Diatom Adhesion Research Articles

Synergistic Effect of Multilayered Alginate/Poly(SBMA) Coatings on Marine Antifouling Property.

Alginate (Alg) coatings have attracted attention as protective layers on solid surfaces for marine antifouling applications due to their strong water binding capability and environmentally friendly characteristics. However, the effectiveness of Alg coatings in preventing marine fouling diminishes upon interaction with divalent cations present in seawater. To address this issue, post-modification of the Alg coating is conducted. The carboxyl groups of Alg, which are susceptible sites for interaction with divalent cations, are conjugated with polymerization initiators through metal-mediated coordination bond formation. Subsequently, poly(sulfobetaine methacrylate) (poly(SBMA)) brushes are grown from the initiator-immobilized Alg coatings, resulting in the formation of multilayered Alg/poly(SBMA) coatings. In marine diatom adhesion assays using Amphora Coffeaeformis, multilayered Alg/poly(SBMA) coatings exhibited superior antifouling performance compared to single-layered Alg or poly(SBMA) coating controls.

Amphiphilic Post‐Modification of Red Algae‐Derived Carrageenan Coatings for Balanced Marine Antifouling Applications

AbstractPolysaccharide coatings are of interest for marine antifouling applications because of their good marine antifouling properties and environmentally benign characteristics. However, the hydrophilic nature of polysaccharide coatings can lead to the adsorption of marine sediment, which can negatively impact their antifouling properties. Amphiphilic modification of polysaccharide coatings has been demonstrated to address these issues. In this study, we report a simple method for post‐modification of a sulfated polysaccharide carrageenan (CAR) coating to make it amphiphilic. A hydrophilic CAR coating is first formed on solid substrates, followed by grafting hydrophobic molecules onto the CAR‐coated surfaces through metal‐ion‐mediated coordinate bond formation. The resulting amphiphilic CAR coating effectively reduces both marine sediment (silt) adsorption and marine diatom adhesion, achieving a balanced marine antifouling performance.

Formation of Amphiphilic Zwitterionic Thin Poly(SBMA-co-TFEMA) Brushes on Solid Surfaces for Marine Antifouling Applications.

Water molecules can bind to zwitterionic polymers, such as carboxybetaine and sulfobetaine, forming strong hydration layers along the polymer chains. Such hydration layers act as a barrier to impede the attachment of marine fouling organisms; therefore, zwitterionic polymer coatings have been of considerable interest as marine antifouling coatings. However, recent studies have shown that severe adsorption of marine sediments occurs on zwitterionic-polymer-coated surfaces, resulting in the degradation of their marine antifouling performance. Therefore, a novel approach for forming amphiphilic zwitterionic polymers using zwitterionic and hydrophobic monomers is being investigated to simultaneously inhibit both sediment adsorption and marine fouling. In this study, amphiphilic zwitterionic thin polymer brushes composed of sulfobetaine methacrylate (SBMA) and trifluoroethyl methacrylate (TFEMA) were synthesized on Si/SiO2 surfaces via surface-initiated atom transfer radical polymerization. For this, a facile metal-ion-mediated method was developed for immobilizing polymerization initiators on solid substrates to subsequently form poly(SBMA-co-TFEMA) brushes on the initiator-coated substrate surface. Poly(SBMA-co-TFEMA) brushes with various SBMA/TFEMA ratios were prepared to determine the composition at which both marine diatom adhesion and sediment adsorption can be prevented effectively. The results indicate that poly(SBMA-co-TFEMA) brushes prepared with an SBMA/TFEMA ratio of 3:7 effectively inhibit both sediment adsorption and marine diatom adhesion, thereby exhibiting balanced marine antifouling properties. Thus, the findings of this study provide important insights into the design of amphiphilic marine antifouling materials.

