Adhesion behaviors on superhydrophobic surfaces

Strong, bacteriostatic and transparent polylactic acid-based composites by incorporating quaternary ammonium cellulose nanocrystals

Renewable natural fibers (e.g., cellulose nanocrystals (CNCs)) are being applied for reinforcing bio-based polylactic acid (PLA). For improvement in the interfacial compatibility between CNCs and PLA and the dispersibility of CNCs, a quaternary ammonium salt-coated CNCs (Q-CNCs) hybrid was prepared in this study based on an esterification self-polymerization method, and such hybrid was further utilized as a new strengthening/toughening nanofiller for producing the Q-CNCs-reinforced PLA composite. The results confirmed that quaternary ammonium salt coatings could efficiently enhance CNCs/PLA interfacial compatibility via mechanical interlocking and semi-interpenetrating networks. Attributing to the synergistic effect of quaternary ammonium salts and CNCs, a considerable enhancement in processing, mechanical, and thermal properties was gained in the obtained Q-CNCs-reinforced PLA composite. With the addition of 0.5 wt% Q-CNCs, the tensile strength, Young's modulus, and elongation at break of the Q-CNCs-reinforced PLA composite was raised by approximately 23 %, 37 % and 18 %, respectively; compared with pure PLA, the obtained composite had excellent bacteriostatic properties and good transparency. This work discusses the development of high-performance, low-cost and sustainable PLA-based composites on a potential application in packaging materials.

Modern Microbiological Methods to Detect Biofilm Formation in Orthopedy and Suggestions for Antibiotic Therapy, with Particular Emphasis on Prosthetic Joint Infection (PJI)

Biofilm formation is a serious problem that relatively often causes complications in orthopedic surgery. Biofilm-forming pathogens invade implanted foreign bodies and surrounding tissues. Such a condition, if not limited at the appropriate time, often requires reoperation. This can be partially prevented by selecting an appropriate prosthesis material that prevents the development of biofilm. There are many modern techniques available to detect the formed biofilm. By applying them we can identify and visualize biofilm-forming microorganisms. The most common etiological factors associated with biofilms in orthopedics are: Staphylococcus aureus, coagulase-negative Staphylococci (CoNS), and Enterococcus spp., whereas Gram-negative bacilli and Candida spp. also deserve attention. It seems crucial, for therapeutic success, to eradicate the microorganisms able to form biofilm after the implantation of endoprostheses. Planning the effective targeted antimicrobial treatment of postoperative infections requires accurate identification of the microorganism responsible for the complications of the procedure. The modern microbiological testing techniques described in this article show the diagnostic options that can be followed to enable the implementation of effective treatment.

Fundamentals and Applications of Surface Wetting

In an era defined by an insatiable thirst for sustainable energy solutions, responsible water management, and cutting-edge lab-on-a-chip diagnostics, surface wettability plays a pivotal role in these fields. The seamless integration of fundamental research and the following demonstration of applications on these groundbreaking technologies hinges on manipulating fluid through surface wettability, significantly optimizing performance, enhancing efficiency, and advancing overall sustainability. This Review explores the behavior of liquids when they engage with engineered surfaces, delving into the far-reaching implications of these interactions in various applications. Specifically, we explore surface wetting, dissecting it into three distinctive facets. First, we delve into the fundamental principles that underpin surface wetting. Next, we navigate the intricate liquid-surface interactions, unraveling the complex interplay of various fluid dynamics, as well as heat- and mass-transport mechanisms. Finally, we report on the practical realm, where we scrutinize the myriad applications of these principles in everyday processes and real-world scenarios.

Directional Adhesion of Monodomain Liquid Crystalline Elastomers

Pressure-sensitive adhesives (PSAs) are widely employed in consumer goods, health care, and commercial industry. Anisotropic adhesion of PSAs is often desirable to enable high force capacity coupled with facile release and has typically been realized through the introduction of complex surface and/or bulk microstructures while also maintaining high surface conformability. Although effective, microstructure fabrication can add cost and complexity to adhesive fabrication. Here, we explore aligned liquid crystalline elastomers (LCEs) as directional adhesives. Aligned LCEs exhibit direction-dependent stiffness, dissipation, and nonlinear deformation under load. By varying the cross-link content, we study how the bulk mechanical properties of LCEs correlate to their peel strength and peel anisotropy. We demonstrate up to a 9-fold difference in peel force measured when the LCE is peeled parallel vs perpendicular to the alignment axis. Opportunities to spatially localize adhesion are presented in a monolithic LCE patterned with different director orientations.

Development of Adjustable High- to Low-Adhesive Superhydrophobicity Using Aligned Electrospun Fibers

Superhydrophobic surfaces based on electrospun fibrous structures exhibit advantages of additive manufacturing and enable the passage of gases. Compared to randomly deposited fibers, directionally aligned fibers improve the control of surface wetting by a specified fiber orientation and predictable liquid-fiber contact interface. In this article, we create superhydrophobicity with adjustable adhesion based on the understanding of droplet wetting behavior on directionally aligned fibers. Directionally aligned polystyrene fibers with different diameters and interfiber distances (l) are produced using electrospinning with a rotating fin collector. The wetting behavior of droplets on the surfaces dressed by aligned fibers is characterized, and a thermodynamic model of wetting behavior is established to guide the experimental studies. As a result, high-adhesive superhydrophobicity is achieved on weak hydrophobic substrate surfaces dressed by aligned polystyrene fibers with a diameter of 1.8 μm and l between 5 and 130 μm. Water droplets (2 μL) exhibit a maximum contact angle of 156° and adhere to the fiber-dressed surfaces by tilting upside down. Low-adhesive superhydrophobicity is achieved by introducing an additional layer of aligned fibers to increase the transition energy barrier. On the dual-layer structure with an upper-layer l of 9 μm, droplets show a contact angle of 155° and can readily roll off the surface. Moreover, increasing the upper-layer l to 15 μm reserves the surface to high-adhesive superhydrophobicity.

