual charges from the nanofiber mats, without obviously affecting crystal structure of the fibers. The electric outputs decreased from 1.0 V and 1.2 μA to 0.45 V and 0.5 μA after the residual charges removal. It can be concluded that residue charges play an important role in mechanical-to-electrical energy conversion of electrospun nanofibers. The understanding obtained from this study may supply a strategy for enhancing electric outputs of piezoelectric devices in future. Copyright © 2017 VBRI Press.

Synthesis, Physico-chemical Characteristics And Cellular Behavior Of Poly (lactic-co-glycolic Acid)/ Gelatin Nanofibrous Scaffolds For Engineering Soft Connective Tissues

Farnaz Ghorbani; Hanieh Nojehdehyan; Ali Zamanian; Mazaher Gholipourmalekabadi; Masoud Mozafari

Advanced Materials Letters, 2016, Volume 7, Issue 2, Pages 163-169
DOI: 10.5185/amlett.2016.6003

There have been several attempts to synthesis biodegradable polymeric constructs with adequate porous structures for soft connective tissues. In this study, randomly-oriented PLGA-gelatin nanofibrous scaffolds were synthesized by electrospinning method. We offered an appropriate solvent (2, 2, 2-trifluoroethanol) to dissolve both polymers for achieving a homogenous solution without inducing any toxic effects. The results confirmed the formation of high porous and bead free scaffolds, in which an increase in the injection rate slightly decreased the mechanical, swelling ratio and biodegradation behaviors. The modulus and tensile strength for the scaffolds with the injection rate of 0.2 ml/hr were 0.72 ±0.02 and 2.70 ±0.33, respectively. In addition, the evaluation of cell proliferation demonstrated that L929 fibroblast cells spread well on the scaffolds, indicating that they are able to support cell attachment. A possible chemical bond formation has been also suggested for the blending mixture of PLGA and gelatin molecules.

A Comparative Study Of Polyurethane Nanofibers With Different Patterns And Its Analogous Nanofibers Containing MWCNTs

Javier Macossay; Faheem A Sheikh; Hassan Ahmad; Hern Kim; Gary L Bowlin

Advanced Materials Letters, 2015, Volume 6, Issue 9, Pages 768-773
DOI: 10.5185/amlett.2015.5888

Tissue engineering is a multidisciplinary field that has evolved in various dimensions in recent years. One of the main aspects in this field is the proper adjustment and final compatibility of implants at the target site of surgery. For this purpose, it is desired to have the materials fabricated at the nanometer scale, since these dimensions will ultimately accelerate the fixation of implants at the cellular level. In this study, electrospun polyurethane nanofibers and their analogous nanofibers containing MWCNTs are introduced for tissue engineering applications. Since MWCNTs agglomerate to form bundles, a high intensity sonication procedure was used to disperse them, followed by electrospinning the polymer solutions that contained these previously dispersed MWCNTs. Characterization of the produced nanofibers has confirmed production of different non-woven mats, which include random, semi-aligned and mostly aligned patterns. A simultaneous and comparative study was conducted on the nanofibers with respect to their thermal stability, mechanical properties and biocompatibility. Results indicate that the mostly aligned nanofibers pattern presents higher thermal stability, mechanical properties, and biocompatibility. Furthermore, incorporation of MWCNTs among the different arrangements significantly improved the mechanical properties and cell alignment along the nanofibers.

Electrospun Self-assembled ZnO Nanofibers Structures For Photocatalytic Activity In Natural Solar Radiations To Degrade Acid Fuchsin Dye

Ashish Gupta; Deoram V. Nandanwar; Sanjay R. Dhakate

Advanced Materials Letters, 2015, Volume 6, Issue 8, Pages 706-710
DOI: 10.5185/amlett.2015.5834