Polydopamine‐Mediated, Amphiphilic Poly(Carboxybetaine Methacrylamide‐r‐Trifluoroethyl Methacrylate) Coating with Resistance to Marine Diatom Adhesion and Silt Adsorption

AbstractMarine biofouling–the adhesion of marine organisms onto a ship hull–causes increased fuel consumption, leading to massive carbon dioxide emissions. Many attempts are made to address this issue, and antifouling polymer coatings are extensively investigated owing to their environmental friendliness. Zwitterionic polymers, polysaccharides, and polyethylene glycol are frequently used as surface coatings, demonstrating excellent marine antifouling performance. However, these hydrophilic polymer coatings have a major drawback: when exposed to sediment, various minerals are easily adsorbed by the coatings, causing them to lose their inherent antifouling properties. Amphiphilic polymer coatings have therefore been proposed as alternatives to hydrophilic polymer coatings. In this study, the synthesis of amphiphilic copolymers composed of carboxybetaine methacrylamide and trifluoroethyl methacrylate and the immobilization of these copolymers onto solid surfaces are reported. This method utilizes material‐independent surface‐coating properties and the metal complex‐forming ability of polydopamine to immobilize amphiphilic copolymers onto solid surfaces. The resulting surfaces exhibit good antifouling performance against both diatom adhesion and silt adsorption. As this is a facile and substrate‐independent method for immobilizing polymers, an expectation exists for it to be an effective platform for the coating of new marine antifouling polymers.

Effects of incorporated silicone oils on the antifouling and drag reduction of Fe2O3/PDMS coatings

To develop an environmentally friendly fouling release coating, the effects of different silicone oils on the antifouling and drag reduction of the coating based polydimethylsiloxane (PDMS) reinforced iron oxide (Fe2O3) were investigated. The Fe2O3/PDMS coatings incorporated phenylmethyl silicone oil (PSO), methyl silicone oil (MSO), and a mixture of PSO and MSO were prepared. The surface morphology of the coating and the leaching rate of silicone oil were characterized by CLSM. The mechanical properties, anticorrosion, antifouling, and drag reduction performance of the coating were tested through the stress-strain curves, pull-out test, EIS, bacterial and diatom adhesion experiment, and single turntable torque experiment. Results revealed the leaching rate of PSO was the highest in the air. The hydrophobicity, the surface free energy, the multiple interlayer adhesion strength, the anticorrosion, the resistance to bacterial biofilms and Navicula tenera adhesion, and the drag reduction of the coating with PSO (IO-PSO) were better than those of the coating with MSO (IO-MSO). |Z|1 Hz for the coating IO-PSO immersed for 720 h can still reach the order of 1011 Ω cm2. The maximum drag reduction rate of the coating IO-PSO at 1600 rpm was 3.52 % compared to the epoxy coating.

Settlement behavior and mechanism of Navicula sp. on WLAP/PDMS composite coating under simulative diurnal alternation, constant light and dark conditions

Marine biological fouling is a persistent issue facing the marine industries, which not only causes damage to the underwater facilities but also results in substantial financial losses. Diatoms are one of the most harmful polluters in the ocean. In this paper, novel antifouling coatings inspired by fluorescent coral were reported. Waterproof long afterglow phosphors (WLAP) were introduced into the cross-linked network of polydimethylsiloxane (PDMS). WLAP can absorb and store light energy during the day and emit weak fluorescence at night, which affects the normal physiological activities of diatoms. Through the synergistic mechanism of low surface energy and fluorescence antifouling, excellent antifouling performance is achieved throughout the day. The settlement behavior of Navicula sp. on WLAP/PDMS composite coatings was studied under simulative diurnal alternation, continuous light, and dark conditions. The results demonstrated that the adhesion of diatoms on WLAP/PDMS composite coatings decreased significantly under simulative diurnal alternation. The inhibition effect of the sky-blue composite coating was the most obvious. The attachment reduction rate (ARR) was 35.4% compared with the blank control coating, and the diatom removal rate (DRR) after washing was 42.3%. Constant light conditions also affect the normal physiological activities of diatoms, while the feeble light of coatings is covered. In continuous dark condition, the antifouling abilities of coatings mainly depend on their low surface energy. The composite waterborne coatings prepared in this research is non-toxic and eco-friendly and can recycle solar energy, which supply a new direction for enhancing the static antifouling ability of coatings and an environmentally friendly antifouling strategy, and becomes an important step for sustainable development.

