Development and evaluation of anti-biofouling nano-composite coatings

  • Xueju Su

    Student thesis: Doctoral ThesisDoctor of Philosophy


    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.
    Date of Award2013
    Original languageEnglish
    SupervisorQi Zhao (Supervisor)

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