Creating superhydrophobic and antibacterial surfaces on gold by femtosecond laser pulses

Synthesis, characterization, and antibacterial study of chitosan-zinc oxide nanocomposite-coated superhydrophobic cotton fabric

Awareness of microbial infection, hygiene, and personal health has increased in recent years, particularly in light of the pervasive pandemic encountered by the global community. This has prompted the development of antibacterial and superhydrophobic cotton fabric to address the pressing challenge. In this investigation, we report bio-mediated zinc oxide nanoparticles (ZnO NPs) synthesized using Psidium guajava leaf extract and zinc acetate. Further, the chitosan-ZnO nanocomposite (CS-ZnO) was synthesized and subsequently deposited on cotton fabric (CF) via a facile and cost-effective pad-dry-cure method to produce CS-ZnO-CF. The ZnO NPs, CS-ZnO, and CS-ZnO CF were characterized using FTIR, XRD, SEM-EDAX, TGA and AFM analysis. Additionally, we investigated the mechanical properties and water contact angle (WCA) of uncoated cotton (UCF) and CS-ZnO CF. The CS-ZnO-CF demonstrated good mechanical stability even after 50 abrasion cycles, good washing durability, and good super-hydrophobicity, with a high WCA (153.1°). The antibacterial study indicated that CS-ZnO and CS-ZnO-CF exhibited higher antibacterial activity than UCF against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) bacteria. This study introduces a simple, environmentally friendly, and economically scalable method for producing multifunctional CS-ZnO CF, showcasing its potential for diverse applications.

Dual-Function Femtosecond Laser: β-TCP Structuring and AgNP Synthesis via Photoreduction with Azorean Green Tea for Enhanced Osteointegration and Antibacterial Properties

β-Tricalcium phosphate (β-TCP) is a well-established biomaterial for bone regeneration, highly regarded for its biocompatibility and osteoconductivity. However, its clinical efficacy is often compromised by susceptibility to bacterial infections. In this study, we address this limitation by integrating femtosecond (fs)-laser processing with the concurrent synthesis of silver nanoparticles (AgNPs) mediated by Azorean green tea leaf extract (GTLE), which is known for its rich antioxidant and anti-inflammatory properties. The fs laser was employed to modify the surface of β-TCP scaffolds by varying scanning velocities, fluences, and patterns. The resulting patterns, formed at lower scanning velocities, display organized nanostructures, along with enhanced roughness and wettability, as characterized by Scanning Electron Microscopy (SEM), optical profilometry, and contact angle measurements. Concurrently, the femtosecond laser facilitated the photoreduction of silver ions in the presence of GTLE, enabling the efficient synthesis of small, spherical AgNPs, as confirmed by UV-vis spectroscopy, Transmission Electron Microscopy (TEM), and Fourier Transform Infrared Spectroscopy (FTIR). The resulting AgNP-embedded β-TCP scaffolds exhibited a significantly improved cell viability and elongation of human bone marrow mesenchymal stem cells (hBM-MSCs), alongside significant antibacterial activity against Staphylococcus aureus (S. aureus). This study underscores the transformative potential of combining femtosecond laser surface modification with GTLE-mediated AgNP synthesis, presenting a novel and effective strategy for enhancing the performance of β-TCP scaffolds in bone-tissue engineering.

Recent Developments in the Fabrication and Application of Superhydrophobic Suraces

A superhydrophobic surface is defined as having a contact angle exceeding 150 °C, indicating a remarkable ability to repel water. Generally, superhydrophobicity originates from the utilization of low-surface-energy materials with unique micro- and nanostructures. Superhydrophobic surfaces have gained considerable recognition and are widely employed in diverse areas for anti-icing, oil-water separation, anticorrosion, self-cleaning, blood-repellent, and antibacterial applications. These surfaces can greatly enhance industrial processes by yielding significant performance improvements. In this review, we introduce the basic theories that provide a foundation for understanding the hydrophobic properties of superhydrophobic surfaces. We then discuss current techniques for fabricating superhydrophobic coatings, critically analyzing their strengths and limitations. Furthermore, we provide an overview of recent progress in the application of superhydrophobic materials. Finally, we summarize the challenges in developing superhydrophobic materials and future trends in this field. The insights provided by this review can help researchers understand the basic knowledge of superhydrophobic surfaces and obtain the latest progress and challenges in the application of superhydrophobic surfaces. It provides help for further research and practical application of superhydrophobic surfaces.