Anti-marine biofouling adhesion performance and mechanism of PDMS fouling-release coating containing PS-PEG hydrogel

Polystyrene microspheres compounded with polyethylene glycol–based hydrogel (PS-PEG)/polydimethylsiloxane (PDMS) coatings were prepared using the physical blending method. The chemical structure, surface and interface properties, interlayer adhesion, and tensile properties were tested in this paper. Furthermore, the antifouling performance was evaluated through bovine serum albumin fluorescent protein adsorption testing, marine bacteria adhesion testing, and benthic diatom adhesion testing. The results showed that the coating performance was best when 20 wt% PS-PEG hydrogel was added. Its surface energy was only 19.21 mJ/m2, the maximum breaking strength was 1.24 MPa, the maximum elongation rate was 675 %, the elastic modulus was 2.53 MPa, and the anti-stripping rate was 100 %. In addition, the coating with added 20 wt% PS-PEG hydrogel bacterial adherence rate was 5.36 % and 2.45 % after rinsing and washing, respectively, and the removal rate was 54.29 %. In the benthic diatom adhesion test, the chlorophyll concentration a-value was only 0.0017 mg/L after washing with added 20 wt% hydrogel, and the protein desorption rate was 84.19 % higher than PDMS in the fluorescent protein adsorption test. This coating has the ‘low adhesion’ and ‘desorption’ characteristics in the three growth stages of biofouling. Meanwhile, the low surface energy of the silicone is stable, and the hydrogel also dynamically migrates to the surface to gradually form a hydration layer, both are synergistic. When 20 wt% PS-PEG hydrogel was added, the coating demonstrated excellent antifouling performance due to its high hydration layer, low surface energy, high elasticity, and high interlayer adhesion. This research is expected to contribute to the practical applications of hydrogel coatings in marine antifouling.

The Effect of Conductive Polyaniline on the Anti-Fouling and Electromagnetic Properties of Polydimethylsiloxane Coatings.

In this paper, four conductive polyaniline powders doped in hydrochloric acid, sulfuric acid, phosphoric acid, and sulfonic acid were selected and blended with polydimethylsiloxane to prepare coatings with an electromagnetic absorption effect and fouling desorption effect, respectively. A UV spectrophotometer was used to evaluate the settling rate of the powders. Fourier transform infrared spectrometry, laser confocal microscopy, and scanning electron microscopy were used to observe the morphology and structure of the powder and the coating. The interface properties of the coatings were characterized using a contact angle measurement, the mechanical properties of the coatings using a tensile test, and the electromagnetic properties of the powders and microwave absorption properties of the coatings using vector network analyzers. Meanwhile, the antifouling performance of the coatings was evaluated via the marine bacteria adhesion test and benthic diatom adhesion test, and the effect of conductive polyaniline on the antifouling performance of the coating was analyzed. The results show that adding polyaniline reduced the surface energy of the coating and increased the roughness, mechanical properties and anti-fouling properties of the coating. Moreover, adding appropriate polyaniline powder can enhance the electromagnetic wave loss of the coating. The followings values were recorded for a hydrochloric-acid-doped polyaniline coating: lowest surface energy of 17.17 mJ/m2, maximum fracture strength of 0.95 MPa, maximum elongation of 155%, maximum bandwidth of 3.81 GHz, and peak of reflection loss of -23.15 dB. The bacterial detachment rate of the polydimethylsiloxane (PDMS) samples was only 30.37%. The bacterial adhesion rates of the composite coating containing hydrochloric-acid-doped polyaniline were 4.95% and 2.72% after rinsing and washing, respectively, and the desorption rate was 45.35%. The chlorophyll concentration values were 0.0057 mg/L and 0.0028 mg/L, respectively, and the desorption rate was 54.62%.

