The effects of surface topography on the accumulation of biofouling

Experiments in the laboratory and the natural marine environment examined the changes in the rate of the accumulation of bacterial biofouling for different surface roughness values. The range of surface roughness values examined was that suitable for use in optical sensors. The fouling build-up was found to be greater at around 10 nm rms roughness value than at either 5 or 15 nm. For most materials tested, the fouling build-up at 10 nm was not equalled for roughness values below 25 nm. Different experimental exposure regimes were adopted: a purely static exposure, static exposure followed by dynamic removal of the bacterial layer and fully dynamic exposure where the bacterial suspension flowed across the surface of the samples. The results suggest that the effect of surface roughness on bacterial adhesion is almost instantaneous. The static fouling experiments were repeated with a range of materials and the results were the same, indicating that the response is physical in nature. As the surface imperfections are far smaller than the size of bacteria, it is suggested that the results are due to a similarity between the size and shape of the imperfections and the size and configuration of the adhesive molecules produced by marine bacteria.