Antifouling nanoplatform for controlled attachment ofE. coli

Biofouling is the most common cause of bacterial contamination in implanted materials/devices resulting in severe inflammation, implant mobilization, and eventual failure. Since bacterial attachment represents the initial step toward biofouling, developing synthetic surfaces that prevent bacterial adhesion is of keen interest in biomaterials research. In this study, we develop antifouling nanoplatforms that effectively impede bacterial adhesion and the consequent biofilm formation. We synthesize the antifouling nanoplatform by introducing silicon (Si)/silica nanoassemblies to the surface through ultrafast ionization of Si substrates. We assess the effectiveness of these nanoplatforms in inhibitingEscherichia coli(E. coli) adhesion. The findings reveal a significant reduction in bacterial attachment on the nanoplatform compared to untreated silicon, with bacteria forming smaller colonies. By manipulating physicochemical characteristics such as nanoassembly size/concentration and nanovoid size, we further control bacterial attachment. These findings suggest the potential of our synthesized nanoplatform in developing biomedical implants/devices with improved antifouling properties.

Biofilm Inhibition on Medical Devices and Implants Using Carbon Dots: An Updated Review

Biofilms are an intricate community of microbes that colonize solid surfaces, communicating via a quorum-sensing mechanism. These microbial aggregates secrete exopolysaccharides facilitating adhesion and conferring resistance to drugs and antimicrobial agents. The escalating global concern over biofilm-related infections on medical devices underscores the severe threat to human health. Carbon dots (CDs) have emerged as a promising substrate to combat microbes and disrupt biofilm matrices. Their numerous advantages such as facile surface functionalization and specific antimicrobial properties, position them as innovative anti-biofilm agents. Due to their minuscule size, CDs can penetrate microbial cells, inhibiting growth via cytoplasmic leakage, reactive oxygen species (ROS) generation, and genetic material fragmentation. Research has demonstrated the efficacy of CDs in inhibiting biofilms formed by key pathogenic bacteria such as Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa. Consequently, the development of CD-based coatings and hydrogels holds promise for eradicating biofilm formation, thereby enhancing treatment efficacy, reducing clinical expenses, and minimizing the need for implant revision surgeries. This review provides insights into the mechanisms of biofilm formation on implants, surveys major biofilm-forming pathogens and associated infections, and specifically highlights the anti-biofilm properties of CDs emphasizing their potential as coatings on medical implants.

Comparison of the antimicrobial photocatalytic activities of SiO2 and Au@SiO2 nanostructures in water decontamination

Photocatalytic disinfection of Escherichia coli suspension by silicon dioxide nanoparticles and silicon dioxide/gold nanocomposite in a batch reactor is investigated experimentally and results are compared. Silica nanoparticles were synthesized by Stöber method and pulsed laser ablation method was employed to prepare gold nanoparticles in distilled water. Composition of two nanoparticles species was carried out, using the second harmonic pulse of Nd:YAG laser, whose wavelength is in the absorption spectra of gold nanoparticles. Results confirm a decrease in the bandgap energy of silica nanoparticles after composition. Escherichia coli were selected as an indicator of the microbial water contamination. Disk diffusion method was used to evaluate the antimicrobial potential of SiO2 and Au@SiO2 nanostructures. Photocatalytic activities of both nanostructures were examined in dark, and under the irradiation of UV and visible light. In all conditions, the performance of Au@SiO2 nanocomposites was higher than SiO2 nanoparticles. In dark condition the higher biocidal nature and activity of Au nanoparticles and for the case of UV radiation, decreasing the bandgap energy and recombination rate of SiO2 nanoparticles after composition with Au increased the efficiency. For the case of visible light radiation, surface plasmon resonances effects, and local heat of Au nanoparticles were responsible for increasing the efficiency. RESEARCH HIGHLIGHTS: Doping large bandgap semiconductors nanostructures, such as silica with metal nanoparticles, such as gold will improve their photocatalytic activity to work in visible light. In this mechanism, gold nanoparticles act as effective traps to prevent the recombination of photogenerated electron-hole pairs. Other mechanisms, such as Schottky barrier formation, surface plasmon resonance absorption of gold nanoparticles, and biocidal nature of the gold nanoparticles are effective in increasing the efficiency of Au doped silica nanostructures.