Zinc oxide (ZnO) nanoparticles, self-assembled in the form of one dimensional ZnO nanofibers were synthesized using electrospinning technique from solution of polyvinyl alcohol (PVA) and zinc acetate followed by calcination at 600°C in oxidizing environment. Scanning Electron Microscope (SEM) analysis demonstrates that morphology of ZnO nanofibers having rough surface and corresponding Energy Dispersive Spectrometry (EDAX) confirmed the Zn: O atomic ratio approximately in 50:50. Transmission electron microscopy (TEM) images clearly demonstrate the rough morphology is due to the self-assembling of ZnO nanoparticles having diameter approximately 50nm. X-ray Diffraction (XRD) reveals the polycrystalline structure and Raman spectra show some shifts in phonon modes. The PL graph show exceptional emission at 342nm due to band-band transition. Under solar radiations as produced ZnO nanofibers degrades the 99% of 25ppm acid fuchsine which proven through UV spectra when compared to blank dye solution. This shows that natural solar radiations are sufficient to excite theses self-assembled high surface area ZnO nanofibers to show its photocatalytic activity.

How Ethanol Treatment Affects The Physico-chemical And Biological Characteristics Of Silk Fibroin Nanofibrous Scaffolds

Mazaher Gholipourmalekabadi; Masoud Mozafari; Mojgan Bandehpour; Marzieh Sameni; Hossein Ghanbarian

Advanced Materials Letters, 2015, Volume 6, Issue 5, Pages 391-394
DOI: 10.5185/amlett.2015.5739

In this study, the effects of ethanol treatment on the mechanical and biological characteristics of the nanofibrous silk fibroin (NSF) scaffolds were evaluated. The results obtained from the mechanical tests confirmed that ethanol treatment significantly enhanced the physical properties of the scaffolds through the formation of a ß-sheet structure. It was shown that the ethanol treatment increased the mechanical property and cell viability, while decreased the porosity of the randomly arranged uniform nanofibers. The ultimate tensile strength for the NSF and ethanol-treated NSF (ET-NSF) scaffolds were 0.76 and 1.33 MPa, respectively. In addition, the ethanol treatment positively affected the proliferation rate of rat bone-marrow stromal cells (rBMSCs) without any detectable cytotoxicity. All the results obtained from this study strongly indicated the efficacy of ethanol treatment in enhancement of mechanical and biological characteristics of silk fibroin nanofibrous scaffolds.

Anti-emetic Drug Delivery For Cancer Patients Through Electrospun Composite Nanofibers Transdermal Patch: In Vitro Study

Damanpreet Kaur; Nahar Singh;Sanjay R. Dhakate; Ashish Gupta

Advanced Materials Letters, 2015, Volume 6, Issue 1, Pages 33-39
DOI: 10.5185/amlett.2015.5594

The objective of the present investigation is to deliver antiemetic GH (Granisetron hydrochloride) drug to cancer patient through nanofibers transdermal patch to overcome the problem of chemotherapy induced post-operative side effects like nausea and vomiting. The biodegradable poly vinylalcohol (PVA) and polyvinyl pyrrolidone (PVP) electrospun composite nanofiber based transdermal patch was developed and anti-emetic drug was loaded by active loading in it. The in-vitro drug release from nanofibers patch demonstrates that there is a controlled release pattern of the drug and release rate is varying with PVP content in the composite nanofiber patch. Also from the data of cumulative drug permeation and steady state flux demonstrates that rate of drug release through membrane and permeation across skin increases with increasing concentration of PVP. The drug release follows Higuchi model of kinetics. While marketed drug tablet follows the zero order kinetic model of drug release. The regression values obtained for both the formulations lie in the range of 0.9484 – 0.951 which suggests the mechanism of drug release is due to the diffusion of embedded drug molecule and erosion of polymer from nanofiber an aqueous medium. Thus the present investigation gives impetus to work in the direction of delivering anti-emetic drug through nanofibers transdermal patch.

