Magnetic stimulation has been applied to bone regeneration and fracture non-union treatments, however, the cellular and molecular mechanisms of repair still require better understanding. In this study, a three-dimensional (3D) collagen model has been developed using plastic compression (PC), which produces dense, cellular, and mechanically strong native collagen structures. Osteoblast cells (MG-63, UMR-106, MC3T3-E1), bioactive nano-hydroxyapatite (nHA) and magnetic iron oxide nanoparticles (IONPs), were incorporated into the collagen gels to produce a range of cell-laden models. A magnetic bio-reactor to support cell growth under static magnetic fields (SMFs) was designed and fabricated by 3D printing. The influences of SMFs on cell proliferation, differentiation, extracellular matrix production, mineralisation and gene expression were evaluated. Results demonstrated that SMFs and IONPs stimulated the proliferation, alkaline phosphatase (ALP) production and level of mineralisation of MG-63 cells in vitro. Transmission Electron Microscopy (TEM) examination showed some changes in microstructure of collagen fibres subjected to SMFs. Real-time polymerase chain reaction (PCR) investigation further determined the effects of SMFs on the expression of Runtrelated transcription factor 2 (Runx2), osteonectin (ON), and bone morphogenic protein 2 and 4 (BMP-2 and BMP-4). The stimulating effects were identified as the combination of SMFs and IONPs, which can enhance the osteogenesis process in vitro. The results indicated that the magnetic stimulation influences the matrix/cell interactions, and is capable of encouraging gene expression. Therefore, the collagen model developed in this study not only offers a novel 3D bone model to better understand the effects of magnetic stimulation on osteogenesis, but also paves the way for further applications in tissue engineering and regenerative medicine.

Efficient maritime navigation with the ability to avoid obstructions is an intensive research topic for autonomous navigation in ‘practical’ Unmanned Surface Vehicles (USVs). However, only few of the existing USVs have applied path planning in their navigation systems. Most studies present validation results at the simulation level and do not consider any environmental disturbances. The aim of this research project is to develop practical and efficient path planning algorithms that can generate and optimise the path based on known (or predicted) traffic and environment data with the ability to adapt to different criteria or missions. New risk assessment strategies together with three novel path planning algorithms have been developed to process and evaluate the real-time environmental conditions, to minimise the adverse effects caused by surface currents, and to improve the safety of the generated path for those circumstances where the reliability of the fused navigational data is uncertain. All these algorithms have been tested and verified in simulations with results proving the effectiveness of path generation and low-cost of energy consumption. Experiments using a practical USV have also been carried out to validate the capabilities of the algorithms.

The radial and mixed-inflow turbines have been widely used for the turbocharger application. The design of a turbocharger turbine with good performance still presents a lot of challenges. Apart from the traditional requirements such as high efficiency and low stress, the turbine blade is also required to achieve certain performance targets at multiple operating points, high unsteady efficiency under pulsating flow condition, reduced moment of inertia (MOI) and high vibration characteristic. To meet these challenges it is important to optimise the radial and mixed-inflow turbines for the aerodynamic performance at multiple operating points and the structural performance subject to MOI, stress and vibration constraints. In this thesis we propose an approach based on 3D inverse design method that makes such a design optimisation strategy possible under industrial timescales. Using the inverse design method, the turbine blade geometry is computed iteratively based on the prescribed blade loading distribution. The turbine’s aerodynamic and mechanical performance is evaluated using CFD and Finite Element Analysis (FEA). A linear regression is performed based on the results of a linear DOE study. The number of design parameters is reduced based on a sensitivity analysis of the linear polynomial coefficients. A more detailed DOE with around 60 designs is generated and Kriging is used to construct a response surface model (RSM). Multi-objective genetic algorithm (MOGA) is then used to search the optimal designs which meet multiple constraints and objectives on the Kriging response surface. The radial filament blading is always applied by the conventional design method to reduce the stress, while the inverse designed blade is three-dimensional (3D). Two radial filament modification (RFM) methods are proposed to control the stress level of 3D blades. Radial turbines with a backswept leading edge (LE) designed using the inverse design method show improved cycle-averaged efficiency. An optimal design is obtained through the second optimisation. Its performance is evaluated in both the aerodynamic and mechanical aspects based on CFD and FEA simulations. The CFD model is validated against the experimental results of the baseline design. The numerical results show that the optimal design leads to better performance in almost all aspects including improved efficiency in the low U/Cis (velocity ratio), reduced maximum stress, reduced MOI, and increased vibration frequencies.