Mechanically strong micro-nano fibrillated cellulose paper with improved barrier and water-resistant properties for replacing plastic

Replacing nonbiodegradable plastics with environmentally friendly cellulose materials has emerged as a key trend in environmental protection. This study highlights the development of a strong and hydrophobic micro-nano fibrillated cellulose paper (MNP) through the incorporation of micro-nano fibrillated cellulose fiber (MNF) and chitin nanocrystal (Ch), followed by the impregnation of polymethylsiloxane (PMHS). A low-acid, heat-assisted colloidal grinding strategy was employed to prepare MNF with a high aspect ratio effectively. Ch was incorporated as a reinforcing matrix into the cellulose fiber scaffold through straightforward mechanical mixing and mechanical hot-pressing treatments. Compared to pure MNP, the 5Ch-MNP exhibited a 25 % improvement in tensile strength, reaching 170 MPa, and showed enhanced barrier properties against oxygen and water vapor. The impregnation of PMHS rapidly confers environmentally resistant hydrophobic properties to 1 % PMHS-5Ch-MNP, leading to a water contact angle exceeding 112°, and a 290 % increase in tensile strength under wet conditions. Additionally, the paper demonstrated excellent antibacterial adhesion properties, with the adhesion rates for E. coli and S. aureus exceeding 98 %. This study successfully produced functional cellulose paper with remarkable mechanical properties and barrier properties, as well as hydrophobicity, using a simple, efficient, and environmentally friendly method, making it a promising substitute for petroleum-based plastics.

A Photochemically Active Cu2O Nanoparticle Endows Scaffolds with Good Antibacterial Performance by Efficiently Generating Reactive Oxygen Species

Cuprous oxide (Cu2O) has great potential in photodynamic therapy for implant-associated infections due to its good biocompatibility and photoelectric properties. Nevertheless, the rapid recombination of electrons and holes weakens its photodynamic antibacterial effect. In this work, a new nanosystem (Cu2O@rGO) with excellent photodynamic performance was designed via the in situ growth of Cu2O on reduced graphene oxide (rGO). Specifically, rGO with lower Fermi levels served as an electron trap to capture photoexcited electrons from Cu2O, thereby promoting electron-hole separation. More importantly, the surface of rGO could quickly transfer electrons from Cu2O owing to its excellent conductivity, thus efficiently suppressing the recombination of electron-hole pairs. Subsequently, the Cu2O@rGO nanoparticle was introduced into poly-L-lactic acid (PLLA) powder to prepare PLLA/Cu2O@rGO porous scaffolds through selective laser sintering. Photochemical analysis showed that the photocurrent of Cu2O@rGO increased by about two times after the incorporation of GO nanosheets, thus enhancing the efficiency of photogenerated charge carriers and promoting electron-hole separation. Moreover, the ROS production of the PLLA/Cu2O@rGO scaffold was significantly increased by about two times as compared with that of the PLLA/Cu2O scaffold. The antibacterial results showed that PLLA/Cu2O@rGO possessed antibacterial rates of 83.7% and 81.3% against Escherichia coli and Staphylococcus aureus, respectively. In summary, this work provides an effective strategy for combating implant-related infections.

Improvement of Metal-Doped β-TCP Scaffolds for Active Bone Substitutes via Ultra-Short Laser Structuring

Various efforts have been made to develop antibacterial biomaterials capable of also sustaining bone remodulation to be used as bone substitutes and reduce patient infection rates and related costs. In this work, beta-tricalcium phosphate (β-TCP) was chosen due to its known biocompatibility and use as a bone substitute. Metal dopants were incorporated into the crystal structure of the β-TCP, and disks were produced from this material. Magnesium and strontium, as well as copper and silver, were chosen as dopants to improve the osteogenic and antibacterial properties, respectively. The surface of the β-TCP samples was further modified using a femtosecond laser system. Grid and line patterns were produced on the plates' surface via laser ablation, creating grooves with depths lower than 20 μm and widths between 20 and 40 μm. Raman and FTIR analysis confirmed that laser ablation did not result in the degradation or phase change of the materials, making it suitable for surface patterning. Laser ablation resulted in increased hydrophilicity of the materials, as the control samples (non-ablated samples) have WCA values ranging from 70° to 93° and become, upon laser ablation, superwicking surfaces. Confocal measurements show an increase in specific surface area of 50% to 200% compared to the control. Overall, the results indicate the potential of laser ablation to improve the surface characteristics of β-TCP, which may lead to an improvement in the antibacterial and osteogenic properties of the produced materials.