Effective Antimicrobial Filter From Electrospun Polyacrylonitrile-silver Composite Nanofibers Membrane For Conductive Environments

Anisha Chaudhary; Ashish Gupta; Rakesh B. Mathur; Sanjay R. Dhakate

Advanced Materials Letters, 2014, Volume 5, Issue 10, Pages 562-568
DOI: 10.5185/amlett.2014.572

Electrospun nanofibers based antimicrobial filter were examined for their capability to build conductive environment. An antimicrobial agent, silver nitrate (AgNO3), was added to the nanofibers membrane for its ability to prevent growth of microorganisms over the filter media. In this direction in the present investigation the different fractions of silver nanoparticles were in-situ synthesized in PAN solution and then polyacrylonitrile (PAN)-silver composite nanofibers membrane filter was prepared by electrospinning technique. The resultant solution and PAN-silver composite nanofibers was characterized by UV–visible spectroscopy, scanning electron microscope, atomic force microscope and X-ray diffraction. Antibacterial property of PAN silver composite nanofibers were investigated against gram positive Staphylococcus aureus and gram negative Escherichia coli microorganisms. The formation of clear zone suggests that composite nanofibers containing silver nanoparticles show strong antibacterial activity and it increases with increasing silver content in the composite nanofibers. The PAN-silver composite nanofibers sheet was also examined for filtration of microorganisms and dust particles. It was observed that PAN-silver composite nanofibers filter proven to be an excellent filter for creating microorganism and dust free hygienic environment. Thus electrospun PAN nanofibers filters containing an antibacterial agent can be a promising solution for effective microorganism filtration from indoor air in hospitals or other places which are more prone to bacterial infections.

 Nanofibrous Filtering Materials With Catalytic Activity

Ganna Ungur; Jakub Hruza

Advanced Materials Letters, 2014, Volume 5, Issue 8, Pages 422-428
DOI: 10.5185/amlett.2014.amwc1025

This research describes the fabrication of nanofibrous materials for the air purification with high filtration efficiency and catalytic properties to clean the air from solid particles and emissions of automobile's transport. The polyurethane (PU) nanofibers were modified by particles of SnO2 and CrO2 in the ratio 95/5 to impart catalytic properties in the reaction with emission gases (CO, NOx).The modification process was provided by the introduction of metal’s oxide’s particles of different concentrations (1;2; 3; 4%) into the polymer solution. Reological properties and conductivity of the modified solutions were studied. The viscosity of solutions grew up gradually with increasing of SnO2/CrO2 concentrations. Fiber's samples were produced from modified solutions by the electorstatic fiber forming using Nanospider technology. The morphology of produced fibers was analysed by the Scanning Electron Microscopy (SEM). SEM pictures confirmed the smoothness of fibrous layer. The diameters of fibres were measured with the help of Lucie 32G computer software. The obtained results demonstrated increasing of average diameters of nanofibers for the concentration 1and 2% of catalysts in comparison with the pure PU samples. But fibers with 3 and 4% of SnO2/CrO2 particles showed the decreasing of average fiber diameters. The presence of catalyst on the nanofiber`s surface was proved by the method of Energy Dispersive Spectroscopy (EDS). The catalytic properties of produced nanolayers in the reaction with emission's gases were studied with the measurement setup consisting from the engine, a system of analyzers and UV lamp as a sourse of energy to activate the catalyst. All samples demonstrated good catalytic efficiency. The best result showed the sample of PU nanofibers with 3% of SnO2/CrO: the concentrations of CO and NOx reduced by 81% and 73% respectively. Produced samples are the promising materials for air-conditioning systems.

Synthesis And Characterization Of CuO Electrospum Nanofiber Using Poly(vinyl Acetate)/Cu(CH3COO)2 Annealing Method

Seema Sharma; Rashmi Rani; Radheshyam Rai; T. S. Natarajan

Advanced Materials Letters, 2013, Volume 4, Issue 10, Pages 749-753
DOI: 10.5185/amlett.2013.2425

One dimensional nanofibers of organic and inorganic materials have been used in filters, optoelectronic devices, sensors etc. It is difficult to obtain ultra fine fibers of inorganic materials having lengths in the order of millimeter as they tend to break during formation due to thermal and other mechanical stresses. In this study, we have investigated the mechanism to prevent the defect formation and the breaking of CuO nanofibers by using optimized heat flow rates. CuO nanofibers were obtained by heat treating the poly(vinyl acetate) PVA composite fibers formed by electrospinning. The morphology and structural characteristics of prepared samples were investigated by Scanning electron microscopy, Transmission electron microscopy and X-ray diffraction. It was found that the morphology of the composite and annealed nanofibers could be influenced by the concentration of the polymer content. A lower concentration favors the formation of defects along the fiber and the number of defects reduces when the concentration is increased.

