Anti-fouling paints and coatings are applied to submarines, ship hulls, and acoustic sensors to inhibit the growth and accumulation of unwanted marine life (“biofouling”; e.g., barnacles, tube worms, algae biofilms, etc.). Biofouling increases surface drag and creates noisy flow conditions. Some anti-fouling materials contain poisons (biocides) to discourage the unwanted marine growth while others (foul release type coatings) form extremely slippery surfaces that prevent marine organisms from attaching strongly to their surfaces. Some newer coatings utilize both mechanisms in combination to discourage/prevent biofouling. Several challenges arise with respect to the topsides of submarines. Humans need to walk on the topside of submarines during certain situations. Slippery anti-fouling coatings pose a significant safety risk, as they can lead to falls overboard and potentially serious injuries. The coating must also be mechanically robust enough to not be damaged or de-bonded from protected surfaces due to normal foot traffic and equipment/cargo placement. Currently used anti-fouling paints and coating present both immediate and long-term challenges. If they contain biocides, toxic residues can be tracked inside the submarine, posing a health hazard to the crew. Additionally, the reliance on toxic components raises concerns about the future availability and cost of these materials. Finally, the topside environment is an alternating wet/dry environment, so any antifouling paint/coating/material use there would need to survive desiccation and periods of time when it would be above the waterline for days or months without experiencing a significant drop in effectiveness when it is once again underwater. During the time it is above the waterline/out of the water, the paint/coating/material would need to survive exposure to air and direct sunlight. There is no commercially available solution to this problem. The Navy is seeking novel anti-fouling paints, coatings, or materials and application methods for the anti-fouling products for use on submarine topside surfaces. These solutions must effectively inhibit marine growth while maintaining the flow conditions associated with propulsion efficiency and noise due to turbulent boundary layers, including minimizing drag and turbulent flow at operational speeds. The solution must also allow sailors to maintain steady footing when the topside of the submarine is awash with sea water. Exact characteristics of the submarine hull surface would be considered controlled unclassified information, which will be shared with Phase I performers after they are under contract. The solution(s) will be a useable topside coating that minimizes biofouling on topside surfaces while the submarine is submerged. After it is initially applied, the solution should remain bonded to the protected surfaces and be able to discourage or prevent biofouling for up to 6-8 years without any major maintenance or routine cleaning. Standard Navy requirements for adhesion, color, performance, and durability will be invoked as the candidate materials advance. The Navy seeks this innovation to leverage advancements in non-toxic materials, addressing the long-standing need for safer alternatives in applications currently reliant on toxic substances. Recent advancements in marine antifouling strategies include bioactive antifoulant mechanisms, self-polishing antifouling mechanisms, surface wettability mechanisms, photocatalytic bactericidal mechanisms, and biomimetic antifouling mechanisms. Successful prototypes will be useful for unmanned, undersea vehicles that are handled/retrieved by ship’s crews and stored on deck between missions, as well as the Navy’s intended target of submarine topside surfaces.
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