Biofouling Resistance Research Articles

Chlorine-resistant and dual anti-biofouling reverse osmosis membranes with zwitterionic and quaternary ammonium copolymers via mussel-inspired one-step codeposition

Reverse osmosis (RO) membrane technology encounters challenges such as membrane biofouling and oxidation during practical use, which significantly hinders its further development and application. To improve the chlorine and biofouling resistance of RO membrane, we suggest a method that modifies the mass ratios of zwitterionic and quaternary ammonium copolymers in the mussel-inspired coating layer. This method successfully controls the hydrophilicity and positive charge of the membrane surface, enhancing its overall performance. The plate counting results indicate that the bacterial killing efficiency of the blended modified TFC membrane (50:50) against E. coli and S. aureus is ≥98 %. Thanks to the combined effects of the anti-adhesion zwitterionic copolymer and the antibacterial quaternary ammonium copolymer, the blended modified TFC membrane (50:50) demonstrates superior anti-biofouling performance in dynamic biofouling tests. Furthermore, the desalination performance of the blending modified TFC membrane (50:50) remains stable after long-term exposure to 60,000 ppm·h of active chlorine, while the desalination performance of the pristine TFC membrane significantly declines. In conclusion, our advancements in chlorine-tolerant and anti-biofouling RO membranes could enhance the reliability of RO technology.

Control of membrane biofouling in MBR for wastewater treatment by biohybrid membrane with superhydrophilic self-QQ function

Quorum quenching (QQ) is an effective method for controlling MBR (membrane bioreactor) membrane biofouling by regulating the release of autoinducer during the quorum sensing (QS) process. However, the addition of QQ bacteria solution or QQ carriers inevitably leads to unpredictable effects on MBR microbial systems and operational efficiency (for example, reduced stability of nitrification and denitrification processes, reduced biodegradation efficiency and unbalanced biofilm formation etc.). Here, we present a biohybrid membrane called ES-BM (electrospinning-biohybrid membrane), which features a unique pore size structure consisting of electrospun superhydrophilic nanofiber sheaths, a self-QQ layer (active QQ bacteria are immobilized within the interlayer structure of this biohybrid membrane to inhibit the QS process of biofilm-forming associated bacteria at the source surface where membrane biofouling occurs), and a basement filter layer, which maintain the activity of QQ bacteria for an extended period. The ES-BM extends operational cycles up to 21 days at a constant flux of 24 L/m²/h, which is three times longer than conventional MBR systems. The membrane exhibits exceptional hydrophilicity (water contact angle of approximately 0° within 2 seconds) and high tensile strength (Young’s modulus of 135 MPa). Long-term bioactivity tests confirm the stability and recyclability of the ES-BM. Additionally, microbial community analysis suggests that the biohybrid membrane suppresses the growth of biofilm-related bacteria without significantly affecting the indigenous microbial population, further enhancing system performance. This work demonstrates the potential of ES-BM for improving MBR biofouling resistance and presents insights into scalable electrospinning fabrication techniques.

Visible-light-activated Fe2O3–TiO2 nanoparticles enhance biofouling resistance of polyethersulfone ultrafiltration membranes against marine algae Chlorella vulgaris

