REVIEW | doi:10.20944/preprints202111.0380.v1
Subject: Engineering, Electrical & Electronic Engineering Keywords: PVDF; nanofibers; electrospinning; nanogenerators
Online: 22 November 2021 (11:05:04 CET)
PVDF has special piezo/pyro/ferroelectric, flexibility, low weight, biocompatibility, economical, good chemical/thermal, and high mechanical properties such as excellent nontoxic fiber/film formation. It has polar and nonpolar phases of α, β, γ, ε, and δ that the nonpolar α phase is the most stable one, but the β phase is the best of all because it has good piezo/pyro/ferroelectric properties. Copolymers are attractive because of their low weight, nontoxic, chemical acid resistance, flexibility, and ease of processing. These aspects result in their applications in many fields. They are used for piezoelectric nanogenerators, cooling/heating sensors, electronic devices (fuel cells, lithium-ion batteries (as separators), dye sensitive solar cells), filtration, oil/water separation, and photoelectric nanodevices. This review highlights the main aspects of the last decade's articles, and the focus is on the synthesis methods of PVDF nanofibers and their properties which results in their application in different fields of industry and especially focuses on finding ways to increase the output of PVDF nanofibers nanogenerators (weight/acoustic pressure nanogenerators
REVIEW | doi:10.20944/preprints202104.0711.v1
Online: 27 April 2021 (12:31:25 CEST)
Electro-spun ultra-fine fibers exhibit two significant properties: a high surface-to-volume ratio and a relatively defect-free molecular structure. Due to the high surface-to-volume ratio, electro-spun materials are well suited for activities requiring increased physical contact, such as providing a site for a chemical reaction or filtration of small-sized physical materials. However, electrospinning has many shortcomings, including difficulties in producing inorganic nanofibers and a limited number or variety of polymers used in the process. The fabrication of nanofiber bundles via electrospinning is explored in this analytical study, as well as the relationship between extrinsic electrospinning parameters and the relative abundance of various fiber morphologies. Numerous variables could impact the fabrication of nanofibers, resulting in a variety of morphologies; therefore, adequate ambient conditions and selecting the appropriate solvent for achieving a homogenous polymer solution and uniform electro-spun materials are examined. Finally, common polymers suitable for electrospinning and the promising applications of ultra-fine fibers achieved via electrospinning are studied in this paper.
ARTICLE | doi:10.20944/preprints202203.0355.v1
Subject: Engineering, Mechanical Engineering Keywords: electrospinning; multi-needle electrospinning; scale-up; auxiliary electrodes; nanofibers; non-woven membranes; PVDF
Online: 28 March 2022 (07:52:48 CEST)
Electrospinning has gained a lot of attention in recent years due to its ability to easily produce high-quality polymeric nanofibers. However, electrospinning suffers from limited production capacity and a method to readily scale up this process is needed. One obvious approach includes the use of multiple electrospinning needles operating in parallel. Nonetheless, such an implementation has remained elusive, partly due to the uneven electric field distribution resulting from the Coulombic repulsion between the charged jets and needles. In this work, the uniformization of the electric field was performed for a linear array of twenty electrospinning needles using lateral charged plates as auxiliary electrodes. The effect of the auxiliary electrodes was characterized by investigating the semi-vertical angle of the spun jets, as well as the deposition area and diameter of the fibers. Finite element simulation was also used to analyze the impact of the auxiliary electrodes on the electric field intensity below each needle. Implementing parallel lateral plates as auxiliary electrodes was shown to help achieve uniformization of the electric field, the semi-vertical angle of the spun jet, and the deposition area of the fibers for the multi-needle electrospinning process. The high-quality morphology of the polymer nanofibers obtained by this improved process was confirmed by scanning electron microscopy (SEM). These findings help resolve one of the primary challenges that have plagued the large-scale industrial adoption of this exciting polymer processing technique.
