Antifouling Efficacy Research Articles

Research Progress of Marine Anti-Fouling Coatings

The extended immersion of ships in seawater frequently results in biofouling, a condition characterized by the accumulation of marine organisms such as barnacles and algae. To combat this issue, the application of anti-fouling coatings to the hull surfaces of vessels has emerged as one of the most effective strategies. In response to the increasing global emphasis on environmental sustainability, there is a growing demand for anti-fouling coatings that not only demonstrate superior anti-fouling efficacy but also adhere to stringent environmental standards. The traditional use of organotin-based self-polishing anti-fouling coatings, known for their high toxicity, has been prohibited due to environmental concerns. Consequently, there is a progressive shift toward the development and application of environmentally friendly anti-fouling coatings. This paper reviews the toxicity and application limitations associated with conventional anti-fouling coatings. It provides a comprehensive overview of recent advancements in the field, including the development of novel self-polishing anti-fouling coatings, low surface energy coatings, biomimetic coatings, and nanostructured coatings, each leveraging distinct anti-fouling mechanisms. The paper evaluates the composition and performance of these emerging coatings and identifies key technical challenges that remain unresolved. It also proposes a multi-faceted approach to addressing these challenges, suggesting potential solutions for enhancing the effectiveness and environmental compatibility of anti-fouling technologies. The paper forecasts future research directions and development trajectories for marine anti-fouling coatings, emphasizing the need for continued innovation to achieve both environmental sustainability and superior anti-fouling performance.

Copper tannate nanosheets-embedded multifunctional coating for antifouling and photothermal bactericidal applications

Implant-associated infections (IAIs), triggered by pathogenic bacteria, are a leading cause of implant failure. The design of functionalized coatings on biomedical materials is crucial to address IAIs. Herein, a multifunctional coating with good antifouling effect and antibacterial photothermal therapy (aPTT) performance was developed. The copper tannate nanosheets (CuTA NSs) were formed via coordination bonding of Cu2+ ions and tannic acid (TA). The CuTA NSs were then integrated into the TA and poly(ethylene glycol) (PEG) network to form the TCP coating for deposition on the titanium (Ti) substrates via surface adhesion of TA and gravitational effect. The resulting Ti-TCP substrate exhibited good antifouling property, reactive oxygen species (ROS) scavenging capability and cytocompatibility. The TCP coating exhibited antifouling efficacy in conjunction with aPTT, curtailing the surface adhesion and biofilm formation of pathogens, such as Staphylococcus aureus and Escherichia coli. Notably, the Ti-TCP substrate also exhibited the ability to prevent bacterial infection in vivo in a subcutaneous implantation model. The present work demonstrated a promising approach in designing high-performance antifouling and photothermal bactericidal coatings to combat IAIs.

Effect of Surface Charges in Polymer Coatings on Antifouling Performance in Marine Environments with Sediment.

The antifouling efficacy of hydrophilic polymer coatings is closely related to their surface charge. Many biological foulants such as mammalian cells and marine microalgae possess a negative surface charge, discouraging the use of positively charged polymer coatings for antifouling purposes. Instead, electrically neutral yet hydrophilic polymers have been widely employed, leveraging hydration layers to create a barrier against fouling. However, challenges arise in marine environments where both living marine organisms and sediments can adhere to solid surfaces, rendering previous findings less directly applicable. This study investigates the impact of a polymer coating surface charge on marine antifouling properties. Polymer brushes with various charges are applied to solid substrates, and the adhesion behavior of marine diatoms is assessed under both marine sediment-free and marine sediment conditions. The results underscore the effectiveness of negatively charged polymer brush coatings in marine antifouling, regardless of sediment presence.

