Antifouling properties of ZnO nanorods coating on micropatterned polymers

Biofouling remains a major challenge for submerged materials in marine and industrial environments, reducing performance and increasing maintenance costs. In this study, zinc oxide nanorod (ZnO NR) coatings with dual-scale surface roughness were fabricated on three distinct 3D micropatterned surfaces, designated as D1, D2, and D3. The antifouling performance of the engineered surfaces was evaluated against the bacterium Escherichia coli and the diatom Amphora sp. under laboratory flow conditions, while acute toxicity was assessed using larvae of Litopenaeus vannamei. Fourier transform infrared (FTIR) spectroscopy confirmed the presence of Zn-O stretching vibrations, particularly on the ZnO NR-coated D2 and D3 surfaces. Water contact angle measurements showed that the ZnO NR-coated surfaces were superhydrophobic (≈150-165°) because of their hierarchical micro/nanostructures, whereas the non-coated surfaces exhibited moderate wettability (≈80-90°). ZnO coating reduced bacterial attachment by 60.3%, 48.8%, and 5.8% on the D1, D2, and D3 surfaces, respectively. Diatom coverage was reduced by 9.9%, 72.9%, and 71.8% on the corresponding ZnO-coated surfaces. The enhanced antifouling performance was associated with the combined effects of Zn2+ ions, ROS generation, surface wettability, and micro/nanotopography. The non-coated D1 and D2 surfaces, together with the ZnO-coated D1 surface, exhibited no significant toxicity toward shrimp larvae. In contrast, the ZnO-coated D3 surface exhibited relatively low antifouling performance and higher larval toxicity. Among the tested surfaces, the ZnO-coated D1 micropattern demonstrated the best overall performance by combining high antifouling efficacy with low toxicity. Post-characterization SEM analysis confirmed that the ZnO nanorod coatings remained structurally intact after biological testing, indicating good coating stability under the experimental conditions. These findings demonstrate that combining ZnO nanorod coatings with micropatterned surface topography is a promising strategy for antifouling applications. However, further long-term field evaluations and comprehensive ecotoxicological studies are required to assess the environmental performance of these coatings.