Fur flutter in fluid flow fends off foulers

The fouling of submerged surfaces detrimentally alters stratum properties. Inorganic and organic foulers alike attach to and accumulate on surfaces when the complex interaction between numerous variables governing attachment and colonization is favourable. Unlike naturally evolved solutions, industrial methods of repellence carry adverse environmental impacts. Mammal fur demonstrates high resistance to fouling; however, our understanding of the intricacies of such performance remains limited. Here, we show that the passive trait of fur to dynamically respond to an external flow field dramatically improves its anti-fouling performance over that of fibres rigidly fixed at both ends. We have previously discovered a statistically significant correlation between a group of flow- and stratum-related properties, and the quantified anti-fouling performance of immobile filaments. In this work, we improve the correlation by considering an additional physical factor, the ability of hair to flex. Our work establishes a parametric framework for the design of passive anti-fouling filamentous structures and invites other disciplines to contribute to the investigation of the anti-fouling prowess of mammalian interfaces.

Removal of Free Liquid Layer from Liquid-Infused Catheters Reduces Silicone Loss into the Environment while Maintaining Adhesion Resistance

Silicone urinary catheters infused with silicone liquid offer an effective alternative to antibiotic coatings, reducing microbial adhesion while decreasing bladder colonization and systemic dissemination. However, loss of free silicone liquid from the surface into the host system is undesirable. To reduce the potential for liquid loss, free silicone liquid was removed from the surface of liquid-infused catheters by either removing excess liquid from fully infused samples or by partial infusion. The effect on bacterial and host protein adhesion was then assessed. Removing the free liquid from fully infused samples resulted in a ~64% decrease in liquid loss into the environment compared to controls, with no significant increase in deposition of the host protein fibrinogen or the adhesion of the common uropathogen Enterococcus faecalis. Partially infusing samples decreased liquid loss as total liquid content decreased, with samples infused to 70-80% of their maximum capacity showing a ~85% reduction in liquid loss compared to fully infused controls. Furthermore, samples above 70% infusion showed no significant increase in fibrinogen or E. faecalis adhesion. Together, the results suggest that eliminating free liquid layer, mechanically or through partial infusion, can reduce liquid loss from liquid-infused catheters while preserving functionality.

Anti-Fouling Properties of Phosphonium Ionic Liquid Coatings in the Marine Environment

Biofouling is the buildup of marine organisms on a submerged material. This research tests the efficacy of phosphonium ion gels comprising phosphonium monomers ([P444VB][AOT] and [P888VB][AOT]) and free ionic liquid ([P4448][AOT], [P88814][AOT]) (10 to 50 wt%), varying copper(II) oxide biocide concentrations (0 to 2 wt%), and the docusate anion [AOT]- for added hydrophobicity. The efficacy of these formulations was tested using a seachest simulator protected from light and tidal currents in New Zealand coastal waters over the summer and autumn periods. Anti-fouling performance was correlated with the hydrophobicity of the surface (water contact angle: 14-131°) and biocide concentration. Formulations with higher hydrophobicity (i.e., less free ionic liquid and longer alkyl chain substituents) displayed superior anti-fouling performance. The presence of the copper(II) biocide negatively affected anti-fouling performance via significant increases to hydrophilicity. No correlation was observed between antimicrobial activity and anti-fouling performance. Overall, phosphonium ion gels show potential for combining anti-fouling and foul release properties.

Efficacy of amorphous TiOx-coated surfaces against micro- and macrofouling through laboratory microcosms and field studies

In this study, Soda Lime Glass (SLG) and Stainless Steel (SS316L) substrata coated with Titanium oxide (TiOx) were tested for their efficacy in the laboratory microcosms and in field against micro- and macrofouling. Laboratory microcosm studies were conducted for five days using natural biofilms, single-species diatom (Navicula sp.), and bacterial biofilms, whereas field observations were conducted for 30 days. The TiOx-coating induced change in the mean contact angle of the substratum and rendered SS316L more hydrophilic and SLG hydrophobic, which influenced the Navicula sp. biofilm, and bacterial community structure of the biofilm. Overall, the TiOx-coated SS316L showed minimal microfouling, whereas non-coated SLG exhibited greater efficacy in deterring/preventing macrofouling organisms. Moreover, the reduction in macrofouling could be attributed to high abundance of Actinobacteria. Unraveling the mechanism of action needs future studies emphasizing biochemical processes and pathways.

A Wearable Electrochemical Sensor Based on Anti-Fouling and Self-Healing Polypeptide Complex Hydrogels for Sweat Monitoring

Although continuous monitoring of constituents in complex sweat is crucial for noninvasive physiological evaluation, biofouling on the sweat sensor surface and inadequate flexible self-healing materials restrict its applications. Herein, a fully self-healing and strong anti-biofouling polypeptide complex hydrogel (AuNPs/MoS2/Pep hydrogel) with excellent electrochemical performances was created. The anti-fouling electrochemical sweat sensor was fabricated based on the AuNPs/MoS2/Pep hydrogel to address these issues. It was found that the polypeptide hydrogel was designed to form a network structure and carried abundant hydrophilic groups, resulting in a AuNPs/MoS2/Pep hydrogel with superior anti-biofouling properties in sweat for 30 min and even long-term stability in undiluted human sweat. In addition, SEM, TEM, UV, XPS, and infrared spectrogram demonstrated that the binding force of π-π stacking force between MoS2 and naphthalene groups in the designed peptide endowed the polypeptide complex hydrogel with an excellent self-healing property. Furthermore, the polypeptide complex hydrogel preserved wearable device function of continuously monitoring uric acid (UA) and ascorbic acid (AA) in sweat in situ. This novel fabricated sweat sensor with high anti-biofouling ability, excellent self-healing property, and sensitive and selective analytical capability describes a new opportunity for health monitoring in situ.

Emerging evidence-based innovative approaches to control catheter-associated urinary tract infection: a review

Healthcare settings have dramatically advanced the latest medical devices, such as urinary catheters (UC) for infection, prevention, and control (IPC). The continuous or intermittent flow of a warm and conducive (urine) medium in the medical device, the urinary catheter, promotes the formation of biofilms and encrustations, thereby leading to the incidence of CAUTI. Additionally, the absence of an innate immune host response in and around the lumen of the catheter reduces microbial phagocytosis and drug action. Hence, the review comprehensively overviews the challenges posed by CAUTI and associated risks in patients' morbidity and mortality. Also, detailed, up-to-date information on the various strategies that blended/tailored the surface properties of UC to have anti-fouling, biocidal, and anti-adhesive properties to provide an outlook on how they can be better managed with futuristic solutions.

Passive-Cooling Building Coating with Efficient Cooling Performance and Excellent Superhydrophobicity

Passive-cooling building materials can achieve cooling without external energy consumption, which is an energy-saving and environmentally friendly cooling method. However, the existing passive-cooling building materials have the limitations of high cost, complicated processes, and a toxic organic solvent, which hinders the passive-cooling technology applied in practical building. To overcome these limitations, we developed a facile, high-efficiency, non-toxic, and superhydrophobic passive-cooling building coating (SPCBC) with an efficient cooling capability and excellent durability that was composed of polydimethylsiloxane and SiO2. The fabricated SPCBC demonstrated a high reflectance and a high emittance, showing a superior cooling capability with a 14 °C temperature drop compared with a bare cement surface on a hot summer day. In addition, the SPCBC could not be wetted or contaminated by muddy water, corrosive aqueous solutions, or dust, which presented an excellent anti-fouling and self-cleaning capability. Moreover, the fabricated SPCBC could work outdoors for 30 days, withstand UV irradiation for 30 days, and resist accelerated aging for 100 h without any significant changes in the superhydrophobicity and the cooling capability, meaning that the SPCBC had an outstanding durability. This work provides a new method to facilitate passive-cooling technology to apply in practical building in hot weather regions of the world.