A novel strategy for design of mechanically robust antifouling coatings via bifunctional domain engineering

The issue of biofouling on marine structures carries significant economic and ecological implications, necessitating the development of effective and durable antifouling coatings. Traditional organic antifouling coatings often struggle with mechanical robustness in harsh marine environments, making them fragile and highly susceptible to abrasion. To address these challenges, we propose a novel “bifunctional domain engineering” strategy for designing robust antifouling coatings that combines excellent mechanical strength of a Fe-based amorphous layer and high antifouling efficacy of an incorporated organics. The hard domains consist of Fe-based amorphous micro humps, providing a sturdy framework that enhances the coating's mechanical durability. In contrast, the soft domains comprise epoxy resin infused with Cu2O and 4,5-Dichloro-2-n-octyl-4-isothiazolin-3-one (DCOIT), offering a dual-action antifouling function via controllable antifouling agent release. Evaluation of antifouling performance by lab tests against Pseudomonas aeruginosa, Staphylococcus aureus, and Chlorella algae and practical marine field tests (for 150 days) demonstrates significant reductions in bacterial and algal adhesion (nearly 100 % resistance) with the bifunctional domain engineered coating (referred to as HSR coating), compared to pure amorphous coating. Mechanical durability tests, including abrasion and erosion experiments, underscore the HSR coating's excellent wear resistance. Importantly, the HSR coating maintains its outstanding antifouling properties even after 1000 abrasion cycles, highlighting its potential for long-term marine applications in harsh conditions. This study lays the groundwork for design of robust antifouling coatings capable of withstanding the harsh operating environments while effectively combating biofouling.

Design of U-shaped peptides with long-lasting antifouling efficacy: Toward a feasible electrochemical aptasensor for robust detection in human serum

BackgroundDeveloping biosensors with antifouling properties is essential for accurately detecting low-concentration biomarkers in complex biological matrix, which is imperative for effective disease diagnosis and treatment. Herein, an antifouling electrochemical aptasensor qualifying for probing targets in human serum was explored based on newly-devised peptides that could form inverted U-shaped structures with long-term stability. ResultsThe inverted U-shaped peptides (U-Pep) with two terminals of thiol groups grafted onto the Au-modified electrode showcase superior antifouling properties in terms of high stability against enzymatic hydrolysis and long acting against biofouling in actual biofluids. The construction of the outlined antifouling electrochemical aptasensor just involved the fabrication of Au-deposited poly(3,4 ethylenedioxythiophene) (Au/PEDOT) modified electrode, followed by one-step co-incubation in the peptides and the aptamer probes with the Au/PEDOT electrode. Taking a typical biomarker of alpha-fetoprotein (AFP) for detection, this elegant antifouling aptasenor demonstrated a nice response for probing the target AFP with a low detection limit of 0.27 pg/mL and a wide linear scope of 1.0 pg/mL to 1.0 μg/mL, and furthermore qualified for assaying of AFP in human serum samples with satisfactory accuracy and feasibility. SignificanceThis engineering strategy of U-Pep with long-lasting antifouling efficacy opens a new horizon for high-performance antifouling biosensors suitable for detection in complex bifluids, and it could spark more inspiration for a follow-up exploration of other featured antifouling biomaterials.

Piezoceramic membrane with built-in ultrasound for reactive oxygen species generation and synergistic vibration anti-fouling

Piezoceramic membranes have emerged as a prominent solution for membrane fouling control. However, the prevalent use of toxic lead and limitations of vibration-based anti-fouling mechanism impede their wider adoption in water treatment. This study introduces a Mn/BaTiO3 piezoceramic membrane, demonstrating a promising in-situ anti-fouling efficacy and mechanism insights. When applied to an Alternating Current at a resonant frequency of 20 V, 265 kHz, the membrane achieves optimal vibration, effectively mitigating various foulants such as high-concentration oil (2500 ppm, including real industrial oil wastewater), bacteria and different charged inorganic colloidal particles, showing advantages over other reported piezoceramic membranes. Importantly, our findings suggest that the built-in ultrasonic vibration of piezoceramic membranes can generate reactive oxygen species. This offers profound insights into the distinct anti-fouling processes for organic and inorganic wastewater, supplementing and unifying the traditional singular vibrational anti-fouling mechanism of piezoceramic membranes, and potentially propelling the development of piezoelectric catalytic membranes.