This study investigated the modification of polyethersulfone (PES) ultrafiltration membranes with TiO2 and Fe2O3–TiO2 nanoparticles to enhance their hydrophilicity and biofouling resistance against the marine microalgae Chlorella vulgaris. It is a common freshwater and marine microalga that readily forms biofilms on membrane surfaces, leading to significant flux decline and increased operational costs in ultrafiltration processes. The microalgae cells and their extracellular polymeric substances (EPS) adhere to the membrane surface, creating a dense fouling layer that impedes water permeation. The modified membranes were characterized using contact angle measurements, scanning electron microscopy, and pure water flux/resistance tests. Short-term ultrafiltration experiments evaluated the membranes’ antifouling performance by measuring flux decline, flux recovery ratio, and relative flux reduction during C. vulgaris filtration. The TiO2 membrane showed improved hydrophilicity and antifouling over the pristine PES membrane, while the Fe2O3–TiO2 nanocomposite membrane exhibited the best performance. It reduced the water contact angle and showed only a 5% relative flux reduction compared to 60% for the pristine membrane. SEM images confirmed reduced microalgal deposition on the nanocomposite surface. Long-term tests with microalgal cells under dark and visible light conditions in saline water further assessed the membranes’ biofouling resistance. The Fe2O3–TiO2 membrane maintained 59 L/m2 h water flux under visible light after immersion in the microalgal solution, outperforming the pristine (38 L/m2 h) and TiO2 (52 L/m2 h) membranes. This superior antifouling was attributed to photocatalytic generation of reactive oxygen species inhibiting microalgal adhesion. This study demonstrates a promising strategy for mitigating biofouling in membrane-based water treatment and desalination processes.

A bio-inspired liquid-like smooth copolymer coating with superior biofouling resistance and drag reduction

The marine biofouling and fluid resistance have a detrimental impact on underwater vehicles. It is essential to develop functional material integrated with both antifouling and drag reduction effects for maritime transportation and navigation. Herein, to avoid the disadvantages of common slippery liquid-infused surfaces, such as the complexity of preparation micro/nanopores and the depletion of the lubricant layer, the novel liquid-like coating was fabricated by integrating the synthesized long chain organosilicon monomer (HPSM) to the self-polishing polymer chains. It is that the ingenious design integrated anti-fouling and drag reduction functions. The surface composition and structure, mechanical properties, antifouling and drag reduction properties of the coating were characterized by FT-IR, XPS, SEM, μ-PIV. These results indicated that the unique monomer HPSM endowed the coating with unique liquid-like properties, including special wettability, viscoelasticity and extremely low roughness. The flexibility of HPSM promoted the self-adaption ability of the coating in the seawater environment, which can effectively either reduce the fluid resistance when the fluid flowed through the surface or the adhesion strength of the biofouling, such as lots of protein (BSA) and alga (Porphyridium sp.and Navicula sp.). Moreover, the synergistic effect between liquid-like properties and the interface renewal behavior of self-polishing components further strengthened the antifouling performance of the coating. The marine field test further indicated the comprehensive anti-fouling performance and mechanical stability of the coating in practical application scenarios. This research provided a facile approach for preparing antifouling and drag-reduction coating. Therefore, it was believed to be a great inspiration for the design of functional coating against biofouling and drag reduction in the ship and marine industry field.

Tuning interfacial molecular asymmetry to engineer protective coatings with superior surface anchoring, antifouling and antibacterial properties

Multifunctional robust protective coatings that combine biocompatibility, antifouling and antimicrobial properties play an essential role in reducing host reactions and infection on invasive medical devices. However, developing these protective coatings generally faces a paradox: coating materials capable of achieving robust adhesion to substrates via spontaneous deposition inevitably initiate continuous biofoulant adsorption, while those employing strong hydration capability to resist biofoulant attachment have limited substrate binding ability and durability under wear. Herein, we designed a multifunctional terpolymer of poly(dopamine methyacrylamide-co-2-methacryloyloxyethyl phoasphorylcholine-co-2-(dimethylamino)-ethyl methacrylate) (P(DMA-co-MPC-co-DMAEMA)), which integrates desired yet traditionally incompatible functions (i.e., robust adhesion, antifouling, lubrication, and antimicrobial properties). Direct normal and lateral force measurements, dynamic adsorption tests, surface ion conductance mapping were applied to comprehensively investigate the nanomechanics of coating-biofloulant interactions. Catechol groups of DMA act as basal anchors for robust substrate deposition, while the highly hydrated zwitterion of MPC provides apical protection to resist biofouling and wear. Moreover, the antimicrobial property is conferred through the protonation of tertiary amine groups on DMAEMA, inhibiting infection under physiological conditions. This work provides an effective strategy for harmonizing demanded yet incompatible properties in one coating material, with significant implications for the development of multifunctional surfaces towards the advancement of invasive biomedical devices. Statement of significanceMultifunctional robust protective coatings have been widely utilized in invasive medical devices to mitigate host responses and infection. However, modified surface coatings often encounter a trade-off between robust adhesion to substrates and strong hydration capability for antifouling and antimicrobial properties. We propose a universal strategy for surface modification by dopamine-assisted co-deposition with a multifunctional terpolymer of P(DMA-co-MPC-co-DMAEMA) that simultaneously achieves robust adhesion, antifouling, and antimicrobial properties. Through elucidating the nanomechanics with fundamentally understanding the interactions between the coating and biomacromolecules, we highlight the role of DMA for substrate adhesion, MPC for biofouling resistance, and DMAEMA for antimicrobial activity. This approach presents a promising strategy for constructing multifunctional coatings on minimally invasive medical devices by tuning interfacial molecular asymmetricity to reconcile incompatible properties within one coating.

