Distribution and Depletion of Lubricant on Anti-Fouling Lubricant-Infused Surfaces

Abstract

Lubricant-infused surfaces (LIS), which immobilise a liquid layer on a solid surface, combine the properties of both the liquid and solid surface. These surfaces are exceptionally slippery – droplets easily roll off them, bacteria cannot settle on them, ice cannot adhere to them. Lubricant-infused surfaces represent a paradigm shift in the study of functional surfaces, with the past decade seeing thousands of papers published on the design, application, function and analysis of these surfaces. One particularly exciting avenue of research is the their ability to repel biofouling without the use of banned toxic biocides such as tributyltin (TBT). Unfortunately, the lubricant layer is not entirely immobilised and depletes over time and due to external forces. This Thesis explores the marine antifouling properties of LIS and relates it to the quantity and distribution of lubricant on the surface by developing techniques to quantify and map the lubricant on the surface. The antifouling performance of LIS is tested against marine bacteria, Psuedoalteromonas spp., and in a real-world test. The antifouling ability of these LIS are then related to the amount of lubricant present by measuring the volume of lubricant using a fluorescence technique. To further explore the effect of depletion, the distribution of lubricant is mapped using atomic force microscopy (AFM) meniscus force measurements which allow for precise mapping of the thickness of lubricant at the nanoscale. Using this technique, the antifouling performance of LIS is directly related to the distribution of lubricant on the surface and the effect of different depleting forces on LIS are studied. Specifically, the effect of passing through the air-water interface (unavoidable if deployed in marine environments) is studied, showing that capillarity is the main driving force in stabilising lubricant against this depletion force.