Innovative Acrylic Resin-Hydrogel Double-Layer Coating: Achieving Dual-Anchoring, Enhanced Adhesion, and Superior Anti-Biofouling Properties for Marine Applications.

Traditional anti-corrosion and anti-fouling coatings struggle against the harsh marine environment. Our study tackled this by introducing a novel dual-layer hydrogel (A-H DL) coating system. This system combined a Cu2O-SiO2-acrylic resin primer for anchoring and controlled copper ion release with a dissipative double-network double-anchored hydrogel (DNDAH) boasting superior mechanical strength and anti-biofouling performance. An acrylamide monomer was copolymerized and cross-linked with a coupling agent to form the first irreversible network and first anchoring, providing the DNDAH coating with mechanical strength and structural stability. Alginate gel microspheres (AGMs) grafted with the same coupling agent formed the second reversible network and second anchoring, while coordinating with Cu2+ released from the primer to form a system buffering Cu2+ release, enabling long-term antibacterial protection and self-healing capabilities. FTIR, SEM, TEM, and elemental analyses confirmed the composition, morphology, and copper distribution within the A-H DL coating. A marine simulation experiment demonstrated exceptional stability and anti-fouling efficacy. This unique combination of features makes A-H DL a promising solution for diverse marine applications, from ship hulls to aquaculture equipment.

Comparison of Superhydrophilic, Liquid-Like, Liquid-Infused, and Superhydrophobic Surfaces in Preventing Catheter-Associated Urinary Tract Infection and Encrustation.

Over the past decade, superhydrophilic zwitterionic surfaces, slippery liquid-infused porous surfaces, covalently attached liquid-like surfaces, and superhydrophobic surfaces have emerged as the most promising strategies to prevent biofouling on biomedical devices. Despite working through different mechanisms, they have demonstrated superior efficacy in preventing the adhesion of biomolecules (e.g., proteins and bacteria) compared with conventional material surfaces. However, their potential in combating catheter-associated urinary tract infection (CAUTI) remains uncertain. In this research, we present the fabrication of these four coatings for urinary catheters and conduct a comparative assessment of their antifouling properties through a stepwise approach. Notably, the superhydrophilic zwitterionic coating demonstrated the highest antifouling activity, reducing 72.3% of fibrinogen deposition and over 75% of bacterial adhesion (Escherichia coli and Staphylococcus aureus) when compared with an uncoated polyvinyl chloride (PVC) surface. The zwitterionic coating also exhibited robust repellence against blood and improved surface lubricity, decreasing the dynamic coefficient of friction from 0.63 to 0.35 as compared with the PVC surface. Despite the fact that the superhydrophilic zwitterionic and hydrophobic liquid-like surfaces showed great promise in retarding crystalline biofilm formation in the presence of Proteus mirabilis, it is worth noting that their long-term antifouling efficacy may be compromised by the proliferation and migration of colonized bacteria as they are unable to kill them or inhibit their swarming. These findings underscore both the potential and limitations of these ultralow fouling materials as urinary catheter coatings for preventing CAUTI.

Antibiofouling activity of 1-hexadecyl-3-methylimidazolium chloride against Amphora sp. BARC 104, a fouling diatom isolated from back waters of Kalpakkam

1-Hexadecyl-3-methylimidazolium chloride (C16MimCl), an alkylimidazolium ionic liquid (IL) with a long alkyl side chain (-hexadecyl group) is attractive for antimicrobial applications. However, there are limited studies on the antifouling efficacy of ILs using biofouling organisms especially diatoms. In this study, the antifouling activity of C16MimCl was determined against Amphora sp. BARC 104, a dominant fouling diatom isolated from Kalpakkam coastal waters. Growth of the diatom was inhibited in the presence of IL at varied concentrations starting from 0.15 μM C16MimCl. A complete inhibition in the growth was observed in the presence of 2.5 μM C16MimCl. Adhesion and biofilm formation by Amphora sp. was strongly inhibited at sub-micromolar concentrations of IL. Exposure of diatom cells to IL in acute toxicity assays induced oxidative stress (increased reactive oxygen species generation) and reduced metabolic activity (decreased esterase activity) as revealed by 2,7 -Dichlorodihydrofluorescein diacetate (DCH2FDA) and fluorescein diacetate (FDA) staining, respectively. SYTOX® Green staining and extracellular chlorophyll a measurement revealed a severe membrane damage and leakage of chlorophyll a, respectively, in IL treated diatom cells. These measurements during recovery experiments indicated a permanent damage to cell and thylakoid membranes in the diatom cells. Damage to multiple cellular targets coupled with strong antibiofilm activity suggest potential application of C16MimCl in preparation of antifouling formulations and coatings.