Electroless Deposition for Robust and Uniform Copper Nanoparticles on Electrospun Polyacrylonitrile (PAN) Microfiltration Membranes.

Filtration membranes coated in metals such as copper have dramatically improved biofouling resistance and pathogen destruction. However, existing coating methods on polymer membranes impair membrane performance, lack uniformity, and may detach from their substrate, thus contaminating the permeate. To solve these challenges, we developed the first electroless deposition protocol to immobilize copper nanoparticles on electrospun polyacrylonitrile (PAN) fibers for the design of antimicrobial membranes. The deposition was facilitated by prior silver seeding. Distinct mats with average fiber diameters of 232 ± 36 nm, 727 ± 148 nm and 1017 ± 80 nm were evaluated for filtration performance. Well-dispersed copper nanoparticles were conformal to the fibers, preserving the open-cell architecture of the membranes. The copper particle sizes ranged from 20 to 140 nm. Infrared spectroscopy revealed the PAN fiber mats' relative chemical stability/resistance to the copper metallization process. In addition, the classical cyclization of the cyano functional group in PAN was observed. For model polystyrene beads with average sizes of 3 μm, Cu NP-PAN fiber mats had high water flux and separation efficiency with negligible loss of Cu NP from the fibers during flow testing. Fiber size increased flux and somewhat decreased separation efficiency, though the efficiency values were still high.

Constructing 2D Polyphenols-Based Crosslinked Networks for Ultrafast and Selective Uranium Extraction from Seawater.

The role of tannins (TA), a well-known abundant and ecologically friendly chelating ligand, in metal capture has long been studied. Different kinds of TA-containing adsorbents are synthesized for uranium capture, while most adsorbents suffer from unfavorable adsorption kinetics. Herein, the design and preparation of a TA-containing 2D crosslinked network adsorbent (TANP) is reported. The ≈1.8-nanometer-thick TANP films curl up into micrometer-scale pores, which contribute to fast mass transfer and full exposure of active sites. The coordination environment of uranyl (UO2 2+) ions is explored by integrated analysis of U L3-edge XANES and EXAFS. Density functional theory calculations indicate the energetically favorable UO2 2+ binding. Consequently, TANP with excellent adsorption kinetics presents a high uranium capture capacity (14.62mg-Ug-Ads-1) and a high adsorption rate (0.97mgg-1day-1) together with excellent selectivity and biofouling resistance. Life cycle assessment and cost analysis demonstrate that TANP has tremendous potential for application in industrial-scale uranium extraction from seawater.