Surface antibacterial properties enhanced through engineered textures and surface roughness: A review

The spread of bacteria through contaminated surfaces is a major issue in healthcare, food industry, and other economic sectors. The widespread use of antibiotics is not a sustainable solution in the long term due to the development of antibiotic resistance. Therefore, surfaces with antibacterial properties have the potential to be a disruptive approach to combat microbial contamination. Different methods and approaches have been studied to impart or enhance antibacterial properties on surfaces. The surface roughness and texture are inherent parameters that significantly impact the antibacterial properties of a surface. They are also directly related to the previously employed machining and treatment methods. This review article discusses the correlation between surface roughness and antibacterial properties is presented and discussed. It begins with an introduction to the concepts of surface roughness and texture, followed by a description of the most commonly utilized machining methods and surface. A thorough analysis of bacterial adhesion and growth is then presented. Finally, the most recent studies in this research area are comprehensively reviewed. The studies are sorted and classified based on the utilized machining and treatment methods, which are divided into mechanical processes, surface treatments and coatings. Through the systematic review and record of the recent advances, the authors aim to assist and promote further research in this very promising and extremely important direction, by providing a systematic review of recent advances.

Modeling of Short-Pulse Laser Interactions with Monolithic and Porous Silicon Targets with an Atomistic-Continuum Approach

The acquisition of reliable knowledge about the mechanism of short laser pulse interactions with semiconductor materials is an important step for high-tech technologies towards the development of new electronic devices, the functionalization of material surfaces with predesigned optical properties, and the manufacturing of nanorobots (such as nanoparticles) for bio-medical applications. The laser-induced nanostructuring of semiconductors, however, is a complex phenomenon with several interplaying processes occurring on a wide spatial and temporal scale. In this work, we apply the atomistic-continuum approach for modeling the interaction of an fs-laser pulse with a semiconductor target, using monolithic crystalline silicon (c-Si) and porous silicon (Si). This model addresses the kinetics of non-equilibrium laser-induced phase transitions with atomic resolution via molecular dynamics, whereas the effect of the laser-generated free carriers (electron-hole pairs) is accounted for via the dynamics of their density and temperature. The combined model was applied to study the microscopic mechanism of phase transitions during the laser-induced melting and ablation of monolithic crystalline (c-Si) and porous Si targets in a vacuum. The melting thresholds for the monolithic and porous targets were found to be 0.32 J/cm2 and 0.29 J/cm2, respectively. The limited heat conduction mechanism and the absence of internal stress accumulation were found to be involved in the processes responsible for the lowering of the melting threshold in the porous target. The results of this modeling were validated by comparing the melting thresholds obtained in the simulations to the experimental values. A difference in the mechanisms of ablation of the c-Si and porous Si targets was considered. Based on the simulation results, a prediction regarding the mechanism of the laser-assisted production of Si nanoparticles with the desired properties is drawn.

Effect of sulfonation time on physicochemical, osteogenic, antibacterial properties and biocompatibility of carbon fiber reinforced polyether ether ketone

The carbon fiber reinforced polyetheretherketone (CFR-PEEK) has been increasingly used in orthopedics dentistry due to its excellent biocompatibility and mechanical properties. However, the biological inertness and poor antibacterial activity limit its clinical applications. This paper focused on the performances of CFR-PEEK with porous morphology that were exposed to different sulfonation periods (1, 3, 5, and 10 min, corresponding to CP-S1, CP-S3, CP-S5, and CP-S10, respectively). Residual sulfuric acid was removed by acetone rinsing, NaOH immersion, and hydrothermal treatment before in vitro and in vivo studies. The results showed some significant difference in the physicochemical properties, including energy dispersive X-ray spectroscopy (EDS) map of sulfur atoms, X-ray photoelectron spectroscopy (XPS) of valences of sulfur ions, Fourier transformation infrared spectroscopy (FTIR), hydrophilicity, hardness, and elastic modulus among CP-S3, CP-S5, and CP-S10. However, CP-S5 and CP-S10 were more effective in promoting the proliferation, adhesion, and osteogenic differentiation of seeded bone mesenchymal stem cells (BMSCs) and growth inhibition of S. aureus and P. gingivalis compared with other groups. Furthermore, the CP-S5 and CP-S10 samples achieved better cranial bone repair than the non-sulfonation group in a rat model. Therefore, it can be inferred that both 5 and 10 min are viable sulfonation durations for 30% CFR-PEEK. These findings provide a theoretical basis for developing CFR-PEEK for clinical applications.

