N112-166 TITLE: Bio-inspired Marine Biofouling-control Coatings

TECHNOLOGY AREAS: Ground/Sea Vehicles, Materials/Processes

ACQUISITION PROGRAM: Future FNC related to "Clean Hull Technologies for a Green Navy" , EPE

OBJECTIVE: The objective for this topic is to develop durable, non-toxic, marine biofouling-control coatings that use a mechanism-based approach to interfere with bioadhesive processing and/or curing. Ideally proposals will exploit recent knowledge regarding the synthesis, secretion, cross-linking and/or curing of biological adhesives manufactured by barnacles, tubeworms, mussels, and/or seaweeds to interrupt or inhibit adhesive formation to prevent settlement, adhesion, or growth of these organisms. Successful coatings will utilize a strategy that incorporates chemistry/biochemistry-based approaches that by design will target the organism�s bioadhesives, as opposed to purely physical approaches such as foul release or textured surfaces.

DESCRIPTION: Marine biofouling causes increased drag on vessels, leading to increased fuel costs, ship husbandry costs and decreases in operational readiness. Recent analysis of coating/maintenance costs associated with hull biofouling for a single class of Navy vessels (DDG-51; 22% of the wetted hull area of the current Navy fleet) is estimated to be $56M per year or $1B over 15 years1.

Current marine biofouling control coatings utilize copper to prevent the settlement of organisms. However, increasing environmental regulation of this heavy metal makes identification of non-toxic alternatives that also meet the Navy�s desired lifecycle and performance needs desirable. Foul release coatings are non-toxic, and consist of compliant and �slippery� materials to discourage adhesion by marine biofoulers such as barnacles and tubeworms. Their expense, lack of durability, and need for frequent in-water husbandry has limited their use by the Navy.

Macrofouling organisms span length scales from �M to dM, and generally settle on surfaces as an immature form (�m-mm), completing their development once adhered to the substrate. Textured, non-toxic polymeric surfaces show great promise for discouraging settlement by larval forms of some fouling organisms, but the longevity of these coatings under typical vessel conditions has not been established.

Given the shortcomings noted above for various types of commercially available and developmental biofouling-control coatings, new approaches are needed.

Recently, mechanistic details about the bioadhesives that are produced by various macrofouling organisms have been published regarding the secretion, cross-linking or curing of these adhesives2-5. These mechanisms have included free-radical-mediated cross-linking, enzyme-catalyzed protein modification and cross-linking, and development of specific protein hierarchial structures (e.g., amyloid-like fibrils). Scientists have begun to translate these studies into experimental coatings systems, through covalent linkage of settlement or adhesion inhibitors into polymers2. What is desired for this topic is to encourage new approaches for durable, biofouling-control coatings that function by inhibiting bioadhesive production, secretion, curing or surface attachment yet do not release toxic components to the environment. Coatings that contain metals such as Zn, Ni, Ag, or Cu are not of interest to this topic.

PHASE I: The objectives are: (i) to develop a coating concept and prepare initial coatings on a small scale for testing in the laboratory with in-house assays and/or possibly through collaborations with other ONR-funded lab assays; (ii) to deliver twelve coated microscope slides per coating for one or two coating variants to ONR for lab scale testing. [ONR currently supports labs that perform coatings screening assays using marine diatoms, algal zoospores, barnacle larvae, adult barnacles, and tubeworms.]

PHASE II: To perform further development and testing of the coating system. This includes both further development of the coating based on lab assays and scale-up of the proposed approach(es) into a viable coating systems. Studies shall be performed to assure the coating(s) is stable when exposed to seawater. Toxicity studies of coating(s) and leachate(s) with common marine indicator species should be performed to demonstrate the coating(s) is non-toxic. Iterative testing, refinement and optimization of the coating will be accomplished by performing static immersion field tests of small panels for fouling measurements. It is anticipated that the final coating at the end of phase II will be equal to or better than the performance of existing non-toxic coatings (e.g. silicone fouling-release coatings).

PHASE III: Prepare large panels for in-service hull panel testing that will be performed in coordination with NAVSEA.

PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: International, national and local environmental regulations are focused on reducing environmental impact of marine coatings, as evidenced by bans on organotin coatings and increased scrutiny of copper-based coatings. Development of a cost-effective yet durable and non-toxic biofouling-control would find applicability in the pleasure craft, commercial shipping, and military vessel coating markets. Estimated global market size for 2012 is $4.7B or over 900 million liters of paint (http://www.thefreelibrary.com/Marine+coatings+market%3a+growth+in+the+marine+coatings+market+can+be...-a0200408710).

REFERENCES:
1. M.P. Schultz, J.A. Bendick, E.R. Holm and W.M. Hertel (2011) Economic impact of biofouling on a naval surface ship. Biofouling, 27: 1, 87-98.

2. Gohad, N.V., Shah, N.M., Metters, A.T., Mount, A.S., (2010) Noradrenaline deters marine invertebrate biofouling when covalently bound in polymeric coatings. Journal of Experimental Marine Biology and Ecology, Volume 394, Issues 1-2, 30 October 2010, Pages 63-73.

3. Dickinson, G. H., Vega, I. E., Wahl, K. J., Orihuela, B., Beyley, V., Rodriguez, E. N.,Everett, R. K., Bonaventura, J., and Rittschof, D. (2009) Barnacle cement: a polymerization model based on evolutionary concepts, J Exp Biol 212, 3499-3510.

4. Wilker, J. J. (2010), The Iron-Fortified Adhesive System of Marine Mussels. Angewandte Chemie International Edition, 49: 8076�8078

5. Barlow, D., Dickinson, G. H., Orihuela-Diaz, Kulp, J., Rittschof, D., and K. Wahl 2010. Functional amyloid and bio-adhesion: Characterization of amyloid-like nanofibrils composing the adhesive plaque of the barnacle Balanus amphitrite. Langmuir, 26: 6549-6556

KEYWORDS: biofouling, anti-fouling coating, bioadhesive, marine paint, barnacle, glue curing

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