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Though the past two decades have seen a dramatic increase in research toward self-cleaning repellent surfaces, multiple challenges exist in the creation of biorepellent surfaces for everyday use. Environmental concerns persist with many of the chemicals utilized in this field and the need for scalable, low-cost alternatives remains. Spread of pathogens including bacteria and viruses in healthcare and public settings also presents a need for stable surfaces. In the work presented here, we report on the current status of antimicrobial nanomaterials and coatings toward virus repellency, followed by an investigation into the application of polysiloxane nanostructures in creation of flexible hierarchical surfaces. Using n-propyltrichlorosilane (n-PTCS) coated on activated polyolefin (PO) we were able to demonstrate superhydrophobicity, reporting water contact angles above 153° paired with <1° sliding angles on hierarchical surfaces. A transfer assay, that closely mimics contact with high-touch surfaces, using Escherichia coli K-12 transfected with green fluorescent protein (GFP) reported a 1.6-log (97.5%) reduction in fluorescence on surfaces compared to planar PO controls, paired with a 1.2-log (93%) reduction in CFU/mL in comparison to control groups. Additionally, surfaces demonstrated a contact angle of 140.8° with citrated whole blood. Droplets of blood incubated on our surfaces for 15 min showed a 93% reduction in visible staining, while submersion in citrated whole blood for 20 minutes revealed an 87% reduction in blood adhered to the surfaces. The applications for these biorepellent surfaces have widespread potential, including the demonstrated need for prevention of surface contamination to minimize spread of hospital acquired infections (HAIs) within the healthcare system. / Thesis / Master of Applied Science (MASc) / The goal of creating a surface capable of repelling biological samples continues to present challenges due to surface stability, scalability, and cost of manufacturing techniques. Beyond this, many of the existing solutions use fluorine-based chemicals that present a risk to the environment due to the difficulty in breaking down these molecules. This thesis aims to understand the current state of repellent surfaces used for biological applications, including prevention of surface contamination by bacteria and viruses, then investigates the use of more environmentally friendly methods to produce repellent surfaces. Using a silicone-based coating combined with heat induced shrinking of shape memory polymers (SMPs), we have created a flexible surface with multiscale roughness that demonstrates repellency to bacteria and whole blood.

Research was carried out on four main subject areas: playing quality of natural turf; establishment; nitrogen nutrition and stabilisation ofsand rootzones. Apparatus and test methods for determining playing quality are described and procedures for the development of standards for playing quality measures are given. A theoretical analysis of the factors governing playing quality was undertaken which showed that natural turf must be considered in terms of the plant and soil constituents and the manner in which these interact, especially in response to wear. The soil factor grouping is shown to be the most important influence on playing quality, primarily through its effect on moisture retention and throughput. A large-scale field experiment was carried out in order to investigate the effect of five different constructional techniques on playing quality and other aspects of turf performance. Constructional types included: pipe-drainage, slitdrainage, slit-drainage with a 25mm sand layer, a sand carpet and a sand profile construction. The results showed that the sand-based constructions provided the best playing quality but that potential numbers of days lost due to the presence of standing water decreased with increasing constructional sophistication. A review of playing quality of fine turf was carried out and an experiment on ball roll characteristics of five turfgrass specieswas undertaken which showed significant differencesamong species. Two experiments on the establishment of turf using different types of seed and sod were carried out, whose objective was to determine the effects of these experimental treatments on the playing quality, ground cover and water infiltration rate of playing surfaces for both football and golf. Experimental treatments included grades of mature turf, juvenile turf and seed. The most notable finding was the dramatic reduction in water infiltration rate where mature turfwas used for establishment. This was ascribed to a combination of organic and mineral matter imported along with the turf causing blockage of soil macropores and hence reducing water infiltration rate. The effect offertiliser nitrogen on the response of Lolium perenne turf grown on a PruntyMulqueen sand carpet rootzone was studied a field experiment which was subjected to football-type artificial wear treatments during two playing seasons. Measures included ground cover under wear and playing quality. In the case of ground cover and player traction responses to nitrogen showed distinct optima particularly during wear. Ball rebound resilienceand hardness showed no such response. Finally an experiment on the stabilisation ofsand rootzones for sport was carried out the objective of which was to study the effect of artificially strengthening a sand rootzone using randomly oriented tensile inclusions {Netlon mesh elements}. Three different rates of mesh elements, two different sizes and establishment using two types of turf were studied in a field experiment. Mesh element inclusion was found to increase water infiltration rate, traction and hardness. Turf treated by washing to remove adhering soil prior to laying also gave higher infiltration rates and, in addition, affected playing quality.