Toward Effective and Adsorption-Based Antifouling Zipper Brushes: Effect of pH, Salt, and Polymer Design.

The undesired spontaneous deposition and accumulation of matter on surfaces, better known as fouling, is a problematic and often inevitable process plaguing a variety of industries. This detrimental process can be reduced or even prevented by coating surfaces with a dense layer of end-grafted polymer: a polymer brush. Producing such polymer brushes via adsorption presents a very attractive technique, as large surfaces can be coated in a quick and simple manner. Recently, we introduced a simple and scalable two-step adsorption strategy to fabricate block copolymer-based antifouling coatings on hydrophobic surfaces. This two-step approach involved the initial adsorption of hydrophobic-charged diblock copolymer micelles acting as a primer, followed by the complexation of oppositely charged-antifouling diblock copolymers to form the antifouling brush coating. Here, we significantly improve this adsorption-based zipper brush via systematic tuning of various parameters, including pH, salt concentration, and polymer design. This study reveals several key outcomes. First of all, increasing the hydrophobic/hydrophilic block ratio of the anchoring polymeric micelles (i.e., decreasing the hydrophilic corona) promotes adsorption to the surface, resulting in the most densely packed, uniform, and hydrophilic primer layers. Second, around a neutral pH and at a low salt concentration (1 mM), complexation of the weak polyelectrolyte (PE) blocks results in brushes with the best antifouling efficacy. Moreover, by tuning the ratio between these PE blocks, the brush density can be increased, which is also directly correlated to the antifouling performance. Finally, switching to different antifouling blocks can increase the internal density or strengthen the bound hydration layer of the brush, leading to an additional enhancement of the antifouling properties (>99% lysozyme, 87% bovine serum albumin).

Fabrication of Transparent PEGylated Antifouling Coatings via One-Step Pyrogallol Deposition.

Antifouling coatings are critical for many biomedical devices. A simple and universal technique used to anchor antifouling polymers is important in order to expand its applications. In this study, we introduced the pyrogallol (PG)-assisted immobilization of poly(ethylene glycol) (PEG) to deposit a thin antifouling layer on biomaterials. Briefly, biomaterials were soaked in a PG/PEG solution and PEG was immobilized onto the biomaterial surfaces via PG polymerization and deposition. The kinetics of PG/PEG deposition started with the deposition of PG on the substrates, followed by the addition of a PEG-rich adlayer. However, prolonged coating added a top-most PG-rich layer, which deteriorated the antifouling efficacy. By controlling the amounts of PG and PEG and the coating time, the PG/PEG coating was able to reduce more than 99% of the adhesion of L929 cells and the adsorption of fibrinogen. The ultrathin (tens of nanometers) and smooth PG/PEG coating was easily deposited onto a wide variety of biomaterials, and the deposition was robust enough to survive harsh sterilization conditions. Furthermore, the coating was highly transparent and allowed most of the UV and Vis light to pass through. The technique has great potential to be applied to biomedical devices that need a transparent antifouling coating, such as intraocular lenses and biosensors.