Anti-Fouling Strategies of Electrochemical Sensors for Tumor Markers

The early detection and prognosis of cancers require sensitive and accurate detection methods; with developments in medicine, electrochemical biosensors have been developed that can meet these clinical needs. However, the composition of biological samples represented by serum is complex; when substances undergo non-specific adsorption to an electrode and cause fouling, the sensitivity and accuracy of the electrochemical sensor are affected. In order to reduce the effects of fouling on electrochemical sensors, a variety of anti-fouling materials and methods have been developed, and enormous progress has been made over the past few decades. Herein, the recent advances in anti-fouling materials and strategies for using electrochemical sensors for tumor markers are reviewed; we focus on new anti-fouling methods that separate the immunorecognition and signal readout platforms.

Wetting ridges on slippery liquid-infused porous surfaces

Slippery liquid-infused porous surfaces (SLIPS) show remarkable liquid repellency, making them useful for many coating applications. The outstanding repellency of SLIPS comes from a lubricant layer stabilized within and at the surface of a porous template. The stability of this lubricant layer is key for SLIPS to exhibit their unique functionality. The lubricant layer, however, is depleted over time, causing degradation of liquid repellency. The formation of wetting ridges surrounding liquid droplets on the surface of SLIPS is one of the primary sources of lubricant depletion. Here, we present the fundamental understanding and characteristics of wetting ridges and highlight the latest developments that enable the detailed investigation and suppression of wetting ridge formation on SLIPS. In addition, we offer our perspectives on new and exciting directions for SLIPS.

Enhanced Anti-Biofouling Properties of BWRO Membranes via the Deposition of Poly (Catechol/Polyamine) and Ag Nanoparticles

The surface modification of reverse osmosis (RO) membranes to improve their anti-biofouling properties is gaining increased attention. Here, we modified the polyamide brackish water reverse osmosis (BWRO) membrane via the biomimetic co-deposition of catechol (CA)/tetraethylenepentamine (TEPA) and in situ growth of Ag nanoparticles. Ag ions were reduced into Ag nanoparticles (AgNPs) without extraneous reducing agents. The hydrophilic property of the membrane was improved, and the zeta potential was also increased after the deposition of poly (catechol/polyamine) and AgNPs. Compared with the original RO membrane, the optimized PCPA3-Ag10 membrane showed a slight reduction in water flux, and the salt rejection declined, but enhanced anti-adhesion and anti-bacterial activities were observed. The FDR_t of the PCPA3-Ag10 membranes during the filtration of BSA, SA and DTAB solution were 5.63 ± 0.09%, 18.34 ± 0.33% and 34.12 ± 0.15%, respectively, much better than those of the original membrane. Moreover, the PCPA3-Ag10 membrane exhibited a 100% reduction in the number of viable bacteria (B. subtilis and E. coli) inoculated on the membrane. The stability of the AgNPs was also high enough, and these results verify the effectiveness of poly (catechol/polyamine) and the AgNP-based modification strategy for the control of fouling.

Durability and Additional Properties of Anodized Aluminum-Based Coatings with Different Wettability under Natural Conditions

The study aimed to test the durability of coatings under natural conditions. The present study focused on the changes in wettability and additional properties of the coatings under natural conditions. The specimens were subjected to outdoor exposure and additionally immersed in the pond. Impregnating porous anodized aluminum is a popular production method for hydrophobic and superhydrophobic surfaces. However, prolonged exposure of such coatings to natural conditions causes leaching of the impregnate and, thus, the loss of hydrophobic properties. After the loss of hydrophobic properties, all kinds of impurities and fouling adhere better to the porous structure. Additionally, deterioration of anti-icing and anti-corrosion properties was observed. Finally, the self-cleaning, anti-fouling, anti-icing and anti-corrosion properties were comparable or even worse to those of the hydrophilic coating. In the case of superhydrophobic specimens, during outdoor exposure there was no loss of superhydrophobicity, self-cleaning and anti-corrosion properties. Still, despite this, the icing delay time dropped. During outdoor exposure, the structure, which initially had anti-icing properties, may degrade. Nevertheless, the hierarchical structure responsible for the superhydrophobic effect can still be preserved. The superhydrophobic coating initially had the best anti-fouling properties. However, the coating was also gradually losing its superhydrophobic properties during water immersion.

Regulable Polyelectrolyte-Surfactant Complex for Antibacterial Biomedical Catheter Coating via a Readily Scalable Route

Constructing multifunctional surfaces is one of the practical approaches to address catheter-related multiple complications but is generally time-consuming and substrate-dependent. Herein, a novel anti-adhesion, antibacterial, low friction, and robustness coating on medical catheters are developed via a universal and readily scalable method based on a regulable polyelectrolyte surfactant complex. The complex is rapidly assembled in one step by electrostatic and hydrophobic interactions between organosilicon quaternary ammonium surfactant (N⁺ _Si ) and adjustable polyelectrolyte with cross-linkable, anti-adhesive, and anionic groups. The alcohol-soluble feature of the complex is conducive to the rapid formation of coatings on any medical device with arbitrary shapes via dip coating. Different from the conventional polyelectrolyte-surfactant complex coating, the regulated complex coating with nonleaching mode could be stable in harsh conditions (high concentration salt solution, organic reagents, etc.) because of the cross-linked structure while improving the biocompatibility and reducing the adhesion of various bacteria, proteins, and blood cells. The coated catheter exhibits good antibacterial infection in vitro and in vivo, owing to the synergistic effect of N⁺ _Si and zwitterionic groups. Therefore, the rationally designed complex supplies a facile coating approach for the potential development in combating multiple complications of the medical catheter.

Anodized Nanostructured 316L Stainless Steel Enhances Osteoblast Functions and Exhibits Anti-Fouling Properties

Poor osseointegration and infection are among the major challenges of 316L stainless steel (SS) implants in orthopedic applications. Surface modifications to obtain a nanostructured topography seem to be a promising method to enhance cellular interactions of 316L SS implants. In this study, arrays of nanodimples (NDs) having controlled feature sizes between 25 and 250 nm were obtained on 316L SS surfaces by anodic oxidation (anodization). Results demonstrated that the fabrication of NDs increased the surface area and, at the same time, altered the surface chemistry of 316L SS to provide chromium oxide- and hydroxide-rich surface oxide layers. In vitro experiments showed that ND surfaces promoted up to a 68% higher osteoblast viability on the fifth day of culture. Immunofluorescence images confirmed a well-spread cytoskeleton organization on the ND surfaces. In addition, higher alkaline phosphate activity and calcium mineral synthesis were observed on the ND surfaces compared to non-anodized 316L SS. Furthermore, a 71% reduction in Staphylococcus aureus (S. aureus) and a 58% reduction in Pseudomonas aeruginosa (P. aeruginosa) colonies were observed on the ND surfaces having a 200 nm feature size compared to non-anodized surfaces at 24 h of culture. Cumulatively, the results showed that a ND surface topography fabricated on 316L SS via anodization upregulated the osteoblast viability and functions while preventing S. aureus and P. aeruginosa biofilm synthesis.