Fibres show promising applications such as textiles, filtration, sensing and tissue engineering. In this study, an infusion gyration system to produce polymer micro and nano fibres with functions was introduced. By using this method, functional fibres can be formed from polymer solutions mixed with other functional materials. PEO or PVA water solution was used for making the spinning solutions. The fluorescence protein bound with gold nanoparticles was carried by the PEO water solution, from which the fibres assembled with protein were successfully generated through infusion gyration. A mixed molecular weight PVA combined water solution mixed with processed magnetic nanoparticles achieved fabrication of magnetically controllable fibres have the potential for drug release and its demonstration test showed a positive result. This spinning system provides control of the polymer solution flow rate during spinning which affects the fibre morphology such as average diameter and size distribution. The relationship between the spinning parameters and the product properties was studied for better understanding of the method. The analysis of infusion gyration and its fibre forming process was carried out. The fibres were characterised using several methods, such as optical microscopy, SEM, FTIR and UV-Vis, to establish the potential of infusion gyration and to confirm the functions of final fibre product. The infusion gyration system provides a simple micro and nano scale assembly approach to integrate different protein functionalities into nanofibres with potential applications. Magnetic PVA nanofibres are promising for drug delivery.

Sol-gel derived, silica-based bioactive glasses of a ternary system (SiO₂ – CaO – P₂O₅) has the potential to promote hard and soft tissue regeneration. Compared to melt-derived glasses, glasses synthesised from the sol-gel process has the advantage of low processing temperatures, high specific surface areas (SSA) and tailorable porous nanostructures. Using scaffolds as a strategy for tissue engineering, the application of sol-gel derived bioactive glasses in combination with alginate polymers as scaffold composite materials has great potential and therefore requires further study. This thesis investigates the synthesis of bioactive glasses via the sol-gel (acidic) route and the multi-step (alkali) route, through the sol → drying → sintering stages. Sol-gel route nanoparticles derived were heterogeneous in shape, while the multi-step route produced spherical (30 – 90 nm diameter) nanoparticles. Increases in calcium content of the sol led to an increase in pore size and a decrease in SSA. Three dehydration methods: oven, vacuum and freeze drying were devised to control the morphology of nanoparticles. Freeze dried nanoparticles were found to have a rough surface texture, with an aligned ordered porous nanostructure. This led to faster apatite formation when compared to oven dried nanoparticles immersed in simulated body fluid (SBF). A novel internal ionic diffusion cross-linking method of alginate was developed, utilising the glass nanoparticles as nanocarriers, for the synthesis of alginate-bioactive glass composite scaffolds. Strontium chloride (SrCl₂) and copper chloride (CuCl₂), which provided therapeutic ions, were impregnated into the nanocarriers, and were compared to calcium chloride (CaCl₂), as the control. Impregnation efficiency was in the order of CuCl₂ > SrCl₂ ≈ CaCl₂, attributed to Cu²⁺ having the smallest ionic radii and its interaction with silinol groups on the nanocarrier surfaces. Scaffold gelation time was correlated to the type of cross-linking salt, its loading concentration and glass to alginate (G/A) ratio. It was observed that SrCl₂ loaded nanocarriers (BGSr) were most efficient in cross-linking when compared to CuCl₂ and CaCl₂ loaded nanocarriers (BGCu and BGCa respectively), due to Sr²⁺ having a greater affinity towards alginate. Results showed that nanocarriers with the highest SSA possessed the highest impregnation efficiency; however nanocarriers with the largest pore diameter and volume led to the fastest scaffold gelation time. BGCa and BGSr scaffolds showed significant improvements in maintaining stiffness (Young’s modulus) and shear resistance (maximum shear stress) after incubation in aqueous solutions for up to 28 days, which were in contrast to the deterioration in mechanical properties of conventional CaCl₂ cross-linked scaffolds. Calcium ions were detected in the range above 260 ppm in BGCa nanocarrier supernatant, suggesting the gradual release of ions from the nanocarriers, internally diffusing into the scaffold matrix, leading to continuous cross-linking over time. Meanwhile, in vitro biological studies showed fast apatite formation on BGCa cross-linked scaffolds in SBF, with the scaffolds capable of supporting the attachment, growth and proliferation of human osteoblast cells, thus indicating their high bioactivity. Control over glass nanoparticle morphology was achieved and through specific ionic impregnation, the successful synthesis of alginate-bioactive glass composite scaffolds was demonstrated, producing bioactive scaffolds with improved mechanical properties.