published_or_final_version / Physics / Master / Master of Philosophy

published_or_final_version / abstract / Mathematics / Master / Master of Philosophy

published_or_final_version / abstract / Mathematics / Master / Master of Philosophy

published_or_final_version / abstract / Physics / Doctoral / Doctor of Philosophy

published_or_final_version / Computer Science / Doctoral / Doctor of Philosophy

published_or_final_version / Mechanical Engineering / Master / Master of Philosophy

Post-operative osteomyelitis attributing to the biofilm formation on implant surface and medical grade 316L stainless steel have been reported to gain a higher rate of infection among other clinically applied metals. It is believed suppressing bacterial adhesion on implant surface at early stages can help prevent biofilm formation. The major challenges of current antibacterial surface treatments include limited biocompatibility, potential development of antibiotic resistant bacteria, short life cycle and high fabrication cost. In this study, it is aimed to explore the feasibility of an inexpensive and simple surface modification technique to achieve a long-term antibacterial effect on medical grade 316L stainless steel while maintaining its biocompatibility. Thus, a novel 1D nanostructured ZnO nanowire coating that can provide different special topographies and can be easily fabricated by simple hydrothermal method is suggested to coat on stainless steel surfaces. Two kinds of ZnO nanowire coatings, ZnO_5hrs and ZnO_17hrs, are fabricated for further investigation. Relatively well-aligned ZnO nanowires with diameters of ~50 nm were found on ZnO_5hrs samples, while randomly-oriented ZnO nanowires with diameters of ~150 nm were found on ZnO_17hrs samples. In the antibacterial tests, both ZnO_5hrs and ZnO_17hrs samples exhibited excellent antibacterial effects, which represent over 90% of bacterial reduction among all of the tested bacterial strains including S. aureus, P. aeruginosa and E. coli, with exception to the case of ZnO_17hrs sample with S. aureus. It is confirmed that antibacterial Zn2+ ions are released from the coatings during the test and help against bacterial adhesion. On the other hand, it is suspected that the increase in hydrophilicity and special physical topography are also antibacterial factors of the ZnO nanowire coatings. The cytocompatibilities in both ZnO_5hrs and ZnO_17hrs samples were not satisfactory. In the cell adhesion test, the GFP-OB cells did not habitually spread and attach on the treated sample surfaces after 6 hours incubation. Cytotoxicity test results further confirm no viable MC3T3 cells were found on the treated sample surfaces. The cytocompatibility of the coating remains to be improved. In the in-vivo study, the group of rats with ZnO_5hrs rod samples displayed a reduced number of bacterial cells in the implantation site at day 0, as well as a shorter duration (within 8 days) for bacterial termination as compared to that with untreated stainless steel rod samples. The presence of ZnO nanowire coating on medical grade 316L stainless steel rod samples demonstrates the in vivo antibacterial effect. In short, the novel 1D antibacterial ZnO nanowire coating is successfully fabricated and coated on medical grade 316L stainless steel surfaces by a simple and inexpensive hydrothermal method. However, the biocompatibility of the ZnO nanowire coating remains to be improved. One of the critical issues is to engineer the coating in order to precisely control the Zn2+ ions release rate. For future study, the key is to find out how to manipulate the characteristics of special surface topography, together with a controllable release of Zn2+ ions on the ZnO nanowire coating to maximize the antibacterial effect while maintaining the original biocompatibility of medical grade 316L stainless steel. / published_or_final_version / Orthopaedics and Traumatology / Master / Master of Philosophy