Dai, Yanqi; (2025) The Production of Polymeric Fibres Using Nozzle-Pressurised Gyration. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

Materials are the basis for the survival of human beings, as well as the symbol of the development process of human civilisation. Polymeric fibres have been widely used in filtration, energy storage, healthcare, and the environment due to their physical and chemical properties, especially the unique surface effects. The manufacturing of fibrous materials at the micro-scale has emerged as a prominent focus in materials science. Electrospinning is currently one of the most widely adopted fibre production technologies in both academic and industrial fields. Centrifugal spinning, phase separation, template synthesis, and self-assembly are also common methods for fibre formation. Given the rapid growth in market demand and the pressing quest for sustainable production, the development of scalable fibre manufacturing technologies has become increasingly urgent. Pressurised gyration (pressurised spinning or pressure spinning) is a more recent fibre production method. It combines the features of centrifugal spinning and solution blowing for efficient production of fibres through a facile one-pot process. The process involves a perforated cylindrical vessel that spins at high speed, where polymer jets are ejected from orifices due to the combined effects of rotational force and externally applied gas pressure. Originally developed as a scalable alternative to electrospinning, pressurised gyration has been used with a wide range of polymers and allows for high-throughput fibre production. The method has been adapted for various applications, including tissue engineering scaffolds, air/water filters, and drug delivery systems. In this study, a modified nozzle-based pressurised gyration system is developed to improve fibre morphology and spin biopolymer fibres from natural sources. This new spinning system is proven to produce polymeric fibres with greater uniformity and alignment, compared with conventional nozzle-free pressurised gyration. The efficacy of this enhancement is validated across different synthetic polymers (polycaprolactone (PCL), polyvinylpyrrolidone (PVP), and poly(ethylene oxide) (PEO)). The improved fibre alignment effectively enhances their mechanical strength along the fibre length compared to electrospun fibres, which typically exhibit anisotropic properties. In addition, nozzle-pressurised gyration further reduced the fibre diameter. PCL fibres and PVP fibres with diameters of approximately 1 micron and PEO nanofibres with a diameter of 172 nm are produced by nozzle-pressurised gyration. This new method achieves a remarkable fibre production rate that is 20 ~ 40 times higher than that of electrospinning. To expand the application scenarios of nozzle-pressurised gyration, this equipment was further modified by incorporating a CaCl2 coagulation bath to produce alginate fibres, addressing the current challenges associated with the processing of biopolymers. It leverages the precise control and impressive efficiency of nozzle-pressurised gyration, combined with the adaptability of wet-spinning alginate-based materials. This makes it a highly promising and cost-effective technology for scaling up alginate fibre production with simplicity and ease. By meticulously adjusting the solution concentration and the processing parameters, a comprehensive protocol for producing alginate fibres using this innovative method is established. The resulting alginate fibres combine the inherent biological properties of biopolymers and surface characteristics of fine fibres to maximise their potential in biomedical applications, showing 94 ± 2.8% cell viability. Combined with Cinnamomum verum extracts, these alginate-based fibres show significant antibacterial efficiency. The decrease in bacterial adhesion and biofilm formation is detected log 1 ~ log 5 for gram-negative Escherichia coli and gram-positive Staphylococcus aureus bacteria species. The modified nozzle-pressurised gyration device is also being used to spin natural cellulose, sourced from Laminaria hyperborea seaweed and recycled dairy farm waste, into micro-scale fibrous materials. This process explores extended sources of raw materials for nozzle-pressurised gyration, achieving the conversion of low-grade plants into value-added products while also promoting the upcycling and reuse of waste materials. This work aligns with the principles of a circular economy by fostering sustainability and resource efficiency.

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