Ever increasing emissions regulations and demand for fuel economy have brought about great advances in fuel and engine technologies. Improving engine efficiency through the use of fuel additives has been practiced for nearly a century but advances to direct injection gasoline engines have presented new obstacles that need to be overcome. With direct injection systems often suffering from reduced timescales allowed for combustion processes, atomisation and vaporisation characteristics have become of paramount significance. Present study aimed at adding to the field of knowledge by experimentally investigating commercial fuel additives of different functional iti es against their effects on fuel atomisation and combustion characteristics. Fuel atomisation was evaluated through the use of a laser diffraction system and measurement of fuel viscosity and surface tension. Additives from six functional groups were investigated. Additionally, effects of anti-knock and ignition promoting additives on gasoline combustion behaviour were studied in a constant volume combustion vessel and a single cylinder research engine. Flame speed, heat release rate and emissions output were compared for three commercially available combustion improvers. Investigation into the effect of fuel additives on the physical properties and therefore on fuel atomisation and sprays revealed that in commercially employed quantities, no significant change in recorded Sauter Mean Diameter could be observed. Combustion investigations in a combustion vessel demonstrated that the low temperature reactions initiated by ignition promoting additive reduced CO emissions up to 37.7 % which could be attributed to possible reduced flame quenching near combustion chamber walls. However, in high quantities this reduction in CO levels was not experienced. Addition of anti-knock additives resulted in increased NOx emissions, which was thought to result from increased combustion durations. Present work has clarified fuel additive function and interactions with combustion processes and has demonstrated that gasoline fuel additives do not interfere with combustion processes outside their intended functionality.

In this dissertation, polyethylene oxide (PEO) and ethyl cellulose (EC) have been chosen as model polymers to investigate different aspects of electrohydrodynamic processing and forming. In the first part of the work, electrospraying of PEO was attempted choosing a wide range of single solvents and mixed solvents. The selection of solvents affects the solubility and spinnability of PEO and the morphology of electrospun fibres. In the second part of the research the creation of 3D nanofibrous structures using electrospinning of PEO was investigated. The results demonstrate how the process is influenced by physical and processing parameters. It is reported that electrospun polymer nanofibres self-assemble into three dimensional honeycomb-like structures. The underlying mechanism was studied by varying the polymer solution concentration, collecting substrates and collection distance. The polymer solution concentration was found to have a significant effect on the size of the electrospun nanofibres. The nature of the collection substrate and the magnitude of the collection distance affect the electric field strength, the evaporation of solvent and the discharging of nanofibres. Consequently both the collection substrate and the collection distance had a significant influence on the self-assembly of nanofibres. In the third part of the work, the ways in which relative humidity (RH) plays a key role in the formation of porous structures was investigated using the hydrophilic polymer (PEO) and the hydrophobic polymer (EC). The generation of a 3D honeycomb-like structure was achieved using PEO polymer when RH was increased to between 53% and 93%. The optimum RH was found to be 73%. But efforts to generate 3D honeycomb-like structures using EC were unsuccessful throughout the range of RH investigated (53% - 93%). High speed camera imaging has been an important feature of the work carried out in this thesis.

