Cassidy, Sam S; (2023) The Fabrication and Characterisation of Economically Viable Functionalised Surfaces for Superhydrophobic and Antimicrobial Applications. Doctoral thesis (Eng.D), UCL (University College London).

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Abstract

This thesis investigates the fabrication and characterisation of economically viable functionalised surfaces for superhydrophobic and antimicrobial applications. This included the production of a ZnO incorporated PVC nanocomposite, a ZnO stearic acid latex paint, and a ZnO stearic acid polyurethane coating. All samples were produced while avoiding expensive raw materials and using manufacturing techniques viable for large scale production. To begin with, PVC and ZnO nanoparticles were identified as viable materials for an antimicrobial nanocomposite. Samples produced with compression moulding were then tested and proved to be qualitatively antimicrobial against both S. aureus and E. coli. Quantitatively, the samples were shown to kill 99.67% of E. coli, while only having a 58.78% kill against S. aureus. This was followed by mechanism testing that identified singlet oxygen as the nanocomposite’s primary mechanism. A further study of S. aureus was able to rule out carotenoids as its primary method of defence against singlet oxygen. This work was followed by the development of a superhydrophobic paint. The paint was fabricated using predominantly ZnO or SiO2, stearic or palmitic acid, and one of four latexes. Once optimised, the surfaces underwent testing and analysis to determine both the surfaces’ physical and chemical properties. This culminated with a surface producing an x̄ WCA (water contact angle) of 170.3°, while also displaying qualitative antimicrobial properties against both S. aureus and E. coli, while lacking sufficient quantitative antimicrobial properties. Finally, durable superhydrophobic polymer coatings were investigated. Both polyurethane and epoxy surfaces were combined with particles and fatty acids in an effort to produce the coatings. This work achieved a durable superhydrophobic polyurethane coating containing ZnO, with an x̄ WCA of 167.5°, qualitative antimicrobial properties against both S. aureus and E. coli, while again lacking sufficient quantitative antimicrobial properties.

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