Effect of layered double hydroxide-graphene oxide modifier composition on characteristics of polyvinylidene fluoride based nanocomposite membranes in the separation of Cu2+

This research explored the modified polyvinylidene fluoride (PVDF) nanofiber membranes with a composite of layered double hydroxide (LDH) and graphene oxide (GO) to enhance biofouling resistance. The PVDF/LDH-GO nanocomposite membranes were synthesized via vacuum filtration. FTIR analysis confirmed nanocomposite formation with new peaks indicating the presence of GO and LDH. Variations in the LDH:GO ratio affected the physical, mechanical, and performance properties of the membranes. Based on SEM imaging, the 1:1 LDH: GO ratio exhibited the highest Young's modulus and smallest pore sizes. LDH-GO incorporation increased the mechanical strength, porosity, roughness, hydrophilicity, and pure water permeability of the PVDF membranes. The combination of these factors led to balanced permeability and selectivity values towards Cu2+ solution feeds. LDH-GO was proven effective in modifying the PVDF membrane surface for water treatment and inhibiting biofouling up to 64% against E. coli.

Unveiling Mechanistic Insight into Accelerating Oxygen Molecule Activation by Oxygen Defects in Co3O4-x/g-C3N4 p-n Heterojunction for Efficient Photo-Assisted Uranium Extraction from Seawater.

Photo-assisted uranium extraction from seawater (UES) is regarded as an efficient technique for uranium resource recovery, yet it currently faces many challenges, such as issues like biofouling resistance, low charge separation efficiency, slow carrier transfer, and a lack of active sites. Based on addressing the above challenges, a novel oxygen-deficient Co3O4-x/g-C3N4 p-n heterojunction is developed for efficient photo-assisted uranium extraction from seawater. Relying on the defect-coupling heterojunction synergistic effect, the redistribution of molecular charge density formed the built-in electric field as revealed by DFT calculations, significantly enhancing the separation efficiency of carriers and accelerating their migration rate. Notably, oxygen vacancies served as capture sites for oxygen, effectively promoting the generation of reactive oxygen species (ROS), thereby significantly improving the photo-assisted uranium extraction performance and antibacterial activity. Thus, under simulated sunlight irradiation with no sacrificial reagent added, Co3O4-x/g-C3N4 extracted a high uranium extraction amount of 1.08mgg-1 from 25 L of natural seawater after 7 days, which is superior to most reported carbon nitride-based photocatalysts. This study elaborates on the important role of surface defects and inerface engineering strategies in enhancing photocatalytic performance, providing a new approach to the development and design of uranium extraction material from seawater.

Electrodeposition of myristate based superhydrophobic coatings on steel with enhanced corrosion resistance and self-cleaning property

In recent decades, superhydrophobic (SHP) coatings have gained significant attention because of their versatile applications. Superhydrophobic coating is considered as a promising solution to combat corrosion and biofouling issues encountered by steel components in various industries. Using a one-step electrodeposition technique, a superhydrophobic coating with strong corrosion resistance and anti-biofouling property was fabricated on carbon steel in this work. With a water contact angle (WCA) of 170.3 ± 4.2° and a sliding angle (SA) of ∼1°, the wettability of the surface was optimized by varying the electrodeposition potential and deposition time. The as-developed superhydrophobic carbon steel surfaces were characterized by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), laser Raman spectroscopy (LRS), Energy dispersive X-ray (EDS) spectroscopy and X-ray diffraction (XRD). Employing field emission scanning electron microscopy (FESEM), the morphology of the superhydrophobic coatings was examined. Potentiodynamic polarization (PDP) technique was used to study the anti-corrosion property of SHP coating and bare sample in 3.5 wt% NaCl solution. The superhydrophobic coating was found to exhibit 99 % corrosion inhibition efficiency. In addition, the biofouling resistance of the coating was evaluated in both gram-negative and gram-positive bacterial cultures and compared with the uncoated sample. Total viability count (TVC) for the SHP coated samples was 5 orders less as compared to the uncoated sample exposed to gram-negative bacterial culture. Similarly, 4 orders reduction in TVC was estimated for the SHP coated sample as compared to the uncoated sample in gram-positive bacterial culture. The impact of superhydrophobic coating on the corrosion performance and biofouling properties of carbon steel was investigated along with the self-cleaning property and robustness of the coating.

