School of Engineering

Projects

Laboratory measures of barnacle settlement behavior to facilitate the development of novel polymeric fouling-release coatings

Background

The main driver of commercial antifouling coating development is cost to maritime activities stemming from fouling. For ships, increased roughness and hydrodynamic drag that accompany fouling below the waterline translate to reduced speed for a given power output or the need to increase power to maintain speed. Fouling also reduces the vessel’s manoeuvrability, reduces its range and interval between dry-docking, and affects its acoustics. There are also environmental costs: increased fuel consumption results in increased greenhouse gas emissions and there is the potential for the spread of non-indigenous species.

Energy security, maximising vessel performance, increasing dry dock intervals and environmental stewardship are imperative to the US Navy. Naval vessels also present an unique challenge as their special operational parameters with respect to time spent underway and low cruising speeds mean that ship hulls are under intense fouling pressure. The US Navy seeks to protect its fleet from the detrimental effects of fouling through nontoxic means.

Toxic antifouling coatings, still the mainstay for merchant vessels, could limit US Navy access to ports around the world where there is strict environmental legislation on biocide release rates. Fouling control, through nontoxic means, however, remains a major challenge. If biocides are not used, preventing fouling is essentially about interfering with adhesion of organisms. This principal has translated into successful commercial coatings, for the most part based on silicone elastomer technology, that self-clean when exposed to hydrodynamic forces, such as when a ship is underway. Barnacles are a major focus for the ONR antifouling programme as they are the most frequently encountered hard fouling organisms on ships.

Aim

To improve our understanding of the physical properties of surfaces that lead to their voluntary rejection by barnacle cypris larvae and/or that interfere with normal adhesion. 

Objectives

1. To determine systematically the properties of surfaces that are unfavourable to barnacle settlement.

2. To determine whether such surfaces inhibit cyprid settlement by interfering with adhesion and/or by deterring searching behaviour.

3. To explore the fundamental mechanisms of action of fouling-resistant surfaces, vis-à-vis surface selection by cyprids, through hypothesis-driven design of model surfaces.

4. To translate the broader understanding of cyprid settlement behaviour/adhesion that will result from these studies into useful guidelines for directing future coating development.