Liquid-Infused Poly(styrene-b-isobutylene-b-styrene) Microfiber Coating Prevents Bacterial Attachment and Thrombosis

Sustainable Biofilm Inhibition Using Chitosan-Mesoporous Nanoparticle-Based Hybrid Slippery Composites

In recent decades, extensive research has been directed toward mitigating microbial contamination and preventing biofilm formation. However, many conventional antibiofilm methods rely on hazardous and toxic substances, neglecting potential risks to human health and the environment. Moreover, these approaches often rely on single-strategy mechanisms, utilizing either bactericidal or fouling-resistant agents, which have shown limited efficacy in long-term biofilm suppression. In this study, we propose an efficient and sustainable biofilm-resistant slippery hybrid slippery composite. This composite integrates nontoxic and environmentally friendly materials including chitosan, silicone oil-infused polydimethylsiloxane, and mesoporous silica nanoparticles in a synergistic manner. Leveraging the bacteria-killing properties of chitosan and the antifouling capabilities of the silicone oil layer, the hybrid composite exhibits robust antibiofilm performance against both Gram-positive and Gram-negative bacteria. Furthermore, the inclusion of mesoporous silica nanoparticles enhances the oil absorption capacity and self-replenishing properties, ensuring exceptional biofilm inhibition even under harsh conditions such as exposure to high shear flow and prolonged incubation (7 days). This approach offers promising prospects for developing effective biofilm-resistant materials with a reduced environmental impact and improved long-term performance.

Understanding the role of infusing lubricant composition in the interfacial interactions and properties of slippery surface

Liquid-infused surfaces (LISs) have attracted tremendous attention in recent years owing to their excellent surface properties, such as self-cleaning and anti-fouling. Understanding the effect of lubricant composition on LIS performance is of vital importance, which will help establish the criteria to choose suitable infusing lubricants for specific applications. In this work, the role of chemical composition of lubricant in the properties of LISs was investigated. The apparent water contact angle θapp was dependent on the temperature and beeswax/silicone oil ratio. Nevertheless, the trend of moving velocity of water drop on the tilted LISs did not follow that of θapp at 20 °C and 37 °C, which was attributed to the increased lubricant viscosity with beeswax/silicone oil ratio. At 60 °C, the drop velocity and θapp shared the similar variation trend with beeswax/silicone oil ratio, highlighting the significant role of chemistry of the components in beeswax. The alkanes and fatty acids promoted the drop movement, while the fatty acid esters impeded the movement. The interaction forces between water drop and lubricant surfaces were measured using atomic force microscopy. It was demonstrated that the interaction between water drop and lubricant was not the only factor to control the drop movement, while the interaction between lubricant and substrate as well as of lubricant itself also determined the movement. When the adhesions of water-lubricant and lubricant-substrate were similar for different lubricants, the influence of cohesion of lubricant became significant. This work provides useful insights into the fundamental understanding of the interfacial interactions of test drop, infusing lubricant and solid substrate of LISs, and the effect of infusing lubricant composition on the LIS performance.

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

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

Antibacterial photodynamic properties of silver nanoparticles-loaded curcumin composite material in chitosan-based films

In order to cope with the increasingly severe food contamination and safety problems, a powerful sterilization of food packaging material is urgently needed. Chitosan (CS) has potential applications in food packaging due to its good film-forming properties, but its antibacterial activity is not sufficient to meet the needs in practical applications. Silver nanoparticles (AgNPs) have the problem of weak immediate antibacterial activity as a broad-spectrum antibacterial agent. Therefore, in this study, AgNPs@GA@Cur-POTS (AGCP) composite antibacterial system was prepared by combining AgNPs with antibacterial photodynamic therapy using gallic acid (GA) as a reducing agent, curcumin (Cur) as a photosensitizer and perfluorosilane (POTS) for surface modification. The results showed that AGCP could produce a large number of reactive oxygen species under blue light irradiation, killing >90 % of E. coli and S. aureus within 2 h. Subsequently, the composite film of CS loaded with AGCP (CS/AGCP) was prepared by the flow-delay method. The CS/AGCP composite film exhibited excellent barrier properties and antioxidant activity, while its antibacterial rates against E. coli and S. aureus reached 98.44 ± 1.27 % and 99.11 ± 0.24 %, respectively, while the OD630 values of the two groups of bacteria treated with it showed no significant increase in incubation for up to 132 h, exhibiting remarkable and sustained antibacterial effects. Taken together, this work will provide a new strategy for antibacterial food packaging.

