Barnacles anchor themselves to rock and other surfaces.

Barnacles anchor themselves to rock and other surfaces. © Michael Maggs

Researchers at the Agency for Science, Technology and Research (A*STAR) in Singapore have found that engineering the texture of metal surfaces may help to eradicate the problem posed by barnacles in the shipping industry.

The US Navy estimates that unwanted ‘hitchhikers’ like barnacles, which accumulate on ships’ hulls, can reduce ship speed by 10 per cent and increase fuel consumption by a whopping 40 per cent. Coating the hull with poisonous chemicals can help stop this happening, but can have terrible knock-on effects for other marine organisms. William Birch and his colleagues at A*STAR’s Institute of Materials Research and Engineering are working on a more environmentally friendly solution.

Adult barnacles, once attached to a surface, stay there for life. It is up to their tiny mobile larvae to choose a place to settle. To avoid the need for harmful chemicals, the researchers need to find a new way to prevent barnacle larvae settling on ships in the first place. The key to success may lie in creating a surface which the larvae have difficulty latching on to.

An exploring barnacle larva

An exploring barnacle larva © Agency for Science, Technology and Research

Previous studies have shown that barnacle larvae prefer to settle in cracks and depressions that offer better protection from the currents in which they feed, but the way surface texture affects their choice to settle on a micro scale is unknown. To explore this in detail, the researchers decided to compare the behaviour of barnacle larvae on different surfaces.

The team constructed plastic surfaces textures with tiny pillars placed just 10 microns apart. The pillars were five microns or 30 microns high, and ranged from five to 100 microns in diameter.

A smooth surface without pillars was used as a control. Larvae were then allowed to explore the surface and filmed using a microscope.

The larvae seemed unperturbed by five-micron high pillars, as they could still from a firm attachment over them. Thirty-micron high pillars, however, had a dramatic impact on their behaviour. Diameter also had an effect: larvae found it difficult to attach to the sides of slim pillars, and tended to try and squeeze into the cracks between thicker ones. According to Birch:

“These findings have spawned a multidisciplinary research programme whose objective is to engineer patterned surfaces and measure performance by quantifying their interactions with marine organisms,”

References:

Chaw, K. C., Dickinson, G. H., Ang, K. Y., Deng J. & Birch W. R. Surface exploration of Amphibalanus amphitrite cyprids on microtextured surfaces. Biofouling 27, 413–422 (2011).

For further information contact:

Dr William Birch
Institute of Materials Research and Engineering (IMRE)
Agency for Science, Technology and Research, (A*STAR), Singapore
Email: w-birch@imre.a-star.edu.sg