Ferrolectric Nanofibers: Principle, Processing And Applications

Seema Sharma

Advanced Materials Letters, 2013, Volume 4, Issue 7, Pages 522-533
DOI: 10.5185/amlett.2012.9426

Nanotechnology is one of the rapidly growing scientific disciplines due to its enormous potential in creating novel materials that have advanced applications. Electrospinning has been found to be a viable technique to produce materials in nanofiber form. Ferroelectric and/or piezoelectric materials in nanofiber and/or nanowire form have been utilized for producing energy harvesting devices, high frequency transducers, implanted biosensors, vibration absorbers and composite force sensors, etc. An in-depth review of research activities on the development of ferroelectric nanofibers, fundamental understanding of the electrospinning process, and properties of nanostructured fibrous materials and their applications is provided in this article. A detailed account on the type of fibers that have been electrospun and their characteristics is also elaborated. It is hoped that the overview article will serve as a good reference tool for nanoscience researchers in ferroelectric materials.

A Study On The Electrospinning Behaviour And Nanofibre Morphology Of Anionically Charged Lignin

Makoto Schreiber; Singaravelu Vivekanandhan; Amar Kumar Mohanty; Manjusri Misra

Advanced Materials Letters, 2012, Volume 3, Issue 6, Pages 476-480
DOI: 10.5185/amlett.2012.icnano.336

The electrospinnability of anionically charged sodium carbonate lignin using positive-voltage electrospinning was explored. The lignin was mixed with polyethylene oxide (PEO) in order to enhance the electrospinning performance by improving the viscoelastic properties. Lignin fibres containing varying concentrations of lignin were obtained by employing various applied voltages. The effect of increased lignin content on the electrospinning behaviour and the obtained fibre morphologies were observed. The electrospun fibres were characterised using scanning electron microscopy (SEM) to investigate their microstructure. SEM analysis showed the formation of well defined lignin fibres and the results indicate that the morphologies are highly depend on the PEO:lignin composition.

Effect Of Processing Parameters On Morphology And Thermal Properties Of Electrospun Polycarbonate Nanofibers

Advanced Materials Letters, 2010, Volume 1, Issue 3, Pages 200-204
DOI: 10.5185/amlett.2010.8148

In the present contribution, it has been reported about the effect of solvent, solvent concentration, flow rate and applied voltage on the fabrication of electrospun polycarbonate (PC) nanofibers. The morphology of fibers was studied by optical and scanning electron microscope. It is observed that morphology of fibers depends upon the concentration of PC or viscosity of the solution, vapor pressure and diffusion coefficient of solvent. In fact, when viscosity of the solution is very low, beads or droplets are formed instead of fibers. The same problem arises when the viscosity of the solution is too high due to high surface tension. In this case, jet formation will not be observed and the solution will coagulate at the tip of needle. Tetrahydrofuran (THF) easily diffuses with polymer, at higher concentration of PC and at higher flow rate of solution; fibers of micron size are formed because of high vapor pressure of THF. On the other hand, in case of mixed solvents (DMF and THF), by controlling processing parameters one can get fiber diameter up to 200 nm. The study of Differential Scanning Calorimetry (DSC) indicates that less amount of heat energy is absorbed during endothermic reaction and there is a slight increase in glass transition temperature of nanofibers. Thermogravimetric analysis (TGA) shows an increase in thermal stability of PC nanofibers by 40ºC as compared to PC granules. This is due to the alignment of PC polymeric chains during stretching and whipping that occurs while electro spinning process.