Fabrication of Superhydrophobic Water-Pinning Surfaces through Integration of Silica Colloids into Cellulose Nanocrystals

The water-pinning effect is a phenomenon in which water droplets adhere to a surface and do not roll off, even when the surface is tilted or turned upside down. This effect holds great potential for applications in various areas, such as dew collection in arid regions, anti-drip function for a greenhouse, and liquid transport and control. However, creating surfaces that exhibit this effect poses challenges, necessitating materials with both hydrophobicity and high adhesive force along with a scalable, cost-effective method to produce the essential geometries that have not yet been established. To address these challenges, we propose a straightforward coating approach involving silica nanoparticles (SiO2) and cellulose nanocrystals (CNCs) to fabricate artificial water-pinning surfaces. We assessed the water-pinning ability of the coated surface through measurements of the contact angle, contact radius, and hysteresis. Remarkably, the coated surface exhibited a contact angle of approximately 153.87° and a contact radius of around 0.89 mm when a 10 μL water droplet was applied, demonstrating its resistance to rolling off, even at a tilting angle of 90°. The droplet only began to fall when its volume reached approximately 33 μL, requiring a substantial water pinning force of 323.4 μN. We also investigated the physicochemical characteristics of the SiO2@CNC coating surface, including morphology, chemical composition, and chemical structure, to unravel the underlying mechanism behind its water-pinning ability. Our proposed fabrication method offers a promising avenue for the development of functional biopolymer-based surfaces capable of precisely manipulating water droplets.

Silica Nanoparticle-Infused Omniphobic Polyurethane Foam with Bacterial Anti-Adhesion and Antifouling Properties for Hygiene Purposes

In this study, a method for preventing cross-infection through the surface coating treatment of polyurethane (PU) foam using functionalized silica nanoparticles was developed. Experimental results confirmed that the fabricated PU foam exhibited omniphobic characteristics, demonstrating strong resistance to both polar and nonpolar contaminants. Additionally, quantitative analysis using the pour plate method and direct counting with a scanning electron microscope determined that the treated material exhibited anti-adhesion properties against bacteria. The fabricated PU foam also demonstrated a high level of resistance to the absorption of liquids commonly found in medical facilities, including blood, 0.9% sodium chloride solution, and 50% glycerol. Mechanical durability and stability were verified through repeated compression tests and chemical leaching tests, respectively. The proposed coated PU foam is highly effective at preventing fouling from polar and nonpolar fluids as well as bacteria, making it well-suited for use in a range of fields requiring strict hygiene standards, including the medical, food, and environmental industries.

Antibacterial Superhydrophobic Cotton Fabric with Photothermal, Self-Cleaning, and Ultraviolet Protection Functionalities

Cotton fabrics with superhydrophobic, antibacterial, UV protection, and photothermal properties were developed using Ag/PDMS coatings, and the role of coating formulations on the obtained functionalities was studied. Specific attention was paid to understanding the relationships between the fabrics' superhydrophobicity and antibacterial activity against Escherichia coli (E. coli) bacteria. UV protection performance of Ag/PDMS coatings was thoroughly evaluated based on the variation of UV transmission rate through coated fabrics and photoinduced chemiluminescence spectra. Moreover, the effect of silver nanoparticles (Ag NPs) and PDMS on developing a photothermal effect on fabrics was discussed. It was found that the content of Ag NPs and PDMS played critical roles in determining the water contact angle (WCA) on modified fabrics. The largest WCA was 171.31°, which was durable even after numerous accelerated wash cycles and abrasions. Antibacterial activity of fabrics showed the positive effect of pure PDMS in bacterial growth inhibition. Moreover, it was found that the antibacterial performance was greatly affected by the content of Ag NPs loaded on fabrics rather than their superhydrophobic status. Moreover, increasing the content of Ag NPs boosted the UV protection level of fabrics, improved fabrics photostability, and reduced the UV transmission rate through fabrics. Testing the photothermal effect confirmed that the content of Ag NPs and PDMS both played prominent roles, where Ag acted as a photothermal agent and PDMS determined the NIR reflection rate from the coated surface. The modified fabrics were characterized using TGA, SEM, FTIR, and XRD techniques, and it was confirmed that using a higher amount of PDMS increased the amount of Ag NPs deposition on fabrics.

Antibacterial coatings on orthopedic implants

With the aging of population and the rapid improvement of public health and medical level in recent years, people have had an increasing demand for orthopedic implants. However, premature implant failure and postoperative complications frequently occur due to implant-related infections, which not only increase the social and economic burden, but also greatly affect the patient's quality of life, finally restraining the clinical use of orthopedic implants. Antibacterial coatings, as an effective strategy to solve the above problems, have been extensively studied and motivated the development of novel strategies to optimize the implant. In this paper, a variety of antibacterial coatings recently developed for orthopedic implants were briefly reviewed, with the focus on the synergistic multi-mechanism antibacterial coatings, multi-functional antibacterial coatings, and smart antibacterial coatings that are more potential for clinical use, thereby providing theoretical references for further fabrication of novel and high-performance coatings satisfying the complex clinical needs.

The Potential of Surface-Immobilized Antimicrobial Peptides for the Enhancement of Orthopaedic Medical Devices: A Review

Due to the well-known phenomenon of antibiotic resistance, there is a constant need for antibiotics with novel mechanisms and different targets respect to those currently in use. In this regard, the antimicrobial peptides (AMPs) seem very promising by virtue of their bactericidal action, based on membrane permeabilization of susceptible microbes. Thanks to this feature, AMPs have a broad activity spectrum, including antibiotic-resistant strains, and microbial biofilms. Additionally, several AMPs display properties that can help tissue regeneration. A possible interesting field of application for AMPs is the development of antimicrobial coatings for implantable medical devices (e.g., orthopaedic prostheses) to prevent device-related infection. In this review, we will take note of the state of the art of AMP-based coatings for orthopaedic prostheses. We will review the most recent studies by focusing on covalently linked AMPs to titanium, their antimicrobial efficacy and plausible mode of action, and cytocompatibility. We will try to extrapolate some general rules for structure-activity (orientation, density) relationships, in order to identify the most suitable physical and chemical features of peptide candidates, and to optimize the coupling strategies to obtain antimicrobial surfaces with improved biological performance.