The rapid development of the global offshore industry and of amphibious chemical, steel and power plants leads to more intensive use of natural water resources (sea, river and lake water) as a cooling medium. However, heat exchangers using the water as a coolant suffer from biofouling problem, which reduces heat transfer performance significantly. The cost of cleaning and lost output can be extremely high. The high incidence of infections caused by the biofilm formation on the surfaces of medical devices and implants, including catheters and bone fracture fixation pins etc. has a severe impact on human health and health care costs. An approach to reduce biofouling or infection rate is the application of a range of different coatings to the surfaces of equipment. So far the most promising coatings include Ni–P–PTFE coatings and modified diamond like carbon (DLC) coatings etc. However these coatings need to be futher improved and optimised in order to get the best anti-biofouling performance. In this study, a range of novel Ni–P–PTFE-biocide polymer nanocomposite coatings and modified DLC coatings with B, F, N, Si and Ti were designed and produced using electroless plating, magnetron sputter ion-plating and plasma enhanced chemical vapour deposition techniques. The surface properties of the coatings were characterized using surface analysis facilities, including AFM, EDX, OCA-20, SEM and XPS. These nano-composite coatings and nano-structured surfaces were evaluated with bacterial strains that frequently cause heat exchanger biofouling or medical devices-related infections. The experimental results showed that new Ni–P–PTFE-biocide polymer nanocomposite coatings reduced bacterial adhesion by 70% and 94% respectively, compared with Ni–P–PTFE and stainless steel. The experimental results showed that both type and content of the doped elements in DLC coatings had significant influence on bacterial adhesion. The new doped DLC coatings, including Si-N-DLC, F-DLC, B-DLC and Ti-DLC coatings as well as new SiOx-like coatings reduced bacterial adhesion by 60-90% compared with pure DLC and stainless steel. B and Ti-doped DLC coatings also reduced residual protein adhesion by 88-95% compared with pure DLC coatings and stainless steel. In general bacterial adhesion decreased with decreasing total surface energy or with increasing ?- surface energy of the coatings. The bacterial adhesion mechanism of the coatings was explained with extended DLVO theory.

Mechanical properties are important tissue parameters of skin that are useful for understanding skin patho-physiology, and aiding disease diagnosis and treatment. They are indicators of functional changes and pathological variations in the micro-structure. This research thesis studies the intersection of acoustics, optics and biomechanics for skin mechanical properties measurement. Surface acoustic wave (SAW) is induced and applied to a range of different tissue mimicking phantom models, Thiel cadavers and in vivo human skin. Different optical systems, i.e. low coherence interferometer and phase sensitive optical coherence tomography (PhS-OCT), are employed to detect the SAW. The Young’s moduli and thicknesses of model layers are assessed by the analysis of the wave phase velocity curves. The PhS-OCT detection system can also provide the real time high resolution depth-resolved cross-sectional microstructure imaging of the interrogated sample to assist the elasticity evaluation of the heterogeneous tissue. Results prove that the novel combination of optical imaging technology with SAW method is able to assess the elasticity change in both axial and transverse directions in soft material. It can be used to evaluate the mechanical properties of single, double-layer soft tissue mimicking phantoms and different sites of human skin ex vivo and in vivo non-invasively. This study also demonstrates that the SAW method can be successfully utilized to map the elasticity of soft heterogeneous tissues quantitatively. The results represent an important step towards the development of SAW method as a clinical diagnosis tool in dermatology, and may offer potential in diagnostic and therapeutic clinical applications.