Virtual Screening of a Library of Naturally Occurring Anthraquinones for Potential Anti-Fouling Agents

Marine biofouling is the undesired accumulation of organic molecules, microorganisms, macroalgae, marine invertebrates, and their by-products on submerged surfaces. It is a serious challenge for marine vessels and the oil, gas, and renewable energy industries, as biofouling can cause economic losses for these industries. Natural products have been an abundant source of therapeutics since the start of civilisation. Their use as novel anti-fouling agents is a promising approach for replacing currently used, harmful anti-fouling agents. Anthraquinones (AQs) have been used for centuries in the food, pharmaceutical, cosmetics, and paint industries. Citreorosein and emodin are typical additives used in the anti-fouling paint industry to help improve the global problem of biofouling. This study is based on our previous study, in which we presented the promising activity of structurally related anthraquinone compounds against biofilm-forming marine bacteria. To help uncover the anti-fouling potential of other AQ-related structures, 2194 compounds from the COCONUT natural products database were analysed. Molecular docking analysis was performed to assess the binding strength of these compounds to the LuxP protein in Vibrio carchariae. The LuxP protein is a vital binding protein responsible for the movements of autoinducers within the quorum sensing system; hence, interrupting the process at an early stage could be an effective strategy. Seventy-six AQ structures were found to be highly docked, and eight of these structures were used in structure-based pharmacophore modelling, resulting in six unique pharmacophore features.

Anti-Fouling and Anti-Biofilm Performance of Self-Polishing Waterborne Polyurethane with Gemini Quaternary Ammonium Salts

Biofilms are known to be difficult to eradicate and control, complicating human infections and marine biofouling. In this study, self-polishing and anti-fouling waterborne polyurethane coatings synthesized from gemini quaternary ammonium salts (GQAS), polyethylene glycol (PEG), and polycaprolactone diol (PCL) demonstrate excellent antibiofilm efficacy. Their anti-fouling and anti-biofilm performance was confirmed by a culture-based method in broth media, with the biofilm formation factor against Gram-positive (S. aureus) and Gram-negative bacterial strains (E. coli) for 2 days. The results indicate that polyurethane coatings have excellent anti-biofilm activity when the content of GQAS reached 8.5 wt% against S. aureus, and 15.8 wt% against E. coli. The resulting waterborne polyurethane coatings demonstrate both hydrolytic and enzymatic degradation, and the surface erosion enzymatic degradation mechanism enables them with good self-polishing capability. The extracts cyto-toxicity of these polyurethane coatings and degradation liquids was also systematically studied; they could be degraded to non-toxic or low toxic compositions. This study shows the possibility to achieve potent self-polishing and anti-biofilm efficacy by integrating antibacterial GQAS, PEG, and PCL into waterborne polyurethane coatings.

Separation Mechanisms and Anti-Fouling Properties of a Microporous Polyvinylidene Fluoride-Polyacrylic Acid-Graphene Oxide (PVDF-PAA-GO) Composite Membrane with Salt and Protein Solutions

This research demonstrates the preparation of composite membranes containing graphene oxide (GO) and investigates the separation mechanisms of various salts and bovine serum albumin (BSA) solutions. A microporous polyvinylidene fluoride-polyacrylic acid-GO (PVDF-PAA-GO) separation layer was fabricated on non-woven support. The GO-incorporating composite resulted in enlarged pore size (0.16 μm) compared with the control membrane (0.12 μm). The zeta potential of the GO composite was reduced to -31 from -19 mV. The resulting membranes with and without GO were examined for water permeability and rejection efficiency with single salt and BSA solutions. Using the non-woven/PVDF-PAA composite, the permeance values were 88-190 kg/m²hMPa, and the salt rejection coefficients were 9-28% for Na₂SO₄, MgCl₂, MgSO₄, and NaCl solutions. These salt removals were based on the Donnan exclusion mechanism considering the ion radii and membrane pore size. Incorporating GO into the separation layer exhibited limited impacts on the filtration of salt solutions, but significantly reduced BSA membrane adhesion and increased permeance. The negatively charged protein reached almost complete removal (98.4%) from the highly negatively charged GO-containing membrane. The GO additive improved the anti-fouling property of the composite membrane and enhanced BSA separation from the salt solution.

A New Reactor Concept for Single-Chamber Microbial Fuel Cells and Possible Anti-Fouling Strategies for Long-Term Operation

Microbial fuel cells are a promising technology for future wastewater treatment, as it allows cleaning and power generation simultaneously. The bottleneck of microbial fuel cells is often its cathodes because they determine the power output. Gas diffusion electrodes might overcome this bottleneck due to their low production costs and high oxygen reduction rates. However, biofilm formation on the gas diffusion electrodes reduces their performance over time. In this work, a new reactor design of the microbial fuel cell using rotating gas diffusion electrodes is presented. The biofilm growth on the electrode during operation was observed and its effect on the performance of the microbial fuel cell was examined. In addition, different antifouling strategies were investigated over a period of 80 days. It was found that already after 7 days of operation a complete biofilm had grown on an untreated gas diffusion electrode. However, this does not seem to affect the performance of the cells in the beginning. Differences in the performance of the reactors with and without an antifouling strategy only become apparent from day 15 onwards. The use of UV radiation and antibacterial membranes leads to the best results with maximum power densities of approx. 200 mW m^-2 while the untreated microbial fuel cell only achieves a maximum power density of approx. 20 mW m^-2.

Anti-Fouling, Adhesive Polyzwitterionic Hydrogel Electrodes Toughened Using a Tannic Acid Nanoflower

Conductive polyzwitterionic hydrogels with good adhesion properties show potential prospect in implantable electrodes and electronic devices. Adhesive property of polyzwitterionic hydrogels in humid environments can be improved by the introduction of catechol groups. However, common catechol modifiers can usually quench free radicals, resulting in a contradiction between long-term tissue adhesion and hydrogel toughness. By adding tannic acid (TA) to the dispersion of clay nanosheets and nanofibers, we designed TA-coated nanoflowers and nanofibers as the reinforcing phase to prepare polyzwitterionic hydrogels with adhesion properties. The hydrogel combines the mussel-like and zwitterionic co-adhesive mechanism to maintain long-term adhesion in underwater environments. In particular, the noncovalent cross-linking provided by the nanoflower structure effectively compensates for the defects caused by free-radical quenching so that the hydrogel obtained a high stretchability of over 2900% and a toughness of 1.16 J/m³. The hydrogel also has excellent anti-biofouling property and shows resistance to bacteria and cells. In addition, the hydrogel possesses a low modulus (<10 kPa) and ionic conductivity (0.25 S/m), making it an ideal material for the preparation of implantable electrodes.

Influence of coating type, colour, and deployment timing on biofouling by native and non-native species in a marine renewable energy context

Biofouling on marine renewable energy devices presents engineering challenges for this developing sector, and has implications for the spread of marine non-native species (NNS) in coastal waters. This is particularly true at sites with abundant energy resource, little existing infrastructure, and few established NNS. Device coatings, such as antifouling paints, could reduce the risk of NNS spread. Settlement on coatings of various types and colours, representing those likely to be used on renewable energy devices, was assessed in the Orkney Islands, northern Scotland. Assemblage composition, but not overall biofouling cover, varied initially among different coloured surfaces, although differences decreased over time. Different coating types (an anticorrosive paint, a biocidal paint and a fouling-release coating) differed in biofouling abundance and composition for the full duration of the experiment. NNS were mostly, but not completely, absent from antifouling surfaces. These results can help informing antifouling strategies for the marine renewable energy industry.

Effect of different factors on treatment of oily wastewater by TiO2/Al2O3-PVDF ultrafiltration membrane

An ultrafiltration membrane developed by our research group was applied to treat simulated emulsified oil wastewater. ATR-FTIR, SEM, TEM, and Zeta potential analyzes demonstrated that the modified ultrafiltration membrane (MM) has excellent stability and anti-fouling capacity than origin membrane (OM), which possesses a pure water flux of 260 L·m^-2·h^-1 and oil/water (o/w) rejection of 98.5 ± 0.33%. Inorganic salt CaCl₂ has more considerable influence than MgSO₄ and NaCl under the same mass concentration in the two membranes UF process. Along with concentration increasing, flux sharply reduces; meanwhile, the rejection has an opposite trend. Moreover, permeation flux has a maximum value, and the rejection also gets its optimal state under neutral conditions during the pH value of 2-12. The membrane also exhibits excellent anti-fouling performance and anti- o/w adsorption properties with an adsorption rate below 0.8% compared with OM, which has an adsorption rate of nearly 2.1%, respectively. A kind of new UF membrane developed by our research group was applied to treat simulated o/w. ATR-FTIR, SEM, TEM, and Zeta potential analyzes demonstrated that PVDF-Al₂O₃/TiO₂ material has excellent stability and anti-fouling capacity. CaCl₂ has the greatest influence than MgSO₄ and NaCl under the same mass concentration. Moreover, permeation flux has maximum value and the rejection also gets its optimal state under neutral conditions during pH 2-12. The membrane also exhibits excellent anti-fouling performance and anti-O/W adsorption properties with adsorption rate below 0.8% compared with OM which has an adsorption rate nearly 2.1%, respectively.