The mechanism of metal-based antibacterial materials and the progress of food packaging applications: A review

Food packages have been detected carrying novel coronavirus in multi-locations since the outbreak of COVID-19, causing major concern in the field of food safety. Metal-based supported materials are widely used for sterilization due to their excellent antibacterial properties as well as low biological resistance. As the principal part of antibacterial materials, the active component, commonly referred to Ag, Cu, Zn, etc., plays the main role in inhibiting and killing pathogenic microorganisms by destroying the structure of cells. As another composition of metal-based antibacterial materials, the carrier could support and disperse the active component, which on one hand, could effectively decrease the usage amount of active component, on the other hand, could be processed into various forms to broaden the application range of antibacterial materials. Different from other metal-based antibacterial reviews, in order to highlight the detailed function of various carriers, we divided the carriers into biocompatible and adsorptable types and discussed their different antibacterial effects. Moreover, a novel substitution antibacterial mechanism was proposed. The coating and shaping techniques of metal-based antibacterial materials as well as their applications in food storage at ambient and low temperatures are also comprehensively summarized. This review aims to provide a theoretical basis and reference for researchers in this field to develop new metal-based antibacterial materials.

Bioselectivity of silk protein-based materials and their bio-inspired applications

Adhesion to material surfaces is crucial for almost all organisms regarding subsequent biological responses. Mammalian cell attachment to a surrounding biological matrix is essential for maintaining their survival and function concerning tissue formation. Conversely, the adhesion and presence of microbes interferes with important multicellular processes of tissue development. Therefore, tailoring bioselective, biologically active, and multifunctional materials for biomedical applications is a modern focus of biomaterial research. Engineering biomaterials that stimulate and interact with cell receptors to support binding and subsequent physiological responses of multicellular systems attracted much interest in the last years. Further to this, the increasing threat of multidrug resistance of pathogens against antibiotics to human health urgently requires new material concepts for preventing microbial infestation and biofilm formation. Thus, materials exhibiting microbial repellence or antimicrobial behaviour to reduce inflammation, while selectively enhancing regeneration in host tissues are of utmost interest. In this context, protein-based materials are interesting candidates due to their natural origin, biological activity, and structural properties. Silk materials, in particular those made of spider silk proteins and their recombinant counterparts, are characterized by extraordinary properties including excellent biocompatibility, slow biodegradation, low immunogenicity, and non-toxicity, making them ideally suited for tissue engineering and biomedical applications. Furthermore, recombinant production technologies allow for application-specific modification to develop adjustable, bioactive materials. The present review focusses on biological processes and surface interactions involved in the bioselective adhesion of mammalian cells and repellence of microbes on protein-based material surfaces. In addition, it highlights the importance of materials made of recombinant spider silk proteins, focussing on the progress regarding bioselectivity.

Anisotropic Wettability of Bioinspired Surface Characterized by Friction Force

Bioinspired surfaces with special wettabilities attract increasing attention due to their extensive applications in many fields. However, the characterizations of surface wettability by contact angle (CA) and sliding angle (SA) have clear drawbacks. Here, by using an array of triangular micropillars (ATM) prepared by soft lithography, the merits of measuring the friction force of a water droplet on ATM over measurements of CA and SA in characterizing the surface wettability are demonstrated. The CA and SA measurements show ignorable differences in the wettabilities of ATM in opposite directions (1.13%) and that with different periodic parameters under the elongation ranging from 0 to 70%. In contrast, the friction measurement reveals a difference of > 10% in opposite directions. Moreover, the friction force shows a strong dependence on the periodic parameters which is regulated by mechanical stretching. Increasing the elongation from 0 to 50% increases the static and kinetic friction force up to 23.0% and 22.9%, respectively. Moreover, the stick-slip pattern during kinetic friction can reveal the periodic features of the measured surface. The friction force measurement is a sensitive technique that could find applications in the characterization of surface wettabilities.

Adhesion behaviors of water droplets on bioinspired superhydrophobic surfaces

The adhesion behaviors of droplets on surfaces are attracting increasing attention due to their various applications. Many bioinspired superhydrophobic surfaces with different adhesion states have been constructed in order to mimic the functions of natural surfaces such as a lotus leaf, a rose petal, butterfly wings, etc. In this review, we first present a brief introduction to the fundamental theories of the adhesion behaviors of droplets on various surfaces, including low adhesion, high adhesion and anisotropic adhesion states. Then, different techniques to characterize droplet adhesion on these surfaces, including the rotating disk technique, the atomic force microscope cantilever technique, and capillary sensor-based techniques, are described. Wetting behaviors, and the switching between different adhesion states on bioinspired surfaces, are also summarized and discussed. Subsequently, the diverse applications of bioinspired surfaces, including water collection, liquid transport, drag reduction, and oil/water separation, are discussed. Finally, the challenges of using liquid adhesion behaviors on various surfaces, and future applications of these surfaces, are discussed.

One-step laser etching of a bionic hierarchical structure on a silicone rubber surface with thermal and acid/alkali resistance and tunable wettability

Superhydrophobic silicone rubbers with robust physical and chemical stability have promising application potential in the field of flexible electronics. A one-step laser etching strategy is proposed for successfully fabricating superhydrophobic silicone rubbers with bioinspired hierarchical micro/nanostructures. Regular and dense micro/nano spheres gradually accumulate on the modified silicone rubber surface with the increase of laser etching cycles. Owing to the bioinspired hierarchical micro/nano spheres, a 5 μL water droplet on the modified silicone rubber surface exhibits a contact angle of 158 ± 3° and a sliding angle of 5 ± 1°. Moreover, the modified silicone rubber can maintain a stable superhydrophobic state in acid/alkali (pH = 2, 4, 6, 8, and 10) and thermal environments (50-90 °C). Importantly, the contact angle and sliding angle are adjustable depending on the number of laser etching cycles, which is beneficial for the different application requirements. The proposed method for the fast fabrication of superhydrophobic silicone rubbers with tunable wettability can provide an excellent candidate for the protection of flexible electronics in rainy and acid/alkali environments.

