Combining a photocatalyst with microtopography to develop effective antifouling materials

Polydimethylsiloxane surfaces textured with a square-wave linear grating profile (0, 20, 200, 300 and 600 μm), and embedded with a range of photocatalytic titanium dioxide (TiO₂) nanoparticle loadings (3.75, 7.5, 11.25 and 15 wt.%), were used to test the combined efficacy of these technologies as antifouling materials. Settlement of the fouling bryozoan species Bugula neritina was quantified in the laboratory under two intensities of UV light. The lowest settlement rates were observed on 20 μm surfaces. However, texture effects were not as critical to larval settlement as the presence of TiO₂. In conjunction with UV light, TiO₂ completely inhibited larval metamorphosis even at the lowest loading (3.75 wt.%) and the lowest intensity of UV light (24 W m⁻²). Recruitment of B. neritina was also quantified in field trials and showed similar results to laboratory assays. The lowest recruitment was observed on 20 and 200 μm surfaces, with recruitment being significantly lower on all surfaces containing TiO₂. Therefore for B. neritina, although all TiO₂ loadings were effective, 3.75 wt.% can be used as a minimum inhibitory concentration to deter larval settlement and the addition of a 20 μm texture further increases the deterrent effect.