Rational Design of Durable Anti-fouling Coatings with High Transparency, Hardness, and Flexibility

Highly transparent, durable, flexible and smooth coatings with excellent anti-fouling properties have broad applications on cars, windows, and touch screens. However, the coexistence of these multi-functions is difficult to achieve in a single coating material. Here, a coating is developed with excellent performance of high transparency (98.8%), anti-fouling, high hardness (8H), and flexibility simultaneously (TAHF coating). In the material design, methyl etherified melamine formaldehyde resin, hexamethylene diisocyanate trimer, and mono-aminopropyl terminated polydimethylsiloxane (NH₂-PDMS) were used as a polymer matrix to provide surface hardness, a cross-linker was used to provide toughness, and omniphobic groups from NH₂-PDMS were used to provide anti-fouling performance. The TAHF coating has excellent liquid repellence even after six months of outdoor exposure, 260 h of UV light exposure, and 1500 wear and 2000 bending cycles, and its chemical shielding performance is superior to that of a commercial anti-corrosive coating. This strategy would provide a new route for the design of multifunctional anti-fouling coatings for practical applications.

Anti-Fouling Performance of Hydrophobic Hydrogels with Unique Surface Hydrophobicity and Nanoarchitectonics

Hydrogel is a kind of soft and wet matter, which demonstrates favorable fouling resistance owing to the hydration anti-adhesive surfaces. Different from conventional hydrogels constructed by hydrophilic or amphiphilic polymers, the recently invented “hydrophobic hydrogels” composed of hydrophobic polymers exhibit many unique properties, e.g., surface hydrophobicity and high water content, suggesting promising applications in anti-fouling. In this paper, a series of hydrophobic hydrogels were prepared with different chemical structures and water content for anti-fouling investigations. The hydrophobic hydrogels showed high static water contact angles (WCAs > 90°), indicating remarkable surface hydrophobicity, which is abnormal for conventional hydrogels. Compared with the conventional hydrogels, all the hydrophobic hydrogels exhibited less than 4% E. coli biofilm coverage, showing a contrary trend of anti-fouling ability to the water content inside the polymer. Typically, the poly(2-(2-ethoxyethoxy)ethyl acrylate) (PCBA) and poly(tetrahydrofurfuryl acrylate) (PTHFA) hydrogels with relatively high surface hydrophobicity showed as low as 5.1% and 2.4% E. coli biofilm coverage even after incubation for 7 days in bacteria suspension, which are about 0.32 and 0.15 times of that on the hydrophilic poly(N,N-dimethylacrylamide) (PDMA) hydrogels, respectively. Moreover, the hydrophobic hydrogels exhibited a similar anti-adhesion ability and trend to algae S. platensis. Based on the results, the surface hydrophobicity mainly contributes to the excellent anti-fouling ability of hydrophobic hydrogels. In the meantime, the too-high water content may be somehow detrimental to anti-fouling performance.

Ultrafiltration Membranes Functionalized with Copper Oxide and Zwitterions for Fouling Resistance

Polymeric membrane fouling is a long-standing challenge for water filtration. Metal/metal oxide nanoparticle functionalization of the membrane surface can impart anti-fouling properties through the reactivity of the metal species and the generation of radical species. Copper oxide nanoparticles (CuO NPs) are effective at reducing organic fouling when used in conjunction with hydrogen peroxide, but leaching of copper ions from the membrane has been observed, which can hinder the longevity of the CuO NP activity at the membrane surface. Zwitterions can reduce organic fouling and stabilize NP attachment, suggesting a potential opportunity to combine the two functionalizations. Here, we coated polyethersulfone (PES) ultrafiltration membranes with polydopamine (PDA) and attached the zwitterionic compound, thiolated 2-methacryloyloxyethyl phosphorylcholine (MPC-SH), and CuO NPs. Functionalized membranes resulted in a higher flux recovery ratio (0.694) than the unfunctionalized PES control (0.599). Copper retention was high (>96%) for functionalized membranes. The results indicate that CuO NPs and MPC-SH can reduce organic fouling with only limited copper leaching.

Interaction of Lipopolysaccharide-Spiked Blood with Anti-Fouling Polymyxin B-Modified Glass

Bacterial endotoxin, also known as lipopolysaccharide (LPS), plays a major role in the initiation of sepsis, a severe inflammatory condition. Removal of the toxin from blood is one accepted method of patient treatment. Polymyxin B (PMB)-modified columns have been employed successfully for this purpose via extra-corporeal blood-flow systems that incorporate a cartridge for toxin removal. Herein we demonstrate that PMB-modified glass beads are able to reduce the presence of LPS competitively with the equivalent fiber column used in a commercial cartridge. Analysis by gas chromatography-mass spectrometry and ELISA of released fatty acids from the toxin indicates that PMB does not physically capture or significantly remove LPS from the blood samples. In reality, interaction between the surface-bound PMB and the toxin may lead to disaggregation or monomerization of LPS aggregates. As aggregates are the bioactive form of LPS, it is possible that the monomerization of these entities may be the mechanism by which their toxicity is reduced. Moreover, this work indicates that LPS monomers are stabilized subsequent to disaggregation induced by PMB.

Suspended Kirigami Surfaces for Multifoulant Adhesion Reduction

High foulant adhesion remains a critical issue in a wide range of industries, such as ice accretion on aircraft, biofoulants on ships, wax build-up within pipelines, and scale formation in water remediation. Previous anti-fouling surfaces have only shown promise for reducing the adhesion of a single foulant system; a multi-foulant anti-fouling technology remains elusive. Here, we introduce a mechanical metamaterial-based approach to develop anti-fouling surfaces applicable to a wide range of fouling substances. The suspended kirigami inverted nil-adhesion surfaces, or SKINS, show significantly reduced adhesion of ice, different waxes, dried mud, pressure-sensitive adhesive tape, and a marine hard foulant simulant. SKINS mimic the wrinkling of hard films adhered to soft substrates. Foulant adhesion can be minimized by this wrinkling, which may be controlled by tuning the kirigami motif, sheet material, and foulant dimensions. SKINS reduce adhesion mechanically and were found to be independent of surface energy, enabling their fabrication from commonplace hydrophilic polymers like cellulose acetate. Optimized SKINS exhibited extremely low foulant adhesion, for example, ice adhesion strengths less than 5 kPa (a >250-fold reduction from aluminum substates), and were found to maintain their performance on curved surfaces like transmission cables. The low foulant adhesion persisted over 30 repeated foulant deposition and removal cycles, demonstrating the anti-fouling durability of SKINS. Overall, SKINS offers a previously unexplored route to achieving low foulant adhesion that is highly tunable in both geometry and material selection, is applicable to many different fouling substances, and maintains extremely low foulant adhesion even on complex substrates over large fouled interfaces.

