High quality electrospun nanofibres

The data collected relates to the operating parameters of electrospinning, the nanofibre and fibrous membrane properties and the performance evaluation in different applications.

A new way to nanostructure hydrogels : electrospun thermo-responsive islands-in-the-sea nanofibres

Islands-in-the-sea nanofibres are a very interesting system: one polymer (islands) is distributed in fibrillar domains within a second polymer (sea). This fibre geometry is often used in microfiber technologies to obtain very fine fibers, by removing the “sea” polymer. This geometry also allows to combine two polymers with very different properties. In this work this geometry is introduced applied to electrospun hydrogel nanofibers, in a novel fashion, and as a way to improve and stabilize the hydrogel nanofibers. Thermo-responsive islands-in-the-sea nanofibers are here produced by electrospinning solutions of a hydrogel-forming thermo-responsive polymer (crosslinked poly(N-isopropylacrylamide), PNIPAM) and a reinforcing polymer (polyetherketone cardo, PEK-c). The two polymers are thermodynamically incompatible in solution and phase separation takes place, which allows the instant formation of islands-in-the-sea nanofibers upon electrospinning. PNIPAM was then crosslinked post-spinning using an oligomeric silsesquioxane. The formed nanocomposite nanofibers showed intrinsic nanostructure, where the fibril-like PNIPAM domains are intimately adjacent to the strong PEK-c domains. Upon contacting with water, the hydrogel domains became instantly highly swollen, while the PEK-c domains did not. As a result, very wrinkly, swollen fibers were obtained, with increased capillary action, as demonstrated through confocal microscopy. The composite nanofibers in water showed excellent swelling ratios and very fast responses to temperature variations (of the order of 1 second) with morphological and optical effects: variations in fiber-diameter were accompanied by optical transitions: transparent-opaque. The produced hydrogel nanofibers also presented improved mechanical properties (even with small amounts of PEK-c), when compared to their crosslinked-PNIPAM-only nanofibers. It will be also shown how these materials can be used as optical actuators and smart hydrogel platforms with tuneable contact angle and morphology. In brief, this work aims to demonstrate a new platform technology which can be applied to several hydrogel systems, to achieve hydrogel-based composites with new and improved properties, while retaining (and improving) the main properties of the hydrogel. Here this was demonstrated by showing that the composite materials showed thermo-responsiveness, and enhanced transition kinetics.

Electrospun nanofibres

This book deals with an emerging nanofibre-making technology, electrospinning, the functionalities of electrospun nanofibres and their wound healing application. An important fundamental issue, fibre morphological evolution during electrospinning, is clarified. Effective techniques to improve the fibre toughness and control the surface wettability of nanofibre membrane have been developed. These functional nanofibre membranes have been used as dressing materials for healing skin wounds, and shown promising results. This work makes electrospun nanofibre membrane an ideal candidate for wound healing application.

Toughening of a carbon-fibre composite using electrospun poly(Hydroxyether of Bisphenol A) nanofibrous membranes through inverse phase separation and inter-domain etherification

The interlaminar toughening of a carbon fibre reinforced composite by interleaving a thin layer (~20 microns) of poly(hydroxyether of bisphenol A) (phenoxy) nanofibres was explored in this work. Nanofibres, free of defect and averaging several hundred nanometres, were produced by electrospinning directly onto a pre-impregnated carbon fibre material (Toray G83C) at various concentrations between 0.5 wt % and 2 wt %. During curing at 150 °C, phenoxy diffuses through the epoxy resin to form a semi interpenetrating network with an inverse phase type of morphology where the epoxy became the co-continuous phase with a nodular morphology. This type of morphology improved the fracture toughness in mode I (opening failure) and mode II (in-plane shear failure) by up to 150% and 30%, respectively. Interlaminar shear stress test results showed that the interleaving did not negatively affect the effective in-plane strength of the composites. Furthermore, there was some evidence from DMTA and FT-IR analysis to suggest that inter-domain etherification between the residual epoxide groups with the pendant hydroxyl groups of the phenoxy occurred, also leading to an increase in glass transition temperature (~7.5 °C).

Transport properties of multi-layer fabric based on electrospun nanofiber mats as a breathable barrier textile material

Layered fabric systems with an electrospun nanofiber web layered onto a sandwich of woven fabric were developed toexamine the feasibility of developing breathable barrier textile materials. Some parameters of nanofiber mats, including thetime of electrospinning and the polymer solution concentration, were designed to change and barrier properties ofspecimens were compared. Air permeability, water vapor transmission, and water repellency (Bundesmann and hydrostaticpressure tests) were assessed as indications of comfort and barrier performance of different samples. These performancesof layered nanofiber fabrics were compared with a well-known water repellent breathable multi-layered fabric(Gortex).Multi-layered electrospun nanofiber mats equipped fabric (MENMEF) showed better performance in windproof propertythan Gortex fabric. Also, water vapor permeability of MENMEF was in a range of normal woven sport and work clothing.Comparisons of barrier properties of MENMEF and the currently available PTFE coated materials showed that, thoseproperties could be achieved by layered fabric systems with electrospun nanofiber mats.