Subject: Materials Science, Nanotechnology Keywords: PVA; Nanofibers; CNx; Electrospinning; Electrochemical
Online: 12 October 2021 (10:29:37 CEST)
Polyvinyl alcohol (PVA) is highly compatible polymer with biological environments. Specifically, it has been used as a trap for different types of microorganisms in Bio-MEMS, and its properties can be modified to act as an electrode for electrochemical analysis. This study presents a nano-composite developed with PVA, multiwall carbon nanotubes (CNTs) doped with nitrogen, which changes the electrical properties of the polymer and its viscosity to obtain nanofibers by electro-spinning. The proposed nanocomposite was characterized using Fourier transform-infrared and Raman spectroscopy techniques, confirming the presence of the CNTs immersed in the polymer. High-resolution transmission electron microscopy was used to obtain the micrographs that showed the characteristic interplanar distances of the multiwall CNT in the polymeric matrix with values of 3.63 Å. Finally, the CNx mats were exposed to various aqueous solutions in a po-tentiostat to demonstrate the effectiveness of the nanofibers for electrochemical analysis. The CNx-induced changes in the electrical properties of the polymer were identified using cyclic voltammograms, while the electrochemical analysis revealed supercapacitor behavior.
ARTICLE | doi:10.20944/preprints202110.0333.v1
Subject: Chemistry, Applied Chemistry Keywords: Nb2O5; CO2 conversion; Photocatalysis; Electrospinning; Nanofibers.
Online: 22 October 2021 (15:38:01 CEST)
The increase in global warming due to NOx, CO2, and CH4 harmfully different ecosystems and significantly prejudice world life. A promising methodology in this sense is the pollutant conversion into valuable chemicals from photocatalytic processes by reusable photocatalyst. In this way, the present work aimed to produce a Nb2O5 photocatalyst nanofibers system to convert CO2 by the electrospinning method. Based on the collected data, the nanofibers calcination at 600°C for 2 h resulted in the best condition to obtain a homogeneous surface with an average diameter of 84 nm. As a result, the Nb2O5 nanofibers converted CO2 mostly into CO and CH4, reaching values around 8.5 μmol g−1 and 0.55 μmol g−1, respectively.
REVIEW | doi:10.20944/preprints202012.0569.v1
Subject: Materials Science, Biomaterials Keywords: AMD; Biomaterials; electrospinning; membranes; Bruch's membrane
Online: 23 December 2020 (07:23:19 CET)
Abstract: Age-related macular degeneration (AMD) is the leading cause of central blindness in developed countries. It affects people mainly over the age of 50 years. It is a disease of the macula, an area of the retina responsible for sharp central vision. It particularly affects the Bruch’s membrane (BM); a layer in the retina that acts as the basement upon which retinal pigment epithelial cells (RPE) attach and survive. The pathology of AMD is not fully understood, but age is considered the main risk factor. There are two forms; nonexudative, leading to the end-stage of the disease, called nonexudative (or dry) AMD (90% of cases) where fatty deposits called drusen form under the RPE on top of the BM lifting off the RPE, and neovascular (or wet) AMD (10% of cases) where abnormal new blood vessels grow and push through the BM, bleeding in and disrupting the RPE. Neovascular AMD is well controlled with regular antiangiogenic drug injections of anti-vascular endothelial growth factor (anti-VEGF) into the eye, whereas there is no current treatment for nonexudative AMD. Many research groups across the world are working on a treatment for nonexudative AMD. This review discusses the research currently being conducted including cell therapies, development of cell transplantation membranes, targeting other disease structures in affected retina (i.e. drusen), and drug delivery to the retina using nanoparticles. Finally, we include our research contributing to the field; developing a bioactive membrane intended to function two-fold: target diseased structures and transplant healthy RPE to the desired area.
ARTICLE | doi:10.20944/preprints201810.0528.v1
Subject: Engineering, Biomedical & Chemical Engineering Keywords: biocomposites; nanomaterials; measurement; electrical properties; electrospinning
Online: 23 October 2018 (08:43:36 CEST)
Nanoﬁbers appearing functional properties show a great promise as allowing constituents for a wide range of medical applications. In this work, Polycaprolactone (PCL), Silver Nitrate (AgNO3) and Zinc Oxide (ZnO) were used for fabrication of nanofiber composite material by co-axial electrospinning (CAE) process. 5, 10, and 15 wt. % concentrations of PCL were utilized and different amount of AgNO3 and ZnO were used in entire samples. Morphological analyses of the electrospun nanocomposites were done by scanning electron microscopy (SEM) and AgNO3, ZnO and PCL materials’ functional groups were determined by Fourier Transform Infrared Spectroscopy (FTIR). Before co-axial electrospinning, physical properties such as liquid state ac conductivity, density and viscosity were measured for all solutions. Capacitance (Cp) and D-factors (tanδ) of nanocomposite materials are measured for the frequency range of 20Hz – 3MHz and the solid state alternating current (ac) conductivity, permittivity (ε’) and dielectric loss (ε’’) were calculated for all solutions after co-axial electrospinning. Effects of concentration percentages of PCL and AgNO3 on real and imaginary parts of dielectric constant and solid state ac conductivity have been analyzed and comparisons have been made by the results obtained.
