Advanced nanostructured surfaces for the control of biofouling

A modified Diamond-like carbon coating with biofouling and corrosion resistant properties has been developed through AMBIO project. The coatings have potential applications in heat exchangers and pipeline for inhibiting biofouling and corrosion.

A surface-nanostructured coating in which a complex morphology/topography is produced that facilitates release of attached foulants.

A fully automated instrument has been developed to measure the strength of adhesion of adult barnacles to surfaces, including fouling-release coatings. An evaluation of the methodology can be found in the following journal article: Conlan, S.C., Mutton, R.J., Aldred, N. and Clare, A.S. (2008) Evaluation of a fully automated method to measure the critical removal stress of adult barnacles. Biofouling 24: 471-481.

A fully turbulent flow cell has been developed to measure the adhesion strength of cyprids - the colonisation stage of barnacles attached to e.g. fouling-release coatings. The instrument can also be used to compare coatings for ease of removal of other biofouling e.g. biofilm.

An automated waterjet instrument has been developed to measure the adhesion strength of barnacle cyprids and juveniles to surfaces, e.g. fouling-release coatings. A example of the application of the instrument is presented in the following journal article: Aldred, N., Scardino, A., Cavaco, A., de Nys, R., and Clare, A.S. (2010) Attachment strength is a key factor in the selection of surfaces by barnacle cyprids (Balanus amphitrite) during settlement. Biofouling 26: 287-299.

A surface-nanostructured coating in which a complex morphology/topography is produced that facilitates release of attached foulants.

Sol-gel coatings are modified with inorganic nanoclay particles to enhance fouling release properties. The coatings were tested for fouling release of bacteria, algae, and barnacles and showed improved fouling release properties.

A modified Diamond-like carbon coating with biofouling and corrosion resistant properties has been developed through AMBIO project. The coatings have potential applications in heat exchangers and pipeline for inhibiting biofouling and corrosion.

The adsorption of biomolecules on different types of substrates can be monitored by IR and XPS spectroscopes. When these techniques are supported by spectral simulation and molecular simulation the mechanisms of adsorption can be revealed.

Siloxane coatings deposited using plasma-assisted chemical vapour deposition (PACVD) has been developed for the control of aquatic biofouling [1-3]. Biological assays have revealed good antifouling and fouling release properties against Ulva and freshwater bacteria depending on the coating parameters used. These coatings can be used for a number of applications where aquatic biofouling can present a problem. As the coatings are transparent, they can also be used where transparency is a requirement. The coatings have been used in field tests for heat exchangers and under-water equipment with some promising results. Further field testing and optimisation of properties can lead to commercially viable coatings. References: 1 Patent Application, PCT/GB2008/003123 2 L. Akesso et al, Biofouling 25,55-67(2009) 3 L. Akesso et al, Appl. Surf. Sci. 255,6508-6514(2009)

Know-how on the use of laboratory test methods to evaluate anti-fouling coating performance.

The 5-year 6th Framework project, which finished in February 2010, operated at the frontiers of diverse disciplines, including nanotechnology, polymer science, surface science, coating technology, hydrodynamics and marine biology. The project integrated 31 Partners from industries, universities and research organizations and a significant number of end-user 'stakeholders' was involved. Twelve EU Member States were represented as well as Turkey, Israel and Norway. AMBIO demonstrates the strength of the EC's large Integrated Project concept, in that, for the first time in Europe, the efforts of a critical mass of researchers, with diverse skills, and representing several sectors and stakeholder organizations, was concentrated on the challenge presented by the need to introduce novel, non-biocidal technologies to control the economically and environmentally important problem of biofouling.

Titanium and stainless steel surfaces have been functionalised with fluorosilanes, and these surfaces have shown very low adhesion of bacteria derived from natural waters, protecting metal surfaces from problems resulting from biofouling.

A surface-nanostructured coating in which a complex morphology/topography is produced that facilitates release of attached foulants.

Invention of new antifouling agents less damaging the marine environment

During 18 months we perform testing of different coatings on fish net samples in sea water, ranging from 15x15 cm up to 2x2 meters of size. The last stage of the testing included testing of 4 experimental coatings tested together with uncoated nets and commercial standard coatings. The antifouling performance (measured as fouling release effect) was very good for all experimental coating; better than uncoated nets and almost equal to commercial standard coatings. The physical properties of all coatings were good, and irrespective of prize they could be possible replacements for todays biocide antifouling coatings that are in use.

The AMBIO project has contributed to the development of new test methods for the assessment of coating performance by the use of image analysis of high quality digital images.

New protective coatings based on cross-linked silicones in which a surface-active amphiphilic polyacrylate provides low energy surface properties to the elastomer matrix in order to improve the fouling release properties.

