26 research outputs found
Developing novel spinning methods to fabricate continuous multifunctional fibres for bioapplications
No full textDevelopmental work in the field of multifunctional hybrid fibres has revealed a number of characteristics that promise great benefits to their possible use in a broad range of devices and applications including tissue scaffolds and implantable electrodes as well as the accessory energy storage devices necessary to provide power to implantable devices and smart garments. There has, therefore, been much interest and many attempts to produce lightweight, foldable and electroactive multiaxial fibres. The main aim of this thesis is to establish a wet-spinning process to develop three-dimensional coaxial and triaxial electroactive fibres. Using a coaxial wet-spinning method that takes advantage of the electroactivity inherent in a conductive core, we also aim to improve the fibres’ mechanical, biocompatibility and cell adhesion properties by using an appropriate biomaterial for the surrounding sheath, opening up the possibility for its use in many biomedical applications. Although some success has been achieved via the use of either electrospinning or coating approaches, only a few studies have reported the successful fabrication of either coaxial or triaxial fibres via novel application of wet-spinning methodology to the best knowledge of the author. This poor rate of success may be due to the complexity of this method in terms of the number of concurrent solution and processing parameters that need to be optimised and controlled in order to achieve the successful (and consistent) formation of a core-sheath structure in a coagulation bath. Wet-spinning has the advantage that it produces individual, collectable fibres that can be drawn out and tested for their mechanical properties. Electrospinning can produce extremely fine fibres in the form of a non-woven mat; however, the mechanical testing of individual fibres is not feasible. There have been also reported on difficulties involved with preparation of fibres using already charged polymer backbones via electrospinning wherein a stable jet cannot be achieved and no nanofibres will form, although single droplets may be achieved (electrospray). In addition to this, there is a limitation in choosing the maximum concentration for a given solution by which it could flow. Consequently, the molecular weight and the concentration as long as a solvent with the necessary volatility which can be spun this way, are within a certain range. Thus, although this method shows a lot of promise, these restrictions are placed on the spinnability of certain polymers by solution parameters like viscosity and surface charging. As a result of this research, the production of continuous core sheath fibres has been achieved using a variety of materials. Hydrogels have been used as the sheath components since they provide mechanical and structural properties that mimic many tissues and their extracellular matrix. Organic conductors such as graphene and intrinsically conducting polymers have been useful in the creation of electrical pathways within the inner core where they are able to provide safe electrical stimulation of the surrounding tissue – enhancing the electro-cellular communication process - whilst also avoiding undesirable chemical reactions and cell damage
Wet-Spun Biofiber for Torsional Artificial Muscles
No full textThe demands for new types of artificial muscles continue to grow and novel approaches are being enabled by the advent of new materials and novel fabrication strategies. Self-powered actuators have attracted significant attention due to their ability to be driven by elements in the ambient environment such as moisture. In this study, we demonstrate the use of twisted and coiled wet-spun hygroscopic chitosan fibers to achieve a novel torsional artificial muscle. The coiled fibers exhibited significant torsional actuation where the free end of the coiled fiber rotated up to 1155 degrees per mm of coil length when hydrated. This value is 96%, 362%, and 2210% higher than twisted graphene fiber, carbon nanotube torsional actuators, and coiled nylon muscles, respectively. A model based on a single helix was used to evaluate the torsional actuation behavior of these coiled chitosan fibers.</p
Fabrication of Coaxial Wet-Spun Graphene-Chitosan Biofibers
No full textOne-step continuous wet-spinning of coaxial electroactive fibres of chitosan/graphene oxide (Chit/GO) via a facile method is introduced for the first time, eliminating the need for post-treatment processes. Spinnability of coaxial fibres as well as their characterization for several properties is investigated. L-ascorbic acid was found to reduce graphene oxide under mild conditions to create conductivity in the final fibre. As-prepared fibres were found to be cytocompatible with good electrical conductivity and mechanical properties. SEM images from the cross-section of Chit/GO fibres showed an irregular shaped multifilament GO fibre covered with a cylinder-shaped sheath of chitosan. Coaxial fibres had an ultimate tensile stress and elastic modulus that increased 8 500% and 3 350%, respectively compared to the graphene oxide fibres alone