Design of Surfaces with Persistent Antimicrobial Properties on Stainless Steel Developed Using Femtosecond Laser Texturing for Application in "High Traffic" Objects

Metal-based high-touch surfaces used for diverse applications in everyday use, like handrails, playground grab handles, doorknobs, ATM touch pads, and desks, are the most common targets for pollution with a variety of microbes; there is thus a need to improve their antimicrobial properties, an issue which has become a challenge in recent years, particularly after the COVID-19 pandemic. According to the World Health Organization (WHO), drug-resistant pathogens are one of the main concerns to global health today, as they lead to longer hospital stays and increased medical costs. Generally, the development of antimicrobial surfaces is related to the utilization of chemical methods via deposition on surfaces in the forms of various types of coatings. However, the addition of chemical substances onto a surface can induce unwanted effects, since it causes surface chemistry changes and, in some cases, cannot provide long-lasting results. A novel approach of utilising ultra-short laser radiation for the treatment of metallic surfaces by inducing a variety of micro- and nanostructuration is elaborated upon in the current research, estimating the optimum relation between the wettability and roughness characteristics for the creation of antimicrobial properties for such high-touch surfaces. In the current study, AISI 304-304L stainless steel metal was used as a benchmark material. Surface texturing via laser ablation with femtosecond laser pulses is an effective method, since it enables the formation of a variety of surface patterns, along with the creation of bimodal roughness, in one-step processing. In this investigation, a precise approach toward developing hydrophobic stainless steel surfaces with tunable adherence using femtosecond laser-induced modification is described. The impact of basic femtosecond laser processing parameters, like the scanning velocity, laser energy, and wettability properties of the laser-processed stainless steel samples, are examined. It is identified that the topography and morphology of laser-induced surface structures can be efficiently changed by adapting the laser processing parameters to create structures, which facilitate the transfer of surface properties from extremely low to high surface wettability.

Antibacterial and biofilm-inhibiting cotton fabrics decorated with copper nanoparticles grown on graphene nanosheets

Infectious pathogens can be transmitted through textiles. Therefore, additional efforts are needed to develop functional fabrics containing antimicrobial substances to prevent the growth of antibiotic-resistant bacteria and their biofilms. Here, we developed a cotton fabric coated with reduced graphene oxide (rGO) and copper nanoparticles (Cu NPs), which possessed hydrophobic, antimicrobial, and anti-biofilm properties. Once the graphene oxide was dip-coated on a cellulose cotton fabric, Cu NPs were synthesized using a chemical reduction method to fabricate an rGO/Cu fabric, which was analyzed through FE-SEM, EDS, and ICP-MS. The results of our colony-forming unit assays indicated that the rGO/Cu fabric possessed high antibacterial and anti-biofilm properties against Escherichia coli, Pseudomonas aeruginosa, Staphylococcus epidermidis, Corynebacterium xerosis, and Micrococcus luteus. Particularly, the fabric could inhibit the growth of E. coli, C. xerosis, and M. luteus with a 99% efficiency. Furthermore, our findings confirmed that the same concentrations of rGO/Cu had no cytotoxic effects against CCD-986Sk and Human Dermal Fibroblast (HDF), human skin cells, and NIH/3T3, a mouse skin cell. The developed rGO/Cu fabric thus exhibited promising applicability as a cotton material that can maintain hygienic conditions by preventing the propagation of various bacteria and sufficiently suppressing biofilm formation while also being harmless to the human body.