ARTICLE | doi:10.20944/preprints201612.0133.v1
Subject: Materials Science, General Materials Science Keywords: MoS2; carbon nanofibers; electrospinning; anode material
Online: 28 December 2016 (10:49:33 CET)
The one-dimensional MoS2/carbon nanofibers (1D MoS2/CNFs) are synthesized by electrospinning using exfoliated MoS2 nanosheets and polyacrylonitrile as raw materials. The exfoliated MoS2 nanosheets with size of about 150 nm are encapsulated in carbon nanofibers, and the free-standing MoS2/CNFs can be easily cut into flexible tablet and directly used as binder-free anode for lithium storage. The resultant 1D MoS2/CNFs exhibit a very high reversible capacity of 700 mAh g-1 at 100 mA g-1 after 50 cycles, high rate capacity (450 mAh g-1 at 1000 mA g-1 after 200 cycles) and good cycle stability.
ARTICLE | doi:10.20944/preprints202207.0023.v1
Subject: Materials Science, Biomaterials Keywords: electrospinning; morphology structures; propolis; polycaprolactone; drug delivery
Online: 1 July 2022 (17:39:00 CEST)
The structure of wound dressing materials presents one of the most relevant characteristics for effective skin tissue repair. Electrospinning is a common technique used to produce polymeric fibres that can mimic fibrillar disposition of skin extracellular matrix, favouring cell migration, and thus regeneration of the damaged tissue. Moreover, beads, also known as by-products of electrospinning, have potential as reservoirs for sustained drug release. Processing parameters, such as molecular weight and viscosity of the polymer solution, can affect the desirable morphologies of electrospun films. Thereby, this work had the purpose of producing and characterized electrospun polycaprolactone (PCL) mats loaded with propolis, a popular extract in traditional medicine with potential for skin repair aid. Films with different morphologies were obtained depending on the storage period of the solution prior to the lectrospinning, probably due to the PCL hydrolysis. FTIR analyses of the extract confirmed propolis composition. GPC and viscosity analyses demonstrated that the decrease in molar mass over the storage period was responsible for nanostructure diversity. Propolis acts as a lubricant agent, affecting the spun solutions' viscosity and the thermal properties and hydrophilicity of the films. All films are within the value range of the water vapour transpiration rate of the commercial products. The presence of beads did not affect the propolis release pattern. However, "in vitro" wound healing assay showed that propolis-loaded films composed by beaded fibres increased the cell migration process. Thus, it can be inferred that these films presented the potential for wound dressing application.
Subject: Materials Science, Biomaterials Keywords: bee pollen; nanofiber; biomaterial; green production; electrospinning
Online: 7 May 2021 (15:37:46 CEST)
Green electrospun materials are gaining popularity in the quest for a more sustainable environment for human life. Bee pollen (BP) is a valuable apitherapeutic product, and has many beneficial features such as, antioxidant and antibacterial properties. Alginate is a natural and low-cost polymer. Both natural materials show good compatibility with human tissues for biomedical applications and have no toxic effect on the environment. In this study, bee pollen-loaded sodium alginate and polyvinyl alcohol (SA/PVA) nanofibrous mats were fabricated by the electrospinning technique. The green electrospun nanofibrous mats were analyzed by scanning electron microscopy (SEM), Fourier transforms infrared spectroscopy (FTIR), and differential scanning calorimeter (DSC). According to the findings of the study, the toxin-free electrospinning method is suitable for producing green nanomaterial. Because of the useful properties of the bee pollen and the favorable biocompatibility of the alginate fibers, the bee pollen-loaded SA/PVA electrospun mats have the potential for use in a variety of biomedical applications
ARTICLE | doi:10.20944/preprints201810.0231.v1
Subject: Medicine & Pharmacology, Other Keywords: drug release; electrospinning; paclitaxel; polycaprolactone; 3D matrix
Online: 11 October 2018 (06:09:26 CEST)
Paclitaxel is a natural, highly lipophilic anti proliferative drug widely used in medicine. We have studied the release of tritium-labeled paclitaxel (3H-PTX) from matrices destined for the coating of vascular stents and produced by the electrospinning method from the solutions of polycaprolactone (PCL) with paclitaxel (PTX) in hexafluoisoropropanol (HFIP) and/or solutions of PCL with PTX and human serum albumin (HSA) in HFIP or HIFP-dimethyl sulphoxide (DMSO) blend. The release of PTX has been shown to depend on the solvent and the composition of electrospinning solution, as well as the composition of the surrounding medium, particularly the concentration of free PTX and PTX-binding biomolecules present in human serum. It was shown that 3D matrices can completely release PTX without weight loss. Two-phase PTX release from optimized 3D matrices was obtained: ~27% of PTX was released in the first day, another 8% were released over the next 26 days. Wherein ~2.8%, ~2.3%, and ~0.25% of PTX was released on day 3, 9, and 27, respectively. Considering PTX toxicity, the rate of its diffusion through the arterial wall, and the data obtained the minimum cytostatic dose of the drug in the arterial wall will be maintained for at least three months.