Enzyme initiated in situ gelation as an oxygen-tolerant, high adhesive, and versatile strategy for hydrogel coating preparation

Hydrogel coatings have great potential for applications in antifouling, biomedical, and electronic fields, but the lack of preparation strategies with mild gel-forming conditions, high adhesion, and versatility hinders their widespread use. Herein, a method called glucose oxidase (GOD)-initiated in situ gelation (GOD-IIG) is developed for preparing hydrogel coatings. The procedure includes immobilizing Fe[Gly]2 and GOD on the surface of the substrates by forming an intermediate layer using epoxy resin, and then immersing the pre-treated substrates into a monomer solution to initiate polymerization. In situ gelation on the surface of the substrates is triggered by free radicals generated through the redox reaction between ferrous glycine (Fe[Gly]2) and hydrogen peroxide (H2O2) produced by the GOD-catalyzed glucose oxidation process, which can be carried out in open-air environments. Using the GOD-IIG method, hydrogel coatings constructed from common low-adhesive polymers displayed an adhesive strength of up to 686 kPa and stable underwater adhesion for at least 7 days. Moreover, this method shows controllable hydrogel thickness and recyclable monomer solution for at least 25 times at room temperature. It is also applicable to a variety of hydrogel structures and substrates, such as plastic, metal, and glass, regardless of flatness or geometry. In order to demonstrate the applications of hydrogel coatings prepared by GOD-IIG method, the lubrication and antifouling abilities of the coatings were assessed, and the results indicated that the coatings had good hydration lubrication as well as oil and biofouling resistance. This method holds promise for advancing the preparation of hydrogel coatings and has potential applications in the fields of electrical, biological, and environmental engineering.

Unveiling the microbial diversity of biofilms on titanium surfaces in full-scale water-cooling plants using metagenomics approach.

Microbial colonization on the titanium condenser material (TCM) used in the cooling system leads to biofouling and corrosion and influences the water supply. The primary investigation of the titanium condenser was infrequently studied on characterizing biofilm-forming bacterial communities. Different treatment methods like electropotential charge, ultrasonication, and copper coating of titanium condenser material may influence the microbial population over the surface of the titanium condensers. The present study aimed to catalog the primary colonizers and the effect of different treatment methods on the microbial community. CFU (1.7 × 109CFU/mL) and ATP count (< 5000 × 10-7 relative luminescence units) showed a minimal microbial population in copper-coated surface biofilm as compared with the other treatments. Live and dead cell result also showed consistency with colony count. The biofilm sample on the copper-coated surface showed an increased dead cell count and decreased live cells. In the metagenomic approach, the microbiome coverage was 10.06Mb in samples derived from copper-coated TCM than in other treated samples (electropotential charge-17.94Mb; ultrasonication-20.01Mb), including control (10.18Mb). Firmicutes preponderate the communities in the biofilm samples, and Proteobacteria stand next in the population in all the treated condenser materials. At the genus level, Lactobacillaceae and Azospirillaceae dominated the biofilm community. The metagenome data suggested that the attached community is different from those biofilm samples based on the environment that influences the bacterial community. The outcome of the present study depicts that copper coating was effective against biofouling and corrosion resistance of titanium condenser material for designing long-term durability.