Bacterial Biofilm Formation on Biomaterials and Approaches to Its Treatment and Prevention

Bacterial biofilms can cause widespread infection. In addition to causing urinary tract infections and pulmonary infections in patients with cystic fibrosis, biofilms can help microorganisms adhere to the surfaces of various medical devices, causing biofilm-associated infections on the surfaces of biomaterials such as venous ducts, joint prostheses, mechanical heart valves, and catheters. Biofilms provide a protective barrier for bacteria and provide resistance to antimicrobial agents, which increases the morbidity and mortality of patients. This review summarizes biofilm formation processes and resistance mechanisms, as well as the main features of clinically persistent infections caused by biofilms. Considering the various infections caused by clinical medical devices, we introduce two main methods to prevent and treat biomaterial-related biofilm infection: antibacterial coatings and the surface modification of biomaterials. Antibacterial coatings depend on the covalent immobilization of antimicrobial agents on the coating surface and drug release to prevent and combat infection, while the surface modification of biomaterials affects the adhesion behavior of cells on the surfaces of implants and the subsequent biofilm formation process by altering the physical and chemical properties of the implant material surface. The advantages of each strategy in terms of their antibacterial effect, biocompatibility, limitations, and application prospects are analyzed, providing ideas and research directions for the development of novel biofilm infection strategies related to therapeutic materials.

Effect of Femtosecond Laser-Irradiated Titanium Plates on Enhanced Antibacterial Activity and Preservation of Bacteriophage Stability

Titanium (Ti) is widely recognized for its exceptional properties and compatibility with medical applications. In our study, we successfully formed laser-induced periodic surface structures (LIPSS) on Ti plates with a periodicity of 520-740 nm and a height range of 150-250 nm. To investigate the morphology and chemical composition of these surfaces, we employed various techniques, including field emission scanning electron microscopy, energy dispersive X-ray spectroscopy, atomic force microscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy. Additionally, we utilized a drop-shape analyzer to determine the wetting properties of the surfaces. To evaluate the antibacterial activity, we followed the ISO 22196:2011 standard, utilizing reference bacterial cultures of Gram-positive Staphylococcus aureus (ATCC 25923) and Gram-negative Escherichia coli (ATCC 25922). The results revealed enhanced antibacterial properties against Staphylococcus aureus by more than 99% and Escherichia coli by more than 80% in comparison with non-irradiated Ti. Furthermore, we conducted experiments using the Escherichia coli bacteriophage T4 (ATCC 11303-B4) and the bacterial host Escherichia coli (ATCC 11303) to investigate the impact of Ti plates on the stability of the bacteriophage. Overall, our findings highlight the potential of LIPSS on Ti plates for achieving enhanced antibacterial activity against common bacterial strains while maintaining the stability of bacteriophages.

Fano resonant optical coatings platform for full gamut and high purity structural colors

Structural coloring is a photostable and environmentally friendly coloring approach that harnesses optical interference and nanophotonic resonances to obtain colors with a range of applications including display technologies, colorful solar panels, steganography, décor, data storage, and anticounterfeiting measures. We show that optical coatings exhibiting the photonic Fano Resonance present an ideal platform for structural coloring; they provide full color access, high color purity, high brightness, controlled iridescence, and scalable manufacturing. We show that an additional oxide film deposited on Fano resonant optical coatings (FROCs) increases the color purity (up to 99%) and color gamut coverage range of FROCs to 61% of the CIE color space. For wide-area structural coloring applications, FROCs have a significant advantage over existing structural coloring schemes.

Antibacterial properties of antimicrobial peptide HHC36 modified polyetheretherketone

Introduction

Polyetheretherketone (PEEK) is considered to be a new type of orthopedic implant material due to its mechanical properties and biocompatibility. It is becoming a replacement for titanium (Ti) due to its near-human-cortical transmission and modulus of elasticity. However, its clinical application is limited because of its biological inertia and susceptibility to bacterial infection during implantation. To solve this problem, there is an urgent need to improve the antibacterial properties of PEEK implants.

Methods

In this work, we fixed antimicrobial peptide HHC36 on the 3D porous structure of sulfonated PEEK (SPEEK) by a simple solvent evaporation method (HSPEEK), and carried out characterization tests. We evaluated the antibacterial properties and cytocompatibility of the samples in vitro. In addition, we evaluated the anti-infection property and biocompatibility of the samples in vivo by establishing a rat subcutaneous infection model.

