Development of biomimetic water-repellent surfaces based on zinc oxide nanopillars for antibiofouling applications

Zhang, Jitao ORCID: 0000-0002-9096-9266 (2025). Development of biomimetic water-repellent surfaces based on zinc oxide nanopillars for antibiofouling applications. University of Birmingham. Ph.D.

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Abstract

Biofouling, particularly bacterial adhesion and subsequent biofilm formation, significantly impacts medical device efficacy and patient health, presenting serious healthcare challenges and increased medical costs. Conventional approaches, such as antibiotics and chemical coatings, often face limitations due to resistance development, toxicity, and durability concerns. This thesis investigates a novel approach combining biomimetic zinc oxide (ZnO) nanopillar structures with advanced water-repellent surface modifications to simultaneously achieve robust antibacterial and water-repellent properties. Optimized ZnO nanopillar arrays were successfully fabricated through hydrothermal synthesis method, demonstrating exceptional bactericidal effects mediated by photocatalytic generated reactive oxygen species (ROS). Subsequent modifications included the development of biomimetic superhydrophobic (SHS) and lubricant-infused surfaces (LIS), effectively reducing bacterial adhesion by significantly decreasing droplet-surface interactions.
The superhydrophobic ZnO nanopillar surfaces display exceptional water repellency. The contact-angle hysteresis is confined to just 2–3°, and water droplets roll off at a tilt angle of only 1°. Additionally, droplets impacting the surfaces with different Weber numbers indicating that a robust Cassie–Baxter wetting state was maintained. These surfaces effectively inhibited model pathogenic bacteria gram-positive Staphylococcus aureus (S. aureus) and gram-negative Escherichia coli (E. coli) without the need for UV or antimicrobial agents.
Additionally, a biomimetic lubricant-infused surface based on nanopillar structures of zinc oxide (LIS-ZnO) is reported. Inherent antibacterial activity and an effective reduction in bacterial attachment against E. coli and Pseudomonas syringae pv. syringae (Pss), which exhibit different biofilm formation modes, are exhibited by this type of surface. LIVE/DEAD assays, employed with confocal microscopy, indicated that bacteria were killed after 24 hours of incubation on the surface. This outcome was attributed to the photocatalytic activity possessed by the underlying ZnO nanopillars, as demonstrated by the effective degradation of cyanine-based fluorescent dyes within a 5-hour observation period. Furthermore, the adherent bacterial signals observed on the LIS-ZnO surfaces were the lowest among all tested samples. Specifically, colony formation units of E. coli and Pss were reduced by approximately 70% and 35%, respectively, compared to a superhydrophobic surface based on the same nanopillars. These attributes render the LIS-ZnO surfaces a potential candidate for use in healthcare industries to resist bacterial adhesion and address biofouling.
Overall, this work presents a scalable strategy based on biomimetic water-repellent ZnO nanopillar surfaces, offering a robust and long-lasting antibiofouling solution for medical interfaces. The combined bactericidal and anti-adhesion effects have the potential to significantly reduce device-associated infections, contributing to improved patient outcomes and reduced healthcare costs.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):