Fabrication of antibacterial nanopatterned coatings inspired by wings of insects

Summary

Bacterial fouling is a pervasive process responsible for catastrophic failure and fatal health issues in industrial and biomedical settings. To minimize the medical and environmental risks associated with biochemical treatments of bacterial fouling, this project investigates the potential of an alternative physical approach mimicking natural antibacterial materials. Seeking inspiration for antibacterial materials in natural species, insects stand out as impressive examples; supreme antifouling functionalities are often found in wings of flying species of insects. The surface of insect wings is decorated with biodegradable chemicals that manifest long lasting self-cleaning and antifouling effects. These desirable qualities are believed to arise from the intricate nanoscale self-assemblies of waxes on the epicuticular surface of the wings. Such materials can potentially resist deposition/adhesion of bacteria (antifouling) and/or cause death through mechanical interactions with the cells (bactericidal effect), however, the exact antibacterial mechanism of insect wings and its effectiveness under relevant dynamic conditions remain ambiguous. This multidisciplinary project aims to resolve the physico-chemical properties of naturally available functional nanomaterials to derive inspiration for the efficient design and scalable fabrication anti-biofouling coatings. In particular, morphological and chemical properties of different species dragonflies, damselflies and cicada will be examined. Additionally, their performance under the impact of isolated droplets and continuous flow of pure and contaminated fluids will be investigated experimentally. Following the characterisation of natural examples, the project will develop new fabrication methods to achieve engineered counterparts. To achieve a sustainable and scalable nanofabrication method, this project will use crystallisation as a tool to manufacture biomimetic nanopatterned surfaces using waxes that are directly extracted from natural antifouling materials. Findings of the project will not only enrich our limited understanding of such complex natural systems, but also advance the design and fabrication approaches for new generations of functional materials.

Nature generously offers access to a rich collection of multi-functional micro- and nano- biomaterials that we have only began to observe, apprehend, and reproduce in the past decades. Among all, insect wings, decorated with intricate networks of nanoscale structures, are flawless models of superhydrophobic, low-friction and antifouling surfaces that could prove beneficial in a variety of engineering and biomedical applications. This is an interdisciplinary PhD project set at the interface of biology, fluid mechanics, nanomaterials and microbiology seeking correlations between nanoscale patterns on the wings of various species of insects and their antibacterial performance in the vicinity of contaminated fluid environments. The main aims of the research are to (1) explore functionality of natural model surfaces observed in insect wings and (2) investigate the effectiveness of fluid-based manufacturing techniques for biomimetic fabrication of their engineering counterparts.

Experimental investigations in the first phase of the project will involve: surface nanostructure and wetting characterisation, and frictional and fouling analysis. Analysis of antifouling functionalities will investigate effectiveness of the surfaces exposed to flows of nano- and micro-scale colloidal solutions, such as natural/synthetic polymer and colloidal solutions, to mimic fouling process observed in industrial and biomedical applications. Second phase of the project will be focused on the development of a fluid-based fabrication technique, based on crystallisation. With the goal to develop a sustainable nano-fabrication approach, in terms of material and process, effectiveness of crystallisation in thin film solutions of natural waxes will be explored to achieve spontaneous formation of nanopatterned materials at low energy/material cost over large surface areas. A range of analytical techniques will be employed for characterisation of natural and biomimetic surfaces: cross-polarised and scanning electron microscopy, atomic force microscopy, surface profilometry and X-ray diffraction crystallography will be used to analyse surface nano-topographies and chemical structures. Static and dynamic contact angle measurements will provide wetting characterisation. Lubrication/flow friction analyses will be performed side-by-side antifouling investigations, using tribological and microfluidics experimental platforms. Findings of this interdisciplinary project will upgrade our understanding of natural functional surfaces and promote development of smart energy-efficient manufacturing techniques for healthcare and engineering applications.

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