Superhydrophobic Coating Based on Porous Aluminum Oxide Modified by Polydimethylsiloxane (PDMS)

The aim of this study was to obtain a superhydrophobic coating by modifying anodized aluminum using polydimethylsiloxane (PDMS). In order to obtain a superhydrophobic coating on an aluminum substrate, a multistage treatment was implemented. Specimens of aluminum were treated by abrasive blasting, anodization in sulfuric acid, impregnation by PDMS, rinsing in toluene to remove excess of PDMS, and curing. A rough surface with an additional low free energy layer on it resulted in a superhydrophobic effect. The coating obtained has an average contact angle of 159°. The specimens were tested in terms of durability in natural conditions. Additionally, anti-icing and anti-fouling properties were evaluated. The coating was compared with anodized aluminum obtained by a basic process.

Fabrication of Low-Fouling Surfaces on Alkyne-Functionalized Poly-(p-xylylenes) Using Click Chemistry

A facial, versatile, and universal method that breaks the substrate limits is desirable for antifouling treatment. Thin films of functional poly-p-xylylenes (PPX) that are deposited using chemical vapor deposition (CVD) provide a powerful platform for surface immobilization of molecules. In this study, we prepared an alkyne-functionalized PPX coating on which poly (sulfobetaine methacrylate-co-Az) could be conjugated via click chemistry. We found that the conjugated polymers were very stable and inhibited cell adhesion and protein adsorption effectively. The same conjugation strategy could also be applied to conjugate azide-containing poly (ethylene glycol) and poly (NIPAAm). The results indicate that our method provides a simple and robust tool for fabricating antifouling surfaces on a wide range of substrates using CVD technology of functionalized poly (p-xylylenes) for biosensor, diagnostics, immunoassay, and other biomaterial applications.

Unraveling the Structured Solvation Shell of Zwitterion Nanoparticles for Controlled Release of Nitric Oxide

Zwitterions have been attracting emerging attention as an anti-fouling polymer. However, the relationship between structured solvation shells and controlled drug release induced by deceleration of water molecule's translational and vibrational motions of zwitterions is an uncharted territory. Herein, sulfobetaine zwitterion nanoparticles (ZWNPs) were designed as a stable nitric oxide (NO)-delivering carrier. The condensed water structure of the solvation shell at its isoelectric point (PI) and the loose structure of water under different pH conditions were investigated through rheological and thermodynamical analyses. The ZWNPs showed a sustained-release profile at the PI, which presented a structured solvation barrier. On the other hand, NO-loaded ZWNPs showed different release profiles with the burst release at pH 5.5. Notably, an increased cell proliferation rate and a decreased antibacterial effect were observed at the same concentration depending on solvation shell's characteristics.

Oil-Membrane Protection of Electrochemical Sensors for Fouling- and pH-Insensitive Detection of Lipophilic Analytes

To take full advantage of the reagent- and label-free sensing capabilities of electrochemical sensors, a frequent and remaining challenge is interference and degradation of the sensors due to uncontrolled pH or salinity in the sample solution or foulants from the sample solution. Here, we present an oil-membrane sensor protection technique that allows for the permeation of hydrophobic (lipophilic) analytes into a sealed sensor compartment containing ideal salinity and pH conditions while simultaneously blocking common hydrophilic interferents (proteins, acids, bases, etc.) In this paper, we validate the oil-membrane sensor protection technique by demonstrating continuous cortisol detection via electrochemical aptamer-based (EAB) sensors. The encapsulated EAB cortisol sensor exhibits a 5 min concentration-on rise time and maintains a measurement signal of at least 7 h even in the extreme condition of an acidic solution of pH 3.

Anti-Foulant Ultrafiltration Polymer Composite Membranes Incorporated with Composite Activated Carbon/Chitosan and Activated Carbon/Thiolated Chitosan with Enhanced Hydrophilicity

A rapid increase in population worldwide is giving rise to the severe problem of safe drinking water availability, necessitating the search for solutions that are effective and economical. For this purpose, membrane technology has shown a lot of promise but faces the challenge of fouling, leading to a reduction in its lifetime. In this study, ultrafiltration polyethersulfone membranes were synthesized in two different concentrations, 16% wt. and 20% wt., using the phase inversion method. Chitosan and activated carbon were incorporated as individual fillers and then as composites in both the concentrations. A novel thiolated chitosan/activated carbon composite was introduced into a polyethersulfone membrane matrix. The membranes were then analyzed using Attenuated Total Reflection–Fourier-Transform Infrared spectroscopy(ATR-FTIR), Scanning Electron Microscopy (SEM), optical profilometry, gravimetric analysis, water retention, mechanical testing and contact angle. For membranes with the novel thiolated chitosan/activated carbon composite, Scanning Electron Microscopy micrographs showed better channels, indicating a better permeability possibility, reiterated by the flux rate results. The flux rate and bovine serum albumin flux were also assessed, and the results showed an increase from 105 L/m²h to 114 L/m²h for water flux and the antifouling determined by bovine serum albumin flux increased from 23 L/m²h to 51 L/m²h. The increase in values of water uptake from 22.84% to 76.5% and decrease in contact angle from 64.5 to 55.7 showed a significant increase in the hydrophilic character of the membrane.

Preparation and Characterization of MWCNTs/PVDF Conductive Membrane with Cross-Linked Polymer PVA and Study on Its Anti-Fouling Performance

Based on carboxylated multi-walled carbon nanotubes (MWCNTs-COOH), a MWCNTs/PVDF conductive membrane was prepared by a vacuum filtration cross-linking method. The surface compositions and morphology of conductive membranes were studied by X-ray photoelectron spectroscopy and high-resolution field emission scanning electron microscopy, respectively. The effects of cross-linked polymeric polyvinyl alcohol (PVA) on the conductive membrane properties such as the porosity, pore size distribution, pure water flux, conductivity, hydrophilicity, stability and antifouling properties were investigated. Results showed that the addition of PVA to the MWCNTs/PVDF conductive membrane decreased the pure water flux, porosity and the conductivity. However, the hydrophilicity of the modified MWCNTs/PVDF conductive membrane was greatly improved, and the contact angle of pure water was reduced from 70.18° to 25.48° with the addition of PVA contents from 0 wt% to 0.05 wt%. Meanwhile, the conductive membranes with higher content had a relatively higher stability. It was found that the conductive functional layer of the conductive membrane had an average mass loss rate of 1.22% in the 30 min ultrasonic oscillation experiment. The tensile intensity and break elongation ratio of the conductive membrane are improved by the addition of PVA, and the durability of the conductive membrane with PVA was superior to that without PVA added. The electric assisted anti-fouling experiments of modified conductive membrane indicated that compared with the condition without electric field, the average flux attenuation of the conductive membrane was reduced by 11.2%, and the membrane flux recovery rate reached 97.05%. Moreover, the addition of PVA could accelerate the clean of the conductive membranes.

The Antifouling and Drag-Reduction Performance of Alumina Reinforced Polydimethylsiloxane Coatings Containing Phenylmethylsilicone Oil

Fouling-release coatings reinforced with micro-alumina and nano-alumina were prepared based on polydimethylsiloxane (PDMS) containing phenylmethylsilicone oil. The surface properties, mechanical properties, leaching behavior of silicone oil, anti-fouling and drag-reduction performance of the coating were studied. The results show that the addition of alumina can significantly improve the tensile strength, elastic modulus and Shore’s hardness of the coating. The adhesion experiments of marine bacteria and Navicula Tenera show that the addition of alumina can reduce the antifouling performance of the coating, which is related to the stripping mode of fouling organisms. The fouling organisms leave the coating surface by shearing, and the energy required for shearing is proportional to the elastic modulus of the coating. At 800–1400 rpm, the addition of alumina will reduce the drag reduction performance of the coating, which is related to the drag reduction mechanism of PDMS. PDMS counteracts part of the resistance by surface deformation. The larger the elastic modulus is, the more difficult the surface deformation is. The experiment of silicone oil leaching shows that the increase of alumina addition amount and the decrease of particle size will inhibit the leaching of silicone oil.