Pathogen-Repellent Plastic Warp with Built-In Hierarchical Structuring Prevents the Contamination of Surfaces with Coronaviruses

Amidst the COVID-19 pandemic, it is evident that viral spread is mediated through several different transmission pathways. Reduction of these transmission pathways is urgently needed to control the spread of viruses between infected and susceptible individuals. Herein, we report the use of pathogen-repellent plastic wraps (RepelWrap) with engineered surface structures at multiple length scales (nanoscale to microscale) as a means of reducing the indirect contact transmission of viruses through fomites. To quantify viral repellency, we developed a touch-based viral quantification assay to mimic the interaction of a contaminated human touch with a surface through the modification of traditional viral quantification methods (viral plaque and TCID50 assays). These studies demonstrate that RepelWrap reduced contamination with an enveloped DNA virus as well as the human coronavirus 229E (HuCoV-229E) by more than 4 log 10 (>99.99%) compared to a standard commercially available polyethylene plastic wrap. In addition, RepelWrap maintained its repellent properties after repeated 300 touches and did not show an accumulation in viral titer after multiple contacts with contaminated surfaces, while increases were seen on other commonly used surfaces. These findings show the potential use of repellent surfaces in reducing viral contamination on surfaces, which could, in turn, reduce the surface-based spread and transmission.

Approaches to inhibit biofilm formation applying natural and artificial silk-based materials

The discovery of penicillin started a new era of health care since it allowed the effective treatment of formerly deadly infections. As a drawback, its overuse led to a growing number of multi-drug resistant pathogens. Challenging this arising threat, material research focuses on the development of microbe-killing or microbe repellent agents implementing such functions directly into materials. Due to their biocompatibility, non-immunogenicity and mechanical strength, silk-based materials are attractive candidates for applications in the biomedical field. Furthermore, it has been observed that silks display high persistency in their natural environment giving reason to suspect that they might be attractive candidates to prevent microbial infestation. The current review describes the process of biofilm formation on medical devices and the most common strategies to prevent it, divided into effects of surface topography, material modification and integrated additives. In this context, recent state of the art developments in the field of natural and artificial silk-based materials with microbe-repellant or antimicrobial properties are addressed. These silk properties are controversially discussed and conclusions are drawn as to which parameters will be decisive for the successful design of new bio-functional materials based on the blueprint of silk proteins.

Prediction of Droplet Sliding on the Continuity of the Three-Phase Contact Line

Many animals and plants have evolved wonderful hydrophobic abilities to adapt to the complex climate environment. The microstructure design of a superhydrophobic surface focuses on bionics and will be restricted by processing technology. Although certain functions can be achieved, there is a lack of unified conclusion on the wetting mechanism and a few quantitative analyses of the continuity of the three-phase contact line. Therefore, the relationship between the surface microstructure of the lattice pattern and the critical sliding angle of the water droplet in the Cassie state was investigated in this paper, and we proposed a method to quantitatively analyze the continuity of the three-phase contact line by a dimensionless length f. The results showed that the three-phase contact line was an important factor to determine the sliding performance of the droplet. The upward traction force generated by the surface tension through the force analysis on the three-phase contact line can enhance the sliding ability of the droplet on the solid surface. There was a good negative linear correlation between the critical sliding angle and dimensionless length, which provided a guiding basis for the optimal design of superhydrophobic surfaces.

Carbon Nanomaterials Modified Biomimetic Dental Implants for Diabetic Patients

Dental implants are used broadly in dental clinics as the most natural-looking restoration option for replacing missing or highly diseased teeth. However, dental implant failure is a crucial issue for diabetic patients in need of dentition restoration, particularly when a lack of osseointegration and immunoregulatory incompetency occur during the healing phase, resulting in infection and fibrous encapsulation. Bio-inspired or biomimetic materials, which can mimic the characteristics of natural elements, are being investigated for use in the implant industry. This review discusses different biomimetic dental implants in terms of structural changes that enable antibacterial properties, drug delivery, immunomodulation, and osseointegration. We subsequently summarize the modification of dental implants for diabetes patients utilizing carbon nanomaterials, which have been recently found to improve the characteristics of biomimetic dental implants, including through antibacterial and anti-inflammatory capabilities, and by offering drug delivery properties that are essential for the success of dental implants.

Recent Strategies to Combat Infections from Biofilm-Forming Bacteria on Orthopaedic Implants

Biofilm-related implant infections (BRII) are a disastrous complication of both elective and trauma orthopaedic surgery and occur when an implant becomes colonised by bacteria. The definitive treatment to eradicate the infections once a biofilm has established is surgical excision of the implant and thorough local debridement, but this carries a significant socioeconomic cost, the outcomes for the patient are often poor, and there is a significant risk of recurrence. Due to the large volumes of surgical procedures performed annually involving medical device implantation, both in orthopaedic surgery and healthcare in general, and with the incidence of implant-related infection being as high as 5%, interventions to prevent and treat BRII are a major focus of research. As such, innovation is progressing at a very fast pace; the aim of this study is to review the latest interventions for the prevention and treatment of BRII, with a particular focus on implant-related approaches.

Coating Technologies for Copper Based Antimicrobial Active Surfaces: A Perspective Review

Microbial contamination of medical devices and treatment rooms leads to several detrimental hospital and device-associated infections. Antimicrobial copper coatings are a new approach to control healthcare-associated infections (HAI’s). This review paper focuses on the efficient methods for depositing highly adherent copper-based antimicrobial coatings onto a variety of metal surfaces. Antimicrobial properties of the copper coatings produced by various deposition methods including thermal spray technique, electrodeposition, electroless plating, chemical vapor deposition (CVD), physical vapor deposition (PVD), and sputtering techniques are compared. The coating produced using different processes did not produce similar properties. Also, process parameters often could be varied for any given coating process to impart a change in structure, topography, wettability, hardness, surface roughness, and adhesion strength. In turn, all of them affect antimicrobial activity. Fundamental concepts of the coating process are described in detail by highlighting the influence of process parameters to increase antimicrobial activity. The strategies for developing antimicrobial surfaces could help in understanding the mechanism of killing the microbes.

Fabrication of a superhydrophobic surface by modulating the morphology of organogels

A low-molecular weight organic gelator (LMOG) bearing a hydrazine linkage and end-capped by alkoxy-substituted phenyl, namely 1,4-bis[(3,4-bisoctyloxyphenyl)hydrozide]phenylene (BPH-8), was used to facilely fabricate superhydrophobic surfaces by the drop-casting method. High quality superhydrophobic surfaces could be successfully prepared in one step in a mixed solvent of ethanol and tetrahydrofuran. The wettability of the surfaces can be modulated from superhydrophobicity to hydrophobicity through changing the ethanol and tetrahydrofuran ratio of the mixed solvent. SEM and AFM images demonstrated that the morphologies changed from hierarchical micro/nano structures to porous structures with increasing content of tetrahydrofuran. This might be the main reason for the wettability change. It was confirmed that these molecules self-assemble into a lamellar structure and show priority growth in one dimension to form nano-scaled fibers. This work not only demonstrated the superiority of superhydrophobic surface preparation through molecular self-assembly, but also offered an easy way to extend its application in the field of surface science.