Reducing Emitter Clogging in Drip Fertigation Systems by Magnetization Technology

The issue of emitter clogging is a common phenomenon in drip fertigation systems, which causes uneven irrigation and fertilization. However, efficient and environmentally friendly methods are scarcely available for alleviating clogging. In the present study, we investigated the anti-fouling efficacy of three magnetic field strength levels (0, 0.4 T and 0.6 T) on emitter clogging in drip fertigation systems. Our results show that magnetized water treatment could effectively relieve emitter clogging and delay the occurrence time of clogging, which increased the average discharge variation rate (Dra) by 37.00–61.64% and decreased the dry weight (DW) by 53.00–69.29% compared with non-magnetized water treatments. X-rays were used to estimate the compositions of the main clogging substances, and the results show that phosphates were the dominant substances that induced emitter clogging. In addition, magnetized water treatment effectively reduced the contents of chemical and particulate fouling, as exhibited by a decrease in phosphates, silicate and quartz by 53.17–69.58%, 47.22–61.95% and 43.18–74.80%, respectively. In comparison, the higher strength of magnetized water treatment (0.6 T) was better in clogging control, which increased Dra and the Christiansen of uniformity (CU) by 24.64% and 43.96%, respectively, and the DW was reduced by 34.67% compared with that of 0.4 T. This study proves that magnetized water treatment is an effective, chemical-free treatment method with great potential for fouling control technology, and it is helpful for the further promotion of drip fertigation technology.

Antifouling graphene oxide membranes for oil-water separation via hydrophobic chain engineering

Engineering surface chemistry to precisely control interfacial interactions is crucial for fabricating superior antifouling coatings and separation membranes. Here, we present a hydrophobic chain engineering strategy to regulate membrane surface at a molecular scale. Hydrophilic phytic acid and hydrophobic perfluorocarboxylic acids are sequentially assembled on a graphene oxide membrane to form an amphiphilic surface. The surface energy is reduced by the introduction of the perfluoroalkyl chains while the surface hydration can be tuned by changing the hydrophobic chain length, thus synergistically optimizing both fouling-resistance and fouling-release properties. It is found that the surface hydration capacity changes nonlinearly as the perfluoroalkyl chain length increases from C4 to C10, reaching the highest at C6 as a result of the more uniform water orientation as demonstrated by molecular dynamics simulations. The as-prepared membrane exhibits superior antifouling efficacy (flux decline ratio <10%, flux recovery ratio ~100%) even at high permeance (~620 L m−2 h−1 bar−1) for oil-water separation.

The antifouling efficacy of crude extracts isolated from mollusc species (Paratapes textilis)

Mollusca represent the second-largest animal phylum in the marine realm. In the present study, antifouling activity of different extracts isolated from Mollusc species Paratapes textilis was investigated. The shell acid insoluble matrix (SAIM), crude meat extract (CME), protein extract of mussel meat (PME), lipid extract of mussel meat (LME), and carbohydrates extract of mussel meat (GME) were added by small amounts (2% w/w) to the marine paint formulations. These marine paint formulations was immersed in the Eastern Harbor for 199 days beside the negative control (paint composition without any active materials) and commercial marine paint SIPES as positive control. The results showed that the prepared antifouling paint formulations could resist algal formations on coated panels. The best result was obtained for steel panel coated with the paint formulation containing CME as it showed less than 5% of fouling organisms at the end of study period (199 days). On GC-MS spectrum, CME revealed three major compounds of 47 components, 15-methyltricyclo[6.5.2(13,14).0(7,15)]pentadeca-1,3,5,7,9,11,13-heptene, 1,4-benzenediol,2-(1,1-dimethylethyl)-5-(2-propenyl)-, and 3,4-dihydro-2H-1,5-(3″-T-butyl)benzodioxepine, accounting for 16.1% of total extract composition. The slightly increase of fouling organisms on steel panels coated with other paint formulations ranged from 10% (GME) to 50% (SAIM and PME) compared to negative control (55%) and positive control (97%) after 199 days of panels immersion. Therefore, CME showed effective results against fouling organisms after 199 days of panels immersion in the Eastern Harbor compared to positive control based on ANOVA analysis despite the eutrophic condition observed in this area.

Posidonia oceanica (L.) (Delile, 1813) extracts as a potential booster biocide in fouling-release coatings.