Slippery Antifouling Polymer Coatings Fabricated Entirely from Biodegradable and Biocompatible Components

We report the design of slippery liquid-infused porous surfaces (SLIPS) fabricated from building blocks that are biodegradable, edible, or generally regarded to be biocompatible. Our approach involves infusion of lubricating oils, including food oils, into nanofiber-based mats fabricated by electrospinning or blow spinning of poly(ε-caprolactone), a hydrophobic biodegradable polymer used widely in medical implants and drug delivery devices. This approach leads to durable and biodegradable SLIPS that prevent fouling by liquids and other materials, including microbial pathogens, on objects of arbitrary shape, size, and topography. This degradable polymer approach also provides practical means to design "controlled-release" SLIPS that release molecular cargo at rates that can be manipulated by the properties of the infused oils (e.g., viscosity or chemical structure). Together, our results provide new designs and introduce useful properties and behaviors to antifouling SLIPS, address important issues related to biocompatibility and environmental persistence, and thus advance new potential applications, including the use of slippery materials for food packaging, industrial and marine coatings, and biomedical implants.

Transparent and Highly Flexible Hierarchically Structured Polydimethylsiloxane Surfaces Suppress Bacterial Attachment and Thrombosis Under Static and Dynamic Conditions

The surface fouling of biomedical devices has been an ongoing issue in healthcare. Bacterial and blood adhesion in particular, severely impede the performance of such tools, leading to poor patient outcomes. Various structural and chemical modifications have been shown to reduce fouling, but all existing strategies lack the combination of physical, chemical, and economic traits necessary for widespread use. Herein, a lubricant infused, hierarchically micro- and nanostructured polydimethylsiloxane surface is presented. The surface is easy to produce and exhibits the high flexibility and optical transparency necessary for incorporation into various biomedical tools. Tests involving two clinically relevant, priority pathogens show up to a 98.5% reduction in the biofilm formation of methicillin-resistant Staphylococcus aureus and Pseudomonas aeruginosa. With blood, the surface reduces staining by 95% and suppresses thrombin generation to background levels. Furthermore, the surface shows applicability within applications such as catheters, extracorporeal circuits, and microfluidic devices, through its effectiveness in dynamic conditions. The perfusion of bacterial media shows up to 96.5% reduction in bacterial adhesion. Similarly, a 95.8% reduction in fibrin networks is observed following whole blood perfusion. This substrate stands to hold high applicability within biomedical systems as a means to prevent fouling, thus improving performance.

Intrusion of liquids into liquid-infused surfaces with nanoscale roughness

We present a theoretical study of the intrusion of an ambient liquid into the pores of a nanocorrugated wall w. The pores are prefilled with a liquid lubricant that adheres to the walls of the pores more strongly than the ambient liquid does. The two liquids are modeled as a binary liquid mixture of two species of particles, A and B. The mixture can decompose into a liquid rich in A particles, representing the ambient liquid, and another one rich in B particles, representing the liquid lubricant. The wall is taken to attract the B particles more strongly than the A particles. The ratio w-A/w-B of these interaction strengths is changed in order to tune the contact angle θ_{AB} formed by the A-rich/B-rich liquid interface between the two fluids and a planar wall, composed of the same material as the one forming the pores. We use classical density functional theory in order to capture the effects of microscopic details on the intrusion transition, which occurs as the concentration of the minority component or the pressure in the bulk of the ambient liquid is varied, moving away from bulk liquid-liquid coexistence within the single-phase domain of the A-rich bulk ambient liquid. These liquid structures have been studied as a function of the contact angle θ_{AB} and for various widths and depths of the pores. We also studied the reverse process in which a pore initially filled with the ambient liquid is refilled with the liquid lubricant. The location of the intrusion transition, with respect to its dependence on the contact angle θ_{AB} and the width of the pore, qualitatively follows the corresponding shift of the capillary-coexistence line away from the bulk liquid-liquid coexistence line, as predicted by a macroscopic capillarity model. Quantitatively, the transition found in the microscopic approach occurs somewhat closer to the bulk liquid-liquid coexistence line than predicted by the macroscopic capillarity model. The quantitative discrepancies become larger for narrower cavities. In cases in which the wall is completely wetted by the lubricant (θ_{AB}=0) and for small contact angles, the reverse transition follows the same path as for intrusion; there is no hysteresis. For larger contact angles, hysteresis is observed. The width of the hysteresis increases with increasing contact angle. A reverse transition is not found inside the domain within which the ambient liquid forms a single phase in the bulk once θ_{AB} exceeds a geometry-dependent threshold value. According to the macroscopic capillarity theory, for the considered geometry, this is the case for θ_{AB}>54.7^{∘}. Our computations show, however, that nanoscale effects shift this threshold value to much higher values. This shift increases strongly if the widths of the pores become smaller (below about ten times the diameter of the A and B particles).

