Construction of highly hydrated and mechanically strong anti-fouling coatings for deep-sea probes based on poly(vinyl alcohol) tannic acid zwitterion coatings

The marine biofouling of deep-sea exploration equipment has compromised its normal purpose of detecting marine resources, and conventional self-renewing hydrogel coatings have become unsuitable for precision instruments due to the release of antifouling agents or heavy metals. Zwitterions exhibit excellent antifouling ability due to the hydration layer formed by molecules with equal amounts of cationic and anionic groups, resulting in an overall neutral charge. Herein, a non-releasing, mechanically strong surface hydrogel coating suitable for deep-sea probes was successfully prepared based on sulfobetaine-tannic acid zwitterionic hydrogel coatings (PVATAZ), aiming to achieve high antifouling performance. Benefiting from the hydration layer generated by the zwitterion and the significant mechanical performance of strong hydrogen bonding between poly(vinyl alcohol) and tannic acid (TA), the resulting optimized PVATAZ hydrogel coatings exhibited excellent antifouling performance and high tensile strength. Specifically, under stress up to 0.41 MPa, elongations can reach up to 228% and the colony forming units of E. coli and S. aureus in PVATAZ are 0.08 and 0.05 per milliliter, respectively. The efficiency of zwitterion-containing hydrogel coatings in resisting marine fouling while being environmentally friendly renders them promising as hydrogel coatings for deep-sea probes.