ARTICLE | doi:10.20944/preprints201806.0396.v1
Subject: Engineering, Energy & Fuel Technology Keywords: Supercapacitors; Stretchable; SBS nanofiber; Carbon nanotube; Electrospinning
Online: 25 June 2018 (15:20:50 CEST)
We report a new fabrication method for a fully stretchable supercapacitor based on single wall carbon nanotube (SWCNT)-coated electrospun rubber nanofibers as stretchable supercapacitor electrodes. The deposition conditions of SWCNT on hydrophobic rubber nanofibers are experimentally optimized to induce a uniform coating of SWCNT. For surfactant-assisted coating of SWCNT, both water contact angle and sheet resistance were the lowest compared to the cases with other surface treatment methods, indicating the most effective coating approach. The excellent electromechanical properties of this electrode under the stretching condition is demonstrated by the measurement of Young’s modulus and normalized sheet resistance. This superb tolerance of the electrode with respect to stretching results from i) high aspect ratios of both nanofiber templates and the SWCNT conductors, ii) highly elastic nature of rubbery nanofiber, and iii) strong adherence of SWCNT-coated nanofiber on the elastic ecoflex substrate. Electrochemical and electromechanical measurements on the stretchable supercapacitor devices reveal that the volumetric capacitance (15.2 F cm-3 at 0.021 A cm-3) of the unstretched state is maintained for strains of up to 40 %. At this level of strain, the capacitance after 1,000 charge/discharge cycles is not significantly reduced. The high stability of our stretchable device suggests potential future applications in various types of wearable energy storage devices.
ARTICLE | doi:10.20944/preprints202210.0193.v1
Subject: Materials Science, Surfaces, Coatings & Films Keywords: artificial interface; coulombic efficiency; electrospinning; MnO2 Cathode; PVDF
Online: 13 October 2022 (11:45:38 CEST)
Uncontrollable Zn dendrite formations and parasitic side reactions on Zn electrodes induce poor cycling stability and safety issues, preventing the large-scale commercialization of Zn-ion batteries. Herein, to achieve uniform Zn deposition and suppress side reactions, an electrospun ferroelectric poly(vinylidene fluoride-co-trifluoroethylene) copolymer, a [P(VDF-TrFE)] nanofiber layer, is introduced as an artificial solid-electrolyte interface on a Cu substrate acting as a current collector. The aligned molecular structure of β-P(VDF-TrFE) can effectively suppress localized current density on the Cu surface, lead to uniform Zn deposition, and suppress side reactions by preventing direct contact between electrodes and aqueous electrolytes. The half-cell configuration formed by the newly fabricated electrode can achieve an average coulombic efficiency of 99.2% over 300 cycles without short circuiting at a current density of 1 mA cm-2 and areal capacity of 1 mAh cm-2. Stable cycling stability is also maintained for 200 cycles at a current density of 0.5 A g-1 in a full-cell test using MnO2 as a cathode.