Superhydrophobic, photo-sterilize, and reusable mask based on graphene nanosheet-embedded carbon (GNEC) film

The 2019 coronavirus disease (COVID-19) has affected more than 200 countries. Wearing masks can effectively cut off the virus spreading route since the coronavirus is mainly spreading by respiratory droplets. However, the common surgical masks cannot be reused, resulting in the increasing economic and resource consumption around the world. Herein, we report a superhydrophobic, photo-sterilize, and reusable mask based on graphene nanosheet-embedded carbon (GNEC) film, with high-density edges of standing structured graphene nanosheets. The GNEC mask exhibits an excellent hydrophobic ability (water contact angle: 157.9°) and an outstanding filtration efficiency with 100% bacterial filtration efficiency (BFE). In addition, the GNEC mask shows the prominent photo-sterilize performance, heating up to 110 °C quickly under the solar illumination. These high performances may facilitate the combat against the COVID-19 outbreaks, while the reusable masks help reducing the economic and resource consumption.

ELECTRONIC SUPPLEMENTARY MATERIAL

Supplementary material (further details of electron cyclotron resonance (ECR) sputtering system, deposition of GNEC film, fabrication of GNEC mask, and characterization of the GNEC mask) is available in the online version of this article at 10.1007/s12274-020-3158-1.

Functional Superhydrophobic Surfaces with Spatially Programmable Adhesion

A superhydrophobic surface that has controllable adhesion and is characterized by the lotus and petal effects is a powerful tool for the manipulation of liquid droplets. Such a surface has considerable potential in many domains, such as biomedicine, enhanced Raman scattering, and smart surfaces. There have been many attempts to fabricate superhydrophobic films; however, most of the fabricated films had uniform adhesion over their area. A patterned superhydrophobic surface with spatially controllable adhesion allows for increased functions in the context of droplet manipulation. In this study, we proposed a method based on liquid-crystal/polymer phase separation and local photopolymerization to realize a superhydrophobic surface with spatially varying adhesion. Materials and topographic structures were analyzed to understand their adhesion mechanisms. Two patterned surfaces with varying adhesion were fabricated from a superhydrophobic material to function as droplet guides and droplet collectors. Due to their easy fabrication and high functionality, superhydrophobic surfaces have high potential for being used in the fabrication of smart liquid-droplet-controlling surfaces for practical applications.

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.

Effect of surface characteristics on the antibacterial properties of titanium dioxide nanotubes produced in aqueous electrolytes with carboxymethyl cellulose

Nanotubular structures were produced on a commercially pure titanium surface by anodization in an aqueous electrolyte that contained carboxymethyl cellulose and sodium fluoride. The internal diameters obtained were about 100, 48, and 9.5 nm, respectively. Several heat treatments at 200, 350, and 600°C were made to produce nanotubes with different titanium dioxide polymorphs (anatase, rutile). All tested surfaces were superhydrophilic, this behavior was maintained after at least 30 days, regardless of the heat treatment. Although in previous works the nanotube features effect on the bacteria behavior had been studied; this item still unclear. For the best of our knowledge, the effect of small internal diameters (about 10 nm) with and without heat treatment and with and without ultraviolet (UV) irradiation on the bacteria strains comportment has not been reported. From our results, both the internal diameter and the postanodized treatments have an effect on the bacteria strains comportment. All nanotubular coatings UV treated and heat treated at 350 and 600°C; despite they have different inner diameters, inhibit the bacteria growth of both Staphylococcus aureus and Pseudomonas aeruginosa strains. The nanotubular coatings obtained at 20 V and heat treated at 350°C produced the lower bacteria adhesion against both strains evaluated.

Preparation and Evaluation of Nanofibrous Hydroxypropyl Cellulose and β-Cyclodextrin Polyurethane Composite Mats

A series of nanofibrous composite mats based on polyurethane urea siloxane (PUUS), hydroxypropyl cellulose (HPC) and β-cyclodextrin (β-CD) was prepared using electrospinning technique. PUUS was synthesized by two steps solution polymerization procedure from polytetramethylene ether glycol (PTMEG), dimethylol propionic acid (DMPA), 4,4'-diphenylmethane diisocyanate (MDI) and 1,3-bis-(3-aminopropyl) tetramethyldisiloxane (BATD) as chain extender. Then, the composites were prepared by blending PUUS with HPC or βCD in a ratio of 9:1 (w/w), in 15% dimethylformamide (DMF). The PUUS and PUUS based composite solutions were used for preparation of nanofibrous mats. In order to identify the potential applications, different techniques were used to evaluate the chemical structure (Fourier transform infrared-attenuated total reflectance spectroscopy-FTIR-ATR), morphological structure (Scanning electron microscopy-SEM and Atomic force microscopy-AFM), surface properties (contact angle, dynamic vapors sorption-DVS), mechanical characteristics (tensile tests), thermal (differential scanning calorimetry-DSC) and some preliminary tests for biocompatibility and microbial adhesion.

Advances in photocatalytic self-cleaning, superhydrophobic and electromagnetic interference shielding textile treatments

The use of nanomaterials in textiles provides many new opportunities and advantages for users and manufacturers; however, it comes with some of its downsides and challenges which need to be understood and overcome for enhancing the applicability of these products. This review article discusses the recent progress in developing self-cleaning and conductive textiles as two of the leading research fields of smart textiles. In particular, different aspects of fabricating nanocoatings for photocatalytic self-cleaning, superhydrophobic and electromagnetic interference (EMI) shielding effect will be brought to light. The theoretical concepts, mechanisms, latest fabrication methods along with their potential applications will be discussed. Moreover, the current drawbacks of these fields will be underlined and some recommendations for future research trajectories in terms of performance, current limitations, sustainability and safety will be proposed. This review article provides a comprehensive review on the state-of-the-art achievements in the field, which will be a valuable reference for researchers and decision makers.