Results

The characterization test results showed that HHC36 was successfully fixed on the surface of SPEEK and released slowly for 10 days. The results of antibacterial experiments in vitro showed that HSPEEK could reduce the survival rate of free bacteria, inhibit the growth of bacteria around the sample, and inhibit the formation of biofilm on the sample surface. The cytocompatibility test in vitro showed that the sample had no significant effect on the proliferation and viability of L929 cells and had no hemolytic activity on rabbit erythrocytes. In vivo experiments, HSPEEK can significantly reduce the bacterial survival rate on the sample surface and the inflammatory reaction in the soft tissue around the sample.

Discussion

We successfully loaded HHC36 onto the surface of SPEEK through a simple solvent evaporation method. The sample has excellent antibacterial properties and good cell compatibility, which can significantly reduce the bacterial survival rate and inflammatory reaction in vivo. The above results indicated that we successfully improved the antibacterial property of PEEK by a simple modification strategy, making it a promising material for anti-infection orthopedic implants.

Comparing Water Transport Properties of Janus Membranes Fabricated from Copper Mesh and Foam Using a Femtosecond Laser

One of the important aspects of manipulating and controlling liquid transport is the design of membrane surfaces. Janus membranes with opposite wettability characteristics can be manufactured for efficient directional water transfer. In this work, two types of materials were used to fabricate membranes with an asymmetric wettability behavior: copper foam and copper mesh. One side of the membranes was treated by scanning with a femtosecond laser beam, as a result of which it was converted to a superhydrophilic state, while the untreated side remained hydrophobic. Both membranes demonstrated excellent properties of a water diode through which water droplets could easily pass from the hydrophobic side to the hydrophilic side, but not vice versa. This behavior was achieved by finding the optimal laser scanning speed. This type of Janus membrane has found applications in collecting water droplets from fog; therefore, the samples obtained were also tested in terms of harvesting micro-droplets. The Janus mesh-based structure has demonstrated a higher water collection efficiency (3.9 g/cm² h) compared to the foam-based membrane (2.5 g/cm² h). Since the fog-water conversion efficiency decreased over time (to 0.5 g/cm² h in 2 weeks) due to the absorbance of organic pollutants, a coating of titanium oxide was applied to the laser-treated side of the Janus membranes. As a result, the effective function of the systems became distinctly long-lasting and was well maintained for at least 60 days. Moreover, the fabricated systems were protected from further degradation by simply placing them under sunlight for several hours. Our results prove to be useful in developing asymmetric hydrophobic-superhydrophilic membranes, which have potential applications in high-precision drop control and in harvesting water from arid environments.

The use of remote Femto Second technology in the preparation of black silicon material and optical devices

The research aims to study the application of remote Femto Second (FS) technology in black silicon material preparation and optical devices. Based on the principle and characteristic research of FS technology, the interaction between FS and silicon is adopted to propose a scheme for preparing black silicon material through experiments. Moreover, the experimental parameters are optimized. Then, the scheme of using the FS for etching polymer optical power splitter as a new technical means is proposed. In addition, while ensuring processing accuracy, the appropriate process parameters of laser etching photoresist are obtained. The results show that the performance of black silicon prepared with SF6 as the background gas is greatly improved in the 400-2200nm range. However, the performance of black silicon samples with the two-layer structure etched at different laser energy densities has little difference. Black silicon with a Se+Si two-layer film structure has the best optical absorption performance in the infrared range of 1100nm-2200nm. Besides, the optical absorption rate is the highest when the laser scanning rate is 0.5mm/s. In the band of >1100nm, when the maximum laser energy density is 6.5kJ/m2, the overall absorption of the etched sample is the worst. The absorption rate is the best when the laser energy density is 3.9kJ/m2. It suggests that the proper parameter selection greatly impacts the quality of the final laser-etched sample.