Enhanced marine biofouling and corrosion resistance through springtails-inspired papillate-like micropillar arrays surface modified by antimicrobial peptide

Marine biological fouling has a serious impact on artificial facilities, and traditional antifouling coatings are not beneficial to green development, which lead to the urgent to develop green strategies that can effectively prevent fouling. In this study, an innovative confluence of physical and biological approaches was employed to mitigate the harm caused by biofouling on a material substrate. Firstly, a hierarchical microstructured morphology was prepared on an aluminum surface by reactive ion etching and characterised. The antibacterial peptide, A-2S, was surface modified with dopamine as a coupling agent to produce a physico-biological synergistic antifouling surface. X-ray photoelectron spectroscopy, fourier transform infrared spectroscopy, and electrochemical experiments were then used to analyse the binding effect and corrosion resistance performance. A-2S was successfully modified on the sample surface and exhibited good corrosion resistance with a corrosion inhibition efficiency of 86.57 %. Compared to a bare aluminum plate, the microstructure surface has a certain inhibitory effect on fouling organisms, and the antifouling performance decreases over time. In contrast, the antimicrobial peptide synergistic surfaces demonstrated superior durable antifouling performance. Compared with the 50 % of the antifouling performance on the microstructure surface, the synergistic surface has a unique contact point effect of the microstructure and excellent antibacterial and bactericidal properties of antimicrobial peptides, resulting in a surface antifouling performance of over 80 %. The synergistic modification method enhanced the corrosion resistance of the material and reduced the adhesion of fouling organisms, mitigating the harm caused by biofouling on the marine equipment substrate.

Superhydrophilic Photothermal-Responsive CuO@MXene Nanofibrous Membrane with Inherent Biofouling Resistance for Treating Complex Oily Wastewater.

MXene, a recently emerged 2D material, has garnered substantial attention for a myriad of applications. Despite the growing interest, there remains a noticeable gap in exploring MXene-based membranes for the simultaneous achievement of photomodulated oil/water separation, bacterial resistance, and the removal of pollutants in the treatment of oily wastewater. In this work, we have successfully synthesized a novel multifunctional CuO@MXene-PAN nanofibrous membrane (NFM) featuring unique nanograin-like structures. Benefitting from these unique structures, the resultant membrane shows excellent superwetting properties, significantly enhancing its performance in oil/water separation. In addition, the membrane's photothermal property boosts its permeance by 40% under visible light illumination within 30 min. Furthermore, the resultant membrane shows decent dye removal efficiency in an aqueous solution, e.g., Rhodamine B (RhB), promoting efficient degradation with high reusability under visible light. Most remarkably, the resultant membrane exhibits superior anti-biofouling capability and consistently resists the adhesion of microorganisms such as cyanobacteria over a 14 day period. Thus, the combined effect of superior superwetting properties, photothermal responsivity, photocatalytic activity, and the antibacterial effect in CuO@MXene-PAN NFM contributes to the efficient treatment of intricate oily wastewater. This synergistic combination of superior properties in the membrane could be an appealing strategy for the broad development of multifunctional materials to prevent fouling during actual separation performance.

Promising porous materials for uranium extraction from seawater

Uranium extraction from seawater is a promising approach for ensuring continued uranium fuel supply to the nuclear power industry. However, extracting uranium by this route is challenging due to the low concentration of uranium, high ionic strength, and marine micro-organisms in seawater. Recently, a range of novel porous adsorbent materials have been developed for uranium extraction from ocean water. These adsorbents rely on specific pore characteristics and functional groups (hydroxyl, carboxyl, amidoxime, phosphate, etc.) to achieve a high affinity and selectivity for uranyl ions (UO22+) relative to other ions. Relying strongly on coordination principles, specific binding sites for uranium are assembled in these porous materials, with cooperative actions of several functional groups often used to achieve strong uranium capture and adsorption selectivity. In addition to traditional adsorbents, adsorption-photocatalytic and adsorption-electrocatalytic materials are also being pursued, which include both specific adsorption sites and photocatalytic or electrocatalytic moieties in their frameworks. These innovative strategies allow the conversion of uranyl ions into harvestable solid products (such as UO2 or Na2O(UO3·H2O)x) and result in high extraction efficiencies together with good biofouling resistance. This perspective aims to capture some of the recent breakthroughs in the design of porous materials for selective uranium extraction from seawater.