ARTICLE | doi:10.20944/preprints202209.0421.v1
Subject: Materials Science, Nanotechnology Keywords: electrospinning; microfibers; piezoelectric crystals; nitroanilines; fluorescence; functional organic materials
Online: 27 September 2022 (10:22:10 CEST)
N,N-dimethyl-4-nitroaniline (NNDM4NA, C8H10O2N2), is a superelastic and superplastic charge-transfer molecular crystal with a high molecular dipole moment, µ=7.95 D, which crystal-lizes in the acentric polar point group 2. Highly aligned poly-l-lactic acid (PLLA) polymer micro-fibers with embedded NNDM4NA nanocrystals were fabricated using the electrospinning tech-nique. The composite fibers display an extraordinarily high piezoelectric output response, where for a small stress of 5.0x103 Nm-2, an effective piezoelectric voltage coefficient of geff=3.6 VmN-1 was obtained. The fibers were found to display solid state blue fluorescence with a long (147 ns) life-time decay. Furthermore, the composite fibers exhibit an average increase of 67% on the Young modulus reaching 55 MPa, while the tensile strength reaches 2.8 MPa when compared with solely PLLA fibers. The results show that nanocrystals, from small organic molecules, with elastic and piezoelectric properties form hybrid functional 2-dimensional luminescent array which are me-chanical strong and generate high output voltages making them promising for applications in energy harvesting and as solid-state blue emitters.
ARTICLE | doi:10.20944/preprints202201.0056.v1
Subject: Materials Science, Nanotechnology Keywords: Electrospinning; ZnSnO3/ZnO nanofibers; Sensing performance; n-n heterojunction
Online: 6 January 2022 (09:51:23 CET)
In this work, a novel heterojunction based on ZnSnO3/ZnO nanofibers was prepared using electrospinning method. The crystal, structural and surface compositional properties of sample based on ZnSnO3 and ZnSnO3/ZnO composite nanofibers were investigated by X-ray diffractometer (XRD), Scanning electron microscope (SEM), X-ray photoelectron spectrometer (XPS) and Brunauer-Emmett-Teller (BET). Compared to pure ZnSnO3 nanofibers, the ZnSnO3/ZnO heterostructure nanofibers display high sensitivity and selectivity response with fast response towards ethanol gas at low operational temperature. The sensitivity response of sensor based on ZnSnO3/ZnO composite nanofibers were 19.6 towards 50 ppm ethanol gas at 225°C, which was about 1.5 times superior than that of pure ZnSnO3 nanofibers, which can be owed mainly to the presence of oxygen vacancies and the synergistic effect between ZnSnO3 and ZnO.
REVIEW | doi:10.20944/preprints202104.0782.v2
Subject: Materials Science, General Materials Science Keywords: electrospinning; negative electrode materials; carbon nanofibers; free-standing; supercapacitor
Online: 10 May 2021 (09:34:34 CEST)
The development of smart negative electrode materials with high capacitance for use in supercapacitors remains challenging. Although there have been several types of electrode materials with high capacitance used in energy storage, carbon-based materials are the most reliable electrodes due to their high conductivity, high power density and excellent stability. The most common complaint about general carbon materials is that these as-formed electrode materials can hardly ever be used as free-standing electrodes. Free-standing carbon-based electrodes are in high demand and are a passionate topic of energy storage research. Electrospun nanofibers are a potential candidate to fill this gap. However, the as-spun carbon nanofibers (ECNFs) have low capacitance and energy density on their own. To this end, several attempts have been made to improve these characteristics. In this review, we introduce negative electrode materials that have been developed. Moreover, this review places special attention to the advances of electrospun nanofiber-based negative electrode materials and their limitations. Based on the above information, we put forth a future perspective on how these limitations can be overcome to meet the demands of next-generation smart devices.
ARTICLE | doi:10.20944/preprints202201.0127.v1
Subject: Materials Science, Nanotechnology Keywords: electrospinning; porous carbon nanofibers; oxygen reduction reaction; oxygen evolution reaction
Online: 10 January 2022 (15:23:04 CET)
Recently, electrocatalysts for oxygen reduction reactions (ORRs) as well as oxygen evolution reactions (OERs) hinged on electrospun nanofiber composites have attracted wide research attention. Transition metal elements and heteroatomic doping are important methods used to enhance their catalytic performances. Lately, the construction of electrocatalysts based on metal-organic framework (MOF) electrospun nanofibers has become a research hotspot. In this work, bimetallic NixCoy-ZIF nanocrystals were synthesized in an aqueous solution, followed by NixCoy-ZIF/PAN electrospun nanofiber precursors, which were prepared by a simple electrospinning method. Bimetal (Ni-Co) porous carbon nanofiber catalysts doped with nitrogen, oxygen, and sulfur elements were obtained at high-temperature carbonization treatment in different atmospheres (Ar, Air, and H2S), respectively. The morphological properties, structures, and composition were characterized by SEM, TEM, SAED, XRD, and XPS. Also, the specific surface area of materials and their pore size distribution was characterized by BET. Linear sweep voltammetry curves investigated catalyst performances towards oxygen reduction and evolution reactions. Importantly, Ni1Co2-ZIFs/PAN-Ar yielded the best ORR activity, whereas Ni1Co1-ZIFs/PAN-Air exhibited the best OER performance. This work provides significant guidance for the preparation and characterization of multi-doped porous carbon nanofibers carbonized in different atmospheres.