Slippery 3-dimensional porous bioabsorbable membranes with anti-adhesion and bactericidal properties as substitute for vaseline gauze

Vaseline gauze is a common type of wound dressing that consist of absorbent gauze impregnated with white petrolatum. It has excellent anti-adhesive property which can reduce trauma during dressing changes. However, this kind of wound dressing doesn't have bacterial killing property. Thus, a new kind of wound dressing that has anti-adhesive and bactericidal properties is needed urgently. Creating slippery liquid-impregnated porous surfaces (SLIPS) that insensitive to the structure of porous solid are generally viewed as a new anti-adhesion strategy. To expand the potential utility of SLIPS as substitute for vaseline gauze, dual-functional slippery membranes with anti-adhesion and bactericidal properties by using triclosan, vegetable oils and polylactic acid (PLA) were prepared. It's demonstrated that the triclosan-loaded/vegetable oils-infused PLA membranes (T/V-PM) has good cytocompatibility in vitro. Notably, the T/V-PM can gradually release biocide molecule into surrounding aqueous media. Moreover, the T/V-PM can kill planktonic bacterial cells without loss of their antifouling property. The in vivo study revealed that the T/V-PM can prevent the secondary injuries during wound dressing changes. This simple and low-cost strategy can be applied to inhibit blood and bacterial adhesion, and prevent tissue adhesion at the wound site. It's confirmed that the T/V-PM have great potential as substitute for vaseline gauze.

Synthesis of linear and star-shaped telechelic polyisobutylene by cationic polymerization

Hydroxyl-terminated linear and star-shaped telechelic polyisobutylene have been successfully synthesized by living cationic polymerization using propylene oxide (PO)/Titanium tetrachloride (TiCl₄) as the initiator system. A one-step method to prepare the terminal hydroxyl group was realized by selecting the cheap and beautiful epoxide as the functional initiator, which has the prospect of industrial application. The polymerization mechanism was proposed by the end structure analysis and Gaussian calculation results. At the same time, the living linear macromolecular chain was used as the starting point to react with divinyl compounds for synthesis of star-shaped hydroxyl-terminated polyisobutylene. The effects of initiator-crosslinking agent ratio, arm length, and reaction time on the coupling reaction were studied.

Hydroxyl-terminated linear and star-shaped telechelic polyisobutylene have been successfully synthesized by living cationic polymerization using propylene oxide (PO)/Titanium tetrachloride (TiCl₄) as the initiator system.

Blow-Spun Collagen Nanofibrous Spongy Membrane: Preparation and Characterization

Fibrous biotextiles are very popular structural forms that are widely used in medical products and devices ranging from sutures, bandages, wound dressing, and patches to all kinds of artificial grafts such as ligaments, tendons, blood vessels, heart valves, and tissue engineered scaffolds. Blow-spinning is a recently developed technique that enables the large-scale and efficient production of ultrathin fibers with diameters ranging from micrometer to nanometer. In this study, the blow-spinning process and parameters were optimized to steadily fabricate collagen nanofibers by ejecting a collagen solution with constant airflow with precisely controlled diameter and alignment. Different from the electrospun collagen nanofibrous membrane, the blow-spun one was fluffy and spongy with high porosity. It was observed that the blow-spun collagen membrane could better maintain the fiber structure after chemical crosslinking in comparison with the electrospun membrane crosslinked in the same condition, which probably attributed to the good porosity and permeability of crosslinking agent within the membranes. The in vitro cell culture of Schwann cells on the blow-spun collagen nanofibrous spongy membrane showed its good biocompatibility for cell attachment, growth, and migration into the membrane, implying its potential in biomedical applications. Besides, there is no requirement for electroconductivity of the polymer solution and collector in blow-spinning. In brief, our results indicated that blow-spinning is an accessible and efficient technique to prepare nanofibers of synthetic and natural polymers, which has a great prospect in the large-scale production of biotextile medical devices and tissue engineered scaffolds. Impact statement Solution blow-spinning is a recently developed fiber fabrication technology with efficient and large-scale production. In this study, we successfully prepared collagen nanofibrous membrane with precisely controlled diameter and alignment by blow-spinning. The blow-spun collagen nanofibrous spongy membrane could better maintain the fiber structure after chemical crosslinking, which showed good biocompatibility for cell spreading and migration inward.

Fabrication of Slippery Liquid-Infused Coatings in Flexible Narrow-Bore Tubing

We report a layer-by-layer suction-and-flow approach that enables the fabrication of polymer-based "slippery" liquid-infused porous surfaces (SLIPS) in the confined luminal spaces of flexible, narrow-bore tubing. These SLIPS-coated tubes can prevent or strongly reduce surface fouling after prolonged contact, storage, or flow of a broad range of complex fluids and viscoelastic materials, including many that are relevant in the contexts of medical devices (e.g., blood and urine), food processing (beverages and fluids), and other commercial and industrial applications. The robust and mechanically compliant nature of the nanoporous coating used to host the lubricating oil phase allows these coated tubes to be bent, flexed, and coiled repeatedly without affecting their inherent slippery and antifouling behaviors. Our results also show that SLIPS-coated tubes can prevent the formation of bacterial biofilms after prolonged and repeated flow-based exposure to the human pathogen Staphylococcus aureus and that the anti-biofouling properties of these coated tubes can be further improved or prolonged by coupling this approach with strategies that permit the sustained release of broad-spectrum antimicrobial agents. The suction-and-flow approach used here enables the application of slippery coatings in the confined luminal spaces of narrow-bore tubing that are difficult to access using several other methods for the fabrication of liquid-infused coatings and can be applied to tubing of arbitrary length and diameter. We anticipate that the materials and approaches reported here will prove useful for reducing or preventing biofouling, process fouling, and the clogging or occlusion of tubing in a wide range of consumer, industrial, and healthcare-oriented applications.