A silicone coating containing natural borneol fluorinated side chains with excellent static antifouling properties

Nowadays, the development of sustainable nontoxic antifouling coatings is urgent. In this work, the isobornyl as antifouling groups and dodecfluoroheptyl were introduced into the silicone side chains to prepare the environment-friendly silicone antifouling coatings. The synergistic effect of natural borneol and dodecfluoroheptyl improved the static antifouling ability of silicone coating. The coatings exhibited good optical clarity (>92%, 400–800 nm), high adhesion (>2 MPa, steel plates) and excellent fouling release and self-cleaning ability. For example, PDMS-F-PIBO-23 coating had excellent antibacterial and antifouling activities. It’s antibacterial resistance to marine bacteria (Pseudomonas sp.) reached 95.6%, which reduced the coverage area of biofilm by 86.9%, and effectively prevented the adhesion of diatoms. This remarkable antibacterial and antifouling performance was attributed to the complex molecular structure of natural non-toxic borneol and the enrichment of fluoropolymers. Field tests at Yellow Sea showed that the coating had good antifouling ability and could be used for >6 months. Most importantly, compared with traditional coatings containing toxic fungicides, the coating is less harmful to the marine ecological balance. This research provides more possibilities for marine antifouling coatings design and preparation which is expected to be applied in marine, medical and other antipollution fields.

Gliding toward new discoveries in diatom adhesion and motility.

Gliding toward new discoveries in diatom adhesion and motility.

Nanotechnology: the Alternative and Efficient Solution to Biofouling in the Aquaculture Industry.

Biofouling is a global issue in aquaculture industries. It adversely affects marine infrastructure (ship's hulls, mariculture cages and nets, underwater pipes and filters, building materials, probes, and sensor devices). The estimated cost of managing marine biofouling accounts for 5-10% of production cost. Non-toxic foul-release coating and biocide-based coating are the two current approaches. Recent innovation and development of a surface coating with nanoparticles such as photocatalytic zinc oxide nanocoating on fishing nets, copper oxide nanocoating on the water-cooling system, and silver nanoparticle coating to inhibit microalgal adhesion on submerged surfaces under natural light (photoperiod) could present meaningful anti-biofouling application. Nanocoating of zinc, copper, and silver oxide is an environmentally friendly surface coating strategy that avoid surface adhesion of bacteria, diatoms, algal, protozoans, and fungal species. Such nanocoating could also provide a solution to strains tolerant to Cu, Zn, and Ag. This draft of the special issue demonstrates the anti-biofouling potential of various metal and metal oxide nanoparticle coating to combat aquaculture industry biofouling problems.

Effect of Microwave-Assisted Curing on Properties of Waterborne Silicone Antifouling Coatings.

Waterborne silicone coatings are prepared in this paper by using silicone emulsion as a film-forming material, γ-methacryloxypropyltrimethoxysilane, and dibutyltin dilaurate as a curing agent and a catalyst, respectively. The corresponding coatings are obtained by controlling different microwave times to accelerate the coating curing. The surface morphology, roughness, surface properties, mechanical properties, and antifouling properties of the coating are studied by laser confocal microscope, contact angle measurement, tensile test, marine bacterial attachment test, and benthic diatom adhesion test. Additionally, the action mechanism of microwaves in the curing process of the coatings is also discussed. The results show that the microwave can greatly reduce the curing time of waterborne silicone coating. It can improve the painting efficiency, the surface roughness of the coating, and the mechanical properties of the coatings. The change in roughness increases the contact angle of the coating, reduces the apparent surface energy, and then improves the antifouling performance. For the coating cured by microwave, with the increase in microwave curing time, the water and diiodomethane contact angles of the coating gradually increase, and the surface energy gradually decreases from about 20 mJ/m2 to 10.8 mJ/m2. With the increase in microwave time, the attachment amount of Navicular Tenera gradually decreases, the removal rate gradually increases, and the removal rate of Navicular Tenera in the coating increases from 15.36% to 31.78%. The bacterial removal rate of the coating can be increases from 11.05% to 22.28% after microwave curing. Microwave-assisted curing is helpful in improving the antifouling and self-cleaning performance of waterborne silicone coatings, showing promising potential applications.