ARTICLE | doi:10.20944/preprints202105.0077.v1
Subject: Materials Science, Biomaterials Keywords: Silk Fibroin; Fluorescence Resonance Energy Transfer (FRET); Confocal Imaging; Electrospinning
Online: 6 May 2021 (12:24:22 CEST)
Silk fibroin is a well-known biopolymer used in several applications in which the interaction with biological tissue is required. In fact, fibroin is extremely versatile and can be shaped to form several constructs useful in tissue engineering applications. Confocal imaging is usually per-formed to test the cells behaviour on the construct and in this context the fibroin autofluorescence is regarded as a problem. In addition, the autofluorescence is not intense enough to provide useful morphological images. In fact, to control study the constructs morphology other techniques are used (i.e. SEM, Micro-CT). In this work we propose a method based on the fluorescence energy transfer (FRET) to suppress the fibroin autofluorescence moving it to higher wavelength accessible to the confocal microscopy for a direct imaging.
ARTICLE | doi:10.20944/preprints202001.0271.v1
Subject: Materials Science, Biomaterials Keywords: Nanomaterials; Electrospun nanofibers; biodegradable 3D scaffolds; Electrospinning; Design of Experiments.
Online: 23 January 2020 (16:23:33 CET)
Electrospinning is known to be an effective and straightforward technique to fabricate polymer non woven matrices made of nano and microfibers. Micro patterned morphology of electrospun matrices results to be outmost advantageous in the biomedical field, since it is able to mimic extracellular matrix (ECM), and favors cell adhesion and proliferation. Controlling electrospun fibers alignment is crucial for the regenerative purposes of certain tissues, such as neuronal and vascular. In this study we investigated the impact of electrospinning process parameters on fiber alignment in tubular nanofibrous matrices made of Poly (L-lactide-co-ε-caprolactone) (PLA-PCL); a Design of Experiments (DoE) approach is here proposed in order to statistically set up the process parameters. The DoE was studied keeping constants the previously set material and environmental parameters; voltage, flow rate and mandrel rotating speed were the process parameters here investigated as variables. Orientation analysis was based on ImageJ and plugin Orientation J analysis of SEM images. The results show that voltage combined with flow rate has significant impact on electrospun fiber orientation, and the greatest orientation is achieved when all the three input parameters (voltage, flow rate and mandrel rotation speed) are at their maximum value.
ARTICLE | doi:10.20944/preprints202112.0457.v1
Subject: Life Sciences, Other Keywords: graft rejection; iPSC; differentiation; cardiomyocytes; electrospinning; CD28; CTLA-4; immune response
Online: 28 December 2021 (17:37:34 CET)
Different types of engineered cardiac constructs are being developed nowadays by many research groups. However, the immunological properties of such artificial tissues are not yet clearly understood. Previously, we have studied microfiber scaffolds carrying iPSC-derived cardiomyocytes. In this work, we evaluated the ability of these tissue-engineered constructs to activate the expression of CD28 and CTLA-4 proteins in T-lymphocytes which are early markers of the immune response. For this purpose electrospun PLA nanofibrous scaffolds were seeded with human iPSCs-CM and cultivated for 2 weeks. After, allogeneic mononuclear cells were co-cultured during 48 hours with 3 groups of samples that were tissue-engineered constructs, pure culture of cardiomyocytes and bare scaffolds followed by analysis of CD28/CTLA-4 expression on T-lymphocytes via flow cytometry. PLA scaffolds and concanavalin A (positive control) stimulation statistically significantly increased CD28 expression on CD4+ cells (up to 61.3% and 66.3%) and on CD8+ cells (up to 17.8% and 21.7%). CD28/CTLA-4 expression didn’t increase during co-cultivation of T-lymphocytes with cardiac engineered constructs and iPSC-CM monolayers. Thus, iPSCs-CM in monolayers and on PLA nanofibrous scaffolds didn’t cause T-cell activation, which allows us to expect that such cardiac constructs are not a cause of rejection after implantation.
