Assessment and down-selection of non-biocidal coatings that prevent the adhesion of fouling organisms in the marine environment requires a hierarchy of laboratory methods to reduce the number of experimental coatings for field testing. Automated image-based methods are described that facilitate rapid, quantitative biological screening of coatings generated through combinatorial polymer chemistry. Algorithms are described that measure the coverage of bacterial and algal biofilms on coatings prepared in 24-well plates and on array panels, respectively. The data are used to calculate adhesion strength of organisms on experimental coatings. The results complement a number of physical and mechanical methods developed to screen large numbers of samples.

In order to facilitate a semi-high throughput approach to the evaluation of novel fouling-release coatings, a 'spinjet' apparatus has been constructed. The apparatus delivers a jet of water of controlled, variable pressure into the wells of 24-well plates in order to facilitate measurement of the strength of adhesion of algae growing on the base of the wells. Two algae, namely, sporelings (young plants) of the green macroalga Ulva and a diatom (Navicula), were selected as test organisms because of their opposing responses to silicone fouling-release coatings. The percentage removal of algal biofilm was positively correlated with the impact pressure for both organisms growing on all the coating types. Ulva sporelings were removed from silicone elastomers at low impact pressures in contrast to Navicula cells which were strongly attached to this type of coating. The data obtained for the 24-well plates correlated with those obtained for the same coatings applied to microscope slides. The data show that the 24-well plate format is suitable for semi-high throughput screening of the adhesion strength of algae.

Crosslinked siloxane–polyurethane coatings were designed, synthesized, formulated, applied, and characterized using combinatorial high-throughput experimentation and eight coatings were selected as candidates for further characterization. First, 72 novel hydroxyalkyl carbamate and dihydroxyalkyl carbamate-terminated poly(dimethylsiloxane) (PDMS) oligomers and their carbamate-linked block copolymers with poly(ε-caprolactone) (PCL) were synthesized using a high-throughput synthesis system. These PDMS oligomers and block copolymers were characterized for their molecular weight using high-throughput Gel Permeation Chromatography (Rapid-GPC). The 72 oligomers were then incorporated into siloxane–polyurethane formulations at four different levels resulting in 288 coatings. After initial screening of these 288 coatings, eight coatings were selected for further characterization. Differential scanning calorimetry, dynamic mechanical analysis, X-ray photoelectron spectroscopy and surface energy analysis demonstrate the presence of PDMS on the surface with a polyurethane underlayer. Pseudo-barnacle adhesion and the attachment strength of reattached live barnacles (Balanus amphitrite) were in good agreement. Out of the eight coatings that were down-selected, two coatings performed well in algal (Ulva), bacterial (Cytophaga lytica, Halomonas pacifica), and barnacle (Balanus amphitrite) laboratory screening assays and are potential candidates for ocean testing.

Coatings libraries achieved through a combinatorial chemistry approach, which may generate tens to hundreds of formulations, can be deposited in an array of 12 patches, each approximately 9 cm(2), on 10 x 20 cm primed aluminum panels. However, existing methods to quantify algal biomass on coatings are unsuitable for this type of array format. This paper describes an algorithm modelled on a probability distribution that quantifies the area of surface covered by a green alga from digital images. The method allows coatings with potential fouling-release properties to be down-selected for further evaluation. The use of the algorithm is illustrated by a set of eight siloxane-polyurethane coatings made using organofunctional poly(dimethylsiloxane) (PDMS) and poly(epsilon-caprolactone)-PDMS-poly(epsilon-caprolactone) (PCL-PDMS-PCL) triblock copolymers along with four PDMS standards which were deposited on one panel. Six replicate panels were seeded with Ulva zoospores which grew into sporelings (small plants) that completely covered the surface. The ease of removal of the Ulva sporeling biofilms was determined by automated water jetting at six different impact pressures. The coverage of the biofilm on the twelve individual formulations after jet washing was quantified from the green colour of digital images. The data are discussed in relation to the composition of the coatings.

The effect of acrylic polyol composition on the properties of crosslinked siloxane-polyurethane coatings was explored. An acrylic polyol library was synthesized using batch solution polymerization and characterized using high-throughput gel permeation chromatography (Rapid-GPC) and differential scanning calorimetry (DSC). Siloxane-polyurethane coatings were prepared from 3-aminopropyl-terminated poly(dimethylsiloxane) (PDMS), the acrylic polyols and a polyisocyanate crosslinker. The siloxane-acrylic-polyurethane coatings were tested for mechanical and physical properties. The siloxane-polyurethane coatings had a systematic variation in glass transition temperature and had water contact angles ranging from 95° to 100°. Many of the coatings also showed a low-force of release in the pseudo-barnacle pull-off adhesion test. Performance testing of the fouling-release properties of the siloxane-polyurethane coatings on array panels with algae, namely the diatom Navicula and sporelings (young plants) of the green seaweed Ulva was also conducted.

The transfer from the self-polishing organotin to tin-free antifouling coatings has created a new learning curve for the shipping industry. This study investigated the hydrodynamic performance of four commercially available antifouling coatings that were subjected to both static and dynamic seawater immersion. The results showed that each coating type developed its own characteristic fouling community and that there were significant differences in drag properties that were further modified by the static or dynamic immersion conditions.

The transfer from the self-polishing organotin to tin-free antifouling coatings has created a new learning curve for the shipping industry. This study investigated the hydrodynamic performance of four commercially available antifouling coatings that were subjected to both static and dynamic seawater immersion. The results showed that each coating type developed its own characteristic fouling community and that there were significant differences in drag properties that were further modified by the static or dynamic immersion conditions. .

Since the composition and abundance of microfouling communities that develop on antifouling coatings reduce the performance and efficiency of ship operations, microfouling was investigated during static and dynamic seawater immersion of four commercial antifouling coatings, of which three were biocide based (tributyltin self-polishing, copper self-polishing, copper ablative) and one was biocide free (silicone fouling release). The total bacterial counts were similar on all coatings after static immersion, but after dynamic immersion the largest decrease in numbers was seen on the fouling release coating. The bacterial population on the fouling release surface was also more heterogeneous than on the biocide-based coatings. After static immersion, diatom populations were dominated by Amphora, Navicula and Synedra; after dynamic immersion, no diatoms could be detected on the copper ablative coating and only Amphora was left on the fouling release coating.