Nanofibers - production, properties and functional applications

With the rapid development of nanoscience and nanotechnology over the last decades, great progress has been made not only in the preparation and characterization of nanomaterials, but also in their functional applications. As an important one-dimensional nanomaterial, nanofibers have extremely high specific surface area because of their small diameters, and nanofiber membranes are highly porous with excellent pore interconnectivity. These unique characteristics plus the functionalities from the materials themselves impart nanofibers with a number of novel properties for applications in areas as various as biomedical engineering, wound healing, drug delivery and release control, catalyst and enzyme carriers, filtration, environment protection, composite reinforcement, sensors, optics, energy harvest and storage , and many others. More and more emphasis has recently been placed on large-scale nanofiber production, the key technology to the wide usages of nanofibers in practice. Tremendous efforts have been made on producing nanofibers from special materials. Concerns have been raised to the safety issue of nanofibrous materials. This book is a compilation of contributions made by experts who specialize in their chosen field. It is grouped into three sections composed of twenty-one chapters, providing an up-to-date coverage of nanofiber preparation, properties and functional applications. I am deeply appreciative of all the authors and have no doubt that their contribution will be a useful resource of anyone associated with the discipline of nanofibers.

3D fibrous structures as cardiovascular implants

Medical textiles are a highly specialised stream of technical textiles industry with a growing range of applications. A significant advancement has been achieved in surgical products or biomedical textiles (implantable/non-implantable) with the advent of 3D textile manufacturing techniques. Cardiovascular soft tissue implants (vascular grafts) have been a field of interest over decades for use of innovative 3D tubular structures in treatment of cardiovascular diseases. In the field of soft tissue implants, knitted and woven tubular structures are being used for large diameter blood vessel replacements. Advent of electrospinning and tissue engineering techniques has been able to provide promising answers to small diameter vascular grafts. The aim of this review is to outline the approaches in vascular graft development utilising different 3D tubular structure forming techniques. The emphasis is on vascular graft development techniques that can help improve treatment efficacy in future.

One-dimensional polyelectrolyte/polymeric semiconductor core/shell structure : sulfonated poly(arylene ether ketone)/polyaniline nanofibers for organic field-effect transistors

A polyelectrolyte/polymeric semiconductor core/shell structure is developed for organic field-effect transistors (OFETs) based on sulfonated poly(arylene ether ketone)/polyaniline core/shell nanofibers via electrospinning and solution-phase selective polymerization. The polyelectrolyte does not work as a gate dielectric, but can provide an internal modulation from the nanointerface of the 1D core/shell nanostructure. The transistor devices display very high mobilities.

Ag/AgCl composite nanoparticles/polyacrylonitrile nanofiber films for visible-light photocatalysis

Ag/AgCl composite nanoparticles/polyacrylonitrile nanofiber films were prepared by electrospinning and subsequent in-situ reduction combining in-situ oxidation strategy. Electrospinning was firstly used to fabricate PAN/AgNO3 composite nanofibers; then the AgNO3 was reduced by in-situ reduction with glycol; finally, an in-situ oxidation between Ag nanoparticles and FeCl3 solution was carried on to prepare the compo-site nanofiber films. The as-prepared materials can be used as high-performance photocatalysts, taking the advantage of the visible-light activity, flexibility, and high photocatalytic kinetics. The present method is helpful for the development of the high-performance membrane based photocatalysts.

Improved hydrogen monitoring properties based on p-NiO/n-SnO2 heterojunction composite nanofibers

Here we demonstrate the preparation and improved hydrogen monitoring properties based on p-NiO/n-SnO2 heterojunction composite nanofibers via the electrospinning technique and calcination procedure. NiO/SnO2 heterojuction composite nanofibers were spin-coated on the ceramic tube with a pair of Au electrodes for the detection of hydrogen. Extremely fast response−recovery behavior (̰3s) has been obtained at the operable temperature of 320 °C, based on our gas sensor, with the detection limit of approximate 5 ppm H₂. The role of the addition of NiO into the SnO₂ nanofibers and the sensing mechanism has also been discussed in this work.

A novel alcohol detector based on ZrO2-doped SnO2 electrospun nanofibers

To overcome the interference of acetone when detecting alcohol, a novel alcohol detector based on zirconia-doped SnO2 nanofibers were fabricated through electrospinning technique and calcination process. The samples have been characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and their gas sensing properties have also been investigated. When exposed to alcohol vapor, the nanofibers containing 15 mol% zirconia exhibit the best sensing properties. Moreover, the sensor holds the successful discrimination between acetone and alcohol, which makes our product a good candidate in fabricating highly selective sensors in practice.