Investigating the formation of functional and smart materials by nanospinning and other spinning techniques

Functional, smart fibres and fibres with different morphologies have been produced from different materials using different spinning methods. The effect of processing parameters on different nano fibre morphologies was studied by SEM. The spinning solution properties such as viscosity, surface tension, conductivity, UV-visible spectra were studied. The fibres were characterised by DSC, FTIR, XRD, strength test. Antibacterial, hygroscopic, humectant Manuka honey (MH) functional nanofibres have been produced successfully by single needle electrospinning (SNE) using polyethylene oxide (PEO) as matrix. Electrospinning parameters such as higher feed rate, higher proportion of MH, lower applied voltage, lower needle to collector distance produced merged, thicker, flat 15% (wt/wt) MHPEO nanofibres and vice versa. 15%MHPEO fibres of diameters from 0.198μm to 0.924μm were produced using different parameters. The 50% and 65% (wt) MHPEO mats showed antibacterial property. DSC result showed reduction in melting temperature as the MH proportion increased. FTIR results showed respective peaks for MH and PEO. MHPEO nanofibres can be used for medical end use such as wound healing. Ethyl cellulose (EC) nanofibres have been successfully electrospun using different combination of toluene and ethanol (0:100, 40:60, 50:50, 60:40,100:0) as solvent by SNE. Round and elongated bead on string to smooth bead-less 15% (wt/wt)EC fibres produced as proportion of toluene increased in the solvent mixture. Thin, bead-less fibres were obtained by 60:40 (toluene: ethanol) with average fibre diameters ranging from 0.483μm to 0.631μm. EC nanofibres have been also produced by high output bubble electrospinning (BE) method. EC fibres of diameters from 0.188μm to 0.41μm were produced by BE. Comparison between effect of electorspinning parameters on fibre revealed that the fibre morphologies followed different trends in SNE and BE. The beaded structure can be used for loading drugs in advanced medical textiles and smooth bead-less fibrous mat can be used for application such as filtration. In order to develop thermochromic (smart) nanofibres by meltelectrospinning, thermochromic polypropylene fibres have been developed by meltspinning. The pure polypropylene and thermochromic. DSC and FTIR results showed separate peaks for the thermochromic effect and for the polypropylene. SEM images verified the presence of thermochromic pigments. Thermochromic filaments can be used in garment fashion, or as sensors in yarn or fabric form

Classification of Electrospinning Methods

Electrospun nanofibers are being used in a variety of performance apparel applications where their unique properties add to their functionality. Those properties include, small fiber diameter, high surface area, potential to combine chemistry, layer thinness, high porosity, filtration properties, and low basis weight. Electrospinning has been considered as an efficient technique for nanofiber web formation. Polymers have been electrospun into nanofibers mostly after being dissolved in solvent and melted. This chapter presents a comprehensive summary of existing electrospinning methods. Electrospinning methods are classified into different categories depend upon jet formation

Correlation of Electrospun Polyvinylpyrrolidone Fiber Mat Thickness with Basis Weight, Fiber Diameter, Pore Size Distribution, and Air Permeability

This project developed correlations between electrospun polyvinylpyrrolidone fiber mat thickness, basis weight, fiber diameter, pore size, and air permeability. The hypotheses were thinner fibers produce thicker mats, pore size decreases with fiber diameter, pore size and permeability decrease as basis weight increases. Project results could be used for modeling or quality control purposes. Fiber diameter distributions were analyzed using a Scanning Electron Microscope and FibraQuant 1.3 software. Four conditions were chosen for further study: 0.284 ± 0.104 µm, 0.379 ± 0.128 µm, 0.520 ± 0.138 µm, and 0.733 ± 0.177 µm. Lower PVP concentrations produced thinner fibers. Sample thickness (nm) was measured then plotted versus basis weight (g/m2). The thinnest diameter fiber produced the thickest mat, due to increased numbers of fibers in the sample area. The pore size distribution and permeability of 0.520 µm diameter fiber samples were measured. Pore diameter (µm) was plotted versus basis weight. Average pore size was larger at low basis weights, decreasing as basis weight increased, due to fiber layers achieving constant compression. Average pore size remained constant after approximately 12.0 g/m2. Permeability (Darcy) was plotted versus pressure drop (PSI). Permeability decreased as pressure drop increased, with no trend between permeability and basis weight