Fabrication of Self-Cleaning Superhydrophobic Surfaces with Improved Corrosion Resistance on 6061 Aluminum Alloys

Aluminum alloys are widely used, but they are prone to contamination or damage under harsh working environments. In this paper, a self-cleaning superhydrophobic aluminum alloy surface with good corrosion resistance was successfully fabricated via the combination of sand peening and electrochemical oxidation, and it was subsequently covered with a fluoroalkylsilane (FAS) film. The surface morphology, surface wettability, and corrosion resistance were investigated using a scanning electron microscope (SEM), an optical contact angle measurement, and an electrochemical workstation. The results show that binary rough structures and an FAS film with a low surface energy on the Al alloy surfaces confer good superhydrophobicity with a water contact angle of 167.5 ± 1.1° and a sliding angle of 2.5 ± 0.7°. Meanwhile, the potentiodynamic polarization curve shows that the corrosion potential has a positively shifted trend, and the corrosion current density decreases by three orders of magnitude compared with that of the original aluminum alloy sample. In addition, the chemical stability of the as-prepared superhydrophobic surface was evaluated by dripping test using solutions with different pH values for different immersion time. It indicates that the superhydrophobic surface could provide long-term corrosion protection for aluminum alloys. Consequently, the as-prepared superhydrophobic surface has excellent contamination resistance and self-cleaning efficacy, which are important for practical applications.

Superhydrophobic Asphalt Pavements: Surface Improvement

The most adverse weather condition for road safety happens when there is water, snow, or ice on the road surface because their presence highly decreases friction. Therefore, it is essential to drain or repel them quickly. If the water drops are repelled from the surface or the ice/snow formation is avoided with the application of superhydrophobic coatings, roads become safer. In order to functionalize the asphalt mixtures used in road pavements, nano/micromaterials, such as Polytetrafluoroethylene (PTFE), TiO2, and SiO2, among others have been applied by spraying coating. The mixes are usually characterized by the water contact angle, and the surface roughness is typically assessed by optical and electron analysis. This research work aims to present a brief overview of superhydrophobic asphalt mixtures.

Implant materials and prosthetic joint infection: the battle with the biofilm

Prosthetic joint infection (PJI) is associated with poor clinical outcomes and is expensive to treat.Although uncommon overall (affecting between 0.5% and 2.2% of cases), PJI is one of the most commonly encountered complications of joint replacement and its incidence is increasing, putting a significant burden on healthcare systems.Once established, PJI is extremely difficult to eradicate as bacteria exist in biofilms which protect them from antibiotics and the host immune response.Improved understanding of the microbial pathology in PJI has generated potential new treatment strategies for prevention and eradication of biofilm associated infection including modification of implant surfaces to prevent adhesion of bacteria.Much research is currently ongoing looking at different implant surface coatings and modifications, and although most of this work has not translated into clinical medicine there has been some early clinical success. Cite this article: EFORT Open Rev 2019;4:633-639. DOI: 10.1302/2058-5241.4.180095.

Crack growth-driven wettability transition on carbon black/polybutadiene nanocomposite coatings via stretching

Ordered topography patterns with a mechanical response are usually designed to achieve wettability switching by geometric parameter changes through mechanical stimuli. However, their fabrication often needs expensive and complicated micro/nano-fabrication processing (e.g. photolithography and ion etching). In this study, a nano-carbon black (CB)/polybutadiene (PB) coating with a Wenzel superhydrophobic state was prepared on a rubber substrate by a facile method combining solution mixing and spraying coating. By stretching the composite coating, the generated cracks divided the continuous coating into new micro-nano mastoids, resulting in the formation of new hierarchical roughness for Cassie superhydrophobicity. The Wenzel-to-Cassie transition behavior was dependent on the CB loading in the coating. During stretching, the cracks propagated more rapidly in the coating with higher CB loading and induced the desired hierarchical structure to consequently enable the Wenzel-to-Cassie transition earlier at a lower stretching strain. The stretched coating presented good anti-wetting (a sliding angle of 5°) and low water adhesion. After releasing, the coating returned to its original Wenzel state by structure recovery. Thus, the switchable wettability of the coating can be adopted for no-loss water droplet transfer by controlling the droplet adhesion through cyclic stretching-releasing, and exhibits good potential for microfluidic and biomedical applications.

Bioinspired Mechanically Robust Metal-Based Water Repellent Surface Enabled by Scalable Construction of a Flexible Coral-Reef-Like Architecture

Mechanical robustness is a central concern for moving artificial superhydrophobic surfaces to application practices. It is believed that bulk hydrophilic materials cannot be use to construct micro/nanoarchitectures for superhydrophobicity since abrasion-induced exposure of hydrophilic surfaces leads to remarkable degradation of water repellency. To address this challenge, the robust mechanical durability of a superhydrophobic surface with metal (hydrophilic) textures, through scalable construction of a flexible coral-reef-like hierarchical architecture on various substrates including metals, glasses, and ceramics, is demonstrated. Discontinuous coral-reef-like Cu architecture is built by solid-state spraying commercial electrolytic Cu particles (15-65 µm) at supersonic particle velocities. Subsequent flame oxidation is applied to introduce a porous hard surface oxide layer. Owing to the unique combination of the flexible coral-reef-like architecture and self-similar manner of the fluorinated hard oxide surface layer, the coating surface retains its water repellency with an extremely low roll-off angle (<2°) after cyclic sand-paper abrasion, mechanical bending, sand-grit erosion, knife-scratching, and heavy loading of simulated acid rain droplets. Strong adhesion to glass, ceramics, and metals up to 34 MPa can be achieved without using adhesive. The results show that the present superhydrophobic coating can have wide outdoor applications for self-cleaning and corrosion protection of metal parts.

Programmable Liquid Adhesion on Bio-Inspired Re-Entrant Structures

Surfaces combining antispreading and high adhesion can find wide applications in the manipulation of liquid droplets, generation of micropatterns and liquid enrichment. To fabricate such surfaces, almost all the traditional methods demand multi-step processes and chemical modification. And even so, most of them cannot be applied for some liquids with extremely low surface energy. In the past decade, multiply re-entrant structures have aroused much attention because of their universal and modification-independent antiadhesion or antipenetration ability. Unfortunately, theories and applications about their liquid adhesion behavior are still rare. In this work, inspired by the springtail skin and gecko feet in the adhered state, it is demonstrated that programmable liquid adhesion is realized on the 3D-printed micro doubly re-entrant arrays. By arranging the arrays reasonably, three different Cassie adhesion behaviors can be obtained: I) no residue adhesion, II) tunable adhesion, and III) absolute adhesion. Furthermore, various arrays are designed to tune macro/micro liquid droplet manipulation, which can find applications in the transportation of liquid droplets, liquid enrichment, generation of tiny droplets, and micropatterns.