Intrinsically Antifouling, soft and conformal bioelectronic from scalable fabrication of Thin-Film OECT arrays by zwitterionic polymers

Thin-film bioelectronic arrays, emerging as a new medical tool, offers significant opportunities for health monitoring, medical diagnosis, medical treatment, life science studies, etc. Thin film devices face several challenges, including biofouling which hinders targeted electrocoupling in complex biological environments, high surface Young's modulus that causes mechanical mismatches with biological matter, and poor surface adhesion that makes it difficult to conform to undeveloped biosurfaces. Here, we developed a universal lithography fabrication platform with high yield, uniformity, and precision to prepare a biomimetic thin-film organic electrochemical transistor (OECT) array featuring intrinsic biofouling resistance, tissue-like surface softness, and strong adhesion to undeveloped surfaces. This fabrication platform is based on the photolithography fabrication of zwitterionic-polymer-based conducting channels and hermetic encapsulation systems without compromising their electrical properties and low permeability. The all-zwitterionic feature softens the surface and helps prevent proteins and cells from approaching the encapsulation and channel surface, thus protecting the OECT array from interference from nonspecific protein and cell interactions. The strong capillary force from the hydrated zwitterions drives the thin-film device to conform well on nonplanar surfaces. Utilizing this biomimetic device, we successfully demonstrated cell-selective electrocoupling in the presence of white blood cells (WBCs) and simultaneously realized close and stable on-skin electrocardiogram (ECG) monitoring via good skin contact and robust epidermal surface lipid resistance. We envision that our process would provide a versatile platform for producing antifouling and flexible bioelectronic devices that seamlessly integrate with biological systems, and promote the practical application of thin-film bioelectronic arrays in real-life scenarios.

Designing a photocatalytic and self-renewed g-C3N4 nanosheet/poly-Schiff base composite coating towards long-term biofouling resistance.

Inhibiting the adhesion and growth of marine microorganisms through photocatalysis is a potentially efficient and environmentally friendly antifouling strategy. However, the undesired "shading effect" caused by resin coatings and microbial deposition reduces the utilization of the catalysts and leads to a failure in the antifouling active substance on the coating surface. Here, we successfully developed a composite coating (DPC-x) combining g-C3N4 nanosheet (g-C-NS) photocatalysts with degradable green poly-Schiff base resins, which integrates the dual functions of enhanced dynamic self-renewal and photocatalytic antibacterial activities towards long-term anti-biofouling. The controllable and complete degradability of the poly-Schiff base polymer chains and the self-renewal mechanism of the DPC-x coating exposed the internal g-C-NS, which provided a constant stream of photocatalytic reactive interfaces for 100% utilization and release of the photocatalysts. g-C-NS were homogeneously dispersed in the degradable resin coating, significantly enhancing and adjusting the self-renewal rate of the poly-Schiff base resin coating in visible light. The degradation reaction rate of DPC-0.2 (20 wt% g-C-NS) was 40 times that of DPC, thus improving the capabilities of surface self-renewal and fouling-release. Due to the synergistic antifouling mechanism of the efficient antibacterial properties and the enhanced degradation/self-renewal, the antimicrobial rates of DPC and DPC-0.2 were 94.58% and 99.31% in the dark, and 98.2% and 99.87% in visible light. DPC-x has excellent all-weather antimicrobial efficacy and could offer a new perspective on eco-friendly marine antifouling strategies.

Enhancing biofouling resistance in microfiltration membranes through capsaicin-derivative functionalization.