Medfazna reologija: Pregled merilnih tehnik in njen pomen v disperzijah in elekrostatskemu sukanju

Interfacial rheological properties have yet to be thoroughly explored. Only recently, methods have been introduced that provide sufficient sensitivity to reliably determine viscoelastic interfacial properties. In general, interfacial rheology describes the relationship between the deformation of an interface and the stresses exerted on it. Due to the variety in deformations of the interfacial layer (shear and expansions or compressions), the field of interfacial rheology is divided into the subcategories of shear and dilatational rheology. While shear rheology is primarily linked to the long-term stability of dispersions, dilatational rheology provides information regarding short-term stability. Interfacial rheological characteristics become relevant in systems with large interfacial areas, such as emulsions and foams, and in processes that lead to a large increase in the interfacial area such as electrospinning of nanofibers.Medfazne reološke lastnosti so še dokaj neraziskane. Šele pred kratkim so razvili metode, s katerimi je mogoče z zadostno občutljivostjo in natančnostjo določiti viskoelastične lastnosti medfaze. Medfazna reologija opisuje odnos med deformacijo medfaze in silo, ki to deformacijo povzroči. Zaradi različnih deformacij medfazne plasti (strig in raztezanje, oziroma krčenje) se tudi medfazna reologija deli na strižno in dilatacijsko. Strižne reološke lastnosti medfaze se odražajo v dolgotrajni stabilnosti disperzij, medtem ko sedilatacijske predvsem v kratkotrajni stabilnosti. Poznavanje medfaznih reoloških lastnosti je pomembno v sistemih z velikimi medfaznimi površinami, kot so emulzije in pene ter pri procesih, kjer pride do velikega povečanja medfazne površine, kot je elektrostatsko sukanje nanovlaken

Advances in Membrane Technologies

Membrane technologies are currently the most effective and sustainable methods utilized in diversified water filtration, wastewater treatment, as well as industrial and sustainable energy applications. This book covers essential subsections of membrane separation and bioseparation processes from the perspectives of technical innovation, novelty, and sustainability. The book offers a comprehensive overview of the latest improvements and concerns with respect to membrane fouling remediation techniques, issues of bioincompatibility for biomedical applications, and various subareas of membrane separation processes, which will be an efficient resource for engineers

Manufacturing polyacrylonitrile nanowires and nanofibers for sensing and energy storage applications

A novel flow guided assembly approach is presented to well align and accurately position nanowire arrays in pre-defined locations with high throughput and large scale manufacturing capability. In this approach, polyacrylonitrile (PAN)/N, N-dimethylformamide (DMF) solution is first filled in an array of microfluidic channels. Then a gas flow is introduced to blow out most solutions while pushing a little leftover against the channel wall to assemble into polymer nanowires. In this way, highly-ordered nanowires are conveniently aligned in the flow direction and patterned along both sides of the microchannels. In this study, we demonstrated this flow-guided assembly process by producing millimeter-long nanowires across 5 mm x 12 mm area in the same orientation and with basic I-shape , T-shape , and cross patterns. The assembled polymer nanowires were further converted to conductive carbon nanowires through a standard carbonization process. After integrated into electronic sensors, high sensitivity was found in model protein sensing tests. This new nanowire manufacturing approach is anticipated to open new doors to the fabrication of nanowire-based sensing systems and serve as the Good Manufacturing Practices (GMP) (a system for ensuring that products are consistently produced and controlled according to quality standards) for its simplicity, low cost, alignment reliability, and high throughput. By using the same polymer solution (polyacrylonitrile (PAN)/N, N- dimethylformamide (DMF) solution), a new, simple, and low-cost method has been developed in the production of porous composite nanofibers via a one-step foaming and electrospinning process. Sublimable aluminum acetylacetonate (AACA) was dissolved into polyacrylonitrile (PAN)/N, N-dimethylformamide (DMF) solution as the foaming agent. Silicon nanoparticles were then added and the resulting suspension solution was further electrospun to produce PAN/silicon composite nanofibers. The PAN nanofibers were then foamed during a thermal stabilization treatment and further carbonized into carbon/silicon composite nanofibers. Such mesoporous composites nanofiber mats were explored as the anode material for lithium ion batteries. Within this composite of nanofiber electrode, carbon nanofibers serve as the conductive media, while silicon nanoparticles ensure high lithium ion capacity and electrical density. The inter-fiber macrovoids and intra-fiber mesopores provide the buffering space to accommodate the huge volume expansion and consequent stress in the composite anode during the alloying process to mitigate electrode pulverization. Its high surface-to-volume ratio helps facilitate lithium ion transport between electrolytes and the active materials. Our electrochemical tests demonstrated higher reversible capacity and better capacity retention with this porous carbon/silicon composite nanofiber anode when compared with that made of nonporous composite nanofibers and CNF alone with similar treatments