A Brief Recap of Microbial Adhesion and Biofilms

Food and beverage industries operate their production units under stringent hygiene standards to verify high-quality products. However, the presence of biofilms can cause hygienic problems in the industries in the case of pathogenic organisms. Microorganisms can form biofilms, which are resistant to cleaning and disinfection. Microorganisms in biofilms are closely packed in a matrix that acts as a barrier to cleaning and disinfection. Biofilms are observed in processing equipment and open surfaces, resulting in food safety problems or weakening of production efficiency. This review provides a recap of the biofouling process, including the production mechanisms and control techniques of microbial adhesion. Microbial adhesion and colonization are the sine qua non of the establishment of bacterial pathogenesis and this report focuses on their prevention.

Simple and Affordable Way To Achieve Polymeric Superhydrophobic Surfaces with Biomimetic Hierarchical Roughness

A water contact angle greater than 150° together with a sliding angle less than 10° is a special surface phenomenon that appears on superhydrophobic surfaces. In this paper, a brief introduction of the development history and present research on superhydrophobic surfaces was given. Polymeric superhydrophobic surfaces with biomimetic hierarchical roughness were fabricated by a simple method of hot embossing without any chemical treatments. Stainless steel meshes with different mesh numbers were used as template. Moreover, the influences of processing parameters, including mesh number, mold temperature, and pressure, were deeply investigated. Hierarchical microplatforms, microfibers, and oriented arrayed nanowrinkles structure on them, which were resembled with the nanowrinkles structure and hierarchical roughness on a red rose petal, were observed by a scanning electron microscope. A water contact angle of 154° can be achieved after parameter optimization. The method proposed in this study offered a fine and affordable choice for the fabrication of polymeric superhydrophobic surfaces. With the rapid development of functional applications in micro- and nanodevices, this method will show greater superiority in large-area and large-scale production due to its advantages of low cost, high efficiency, and high reliability.

Creation of Superhydrophobic Poly(L-phenylalanine) Nonwovens by Electrospinning

From the viewpoint of green chemistry and environmental chemistry, an important challenge in the field of superhydrophobic materials is to create them with only bio-based molecules. We developed superhydrophobic and chemically stable poly(L-phenylalanine) (PolyPhe) nonwovens by electrospinning. PolyPhe was selected because, due to its very rigid chemical structure, it is one of the toughest and most hydrophobic polymers among polymers composed only of amino acids. The water contact angle on the nonwovens is a maximum of 160°, and the droplets are stably adhered and remain still on the nonwoven surface even if it is turned over, thereby suggesting a petal-type superhydrophobicity. The nonwovens show a good chemical stability, and their weight remains unchanged after 5 days immersion in acidic (pH 2) and basic (pH 12) conditions. In addition, the superhydrophobic property is not lost even after the alkali treatment. Such tough superhydrophobic materials are intriguing for further biomedical and environmental applications.

Resistance of Superhydrophobic Surface-Functionalized TiO₂ Nanotubes to Corrosion and Intense Cavitation

The availability of robust superhydrophobic materials with the ability to withstand harsh environments are in high demand for many applications. In this study, we have presented a simple method to fabricate superhydrophobic materials from TiO₂ nanotube arrays (TNTAs) and investigated the resilience of the materials when they are subjected to harsh conditions such as intense cavitation upon ultrasonication, corrosion in saline water, water-jet impact, and abrasion. The TNTAs were prepared by anodization of Ti foil in buffered aqueous electrolyte containing fluoride ions. The hydrophilic TNTAs were functionalized with octadecylphosphonic acid (ODPA) or 1H, 1H′, 2H, 2H′-perfluorodecyl phosphonic acid (PFDPA) to form a self-assembled monolayer on the TNTA surface to produce superhydrophobic ODPA@TNTA or PFDPA@TNTA surfaces. The superhydrophobic ODPA@TNTA and PFDPA@TNTA have contact angles of 156.0° ± 1.5° and 168° ± 1.5°, and contact angle hysteresis of 3.0° and 0.8°, respectively. The superhydrophobic ODPA@TNTA and PFDPA@TNTA were subjected to ultrasonication, corrosion in saline water, and water-jet impact and abrasion, and the resilience of the systems was characterized by electrochemical impedance spectroscopy (EIS), contact angle (CA) measurements, diffuse reflectance Fourier transform infrared spectroscopy (DRIFTS), and field-emission scanning electron microscopy (FESEM). The results presented here show that superhydrophobic ODPA@TNTA and PFDPA@TNTA are robust and resilient under the harsh conditions studied in this work, and indicate the potential of these materials to be deployed in practical applications.

A biomimetic surface with switchable contact angle and adhesion for transfer and storage of microdroplets

Recently, superhydrophobic surfaces with switchable wettability have attracted much attention. The ability to control the contact angle and adhesion of the multifunctional smart surface will be more beneficial to meet the complex practical applications, but until now this has been a challenge. Inspired by rose petals, we report a smart, biomimetic, and superhydrophobic surface whose wettability can switch reversibly between superhydrophobicity and superhydrophilicity on the Cu substance. At the same time, we can control the adhesion on the as-prepared superhydrophobic surface by covering and removing the ink. Thus, the as-prepared surface can be used as a medium for microdroplet transfer and storage. Compared with the original Cu substrate, electrochemical measurements show that the corrosion inhibition of the superhydrophobic surface is significantly improved. Good corrosion resistance allows the platform to be used to manipulate or store more types of microdroplets, especially corrosive microdroplets. In addition, the as-prepared surface has a good stability which facilitates the practical application of the as-prepared smart surface. This work provides a smart and effective strategy for lossless transfer and patterned storage of microdroplets. It is also promising for the design of new smart interface materials such as for biological cell manipulation, chemical microreaction and other types of microfluidic devices.