Bioabsorbable poly(4-hydroxybutyrate) (P4HB) fibrous membranes as a potential dermal substitute

Dermal substitutes are indispensable for repairing large full-thickness skin defects. Only a few biomaterials for dermal substitution have been put into clinical practice. Therefore, novel artificial dermal substitutes that can meet clinical requirements are in urgent need. Biodegradable poly(4-hydroxybutyrate) (P4HB), which has been approved by the U.S. FDA, can be considered as a possible alternative biomaterial to construct dermal substitutes. In this work, three-dimensional P4HB fibrous membranes were constructed by an electrospinning technique. These P4HB fibrous membranes showed excellent air-permeability, and better water uptake capacity compared to P4HB strip and polycaprolactone (PCL) fibrous membrane controls. The in vitro hemocompatibility and cytotoxicity of P4HB fibrous membranes were investigated. In vivo Sprague-Dawley (SD) rat model studies revealed that P4HB fibrous membranes can be used as artificial dermis to improve wound healing for full-thickness skin defects.

Tailoring Materials with Specific Wettability in Biomedical Engineering

As a fundamental feature of solid surfaces, wettability is playing an increasingly important role in our daily life. Benefitting from the inspiration of biological paradigms and the development in manufacturing technology, numerous wettability materials with elaborately designed surface topology and chemical compositions have been fabricated. Based on these advances, wettability materials have found broad technological implications in various fields ranging from academy, industry, agriculture to biomedical engineering. Among them, the practical applications of wettability materials in biomedical-related fields are receiving remarkable researches during the past decades because of the increasing attention to healthcare. In this review, the research progress of materials with specific wettability is discussed. After briefly introducing the underlying mechanisms, the fabrication strategies of artificial materials with specific wettability are described. The emphasis is put on the application progress of wettability biomaterials in biomedical engineering. The prospects for the future trend of wettability materials are also presented.

Injectable Cell- and Growth Factor-Free Poly(4-hydroxybutyrate) (P4HB) Microspheres with Open Porous Structures and Great Efficiency of Promoting Bone Regeneration

Delivering injectable microspheres in a minimally invasive way to repair complexly shaped tissue defects renders them attractive for clinical use. Especially, open porous microspheres that provide sufficient internal space for cell proliferation and nutrient diffusions can efficiently aid to completing reconstructions of tissue defects. In this work, chemically synthesized and biodegradable poly(4-hydroxybutyrate) (P4HB), which is the U.S. FDA-approved polyhydroxyalkanoate (PHA), was employed for fabricating open porous microspheres using a double-emulsion solvent evaporation method. The influences of fabrication parameters were discussed. It was found that the P4HB-based cell-free and growth factor-free open porous microspheres can enhance osteoblast differentiation of adipose-derived stem cells in vitro and accelerate rat calvarial bone-defect healing in vivo. These results demonstrated that the injectable open porous P4HB microspheres present a remarkable potential in bone tissue regeneration.

Polysiloxane Nanofilaments Infused with Silicone Oil Prevent Bacterial Adhesion and Suppress Thrombosis on Intranasal Splints

Like all biofluid-contacting medical devices, intranasal splints are highly prone to bacterial adhesion and clot formation. Despite their widespread use and the numerous complications associated with infected splints, limited success has been achieved in advancing their safety and surface biocompatibility, and, to date, no surface-coating strategy has been proposed to simultaneously enhance the antithrombogenicity and bacterial repellency of intranasal splints. Herein, we report an efficient, highly stable lubricant-infused coating for intranasal splints to render their surfaces antithrombogenic and repellent toward bacterial cells. Lubricant-infused intranasal splints were prepared by creating superhydrophobic polysiloxane nanofilament (PSnF) coatings using surface-initiated polymerization of n-propyltrichlorosilane (n-PTCS) and further infiltrating them with a silicone oil lubricant. Compared with commercially available intranasal splints, lubricant-infused, PSnF-coated splints significantly attenuated plasma and blood clot formation and prevented bacterial adhesion and biofilm formation for up to 7 days, the typical duration for which intranasal splints are kept. We further demonstrated that the performance of our engineered biointerface is independent of the underlying substrate and could be used to enhance the hemocompatibility and repellency properties of other medical implants such as medical-grade catheters.