Extracción supercrítica de emulsiones para nanoencapsular compuestos bioactivos líquidos lipofílicos : desarrollo y cambio de escala del proceso

Tesis de la Universidad Complutense de Madrid, Facultad de Ciencias Químicas, Departamento de Ingeniería Química, leída el 10-07-2017A wide variety of products containing bioactive compounds have been designed to meet the fundamental needs of society in terms of beauty, health and well-being. Nevertheless, these products do not provide the expected health benefit, because of the low water solubility, low chemical or biochemical stability and the high reactivity of these bioactive compounds, reasons why they lose their biological functionality and bioavailability. Among the different strategies developed to overcome this challenge, biopolymer-based micro- and nanoparticles are the most promising systems to maintain the biological functionality and bioavailability of the bioactive compound and to provide its controlled release in its physiological site of action. A large number of processes exist for obtaining biopolymer-based micro- and nanoparticles. Nonetheless, companies seek rapid and environmentally-friendly production processes that obtain spherical nanoparticles with core-shell structure, controlled particle size distribution and high encapsulation efficiency, which guarantee the health effect. The increasing demand for new products and the drawbacks of the existing processes are causing a steady research for new technological possibilities...De las múltiples estrategias desarrolladas para superar este reto, las micro- y nanopartículas basadas en biopolímeros constituyen el sistema más prometedor para mantener la funcionalidad biológica y la biodisponibilidad del compuesto bioactivo, así como para proporcionar su liberación controlada en el lugar fisiológico de acción. Existe un gran número de procesos para obtener micro- y nanopartículas basadas en biopolímeros. Sin embargo, las compañías buscan procesos de producción rápidos y respetuosos con el medioambiente que obtengan nanopartículas esféricas con estructura núcleo-carcasa, distribución de tamaño de partícula controlada y alta eficiencia de encapsulación, la cuales garanticen el efecto para la salud. La creciente demanda de nuevos productos y las limitaciones de los procesos existentes están causando un aumento en la búsqueda de nuevas posibilidades tecnológicas...Depto. de Ingeniería Química y de MaterialesFac. de Ciencias QuímicasTRUEunpu

Core/shell nanofiber characterization by Raman scanning microscopy

Core/shell nanofibers are becoming increasingly popular for applications in tissue engineering. Nanofibers alone provide surface topography and increased surface area that promote cellular attachment; however, core/shell nanofibers provide the versatility of incorporating two materials with different properties into one. Such synthetic materials can provide the mechanical and degradation properties required to make a construct that mimics in vivo tissue. Many variations of these fibers can be produced. The challenge lies in the ability to characterize and quantify these nanofibers post fabrication. We developed a non-invasive method for the composition characterization and quantification at the nanoscale level of fibers using Confocal Raman microscopy. The biodegradable/biocompatible nanofibers, Poly (glycerol-sebacate)/Poly (lactic-co-glycolic) (PGS/PLGA), were characterized as a part of a fiber scaffold to quickly and efficiently analyze the quality of the substrate used for tissue engineering