The primary focal point in the fabrication of microfiltration membranes revolves around mitigating issues of low permeability stemming from the initial design as well as countering biofouling tendencies. This work aimed to address these issues by synthesizing an antibacterial capsaicin derivative (CD), which was then grafted to the poly(vinylidene fluoride-co-chlorotrifluoroethylene)-g-polymethacrylic acid (P(VDF-CTFE)-g-PMAA) matrix polymer, resulting in an antibacterial polymer (PD). Notably, both CD and PD demonstrated low cytotoxicities. Utilizing PD, a microfiltration membrane (MA) was successfully prepared through non-solvent-induced phase inversion. The pore sizes of the MA membrane were mainly concentrated at around 436 nm, while the pure water flux of MA reached an impressive value of 62 ± 0.17 Lm-2 h-1 at 0.01 MPa. MA exhibited remarkable efficacy in eradicating both Gram-negative (E. coli) and Gram-positive bacteria (Bacillus subtilis) from its surface. Compared with M1 prepared from P(VDF-CTFE), MA exhibited a lower flux decay rate (41.00% vs. 76.03%) and a higher flux recovery rate (84.95% vs. 46.54%) after three cycles. Overall, this research represents a significant step towards the development of a microfiltration membrane with inherent stable anti-biofouling capability to enhance filtration.

Corrosion performance of wire arc additively manufactured NAB alloy

Nickel–aluminum bronzes (NAB) are vital alloys, known for biofouling resistance, crucial for marine and shipbuilding industries. This study examined corrosion performance of NAB samples fabricated by wire arc additive manufacturing (WAAM) in as-built and heat-treated conditions. Microstructural analysis revealed the WAAM-NAB parts primarily consisted of the α-phase (copper) and three types of κ-phases: κII (spherical Fe3Al), κIII (Ni–Al in lamellar shape) within the interdendritic areas, and iron-rich κIV particles dispersed throughout the matrix. In contrast, casting-produced NAB showed the formation of a rosette-like κI phase as well. Corrosion behavior comparisons between the two NAB fabrication methods were also assessed. The microstructural characterizations revealed a rise in the size of the κIV particles after heat-treated at 350 °C for 2 h (HT1). Heat treatment at 550 °C for 4 h (HT2) resulted in a needle-like κV, coarsening of κII, partial spheroidization of κIII, and reduced κIV precipitation. When heat-treated to 675 °C for 6 h (HT3), κII and κV were coarsened, κIII was completely spheroidized, and κIV precipitation was significantly reduced. These microstructural features in HT2 and HT3 conditions steeply decreased their corrosion resistance compared to the WAAM as-built part. The as-built WAAM sample showed superior corrosion resistance in chloride solution, attributed to fewer κ-intermetallic phases and a finer microstructure. The κ-phases, irrespective of morphology, act as the cathodic areas versus the α-dendritic matrix, fostering microgalvanic cell formation. Consequently, precipitation of all cathodic κ-phases draws a higher galvanic current of the anodic α-phase, meaning a lower corrosion resistance.

Acoustofluidics-Assisted Coating of Microparticles.

Microparticles have been applied in many areas, ranging from drug delivery, diagnostics, cosmetics, personal care, and the food industry to chemical and catalytic reactions, sensing, and environmental remediation. Coating further provides additional functionality to the microparticles, such as controlled release, surface modification, bio-fouling resistance, stability, protection, etc. In this study, the conformal coating of microparticles with a positively charged polyelectrolyte (polyallylamine hydrochloride, PAH) by utilizing an acoustofluidic microchip was proposed and demonstrated. The multiple laminar streams, including the PAH solution, were formed inside the microchannel, and, under the traveling surface acoustic wave, the microparticles traversed through the streams, where they were coated with PAH. The results showed that the coating of microparticles can be achieved in a rapid fashion via a microfluidic approach compared to that obtained by the batch method. Moreover, the zeta potentials of the microparticles coated via the microfluidic approach were more uniform. For the unfunctionalized microparticles, the charge reversal occurred after coating, and the zeta potential increased as the width of the microchannel or the concentration of the PAH solution increased. As for the carboxylate-conjugated microparticles, the charge reversal again occurred after coating; however, the magnitudes of the zeta potentials were similar when using the microchannels with different widths or different concentrations of PAH solution.