Focused ultrasound surgery (FUS) or high intensity focused ultrasound (HIFU), is a promising technique for less- or non-invasively destroying unhealthy tissue deep inside the body, without damage to the skin or surrounding tissues. The procedure has been performed under both diagnostic ultrasound and MRI guidance. Treating cancers and metastases in the liver that are unresectable is a potential application for FUS. However the respiratory motion hindered FUS treatment of liver to become a completely non-invasive technique. The method is currently limited to breath-hold treatments under general anaesthesia that is uncomfortable for patients. The purpose of this study is to investigate key issues of US and MRI guided real-time target ablation when the target is in free breathing motion state which is similar to human liver motion. For the ultrasound guided focused ultrasound (USgFUS), diagnostic ultrasound B-mode image was used to track a moving target. The possibility of using strain sonoelastography to assess FUS lesion formation was explored. Multi-layered tissue mimicking phantoms were designed and fabricated to mimic the graphical features of tumours in human livers in diagnostic ultrasound images. The phantom was then fixed onto three motion setups: 1) controllable 1D reciprocal motion stage, 2) controllable 2D reciprocal motion stage, and 3) ventilator driven balloon to mimic breath motion. Active snake tracking was developed to follow the moving phantom to evaluate the tracking accuracy and speed. This method can achieve a speed of 5~6 frames/second with an error less than 1.0 mm. Strain sonoelastography is selected to assess lesion formation for FUS. Through comparisons of the elastograms between pre- and post-FUS around the focal zone, useful information about the FUS-induced lesions could be extracted from the elastographic artefacts. The performance of elastography to assess FUS lesion in egg-white Polyacrylamide (PAA) phantoms and fresh sheep livers was tested. The FUS lesions in the experiment samples (PAA phantoms and fresh sheep livers) were recognizable under strain sonoelastography after image processing. For MRI guided focused ultrasound (MRgFUS), a moving target with similar graphical features of tumours in human liver was tracked via analysing MRI scans. Then letting the ultrasound beam lock onto a moving target was realized via beam-steering by a phased-array HIFU transducer. An MR compatible robotic arm-INNOMOTION was introduced. A fast localization method was developed to make the robotic arm guided HIFU transducer more efficiently. What is more, it becomes a controllable reciprocal moving setup for investigating the raised issues of MRgFUS for motion tracking in this study. Two normal volunteers were scanned via MR scanner. The data was used to 1) design tissue mimicking phantoms with similar graphical features to the volunteer livers, 2) design respiratory motion simulator based on the estimated liver motion parameters, 3) and develop motion tracking algorithm based on the image features of the volunteer livers. The tissue mimicking phantoms appeared to be similar to the structures of volunteer livers in the MR echo planar imaging (EPI) scans. An experiment setup, in which the tissue mimicking phantoms was controlled to move reciprocally, was designed. The off-line MATLAB algorithm based on cross correlation proved to have an acceptable error less than 1.0 mm. A synchronization system between the target motion and beam-steering was built. Several key problems for motion tracking were studied including how to realize beam-steering with a phased-array transducer, how to map target location in the MR frame to the focus position in the transducer frame, and how to use a step-by-step local sonication series to approximate continuous beam-steering. The system’s performance was tested with a series of sonications, in which temperature rises were compared between when the target was moving with and without tracking. A primary conclusion can be made that tracking could decrease the impact of target movement in focused ultrasound ablation. Tracking could be considered as a compensatory method to liver motion caused by respiration during MRgFUS treatment. In conclusion, the thesis proposed a promising research direction to solve the issue of target motion in FUS treatment of human livers and other abdominal organs. The study achieved the target motion tracking both with diagnostic ultrasound and MRI guidance. The focus steering of HIFU transducer was realized accordingly in the MRgFUS, which can allow the focused ultrasound beam to follow a moving target. The strain sonoelastography had proved to become a potential method to assess FUS lesion formation. This study also brings more issues to be solved, e.g. the noise in diagnostic ultrasound during USgFUS tracking, real-time sonoelastography monitoring lesion formation, and new MRI thermometry that is less susceptible to target motion. The real-time image guided FUS would be more promising by overcoming these technical difficulties.