UV-Resistant and Thermally Stable Superhydrophobic CeO2 Nanotubes with High Water Adhesion

A novel type of sticky superhydrophobic cerium dioxide (CeO₂ ) nanotube material is prepared by hydrothermal treatment without any chemical modification. A water droplet on the material surface shows a static water contact angle of about 157° but the water droplet is pinned on the material surface even when the material surface is turned upside down. Interestingly, the as-prepared CeO₂ nanotube material displays durable superhydrophobicity and enhanced adhesion to water under ultraviolet (UV) light irradiation. Importantly, this change in water adhesion can be reversed by heat treatment to restore the original adhesive value of 20 µL. Further, the maximum volume of the water droplet adhered on the material surface of CeO₂ nanotubes can be regulated without loss of superhydrophobicity during the heating treatment/UV-irradiation cycling. Meanwhile, the superhydrophobic CeO₂ nanotube material shows remarkable thermal stability even at temperatures as high as 450 °C, long-term durability in chemical environment, and air-storage and good resistance to oily contaminant. Finally, the potential application in no-loss water transportation of this sticky superhydrophobic CeO₂ material is demonstrated.

Fabrication of Low-Cost Flexible Superhydrophobic Antibacterial Surface with Dual-Scale Roughness

In this work, we report a large-area fabrication of a flexible superhydrophobic bactericidal surface decorated with copper hydroxide nanowires. This involves a simple two-step method which involves growth followed by transfer of the nanowires onto the polydimethylsiloxane (PDMS) surface by mechanical peeling. Additional roughness in PDMS is obtained through incomplete wetting of the nanoscale gaps which leads to dual-scale roughness and superhydrophobicity with a contact angle of 169° and hysteresis of less than 2°. The simplicity of the process makes it low-cost and easily scalable. The process allows fabrication of nonplanar 3D surfaces. The surface shows blood repellence and antibacterial activity against Escherichia coli with more than 5 log reductions in bacterial colony. The surface also shows hemocompatible behavior, making it suitable for healthcare applications. The fabricated surface is found to be extremely robust against stretching, twisting, sandpaper abrasion, solid weight impact, and tape peel test. The surface is found to withstand human weight multiple times without losing its hydrophobicity, making it suitable for several practical scenarios in healthcare and household applications.

Advanced Material-Ordered Nanotubular Ceramic Membranes Covalently Capped with Single-Wall Carbon Nanotubes

Advanced ceramic materials with a well-defined nano-architecture of their surfaces were formed by applying a two-step procedure. Firstly, a primary amine was docked on the ordered nanotubular ceramic surface via a silanization process. Subsequently, single-wall carbon nanotubes (SWCNTs) were covalently grafted onto the surface via an amide building block. Physicochemical (e.g., hydrophobicity, and surface free energy (SFE)), mechanical, and tribological properties of the developed membranes were improved significantly. The design, preparation, and extended characterization of the developed membranes are presented. Tools such as high-resolution transmission electron microscopy (HR-TEM), single-area electron diffraction (SAED) analysis, microscopy, tribology, nano-indentation, and Raman spectroscopy, among other techniques, were utilized in the characterization of the developed membranes. As an effect of hydrophobization, the contact angles (CAs) changed from 38° to 110° and from 51° to 95° for the silanization of ceramic membranes 20 (CM20) and CM100, respectively. SWCNT functionalization reduced the CAs to 72° and 66° for ceramic membranes carbon nanotubes 20 (CM-CNT-20) and CM-CNT-100, respectively. The mechanical properties of the developed membranes improved significantly. From the nanotribological study, Young’s modulus increased from 3 to 39 GPa for CM-CNT-20 and from 43 to 48 GPa for pristine CM-CNT-100. Furthermore, the nanohardness increased by about 80% after the attachment of CNTs for both types of ceramics. The proposed protocol within this work for the development of functionalized ceramic membranes is both simple and efficient.

Antibacterial activity on superhydrophobic titania nanotube arrays

Bacterial infections are a serious issue for many implanted medical devices. Infections occur when bacteria colonize the surface of an implant and form a biofilm, a barrier which protects the bacterial colony from antibiotic treatments. Further, the anti-bacterial treatments must also be tailored to the specific bacteria that is causing the infection. The inherent protection of bacteria in the biofilm, differences in bacteria species (gram-positive vs. gram-negative), and the rise of antibiotic-resistant strains of bacteria makes device-acquired infections difficult to treat. Recent research has focused on reducing biofilm formation on medical devices by modifying implant surfaces. Proposed methods have included antibacterial surface coatings, release of antibacterial drugs from surfaces, and materials which promote the adhesion of non-pathogenic bacteria. However, no approach has proven successful in repelling both gram-positive and gram-negative bacteria. In this study, we have evaluated the ability of superhydrophobic surfaces to reduce bacteria adhesion regardless of whether the bacteria are gram-positive or gram-negative. Although superhydrophobic surfaces did not repel bacteria completely, they had minimal bacteria attached after 24 h and more importantly no biofilm formation was observed.

Surface modifications for antimicrobial effects in the healthcare setting: a critical overview

The spread of infections in healthcare environments is a persistent and growing problem in most countries, aggravated by the development of microbial resistance to antibiotics and disinfectants. In addition to indwelling medical devices (e.g. implants, catheters), such infections may also result from adhesion of microbes either to external solid-water interfaces such as shower caps, taps, drains, etc., or to external solid-gas interfaces such as door handles, clothes, curtains, computer keyboards, etc. The latter are the main focus of the present work, where an overview of antimicrobial coatings for such applications is presented. This review addresses well-established and novel methodologies, including chemical and physical functional modification of surfaces to reduce microbial contamination, as well as the potential risks associated with the implementation of such anticontamination measures. Different chemistry-based approaches are discussed, for instance anti-adhesive surfaces (e.g. superhydrophobic, zwitterions), contact-killing surfaces (e.g. polymer brushes, phages), and biocide-releasing surfaces (e.g. triggered release, quorum sensing-based systems). The review also assesses the impact of topographical modifications at distinct dimensions (micrometre and nanometre orders of magnitude) and the importance of applying safe-by-design criteria (e.g. toxicity, contribution for unwanted acquisition of antimicrobial resistance, long-term stability) when developing and implementing antimicrobial surfaces.