ARTICLE | doi:10.20944/preprints201808.0509.v1
Subject: Materials Science, Polymers & Plastics Keywords: PLLA nanofibers membranes; electrospinning; PPC; PHB; plasticizer; biopolymer blends; water purification
Online: 30 August 2018 (04:16:50 CEST)
Water pollution in developing countries affects the public health of humans and the environment. It is therefore essential to develop environmentally friendly biopolymer, sustainable and low-cost membranes. Biopolymer nanofiber membranes are made by an electrospinning process of polylactic acid (PLLA) with additives. The main objective of this study is to manufacture biodegradable nanofiber membranes for use in filtering the suspended elements in wastewater at the level of drinkable or in agricultural fields. It is known that PLLA is brittle and therefore it is difficult to apply in industry. To solve this problem and enhance its flexibility. Flexible biopolymer polypropylene carbonate (PPC) and plasticizer are the addition in PLLA to reduce its glass transition and enhance its crystallization by adding Poly(3-hydroxy butyrate) PHB. In this work, 20 wt% of PPC was added to PLLA matrix to improve its elasticity and elongation at break. DSC shows that the addition of PPC, PHB, and TEC did affect the thermal properties like Tg, Tcc and Tm of the PLLA blends. The position of the Tg, Tcc, and Tm is shifting, the consequence the chain mobility is increased, therefore the crystallinity is enhanced. Electrospun fibers of PLLA/PPC/PHB/TEC were successfully manufactured. Tensile tester showed the increase in elongation at break of PLLA blend films, the elongation at break increases by 285 times. It observed with the increasing the elongation at break, a decrease in stress strength. After improving the mechanical properties with the higher elongation at break values, this blend is optimal for filtrations process.
ARTICLE | doi:10.20944/preprints202212.0396.v1
Subject: Materials Science, Polymers & Plastics Keywords: Spin Crossover; (Coaxial)-electrospinning; Triazole Complexes; nano fibers; PMMA; Coordination Chemistry; Composites
Online: 21 December 2022 (09:19:47 CET)
We synthesized iron(II)-triazole spin crossover compounds of the type [Fe(atrz)3]X2 and incorporated and deposited them on electrospun polymer nanofibers. In view of possible applications, we chose iron(II)-triazole-complexes that are known to exhibit spin crossover close to ambient temperature. Therefore we used the complexes [Fe(atrz)3]Cl2 and [Fe(atrz)3](2ns)2 (2ns = 2Naphthalenesulfonate) and analyzed them with IR-, UV/Vis and Mossbauer spectroscopy and with a SQUID magnetometer. The synthesized complexes were then in one attempt deposited on fibers of polymethylmethacrylate (PMMA) and in another attempt incorporated into core-shell like PMMA fiber structures. This was done via two different electrospinning methods. Deposition was performed by uniaxial electrospinning and incorporation was performed by coaxial electrospinning. The obtained polymer-complex-composites were then further investitgated by the same methods as the pure complexes as well as by SEM pictures and EDX measurements. The analysis by UV/Vis spectroscopy, Mössbauer spectroscopy and temperature-depended magnetic measurements with the SQUID magnetometer showed that the spin crossover properties were maintained and were not changed after the electrospinning processes and that the complexes were not harmed during the procedure.
ARTICLE | doi:10.20944/preprints201907.0321.v1
Subject: Materials Science, Nanotechnology Keywords: lithium-ion battery; safety; separator; coaxial electrospinning; dual-nozzle; core-shell nanofiber
Online: 28 July 2019 (17:00:49 CEST)
Though the energy density of lithium-ion batteries continues to increase, safety issues related with the internal short-circuit and the resulting combustion of highly flammable electrolyte impede the further development of lithium-ion batteries. It has been well-accepted that a thermal stable separator is important to postpone the entire battery short-circuit and thermal-runaway. Traditional methods to improve the thermal stability of separators includes surface modification and/or developing alternate material systems for separators which may always affect the battery performance negatively. Herein, a thermostable and shrink-free separator with little compromise in battery performance is prepared by coaxial electrospinning and tested. The separator consists of core-shell fiber networks where poly(vinylidene fluoride-hexafluoropropylene) (PVDF-HFP) layer serves as shell and polyacrylonitrile (PAN) as the core. This core-shell fiber network exhibits little or even no shrinking/melting at elevated temperature over 250 °C. Meanwhile, it shows excellent electrolyte wettability and can take large amount of liquid electrolyte three times more than that of conventional Celgard 2400 separator. In addition, the half-cell using LiNi1/3Co1/3Mn1/3O2 as cathode and the aforementioned electrospun core-shell fiber network as separator demonstrates superior electrochemical behavior, stably cycling for 200 cycles at 1 C with a reversible capacity of 130 mAh g-1 and little capacity decay.
