A reduction of settlement probability of Chlorella vulgaris on photo-chemically active ceramics with hierarchical nano-structures

Abstract

Biofouling is defined by the adsorption of biomolecules or microorganisms on technical surfaces, which are causing adverse effects on the functionality (decrease of ship speed) and safety (infections of implants) of quite a number of industrial products. Conventional, anti-biofouling in marine environments is done by coating a technical surface with highly poisonous tin-organic, which have already been banned for environmental protection. Therefore, the developing of biologically benign coatings becomes a long-term pursue for the industry. Here, we study the Chlorella vulgaris settlement on self-disinfecting titanium dioxide surfaces with three different micro-structures: a flat surface, a light harvesting surface with nano-structure and a hierarchical surface structure, spanning over 5 orders of magnitude (from 0.1 nm to 10 μm). These titanium dioxide surfaces were prepared by Ostwald ripening. This sample manufacturing process gains new catalytic properties as a self-cleaning effect, especially for the light harvesting surface with nano-structure (bulk metallic glass). Chlorella vulgaris dispersions were growing in glass flasks together with the different surface samples over the full time of the experiments. Therefore, this study was made as part of a laboratory scale test. It was found, that bulk metallic glass structures made by Ostwald ripening are showing the highest catalytic and at the same time the best self-cleaning effects. Additionally, the Chlorella vulgaris settlement probability was found to depend on the Wenzel roughness. The surfaces with a high Wenzel roughness were the ones with the lowest Chlorella vulgaris settlement. A semi-field test is proving the comparable antibiofouling performance of our surfaces with existing polymeric or sharkskin like structures on the timescale of one month.