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UBC Theses and Dissertations

Superhydrophobic polymeric surfaces : fabrication, wettability, and antibbacterial activity Falah Toosi, Salma


This PhD thesis studies fabrication of superhydrophobic polymeric surfaces, their wetting properties, and their antibacterial activities as potential application to medical sciences. A femtosecond laser technique was used to fabricate mico/nano- structures on the surface of PTFE and PU. The effect of laser parameters (fluence, scanning speed, and overlap) on the wettability of the resulted micro/nano-patterns was studied. Two techniques were used to laser-scan the surface, namely uniaxial and biaxial scan. Uniaxial scan creates channeled morphology with direction-dependent wettability. To produce uniform wettability independent of direction, biaxial scanning was examined, which creates well-defined pillars with very high contact angle (CA) and very low contact angle hysteresis (CAH). To facilitate and speed up the surface micro/nano-structuring, laser-ablation was coupled with thermal imprinting. The metallic femtosecond laser-ablated templates were employed to imprint micron/submicron periodic structures onto the surface of several polymers. The CA of imprinted polymers increased to above 160°, while their CAH varied significantly depending on the surface thermophysical and chemical properties. A unique technique was developed to create superomniphobic patterns on HDPE through hot embossing. The filefish skin dual scale superoleophobic patterns were used as a biological model to develop angled microfiber arrays on HDPE. The obtained bioinspired surface is highly capable of repelling both water and liquids with low surface tensions that meets the superomniphobic criteria. The effect of superhydrophobicity on protein adsorption and bacterial adhesion of laser-ablated PTFE substrates were investigated. Samples were incubated in Gram negative (E.coli) and Gram positive (S.aureus) bacteria cultures, BSA solution, IgG solution, and blood plasma for 4 hours. All superhydrophobic surfaces were found to be more resistant to protein /bacteria adhesion compared to the corresponding smooth samples. However, some of the most superhydrophobic PTFE surfaces were found to exhibit the highest adherence with protein/bacteria; while some other did not allow any adsorption/adherence of protein/bacteria respectively towards the end of the incubation. Besides the CA, CAH, average height of pillars, and spacing distance between iii the pillars, this study showed that there are other roughness factors, which play crucial role in the durability of the superhydrophobic surfaces such as the distribution of pillar heights.

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