Recent progress and challenges in solution blow spinning

In the past 30 years, researchers have worked towards reducing the size of ordinary three-dimensional (3D) materials into 1D or 2D materials in order to obtain new properties and applications of these low-dimensional systems. Among them, functional nanofibers with large surface area and high porosity have been widely studied and paid attention to. Because of the interesting properties of nanofibers, they find extensive application in filtration, wound dressings, composites, sensors, capacitors, nanogenerators, etc. Recently, a variety of nanofiber preparation methods such as melt blowing, electrospinning (e-spinning), centrifugal spinning and solution blow spinning (SBS) have been proposed. This paper includes a brief review of the fundamental principles of the preparation of nanofibers for solution jet spinning, the influence of experimental parameters, and the properties and potential applications of the solution-blown fibers. And the industrialization and challenges of SBS are also included.

The challenge of lubricant-replenishment on lubricant-impregnated surfaces

Lubricant-impregnated surfaces are two-component surface coatings. One component, a fluid called the lubricant, is stabilized at a surface by the second component, the scaffold. The scaffold can either be a rough solid or a polymeric network. Drops immiscible with the lubricant, hardly pin on these surfaces. Lubricant-impregnated surfaces have been proposed as candidates for various applications, such as self-cleaning, anti-fouling, and anti-icing. The proposed applications rely on the presence of enough lubricant within the scaffold. Therefore, the quality and functionality of a surface coating are, to a large degree, given by the extent to which it prevents lubricant-depletion. This review summarizes the current findings on lubricant-depletion, lubricant-replenishment, and the resulting understanding of both processes. A multitude of different mechanisms can cause the depletion of lubricant. Lubricant can be taken along by single drops or be sheared off by liquid flowing across. Nano-interstices and scaffolds showing good chemical compatibility with the lubricant can greatly delay lubricant depletion. Often, depletion of lubricant cannot be avoided under dynamic conditions, which warrants lubricant-replenishment strategies. The strategies to replenish lubricant are presented and range from spraying or stimuli-responsive release to built-in reservoirs.

Bioinspired surfaces with wettability: biomolecule adhesion behaviors

Surface wettability plays an important role in regulating biomolecule adhesion behaviors. The biomolecule adhesion behaviors of superwettable surfaces have become an important topic as an important part of the interactions between materials and organisms. In addition to general research on the moderate wettability of surfaces, the studies of biomolecule adhesion behaviors extend to extreme wettability ranges such as superhydrophobic, superhydrophilic and slippery surfaces and attract both fundamental and practical interest. In this review, we summarize the recent studies on biomolecule adhesion behaviors on superwettable surfaces, especially superhydrophobic, superhydrophilic and slippery surfaces. The first part will focus on the influence of extreme wettability on cell adhesion behaviors. The second part will concentrate on the adhesion behaviors of biomacromolecules on superwettable surfaces including proteins and nucleic acids. Finally, the influences of wettability on small molecule adhesion behaviors on material surfaces have also been investigated. The mechanism of superwettable surfaces and their influences on biomolecule adhesion behaviors have been studied and highlighted.

Design novel three-dimensional network nanostructure for lubricant infused on titanium alloys towards long-term anti-fouling

Titanium alloys, recognized as a marine material with great potential, are currently facing serious biofouling problems, which greatly limits its application range. To improve the antifouling performance of titanium alloys, three unique surface of three-dimensional network, grass-like and linear nanostructures were obtained on titanium alloys via hydrothermal treatment in this work. Further, slippery liquid-infused porous surfaces (SLIPSs) were fabricated on titanium alloys via infusing PFPE lubricant into these nanostructures. Water contact angles and sliding angles of SLIPSs were measured to evaluate the effect of nanostructures on the stability of PFPE lubricant layer. Anti-fouling capability of SLIPSs were investigated by quantifying the cells of chlorella and phaeodactylum tricornutum (P. tricornutum)adhered to titanium alloys. The results shows that all the SLIPSs exhibited remarkable inhibition capacity for the settlement of chlorella and P. tricornutum. Among them, the SLIPS with three-dimensional network nanostructure displayed the longest-term anti-fouling performance, and its reduction rate of P. tricornutum and chlorella reaching 77.2 % and 84.5 % after being cultivated for 21 days, respectively, indicating that there existed a positive correlation between the stability of lubricant layer in the artificial seawater and the antifouling effect.

Bioinspired liquid gating membrane-based catheter with anticoagulation and positionally drug release properties

Catheters are indispensable medical devices that are extensively used in daily medical treatment. However, existing catheter materials continue to encounter many problems, such as thrombosis, single functionality, and inadaptability to environmental changes. Inspired by blood vessels, we develop a self-adaptive liquid gating membrane-based catheter with anticoagulation and positionally drug release properties. Our multifunctional liquid gating membrane-based catheter significantly attenuates blood clot formation and can be used as a general catheter design strategy to offer various drugs positionally releasing applications to comprehensively enhance the safety, functionality, and performance of medical catheters' materials.