Incorporation of Biomass-Based Carbon Nanoparticles into Polysulfone Ultrafiltration Membranes for Enhanced Separation and Anti-Fouling Performance

Functionalized carbon nanomaterials are considered to be an efficient modifier for ultrafiltration membranes with enhanced performance. However, most of the reported carbon nanomaterials are derived from unsustainable fossil fuels, while an extra modification is often essential before incorporating the nanomaterials in membranes, thus inevitably increasing the cost and complexity. In this work, novel functionalized biomass-based carbon nanoparticles were prepared successfully from agricultural wastes of corn stalks through simple one-step acid oxidation method. The obtained particles with the size of ~45 nm have excellent dispersibility in both aqueous and dimethyl formamide solutions with abundant oxygen-containing groups and negative potentials, which can endow the polysulfone ultrafiltration membranes with enhanced surface hydrophilicity, larger pore size, more finger-like pores, and lower surface roughness. Therefore, the separation and anti-fouling performance of membranes are improved simultaneously. Meanwhile, the addition of 0.4 wt% nanoparticles was proved to be the best condition for membrane preparation as excess modifiers may lead to particle aggregation and performance recession. It is expected that these biomass-based carbon nanoparticles are potential modifying materials for improving the separation performance and anti-fouling property of the membranes with great simplicity and renewability, which pave a new avenue for membrane modification and agricultural waste utilization.

Highly Efficient Self-Repairing Slippery Liquid-Infused Surface with Promising Anti-Icing and Anti-Fouling Performance

Smart slippery liquid-infused porous surfaces (SLIPSs) have aroused remarkable attention owing to tremendous application foreground in biomedical instruments and industry. However, challenges still remain in fabricating durable SLIPSs. In this work, a fast and highly efficient self-repairing slippery surface (SPU-60M) was fabricated based on a polyurethane membrane and silicone oil. By introducing a great quantity of reversible disulfide bonds into the polymer backbone and hydrogen bonds in the polymer interchain, this SLIPS material could be quickly repaired in 15 min with 97.8% healing efficiency. Moreover, the self-healing efficiency could be maintained at 42.75% after the 10th cutting-healing cycle. Notably, SPU-60M showed excellent self-repairing ability not only in an ambient environment but also in an underwater environment and at ultralow temperatures. Besides, the icing delay time (DT) of SPU-60M could be prolonged to 1182 s at -15 °C, and the ice adhesion strength was only 10.33 kPa at -30 °C. In addition, SPU-60M had excellent anti-fouling performance with BSA adsorption of 2.41 μg/cm² and Escherichia coli CFU counts of 41 × 10⁴. These findings provide a facile way to design highly efficient self-repairing SLIPSs with multifunctionality.

Advances in the Synthesis and Application of Anti-Fouling Membranes Using Two-Dimensional Nanomaterials

This article provides a comprehensive review of the recent progress in the application of advanced two-dimensional nanomaterials (2DNMs) in membranes fabrication and application for water purification. The membranes fouling, its types, and anti-fouling mechanisms of different 2DNMs containing membrane systems are also discussed. The developments in membrane synthesis and modification using 2DNMs, especially graphene and graphene family materials, carbon nanotubes (CNTs), MXenes, and others are critically reviewed. Further, the application potential of next-generation 2DNMs-based membranes in water/wastewater treatment systems is surveyed. Finally, the current problems and future opportunities of applying 2DNMs for anti-fouling membranes are also debated.

Metal Oxy-Hydroxides with a Hierarchical and Hollow Structure for Highly Efficient Solar-Thermal Water Evaporation

Solar-thermal water evaporation is a promising technology for pure water production. However, the design of low-cost systems for efficient antifouling solar-thermal water evaporation remains a challenge. Herein, an evaporator based on metal oxy-hydroxides with a hierarchical and hollow structure is rationally designed through material selection and structural engineering. The obtained evaporator possesses good light absorption performance, excellent antifouling property against oil, and enhanced heat localization ability. Consequently, the water evaporation rate reaches as high as 1.65 kg m^-2 h^-1 with a solar-thermal conversion efficiency up to 82.3% under 1 sun illumination. More importantly, the evaporator exhibits almost identical evaporation performance in oily wastewater and natural seawater due to its superhydrophilicity and underwater superoleophobicity. This work provides a worth-adopted approach to prepare solar-thermal evaporators with high efficiency and anti-oil-fouling property, highlighting the new application of metal oxy-hydroxide-based materials and the importance of a hierarchical and hollow structure for efficient solar-thermal water evaporation.

The Fate of Nanoparticles In Vivo and the Strategy of Designing Stealth Nanoparticle for Drug Delivery

Nano-drug delivery systems (Nano-DDS) offer powerful advantages in drug delivery and targeted therapy for diseases. Compared to the traditional drug formulations, Nano-DDS can increase solubility, biocompatibility, and reduce off-targeted side effects of free drugs. However, they still have some disadvantages that pose a limitation in reaching their full potential in clinical use. Protein adsorption in blood, activation of the complement system, and subsequent sequestration by the mononuclear phagocyte system (MPS) consequently result in nanoparticles (NPs) to be rapidly cleared from circulation. Therefore, NPs have low drug delivery efficiency. So, it is important to develop stealth NPs for reducing bio-nano interaction. In this review, we first conclude the interaction between NPs and biological environments, such as blood proteins and MPS, and factors influencing each other. Next, we will summarize the new strategies to reduce NPs protein adsorption and uptake by the MPS based on current knowledge of the bio-nano interaction. Further directions will also be highlighted for the development of biomimetic stealth nano-delivery systems by combining targeted strategies for a better therapeutic effect.

A Dopamine/Tannic-Acid-Based Co-Deposition Combined with Phytic Acid Modification to Enhance the Anti-Fouling Property of RO Membrane

Reverse osmosis (RO) membranes are widely used in the field of water treatment. However, there are inevitably various fouling problems during long-term use. Surface engineering of RO membranes, such as hydrophilic modification, has attracted broad attention for improving the anti-fouling performance. In this work, we constructed a green biomimetic composite modification layer on the surface of polyamide membranes using a dopamine (DA)/tannic acid (TA) co-deposited layer to bridge the polyamide surface and hydrophilic phytic acids (PhA). The DA/TA interlayer could firmly adhere to the RO membranes, reducing the aggregation of DA and providing abundant phenolic hydroxyl sites to graft PhA. Meanwhile, the anchored PhA molecule bearing six phosphate groups could effectively improve the superficial hydrophilicity. The membranes were characterized by the SEM, AFM, XPS, water contact angle test, and zeta potential test. After surface modification, the hydrophilicity, smoothness, and surface electronegativity were enhanced obviously. The flux and rejection of the virgin membrane were 76.05 L·m⁻²·h⁻¹ and 97.32%, respectively. While the modified D2/T4-PhA membrane showed decent permeability with a water flux of 57.37 L·m⁻²·h⁻¹ and a salt rejection of 98.29%. In the dynamic fouling test, the modified RO membranes demonstrated enhanced anti-fouling performance toward serum albumins (BSA), sodium alginates (SA), and dodecyl trimethyl ammonium bromides (DTAB). In addition, the modified membrane showed excellent stability in the 40 h long-term test.

