Transparent zwitterionic cellulose nanofibers-based coatings for marine antifouling

Marine optical devices face significant biofouling challenges, which compromise their transparency and disrupt their functionality. Existing coatings, typically relying on toxic biocides or dynamic surfaces, harm the marine environment and fail to meet the signal stability required for high-performance equipment. In this study, we introduce a fully bio-based approach to transparent antifouling coatings by developing zwitterionic cellulose nanofibers (ZCNF) modified with lysine, arginine, and histidine. Notably, this innovative modification exhibits enhanced hydrophilicity and antifouling properties compared to unmodified cellulose nanofibers, while also forming a stable antifouling surface, overcoming the key limitations of conventional materials. Laboratory and marine field tests demonstrate the remarkable long-term performance of ZCNF coatings, achieving up to 90 % antifouling efficiency in controlled environments and 80 % in real-world conditions after 150 days. This work provides a sustainable alternative for marine optical coatings, advancing the application of bio-based nanomaterials to address real-world marine challenges.