Since the banning of tributyltin, the addition of inorganic (metal oxides) and organic (pesticides, herbicides) biocides in antifouling paint has represented an unavoidable step to counteract biofouling and the resulting biodeterioration of submerged surfaces. Therefore, the development of new methods that balance antifouling efficacy with environmental impact has become a topic of great importance. Among several proposed strategies, natural extracts may represent one of the most suitable alternatives to the widely used toxic biocides. Posidonia oceanica is one of the most representative organisms of the Mediterranean Sea and contains hundreds of bioactive compounds. In this study, we prepared, characterized, and assessed a hydroalcoholic extract of P. oceanica and then compared it to three model species. Together, these four species belong to relevant groups of biofoulers: bacteria (Aliivibrio fischeri), diatoms (Phaeodactylum tricornutum), and serpulid polychaetes (Ficopomatus enigmaticus). We also added the same P. oceanica extract to a PDMS-based coating formula. We tested this coating agent with Navicula salinicola and Ficopomatus enigmaticus to evaluate both its biocidal performance and its antifouling properties. Our results indicate that our P. oceanica extract provides suitable levels of protection against all the tested organisms and significantly reduces adhesion of N. salinicola cells and facilitates their release in low-intensity waterflows.

4-Year in-situ assessment of a photocatalytic TiO2/SiO2 antifouling treatment for historic mortar in a coastal city

This manuscript presents a 4 years in-situ evaluation of TiO2/SiO2-based product applied to a mortar seating belonging to the bleachers of the Cadiz Roman Theatre, affected by biofouling and organic deposits. Antifouling performance was studied by colorimetric measurements and ATP analyses. Surface sampling was performed for biofouling identification, being remarkable the presence of filamentous fungi and cyanobacteria. Additionally, antifouling performance was checked during a 4 years in-situ monitoring study. SEM observations, carried out 4 years after the product application, demonstrate that the TiO2 integration in a SiO2 matrix produces a durable coating which allows for prolongation of the antifouling performance over time. According to the results obtained, 4 years after the application of the treatment, the treated area still maintains its antifouling efficacy, exhibiting a 40% reduction in organic deposit and 61% inhibition of biological growth compared to the untreated area. The results of this study show that the application of the SiO2/TiO2-based product may potentially reduce the costs of cleaning and maintenance works. At the same time, it is considered that the antifouling efficacy is more pronounced during the first two years and could be taken into account in the maintenance and re-application actions.

An internal electrostatic force-driven superoleophilic membrane-magnetic nanoparticles coupling system for superefficient water-in-oil emulsions separation

The inefficient separation of water-in-oil emulsions through conventional techniques and the troublesome membrane fouling of membrane technology call for alternative efficient and antifouling membrane separation approaches to meet the increasing demands for global environmental protection and energy recovery. Here, we demonstrate an internal electrostatic force-driven superoleophilic membrane-magnetic particles coupling system enabling water-in-oil emulsions super-efficiently separated. Specifically, as-prepared magnetic nanoparticles significantly facilitate the separation of water-in-oil emulsions due to their superoleophilic behaviors and electrostatic repulsion forces between the magnetic nanoparticles-encapsulated Pickering emulsions. Furthermore, the magnetic nanoparticles incorporate into the membrane to increase the roughness and superoleophilic ability, distinctly leading to superefficient separation capacity for water-in-oil emulsions. Meanwhile, their separation performances are so stable that remarkably outperform other membrane systems during 10-cycle operation owing to the enhanced antifouling efficacy, under the support of electrostatic repulsion forces caused by the magnetic nanoparticles-modified composite membrane and magnetic nanoparticles-encapsulated Pickering emulsions. Hence, the combination of the electrostatic repulsion forces and interfacial forces render the as-constructed superoleophilic membrane-magnetic nanoparticles coupling system dramatically exhibit a remarkably high separation flux of 8.76 × 104 L m−2 h−1 bar−1 for the water-in-toluene emulsion under the conditions of pH of 10 and sodium dodecyl sulfate surfactant, considerably higher than the existing reports of the state-of-the-art membranes. This study will open up new avenues for superefficient and stable separation of water-in-oil emulsions in actual situations, and this concept will be promising for extending to other oil-in-water emulsions and oily waste water treatment.