Concentration Polarization Enabled Reactive Coating of Nanofiltration Membranes with Zwitterionic Hydrogel

In this study, the bottleneck challenge of membrane fouling is addressed via establishing a scalable concentration polarization (CP) enabled and surface-selective hydrogel coating using zwitterionic cross-linkable macromolecules as building blocks. First, a novel methacrylate-based copolymer with sulfobetain and methacrylate side groups was prepared in a simple three-step synthesis. Polymer gelation initiated by a redox initiator system (ammonium persulfate and tetramethylethylenediamine) for radical cross-linking was studied in bulk in order to identify minimum ("critical") concentrations to obtain a hydrogel. In situ reactive coating of a polyamide nanofiltration membrane was achieved via filtration of a mixture of the reactive compounds, utilizing CP to meet critical gelation conditions solely within the boundary layer. Because the feasibility was studied and demonstrated in dead-end filtration mode, the variable extent of CP was estimated in the frame of the film model, with an iterative calculation using experimental data as input. This allowed to discuss the influence of parameters such as solution composition or filtration rate on the actual polymer concentration and resulting hydrogel formation at the membrane surface. The zwitterionic hydrogel-coated membranes exhibited lower surface charge and higher flux during protein filtration, both compared to pristine membranes. Salt rejection was found to remain unchanged. Results further reveal that the hydrogel coating thickness and consequently the reduction in membrane permeance due to the coating can be tuned by variation of filtration time and polymer feed concentration, illustrating the novel modification method's promising potential for scale-up to real applications.

Development of Polythiourethane/ZnO-Based Anti-Fouling Materials and Evaluation of the Adhesion of Staphylococcus aureus and Candida glabrata Using Single-Cell Force Spectroscopy

The attachment of bacteria and other microbes to natural and artificial surfaces leads to the development of biofilms, which can further cause nosocomial infections. Thus, an important field of research is the development of new materials capable of preventing the initial adhesion of pathogenic microorganisms. In this work, novel polymer/particle composite materials, based on a polythiourethane (PTU) matrix and either spherical (s-ZnO) or tetrapodal (t-ZnO) shaped ZnO fillers, were developed and characterized with respect to their mechanical, chemical and surface properties. To then evaluate their potential as anti-fouling surfaces, the adhesion of two different pathogenic microorganism species, Staphylococcus aureus and Candida glabrata, was studied using atomic force microscopy (AFM). Our results show that the adhesion of both S. aureus and C. glabrata to PTU and PTU/ZnO is decreased compared to a model surface polydimethylsiloxane (PDMS). It was furthermore found that the amount of both s-ZnO and t-ZnO filler had a direct influence on the adhesion of S. aureus, as increasing amounts of ZnO particles resulted in reduced adhesion of the cells. For both microorganisms, material composites with 5 wt.% of t-ZnO particles showed the greatest potential for anti-fouling with significantly decreased adhesion of cells. Altogether, both pathogens exhibit a reduced capacity to adhere to the newly developed nanomaterials used in this study, thus showing their potential for bio-medical applications.

Environment-Friendly and Two-Component Method for Fabrication of Highly Hydrophobic Wood Using Poly(methylhydrogen)siloxane

Practical application of wood remains a great challenge because of its highly hydrophilic property. In this work, highly hydrophobic wood was produced using an environment-friendly and two-component package method. Poly(methylhydrogen)siloxane (PMHS) and inhibitor played the key role in the hydrophobicity of wood and the assembly process. The two-component package mechanism was discussed in detail. As a result, the water contact angles of the modified wood surface for the radial and cross sections were 139.5° and 152.9°, respectively, which provided the resultant wood high hydrophobicity and dimensional stability. The two-component package method afforded the wood good anti-fouling property and UV-resistance. In addition, the two-component package method could also be applied in functionalization of filter paper for oil/water separation.

Molecular Understanding and Design of Porous Polyurethane Hydrogels with Ultralow-Oil-Adhesion for Oil-Water Separation

Materials with opposite affinities toward oil and water have been extensively used to coat porous substrates for oil-water separation, but the applications of these materials have been limited by the need for complex coating processes as well as the short-term adherence of these materials onto different substrates under extreme conditions. As reported herein, the robust porous polyurethane hydrogel has been theoretically and structurally designed with ultralow-oil-adhesion properties which is free stand without depending on additional substrates. The combination of superhydrophilic properties along with the underwater superoleophobic behavior of this porous hydrogel allows gravity driven separations of oil-water mixtures, and its antiadhesion performance toward oil prevents undesirable oily fouling. The underwater superoleophobic properties were also illustrated by molecular dynamics simulation to understand the resisting effect of hydrated layers. The as-prepared porous hydrogel shows ultrahigh oil-water separation efficiencies of 99.9% for various oil-water mixtures, ranging from those containing viscous oils (pump oil and peanut oil) to organic solvents (n-hexane, n-hexadecane, and toluene). In addition, this hydrogel is durable even with exposure to various harsh conditions including acidic and basic media (pH 0-14) as well as exposure to mechanical abrasion. We believe that the combination of facile preparation, substrate independence, gravity driven separation, antifouling properties, high durability, as well as the outstanding separation flux and efficiency of this robust porous hydrogel will help to advance the design and application of materials in oil-water separation fields.

Two-Step Dopamine-to-Polydopamine Modification of Polyethersulfone Ultrafiltration Membrane for Enhancing Anti-Fouling and Ultraviolet Resistant Properties

Polydopamine has been widely used as an additive to enhance membrane fouling resistance. This study reports the effects of two-step dopamine-to-polydopamine modification on the permeation, antifouling, and potential anti-UV properties of polyethersulfone (PES)-based ultrafiltration membranes. The modification was performed through a two-step mechanism: adding the dopamine additive followed by immersion into Tris-HCl solution to allow polymerization of dopamine into polydopamine (PDA). The results reveal that the step of treatment, the concentration of dopamine in the first step, and the duration of dipping in the Tris solution in the second step affect the properties of the resulting membranes. Higher dopamine loadings improve the pure water flux (PWF) by more than threefold (15 vs. 50 L/m²·h). The extended dipping period in the Tris alkaline buffer leads to an overgrowth of the PDA layer that partly covers the surface pores which lowers the PWF. The presence of dopamine or polydopamine enhances the hydrophilicity due to the enrichment of hydrophilic catechol moieties which leads to better anti-fouling. Moreover, the polydopamine film also improves the membrane resistance to UV irradiation by minimizing photodegradation's occurrence.

Surface-grafted zwitterionic polymers improve the efficacy of a single antibiotic injection in suppressing S. aureus periprosthetic infections

Implant-associated bacterial infections are difficult to treat due to the tendency of biofilm formation on implant surfaces, which protects embedded pathogens from host defense and impedes antibiotic penetration, rendering systemic antibiotic injections ineffective. Here, we test the hypothesis that implant coatings that reduce bacterial colonization would make planktonic bacteria within the periprosthetic environment more susceptible to conventional systemic antibiotic treatment. We covalently grafted zwitterionic polymer brushes poly(sulfobetaine methacryate) from Ti6Al4V surface to increase the substrate surface hydrophilicity and reduce staphylococcus aureus (S. aureus) adhesion. Using a mouse femoral intramedullary (IM) canal infection model, we showed that the anti-fouling coating applied to Ti6Al4V IM implants, when combined with a single vancomycin systemic injection, significantly suppressed both bacterial colonization on implant surfaces and the periprosthetic infections, outperforming either treatment alone. This work supports the hypothesis that grafting anti-fouling polymers to implant surfaces improves the efficacy of systemic antibiotic injections to combat periprosthetic infections.

Novel Carbon Quantum Dots/Silver Blended Polysulfone Membrane with Improved Properties and Enhanced Performance in Tartrazine Dye Removal

This study produced a novel polysulfone (PSF) membrane for dye removal using lemon-derived carbon quantum dots-grafted silver nanoparticles (Ag/CQDs) as membrane nanofiller. The preparation of CQDs was completed by undergoing hydrothermal treatment to carbonize the pulp-free lemon juice into CQD solution. The CQD solution was then coupled with Ag nanoparticles to form Ag/CQDs nanohybrid. The synthesized powders were characterized in terms of morphologies, functional groups and surface charges. A set of membranes was fabricated with different loadings of Ag/CQDs powder using the nonsolvent-induced phase separation (NIPS) method. The modified membranes were studied in terms of morphology, elemental composition, hydrophilicity and pore size. In addition, pure water flux, rejection test and fouling analysis of the membranes were evaluated using tartrazine dye. From the results, 0.5 wt % of Ag/CQD was identified as the optimum loading to be incorporated with the pristine PSF membrane. The modified membrane exhibited an excellent pure water permeability and dye rejection with improvements of 169% and 92%, respectively. In addition, the composite membrane also experienced lower flux decline, higher reversible fouling and lower irreversible fouling. This study has proven that the addition of CQD additives into membrane greatly improves the polymeric membrane’s properties and filtration performance.