Silicone low surface energy antifouling coating modified by zwitterionic side chains with strong substrate adhesion

Silicone fouling release coatings were receiving increasing concern due to of their eco-friendly properties. However, their poor fouling resistance capability and mechanical properties limited the applications. Herein, we reported a type of silicone low surface energy coating with zwitterionic side chains and the carbamates group was introduced into the Si-O main chain. The carbamates groups and zwitterions provided strong substrate adhesion up to 2.0 MPa through hydrogen bond and ion interaction which also endowed the good mechanical properties higher than 6.0 MPa. The coating had a low surface energy less than 30 mJ·m−2, and exhibited good fouling release properties in the range of 0.3–0.5 MPa. Also, zwitterions gave the coating excellent fouling resistance properties. The bioassays showed that the anti-bacterial efficiency of PDMS-zPDEM-14 coating against Pseudomonas sp. was 94.86%, the coating could inhibit the formation of biofilm (the coverage area was only 13.64%) and effectively prevent the adhesion of diatoms (the density of adhered diatoms was 107 cells/mm2) This work had promising applications in low surface energy marine antifouling coating and interfaces of biomaterials.

Preparation and Properties of PED-TDI Polyurethane-Modified Silicone Coatings.

To explore the influence mechanisms of polyurethane soft segments on modified silicone coatings, a series of modified coatings was prepared by introducing different contents of hydroxypropyl-terminated polydimethylsiloxane (PDMS2200) into the soft segment of polyurethane. ATR-FTIR, NMR, CLSM, AFM, contact angle measurement, the tensile test, bacterial adhesion, and the benthic diatom adhesion test were used to investigate the structure, morphology, roughness, degree of microphase separation, surface energy, tensile properties, and antifouling properties of the modified coatings. The results show that PDMS2200 could aggravate the microphase separation of the modified coatings, increase the surface-free energy, and reduce its elastic modulus; when the microphase separation exceeded a certain degree, increasing PDMS2200 would decrease the tensile properties. The PED-TDI polyurethane-modified silicone coating prepared with the formula of PU-Si17 had the best tensile properties and antifouling properties among all modified coatings.

Cu@C core-shell nanoparticles modified polydimethylsiloxane -based coatings with improved static antifouling performance

PDMS-based fouling release coatings have promising applications in the fields of marine fouling control. However, development of silicone-based coatings with good antifouling / fouling-release property under relative static conditions remains challenging. In this work, a new PDMS-based nanocomposite coating consisting of PDMS matrix and nanofiller of copper@carbon core-shell nanoparticles was developed. Uniformly dispersed Cu@C core-shell in the PDMS matrix enhance the antifouling ability. The PDMS with low surface energy endows the composite coatings with hydrophobicity thus fouling release property. The introduction of Cu@C core-shell/PDMS improves both the Young's modulus, tensile strength and the elongation at break. Furthermore, laboratory bioassay against diatom adhesion and field tests indicated that the PDMS-based nanocomposite coatings with Cu@C core-shell exhibited outstanding antifouling / fouling-release property even under static conditions, showing promising application in marine antifouling.

Effect of Molecular Weights on Metal-Mediated Grafting of Sulfobetaine Polymers onto Solid Surfaces for Non-Biofouling Applications.

The grafting of zwitterionic molecules onto solid surfaces is an important tool for decreasing the unwanted adsorption of biomolecules, such as proteins, bacteria, and cells. This has been achieved through various approaches, such as zwitterionic monolayer/multilayer formation, surface-initiated polymerization of zwitterionic monomers, and grafting of presynthesized zwitterionic polymers. Recently, a coordination-driven approach to grafting zwitterionic polymers onto solid surfaces has been discovered to be an effective method because of its versatility and robustness. However, the bacterial adhesion resistance of zwitterionic polymer grafting has been explored using only one molecular weight, and the non-biofouling performance against other fouling organisms has remained unexamined. In this study, the characteristics of coordination-driven surface zwitteration are systematically investigated. Sulfobetaine (SB) polymers with three different molecular weights are synthesized and employed for surface grafting. Polydopamine is used as a surface primer, and SB polymers are grafted onto the surfaces via the formation of metal-mediated coordinate bonds. The effect of molecular weight on the grafting efficiency and non-biofouling performance is investigated via protein adsorption and marine diatom adhesion assays. The SB polymer with a high molecular weight is found to be crucial for achieving strong resistance to protein adsorption and marine fouling.