Chitosan-Based Materials Featuring Multiscale Anisotropy for Wider Tissue Engineering Applications.

We designed graphene oxide composites with increased morphological and structural variability using fatty acid-coupled polysaccharide co-polymer as the continuous phase. The matrix was synthesized by N, O-acylation of chitosan with palmitic and lauric acid. The obtained co-polymer was crosslinked with genipin and composited with graphene oxide. FTIR spectra highlighted the modification and multi-components interaction. DLS, SEM, and contact angle tests demonstrated that the conjugation of hydrophobic molecules to chitosan increased surface roughness and hydrophilicity, since it triggered a core-shell macromolecular structuration. Nanoindentation revealed a notable durotaxis gradient due to chitosan/fatty acid self-organization and graphene sheet embedment. The composited building blocks with graphene oxide were more stable during in vitro enzymatic degradation tests and swelled less. In vitro viability, cytotoxicity, and inflammatory response tests yielded promising results, and the protein adsorption test demonstrated potential antifouling efficacy. The robust and stable substrates with heterogeneous architecture we developed show promise in biomedical applications.

Sea-trial research on natural product-based antifouling paint applied to different underwater sensor housing materials

Biofouling is a common challenge for underwater sensors, especially for long-term in situ monitoring in marine environments. In this study, we assessed the antifouling efficacy of a paint containing a natural product camptothecin (CPT) on six materials (316 L stainless steel, TC4 titanium alloy, 7075 aluminum alloy, polyoxymethylene, polyvinyl chloride, and Teflon), which are frequently used in the construction of underwater sensor housings. Additionally, a buoy-based sea-trial was performed to test the antifouling performance of the CPT-based paint on housings of three in situ sensors used for practical seawater monitoring applications, namely a spectrophotometer for chemical oxygen demand (COD) measurements and two fluorimeters for biochemical oxygen demand (BOD) and chlorophyll a (Chl a) concentration measurements. The results showed significantly lower macrofouling coverage on the areas painted with the CPT-based paint compared to the unpainted areas for each tested material over 9 months of seawater immersion. The CPT-based paint exhibited different antifouling performance for the different materials; in particular, it exhibited better antifouling performance on the plastic materials compared to the metal materials. Furthermore, when applied on submersible sensor housings in the sea-trial test, the CPT-based paint kept the housings of the COD sensor and the Chl a sensor clean for over 4 months. In addition, the paint prevented fouling of the BOD sensor housing even after 6 months of seawater immersion. Thus, our results suggest that the CPT-based paint could be used as a potential solution to control the biofouling of sensor housings for long-term in situ applications in marine environments.

Mussel-inspired polymeric coatings with the antifouling efficacy controlled by topologies.

Block copolymers with different topologies (linear, loop, 3-armed and 4-armed polymers) containing poly(N-vinylpyrrrolidone) (PVP) antifouling blocks and terminal poly(dopamine-acrylamide) (PDAA) anchoring blocks were synthesized. These polymers can form a robust antifouling nanolayer on various surfaces. The morphologies of the polymer-modified surfaces are strongly dependent on the topologies of the polymers: with the increase of arm numbers, the morphology evolves from the smooth surface to the nanoscale coarse surface. As a result, the hydrophilicity of the coatings increases with the increase of degree of nanoscale roughness, and the 4-armed block copolymer forms a superhydrophilic surface with a water contact angle (WCA) as low as 8.7°. Accordingly, the linear diblock copolymer exhibits the worst antifouling efficiency, while the 4-armed polymer exhibits the best antifouling efficiency. This is the first example systematically showing that the antifouling efficacy could be adjusted simply by the topology of the coatings. Cell viability studies revealed that all of the copolymers exhibit excellent cytocompatibility. These biocompatible polymers with narrowly distributed molecular weight might find niches for antifouling applications in various areas such as anti-protein absorption, anti-bacterial and anti-marine fouling.