Blowspinning: A New Choice for Nanofibers

Blowspinning is a new technique that enables the large-scale production of fibers with diameters ranging from micrometer to nanometer, which is more like a combination of melt-blown and electrospinning but has its own characteristics. This method can be used to deposit fibers in situ and produce various fibrous materials, such as coating, nonwoven, and sponge. These characteristics provide a new strategy for nanofiber application and attract the interest of many researchers. Regarding the blowspinning technique, systematic research had been carried out, involving basic principles, empirical studies, spinning equipment, and application. This review is intended to emphasize trends and gaps in the form of a concise illustration of various research directions.

Dynamic Self-Repairing Hybrid Liquid-in-Solid Protective Barrier for Cementitious Materials

Corrosion and surface fouling of structural materials, such as concrete, are persistent problems accelerating undesirable material degradation for many industries and infrastructures. To counteract these detrimental effects, protective coatings are frequently applied, but these solid-based coatings can degrade or become mechanically damaged over time. Such irreversible and irreparable damage on solid-based protective coatings expose underlying surfaces and bulk materials to adverse environmental stresses leading to subsequent fouling and degradation. We introduce a new concept of a hybrid liquid-in-solid protective barrier (LIB) to overcome the limitations of traditional protective coatings with broad applicability to structural materials. Through optimization of capillary forces and reduction of the interfacial energy between an upper mobile liquid and a lower immobile solid phase, a stable liquid-based protective layer is created. This provides a persistent self-repairing barrier against the infiltration of moisture and salt, in addition to omniphobic surface properties. As a model experimental test bed, we applied this concept to cementitious materials, which are commonly used as binders in concrete, and investigated how the mobile liquid phase embedded within a porous solid support contributes to the material's barrier protection and antifouling properties. Using industry standard test methods for acid resistance, chloride-ion penetrability, freeze-thaw cyclability, and mechanical durability, we demonstrate that LIBs exhibit significantly reduced water absorption and ion penetrability, improved repellency against various nonaqueous liquids, and resistance to corrosion while maintaining their required mechanical performance as structural materials.

Phosphonium Ionic Liquid-Infused Poly(vinyl chloride) Surfaces Possessing Potent Antifouling Properties

Microbial fouling is a costly issue, which impacts a wide range of industries, such as healthcare, food processing, and construction industries, and improved strategies to reduce the impact of fouling are urgently required. Slippery liquid-infused porous surfaces (SLIPSs) have recently been developed as a bioinspired approach to prevent antifouling. Here, we report the development of slippery, superhydrophilic surfaces by infusing roughened poly(vinyl chloride) (PVC) substrates with phosphonium ionic liquids (PILs). These surfaces were capable of reducing viable bacterial adherence by Staphylococcus aureus and Pseudomonas aeruginosa by >6 log10 cfu mL-1 after 24 h under static conditions relative to control PVC. Furthermore, we report the potential of a series of asymmetric quaternary alkyl PILs with varying alkyl chain lengths (C4-C18) and counteranions to act as antimicrobial agents against both Gram +ve and Gram -ve bacteria and illustrate their potential as antimicrobial alternatives to traditional fluorinated lubricants commonly used in the synthesis of SLIPSs.

Life and death of liquid-infused surfaces: a review on the choice, analysis and fate of the infused liquid layer

We review the rational choice, the analysis, the depletion and the properties imparted by the liquid layer in liquid-infused surfaces – a new class of low-adhesion surface.

Droplet Morphology and Mobility on Lubricant-Impregnated Surfaces: A Molecular Dynamics Study

Slippery liquid-infused porous surfaces (SLIPS) are gaining remarkable attention and have advanced performance in many fields. Although all SLIPS are related to lubricant-impregnation within nano/microstructures on a surface, they differ in many aspects, such as the morphology of droplets, the state of cloaking, the wetting edge, and the lubricant thickness. Requirements of the droplet morphology on SLIPS might change according to a specific application. A molecular-dynamics-based numerical model that can correctly simulate SLIPS is developed and is validated by comparing against the theoretical predictions for all possible stable states for a given droplet, lubricant, and solid surface. On the basis of this model, a detailed analysis of the equilibrium states is conducted. In particular, we discover that the four possible stable states on SLIPS predicted by theoretical studies can be extended to eight states by considering the effects of lubricant thickness and surface geometry in addition to the interfacial tension and surface wettability. These findings could be used to determine the conditions under which a thermodynamically stable state exists on SLIPS. The dynamic behavior of a nanodroplet on SLIPS is also studied, which provides insight into how a proper increase in the lubricant thickness might increase the sliding velocity. The above findings and developed model are expected to provide significant guidelines for designing SLIPS.