ARTICLE | doi:10.20944/preprints201907.0201.v2
Subject: Materials Science, Nanotechnology Keywords: lithium ion battery; safety; flame retardant; separator; electrospun fibers; dual-nozzle coaxial electrospinning
Online: 17 September 2019 (12:19:49 CEST)
Lithium-ion batteries have attracted enormous interests recently as promising power sources. However, the safety issue associated with the employment of highly flammable liquid electrolyte impedes the further development of next-generation lithium-ion batteries. Recently, researchers reported the use of electrospun core-shell fiber as the battery separator consisting of polymer layer as protective shell and flame retardants loaded inside as core. In case of a typical battery shorting, the protective polymer shell melts during thermal-runaway and the flame retardants inside would be released to suppress the combustion of the electrolyte. Due to the use of a single precursor solution for electrospinning containing both polymer and flame retardants, the weight ratio of flame retardants is limited and dependent. Herein, we developed a dual-nozzle, coaxial electrospinning approach to fabricate the core-shell nanofiber with a greatly enhanced flame retardants weight percentage in the final fibers. The weight ratio of flame retardants of triphenyl phosphate in the final composite reaches over 60 wt.%. The LiFePO4-based cell using this composite nanofiber as battery separator exhibits excellent flame-retardant property without compromising the cycling stability or rate performances. In addition, this functional nanofiber can also be coated onto commercial separators instead of being used directly as separators.
ARTICLE | doi:10.20944/preprints202210.0236.v1
Subject: Materials Science, Nanotechnology Keywords: organic lead-free perovskites; piezoelectric crystals; nanofiber composites; electrospinning; blue luminescence; functional organic materials
Online: 17 October 2022 (11:51:08 CEST)
Lead-free ferroelectric perovskite N-methyl-N'-diazabicyclo[2.2.2]octonium)–ammonium triio-dide, MDABCO-NH4I3, nanocrystals are embedded in three different polymer fibers fabricated by the electrospinning technique. The nanofibers, which are very flexible and have a high Young modulus, behave as active piezoelectric energy harvesting sources that produce a piezoelectric voltage coefficient up to geff = 3.6 VmN-1 and show a blue intense luminescence band at 325 nm. In this work, the pyroelectric coefficient is reported for the MDABCO-NH4I3 perovskite inserted in electrospun fibers. At the ferroelectric-paraelectric phase transition, the embedded nanocrystals display a pyroelectric coefficient as high as 194×10-6 Cm-2k-1, within the same order of magnitude as that reported for the state-of-the-art bulk ferroelectric triglycine sulfate (TGS). The perovskite nanocrystals embedded into the polymer fibers remain stable, and no degradation is caused by oxidation.
ARTICLE | doi:10.20944/preprints201807.0279.v1
Subject: Engineering, Other Keywords: membrane; forward osmosis; nanofiber; electrospinning; layered interfacial polymerization; layer-by-layer; thin film composite
Online: 16 July 2018 (11:28:07 CEST)
Electrospun nanofiber-supported thin film composite membranes are among the most promising membranes for seawater desalination via forward osmosis. In this study, a high-performance electrospun polyvinylidenefluoride (PVDF) nanofiber-supported TFC membrane was successfully fabricated after molecular layer-by-layer polyelectrolyte deposition. Negatively-charged electrospun polyacrylic acid (PAA) nanofibers were deposited on electrospun PVDF nanofibers to form a support layer consisted of PVDF and PAA nanofibers. This resulted to a more hydrophilic support compared to the plain PVDF nanofiber support. The PVDF-PAA nanofiber support then underwent a layer-by-layer deposition of polyethylenimine (PEI) and PAA to form a polyelectrolyte layer on the nanofiber surface prior to interfacial polymerization, which forms the selective polyamide layer of TFC membranes. The resultant PVDF-LbL TFC membrane exhibited enhanced hydrophilicity and porosity, without sacrificing mechanical strength. As a result, it showed high pure water permeability and low structural parameter values of 4.12 Lm−2h−1bar−1 and 221 µm, respectively, significantly better compared to commercial FO membrane. Layer-by-layer deposition of polyelectrolyte is therefore a useful and practical modification method for fabrication of high performance nanofiber-supported TFC membrane.