Lubricant-Impregnated Surfaces for Mitigating Asphaltene Deposition

Asphaltenes are heavy aromatic components of crude oil. Their complex chemical makeup-an aromatic core surrounded by aliphatic side chains-enables them to adhere to most surfaces. Their buildup in pipes can result in clogging and lead to interruption of production operations and expensive mechanical cleaning. We demonstrate the use of liquid-impregnated surfaces (LIS) to prevent asphaltene deposition and buildup on substrates. Indeed, these surfaces expose a liquid interface to the working fluid, which combines the benefits of a dynamic defect-free surface and tunable interfacial properties. In contrast to bulk additives that are typically mixed into the oil phase, the impregnating liquid also provides the great benefit of protecting the underlying solid surface with a stable and minimal layer of lubricant, thereby reducing costs and eliminating the need for subsequent downstream removal. We first select and confirm the thermodynamic stability of a suitable lubricant and its lack of interaction with asphaltenes. By using a carefully selected system composed of a textured and functionalized solid substrate in conjunction with a fluorinated lubricant, we show that asphaltene adsorption is prevented over long time scales. We further demonstrate the possibility of building such a system with representative industrial materials such as aluminum and expose the resulting substrate to an external shear flow to simulate pipe flow conditions.

Dual-Functional Nanofiltration Membranes Exhibit Multifaceted Ion Rejection and Antifouling Performance

Charged functional groups are often incorporated onto the surface of nanofiltration (NF) membranes to facilitate the selective rejection of multivalent ions over monovalent ions. However, since fouling-resistant surfaces tend to be electrically neutral, the incorporation of charged functionality exacerbates membrane fouling. Multifunctional Janus membrane architectures, which incorporate chemically distinct domains over their cross section, provide a strategy for balancing the competing demands associated with making fouling-resistant, ion rejecting NF membranes. Here, through the controlled exposure of poly(trifluoroethyl methacrylate-co-oligo-(ethylene glycol) methyl ether methacrylate-co-(3-azido-2-hydroxypropyl methacrylate)) copolymer substrates to a series of reactive solutions containing alkyne-terminated molecules, the process for creating dual-functional membranes by using the copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC) reaction was analyzed. Under the appropriate conditions, the CuAAC reaction propagates into the copolymer substrate as a front. This phenomenon results in a process for creating layered domains of distinct functionality whereby the distribution of antifouling zwitterionic moieties and ion rejecting sulfonate moieties can be modified by manipulating the exposure time. The ion rejection and fouling propensity for a family of dual-functional membranes was examined. For short initial reaction times, which introduced a thin antifouling layer on top of an ion rejection layer, the rejection of 1 mM K₂SO₄, 87%, was comparable to the value for full charge control membranes, 90%. Moreover, when exposed to a fouling solution containing bovine serum albumin (BSA), these dual-functional membranes exhibited an 18% decline in normalized flux and recovered 99% of their flux upon rinsing with water. In comparison, the full charge membranes exhibited a 44% decline in normalized flux and recovered 65% of their flux upon washing. As such, the results demonstrate that the controlled functionalization process reported here is capable of balancing antifouling and ion rejection capabilities. Furthermore, the versatile nature of the click chemistry mechanism at the center of this process offers a means by which to design and fabricate multifunctional membranes for numerous future applications.

Recent Advances in Understanding the Protein Corona of Nanoparticles and in the Formulation of "Stealthy" Nanomaterials

In the last decades, the staggering progress in nanotechnology brought around a wide and heterogeneous range of nanoparticle-based platforms for the diagnosis and treatment of many diseases. Most of these systems are designed to be administered intravenously. This administration route allows the nanoparticles (NPs) to widely distribute in the body and reach deep organs without invasive techniques. When these nanovectors encounter the biological environment of systemic circulation, a dynamic interplay occurs between the circulating proteins and the NPs, themselves. The set of proteins that bind to the NP surface is referred to as the protein corona (PC). PC has a critical role in making the particles easily recognized by the innate immune system, causing their quick clearance by phagocytic cells located in organs such as the lungs, liver, and spleen. For the same reason, PC defines the immunogenicity of NPs by priming the immune response to them and, ultimately, their immunological toxicity. Furthermore, the protein corona can cause the physical destabilization and agglomeration of particles. These problems induced to consider the PC only as a biological barrier to overcome in order to achieve efficient NP-based targeting. This review will discuss the latest advances in the characterization of PC, development of stealthy NP formulations, as well as the manipulation and employment of PC as an alternative resource for prolonging NP half-life, as well as its use in diagnostic applications.

Recent Developments in the Design of Non-Biofouling Coatings for Nanoparticles and Surfaces

Biofouling is a major issue in the field of nanomedicine and consists of the spontaneous and unwanted adsorption of biomolecules on engineered surfaces. In a biological context and referring to nanoparticles (NPs) acting as nanomedicines, the adsorption of biomolecules found in blood (mostly proteins) is known as protein corona. On the one hand, the protein corona, as it covers the NPs' surface, can be considered the biological identity of engineered NPs, because the corona is what cells will "see" instead of the underlying NPs. As such, the protein corona will influence the fate, integrity, and performance of NPs in vivo. On the other hand, the physicochemical properties of the engineered NPs, such as their size, shape, charge, or hydrophobicity, will influence the identity of the proteins attracted to their surface. In this context, the design of coatings for NPs and surfaces that avoid biofouling is an active field of research. The gold standard in the field is the use of polyethylene glycol (PEG) molecules, although zwitterions have also proved to be efficient in preventing protein adhesion and fluorinated molecules are emerging as coatings with interesting properties. Hence, in this review, we will focus on recent examples of anti-biofouling coatings in three main areas, that is, PEGylated, zwitterionic, and fluorinated coatings.

Hydrophobic and Anti-Fouling Performance of Surface on Parabolic Morphology

The hydrophobicity and anti-fouling properties of materials have important application value in industrial and agricultural production and people’s daily life. To study the relationship between the unit width L₀ of the parabolic hydrophobic material and the hydrophobicity and anti-fouling properties, the rough surface structure of the parabolic with different widths was prepared by grinding with different SiC sandpapers, and further, to obtain hydrophobic materials through chemical oxidation and chemical etching, and modification with stearic acid (SA). The morphology, surface wetting and anti-fouling properties of the modified materials were characterized by SEM and contact angle measurement. The oil–water separation performance and self-cleaning performance of the materials were explored. The surface of the modified copper sheet forms a rough structure similar to a paraboloid. When ground with 1500 grit SiC sandpaper, it is more conducive to increase the hydrophobicity of the copper sheet surface and increase the contact angle of water droplets on the copper surface. Additionally, the self-cleaning and anti-fouling experiments showed that as L₀ decreases, copper sheets were less able to stick to foreign things such as soil, and the better the self-cleaning and anti-fouling performance was. Based on the oil–water separation experiment of copper mesh, the lower L₀ has a higher oil–water separation efficiency. The results showed that material with parabolic morphology has great self-cleaning, anti-fouling, and oil–water separation performance. The smaller the L₀ was, the larger the contact angle and the better hydrophobic performance and self-cleaning performance were.