Spinning and Applications of Bioinspired Fiber Systems

Natural fiber systems provide inspirations for artificial fiber spinning and applications. Through a long process of trial and error, great progress has been made in recent years. The natural fiber itself, especially silks, and the formation mechanism are better understood, and some of the essential factors are implemented in artificial spinning methods, benefiting from advanced manufacturing technologies. In addition, fiber-based materials produced via bioinspired spinning methods find an increasingly wide range of biomedical, optoelectronic, and environmental engineering applications. This paper reviews recent developments in the spinning and application of bioinspired fiber systems, introduces natural fiber and spinning processes and artificial spinning methods, and discusses applications of artificial fiber materials. Views on remaining challenges and the perspective on future trends are also proposed.

Designing Liquid-Infused Surfaces for Medical Applications: A Review

The development of new technologies is key to the continued improvement of medicine, relying on comprehensive materials design strategies that can integrate advanced therapeutic and diagnostic functions with a variety of surface properties such as selective adhesion, dynamic responsiveness, and optical/mechanical tunability. Liquid-infused surfaces have recently come to the forefront as a unique approach to surface coatings that can resist adhesion of a wide range of contaminants on medical devices. Furthermore, these surfaces are proving highly versatile in enabling the integration of established medical surface treatments alongside the antifouling capabilities, such as drug release or biomolecule organization. Here, the range of research being conducted on liquid-infused surfaces for medical applications is presented, from an understanding of the basics behind the interactions of physiological fluids, microbes, and mammalian cells with liquid layers to current applications of these materials in point-of-care diagnostics, medical tubing, instruments, implants, and tissue engineering. Throughout this exploration, the design parameters of liquid-infused surfaces and how they can be adapted and tuned to particular applications are discussed, while identifying how the range of controllable factors offered by liquid-infused surfaces can be used to enable completely new and dynamic approaches to materials and devices for human health.

Liquid-Infused Surfaces on Electrosurgical Instruments with Exceptional Antiadhesion and Low-Damage Performances

Electrosurgery based on electrosurgical instruments plays an important role in clinical surgery owing to its advantages of ease of operation, low damage, and less pain to the patient. But soft tissue adhesion on electrosurgical instruments is still a major obstacle to improve the operation efficiency and achieve a better surgical result, regardless of so many developed methods to enhance the antiadhesion performance. In this paper, we successfully demonstrated that liquid-infused surfaces (LISs) can significantly improve the antiadhesion performance of electrosurgical instruments. We developed a microcontact printing method to assist the structure fabrication on the small instrument tip to prepare a firmly liquid-held surface. Soft tissue cutting experiments showed that LIS could not only significantly reduce the adhesion force between the tissue and the instrument tip but also lead to a much smaller charring wound. The underlying mechanism was discussed, and further experiments concluded that LIS have a better duration capability. Our study provides a new insight into the antiadhesion design for electrosurgical instruments.

Influence of long-range forces and capillarity on the function of underwater superoleophobic wrinkled surfaces

Underwater superoleophobic surfaces can be considered a particular type of lubricant-infused surface, that have anti-fouling properties by virtue of a trapped water layer that repels oils. However, as their function relies on a water layer being trapped in the surface roughness, it is crucial to understand the factors that determine the layer stability. In this work, the forces that are responsible for the stability of thin liquid films within structured surfaces were quantified, and the conclusions were tested against the performance of wrinkled surfaces as underwater superoleophobic coatings. Here, the system studied was a family of wrinkled surfaces made of hydrophilic poly(4-vinylpyridine) (P4VP), whereby the wrinkle width could be controllably tuned in the range 90 nm to 8000 nm. The van der Waals free energy was quantified and the capillary forces trapping water in the surface micro- and nano-wrinkle structure were estimated. P4VP surfaces with micro-scale wrinkles had underwater superoleophobic properties, and low adhesion to different oils with droplet roll-off angle below 6° ± 1°. Despite the van der Waals free energy of the system pointing to the dewetting of a water film under oil on top of a smooth P4VP film, the wrinkled structure is sufficient to induce a Cassie state with a trapped water layer. The micro-scale wrinkles (average width 4-12 μm) were found to be particularly effective in the trapping of the water in a Cassie non-adhesive state. The P4VP wrinkled surfaces are superamphiphobic, as when they were first infused with oil, and then exposed to a droplet of water under oil, they exhibited superhydrophobic behavior. The P4VP wrinkles have the additional useful feature of being transparent underwater, which makes them useful candidates for the protection of underwater cameras and sensors.