Ship Design and Research Center S.A. was responsible within the Ambio project for a scope of hydrodynamic tests of newly elaborated nanostructured anti-fouling coatings. The objectives concerned: the main surface characteristics of selected coated surfaces, the investigated surface ranking with respect to their hydrodynamics merits, recommendations for fuel saving applications and their surface characterisation and the hydrodynamic testing methodsdevelopment. In order to achieve these targets, a series of testing samples was elaboreted and respective technical documentation manufactured. There were elaborated such samples as big flat plates, axisymmetric bodies, small flat plates and hydrofoils. For testing these samples, special testing rigs at the model basin of CTO were developed and equipped for drag measurements. The manufactured samples were coated with newly elaborated coatings received from project partners. The substrates were done of mild steel and aluminium alloys. On each sample there were applied four layers: shop primer,,anticorrosive, tie- and topcoats. In scope of topcoats six new types of new coatings and two reference ones were applied.For painting purposes the special painting stands were designed and manufactured.In majority of layers the airless spray technique was used; the rest was painted with use of a roller. The painted samples were a subject of coatings thickness and roughness measurements. The fully coated samples were a subject of the drag investigations. The scope of tests was chosen in the way so as to achieve turbulent flow along the coated surfaces and as high as possible Reynolds numbers. The received results have shown that some of newly elaborated coatings have better hydrodynamic properties than the presently used commercial ones.The results made also possible to rank all the tested coatings and to elaborate due recommendations for the possible applications and future experiments. It has resulted from these investigations that use of this new coatings on new ships can significantly reduce propulsive power demands and will make these ships more friendly to the natural environment.

Laboratory scale syntheses of substituted polyphosphazine materials.

KEMA cooperated in the AMBIO project as an End-User. We tested coatings that were developed under controlled laboratory conditions as well as real time circumstances. The coatings are specific for cooling water conduits and for heat exchangers (HE). Especially the latter category provides very interesting possibilities for the future, since the coatings did not have a negative effect on heat transfer. Future coating application in large scale HE has advantages for fouling/scaling/corrosion control and the use of less noble materials, which is cost efficient.

Different binders and fillers have been evaluated for antifouling coatings. Biological testing has been performed by the project partners Uni Birmingham, Dundee and Newcastle as well as TNO. Coatings have been characterized regarding their stability under sea-water, surface energies, wetting behaviour through captive bubble techniques, elasticity via nano-indentation and morphology via scanning force and scanning electron microscopy. Scanning force microscopy reveals subtle changes in nanostructure after sea-water storage.

A new correlation has been developed for calculating interfacial tensions from individual surface tensions. The general form of the correlation derives from the Gibbs fundamental theory for interfacial tensions. The specifics of the correlation were empirically found, based on data for liquid-liquid interfacial tensions.

New nanostructured coatings and coating methods (PACVD plasma polymer and PDMS) for oceanographic instruments result in a bio fouling reduction of some 50%. Reduction of bio fouling will lead to an extended operational period between maintenance cruises to oceanographic monitoring sites. Fields and prototype testing proved the effectiveness of these coatings. Further introduction into manufacturing and application of oceanographic instruments is envisaged.

The research has been devoted to studies of thin coating for marine biofouling applications. The focus has been on the preparation and characterization of model coatings including, for example, self-assembled monolayers (SAMs)on gold and ultrathin hydrogels on glass, gold and polymer surfaces. The hydrogel coatings (polyethylene glycol derivatives) exhibit excellent anti-fouling properties for a range of marine organisms (Ulva Linza, Barnacles ans bacteria). Laboratory based bioassays have been correlated to macromolecular adsorption phenomena of proteins and complex biofluids, and we have found excellent agreement between the two sets of experiments. An interesting correlation between surface composition (wettability) and settlement of Ulva linza zoo spores has also been obtained for a set of carbohydrate SAMs. We have also used self-assembled monolayers as model substrates to gain a deeper understanding of the mechanisms responsible for marine biofouling. A biomimetic approach has been utilized to design and synthesize cationic peptides with anti-microbial activity. These coatings are not useful for as anti-fouling coatings but they have been used to shed some light on the mechanisms behind gregarious settlement. It turns out that the peptides attach the cellular membrane of the spore leading to an abnormal settlement process where the spores attach to the surface in a side-on fashion with out releasing the adhesive glue. Nor do the spores detach the flagellum (swimming organs). A new method based on surface plasmon imaging has been developed to investigate the exploration of surfaces by fouling organism (barnacle cyprids). The results from a first study indicate again an excellent correlation between barnacle cyprid adhesion and settlement. For example, the attachment of cyprids to polyethylene glycol hydrogels and oligo(ethylene glycol) SAMs is non-existent.

In the Ambio project model surfaces based on self assembly and immobilization of biomacromolecules have been applied to reveal fundamental mechanisms in biofouling. Besides, new techniques were developed to understand these processes in greater detail.

Foul-release properties of marine spores was found to be explained by using contact angle hysteresis values of surfaces.

Exploitable results

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