A switchable zwitterionic ester and capsaicin copolymer for multifunctional marine antibiofouling coating

In this work, a multifunctional marine antibiofouling coating was prepared by covalently grafting switchable zwitterionic ester and capsaicin copolymers onto the polydimethylsiloxane (PDMS) network in a one-pot reaction. Zwitterionic esters could kill bacteria via their positive charge and release dead bacterial cells after hydrolysis to antifouling zwitterionic moieties. Meanwhile, chemically conjugated capsaicin molecules could also be sustainedly released via hydrolyzation to repel marine organisms. Compared with the pristine PDMS matrix, the hydrolyzed coating reduced protein adhesion by 88.5%, bacterial adhesion by 99.0%, and diatom adhesion by 99.5%. The adhesion force of pseudo barnacles was reduced by 72.4%. Marine field tests in the Yellow Sea further confirmed that the coating possessed excellent antibiofouling ability for at least 261 days. This study presents a promising strategy for the development of eco-friendly high-efficiency marine antibiofouling coatings.

A facile hydrophilic modification strategy initiated by flame treatment of silicone coatings for marine antifouling application

Non-toxic poly(dimethylsiloxane) (PDMS) elastomer antifouling coatings are used to protect marine equipment from biofouling; however, the coatings cannot resist all fouling organisms. Hydrophilic modification is an effective way to enhance antifouling performances in PDMS but most modification methods are complex and inconvenient. In this work, flame treatment was used to replace other complex surface activation techniques, such as plasmas. The sulfobetaine silane and polyvinyl alcohol (PVA) modifications were developed for flame treatment. The sulfobetaine silane-modified flame-treated PDMS reduced diatom adhesion by 99.0% compared to untreated PDMS. The PVA modification involves a two-step spray process and is simpler than sulfobetaine silane modification. This strategy coats PVA on flame-treated PDMS through the crosslinking effect of boric acid on PVA, which reduced diatom adhesion by 86.6% in the lab and gave better antifouling performances in field tests compare to bare PDMS.

Spray Coating of 2‐ and 3‐D Solid Substrates Using a Sulfated Polysaccharide for Marine Antifouling Applications

AbstractMarine antifouling coating using functional polymers has emerged as an important tool to combat marine fouling. Owing to their natural abundance, polysaccharides represent a more sustainable option than synthetic polymers and carrageenan, a sulfated polysaccharide, is identified as a promising candidate for further research based on its excellent marine antifouling properties. However, existing research has only explored the application of carrageenan‐based coatings for 2D objects, using techniques such as spin‐coating. Here, a spray‐coating method is proposed to apply carrageenan‐based coatings to the surfaces of 2‐ and 3‐D objects. The coated surfaces exhibit high stability under various chemical/physical stresses and high resistance to protein adsorption and marine diatom adhesion.

Silicone Elastomer with Self-Generating Zwitterions for Antifouling Coatings.

Silicone elastomer-based fouling release coatings have been gaining increased attention in marine antibiofouling. However, the lack of fouling resistance limits their application. Introducing a zwitterionic polymer into silicone enhances its fouling resistance, but their incompatibility makes this challenging. In this work, a silicone elastomer with zwitterionic pendant chains has been prepared by grafting a telomer of tertiary carboxybetaine dodecafluoroheptyl ester ethyl acrylate (TCBF) and 3-mercaptopropyltriethoxysilane to the bis-silanol-terminated poly(dimethylsiloxane) (PDMS). The fluorocarbon groups drive the telomer onto the surface in the film formation process, while the TCBF groups hydrolyze and generate zwitterions on the surface, which is confirmed by attenuated total reflection infrared spectra analysis and water contact angle measurements. Bioassays using marine bacteria (Pseudomonas sp.) and diatoms (Navicula incerta) demonstrate that the antifouling efficacy is improved as the telomer content increases. The bacteria and diatom adhesion decreases by 95 and 81%, respectively, for the PDMS with 30 wt % telomer compared with the unmodified PDMS control. Meanwhile, the fouling release performance of PDMS is maintained with a pseudobarnacle removal strength of ∼0.1 MPa. This work provides a facile way to fabricate efficient silicone-based antifouling coatings.