Slippery Liquid-Infused Porous Surfaces (SLIPS) Using Layer-by-Layer Polyelectrolyte Assembly in Organic Solvent

Slippery liquid-infused porous surfaces (SLIPS) have potential impact on a wide range of industries, including healthcare, food packaging, and automobile. A tremendouseffort has been focused on developing novel fabrication methods for making SLIPS. However, current fabrication methods usually involve harsh conditions and complicated postfabrication modifications or are limited to specific substrates. Presented here is a novel method for the fast and facile fabrication of SLIPS. Layer-by-layer (LBL) assembly of branched polyethylenimine and Nafion, a perfluorinated polyelectrolyte, is performed with methanol as the solvent. Hierarchically rough and superhydrophobic surface is obtained directly without further modification on various substrates. The surface properties are shown to highly depend on the LBL assembly parameters, including deposition cycles, dipping time, rinsing time, and drying time between baths. The polyelectrolyte multilayers obtained with this method are infused with Krytox 100 to form SLIPS surfaces, which show excellent omniphobic, antifouling, self-cleaning, flexible, and optical properties. The result of this study not only simplifies the fabrication of SLIPS surfaces, but also provides great insight for making LBL films with specific morphologies.

Marine Antifouling Behavior of Lubricant-Infused Nanowrinkled Polymeric Surfaces

A new family of polymeric, lubricant-infused, nanostructured wrinkled surfaces was designed that effectively retains inert nontoxic silicone oil, after draining by spin-coating and vigorous shear for 2 weeks. The wrinkled surfaces were fabricated using three different polymers (Teflon AF, polystyrene, and poly(4-vinylpyridine)) and two shrinkable substrates (Polyshrink and shrinkwrap), and Teflon on Polyshrink was found to be the most effective system. The volume of trapped lubricant was quantified by adding Nile red to the silicone oil before infusion and then extracting the oil and Nile red from the surfaces in heptane and measuring by fluorimetry. Higher volumes of lubricant induced lower roll-off angles for water droplets, and in turn induced better antifouling performance. The infused surfaces displayed stability in seawater and inhibited growth of Pseudoalteromonas spp. bacteria up to 99%, with as little as 0.9 μL cm^-2 of the silicone oil infused. Field tests in the waters of Sydney Harbor over 7 weeks showed that silicone oil infusion inhibited the attachment of algae, but the algal attachment increased as the silicone oil was slowly depleted over time. The infused wrinkled surfaces have high transparency and are moldable, making them suited to protect the windows of underwater sensors and cameras.

Recent developments in smart antibacterial surfaces to inhibit biofilm formation and bacterial infections

Since their development over 70 years, antibiotics are still the most effective strategy to treat bacterial biofilms and infections.

Solution blow spinning fibres: New immunologically inert substrates for the analysis of cell adhesion and motility

The control of cell behaviour through material geometry is appealing as it avoids the requirement for complex chemical surface modifications. Significant advances in new technologies have been made to the development of polymeric biomaterials with controlled geometry and physico-chemical properties. Solution blow spinning technique has the advantage of ease of use allowing the production of nano or microfibres and the direct fibre deposition on any surface in situ. Yet, in spite of these advantages, very little is known about the influence of such fibres on biological functions such as immune response and cell migration. In this work, we engineered polymeric fibres composed of either pure poly(lactic acid) (PLA) or blends of PLA and polyethylene glycol (PEG) by solution blow spinning and determined their impact on dendritic cells, highly specialised cells essential for immunity and tolerance. We also determined the influence of fibres on cell adhesion and motility. Cells readily interacted with fibres resulting in an intimate contact characterised by accumulation of actin filaments and focal adhesion components at sites of cell-fibre interactions. Moreover, cells were guided along the fibres and actin and focal adhesion components showed a highly dynamic behaviour at cell-fibre interface. Remarkably, fibres did not elicit any substantial increase of activation markers and inflammatory cytokines in dendritic cells, which remained in their immature (inactive) state. Taken together, these findings will be useful for developing new biomaterials for applications in tissue engineering and regenerative medicine.

A Review of the Fundamental Principles and Applications of Solution Blow Spinning

Solution blow spinning (SBS) is a technique that can be used to deposit fibers in situ at low cost for a variety of applications, which include biomedical materials and flexible electronics. This review is intended to provide an overview of the basic principles and applications of SBS. We first describe a method for creating a spinnable polymer solution and stable polymer solution jet by manipulating parameters such as polymer concentration and gas pressure. This method is based on fundamental insights, theoretical models, and empirical studies. We then discuss the unique bundled morphology and mechanical properties of fiber mats produced by SBS, and how they compare with electrospun fiber mats. Applications of SBS in biomedical engineering are highlighted, showing enhanced cell infiltration and proliferation versus electrospun fiber scaffolds and in situ deposition of biodegradable polymers. We also discuss the impact of SBS in applications involving textiles and electronics, including ceramic fibers and conductive composite materials. Strategies for future research are presented that take advantage of direct and rapid polymer deposition via cost-effective methods.