Effects of surface wettability of silicon-incorporated diamond-like carbon films on barnacle larval settlement

The colonization of barnacles on surfaces has detrimental effects on shipping, leisure vessels, heat exchangers, oceanographic sensors, and aquaculture systems. One strategy for avoiding barnacle colonization on surfaces is to utilize surface wettability. Silicone-incorporated diamond-like carbon (Si-DLC) has high hardness and a low friction coefficient, and an increase in the incorporation of Si leads to hydrophobicity. By contrast, oxygen plasma treatment produces hydrophilicity in Si-DLC films. The improved surface wettability of Si-DLC may reduce barnacle colonization. However, few studies have been conducted on barnacle larval settlement in relation to Si-DLC films. The aim of this study is to evaluate barnacle larval settlement on Si-DLC films and on oxygen-plasma-treated Si-DLC films. Si-DLC films were prepared by radio-frequency plasma-enhanced chemical vapor deposition and treated with oxygen plasma. The films were characterized using Raman spectroscopy and X-ray photoelectron spectroscopy. Contact angles of the films were measured to evaluate their hydrophobicity. Barnacle cyprid larva settlement was observed on the Si-DLC and oxygen-plasma-treated Si-DLC films. The contact angle of the Si-DLC-0% film was 69.9 ± 3 . 3 ∘ and increased with Si incorporation. Following oxygen plasma treatment, the contact angle of the Si-DLC-0% films decreased to 10.9 ± 4 . 4 ∘ and gradually increased with Si incorporation. The barnacle cyprid larval settlement ratio for the non-coated stainless plate was 36.4%, whereas that of the DLC films was 15.0%, which decreased with Si incorporation. Following oxygen plasma treatment, the ratio of barnacle cyprid larval settlement in Si-DLC films was lower than for the Si-DLC films. The Si-DLC film was effective in avoiding barnacle adhesion, whereas the oxygen-plasma-treated Si-DLC was even more effective. This study demonstrated the feasibility of Si-DLC for antifouling against barnacles.