Pulse Burst Generation and Diffraction with Spatial Light Modulators for Dynamic Ultrafast Laser Materials Processing

A pulse burst optical system has been developed, able to alter an energetic, ultrafast 10 ps, 5 kHz output pulse train to 323 MHz intra-burst frequency at the fundamental 5 kHz repetition rate. An optical delay line consisting of a beam-splitting polariser cube, mirrors, and waveplates transforms a high-energy pulse into a pulse burst, circulating around the delay line. Interestingly, the reflected first pulse and subsequent pulses from the delay line have orthogonal linear polarisations. This fact allows independent modulation of these pulses using two-phase-only Spatial Light Modulators (SLM) when their directors are also aligned orthogonally. With hybrid Computer Generated Holograms (CGH) addressed to the SLMs, we demonstrate simultaneous multi-spot periodic surface micro-structuring on stainless steel with orthogonal linear polarisations and cylindrical vector (CV) beams with Radial and Azimuthal polarisations. Burst processing produces a major change in resulting surface texture due to plasma absorption on the nanosecond time scale; hence the ablation rates on stainless steel with pulse bursts are always lower than 5 kHz processing. By synchronising the scan motion and CGH application, we show simultaneous independent multi-beam real-time processing with pulse bursts having orthogonal linear polarisations. This novel technique extends the flexibility of parallel beam surface micro-structuring with adaptive optics.

Generation of zinc ion-rich surface via in situ growth of ZIF-8 particle: Microorganism immobilization onto fabric surface for prohibit hospital-acquired infection

Viruses/bacteria outbreaks have motivated us to develop a fabric that will inhibit their transmission with high potency and long-term stability. By creating a metal-ion-rich surface onto polyester (PET) fabric, a method is found to inhibit hospital-acquired infections by immobilizing microorganisms on its surface. ZIF-8 and APTES are utilized to overcome the limitations associated with non-uniform distribution, weak biomolecule interaction, and ion leaching on surfaces. Modified surfaces employing APTES enhance ZIF-8 nucleation by generating a monolayer of self-assembled amine molecules. An in-situ growth approach is then used to produce evenly distributed ZIF-8 throughout it. In comparison with pristine fabric, this large amount of zinc obtained from the modification of the fabric has a higher affinity for interacting with membranes of microorganisms, leading to a 4.55-fold increase in coronavirus spike-glycoprotein immobilization. A series of binding ability stability tests on the surface demonstrate high efficiency of immobilization, >90%, of viruses and model proteins. The immobilization capacity of the modification fabric stayed unchanged after durability testing, demonstrating its durability and stability. It has also been found that this fabric surface modification approach has maintained air/vapor transmittance and air permeability levels comparable to pristine fabrics. These results strongly advocate this developed fabric has the potential for use as an outer layer of face masks or as a medical gown to prevent hospital-acquired infections.

In Situ Surface-Directed Assembly of 2D Metal Nanoplatelets for Drug-Free Treatment of Antibiotic-Resistant Bacteria

The development of antibiotic resistance among bacterial strains is a major global public health concern. To address this, drug-free antibacterial approaches are needed. Copper surfaces have long been known for their antibacterial properties. In this work, a one-step surface modification technique is used to assemble 2D copper chloride nanoplatelets directly onto copper surfaces such as copper tape, transmission electron microscopy (TEM) grids, electrodes, and granules. The nanoplatelets are formed using copper ions from the copper surfaces, enabling their direct assembly onto these surfaces in a one-step process that does not require separate nanoparticle synthesis. The synthesis of the nanoplatelets is confirmed with TEM, scanning electron microscopy, energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FT-IR). Antibacterial properties of the Cu nanoplatelets are demonstrated in multidrug-resistant (MDR) Escherichia coli, MDR Acinetobacter baumannii, MDR Staphylococcus aureus, E. coli, and Streptococcus mutans. Nanoplatelets lead to a marked improvement in antibacterial properties compared to the copper surfaces alone, affecting bacterial cell morphology, preventing bacterial cell division, reducing their viability, damaging bacterial DNA, and altering protein expression. This work presents a robust method to directly assemble copper nanoplatelets onto any copper surface to imbue it with improved antibacterial properties.

Laser-Enabled Surface Treatment of Disposable Endoscope Lens with Superior Antifouling and Optical Properties

Endoscopes are ubiquitous in minimally invasive or keyhole surgeries globally. However, frequent removal of endoscopes from the patient's body due to the lens contaminations results in undesirable consequences. Therefore, a cost-effective process chain to fabricate thermoplastic-based endoscope lenses with superior antifouling and optical properties is proposed in this research. Such multifunctional surface response was achieved by lubricant impregnation of nanostructures. Two types of topographies were produced by femtosecond laser processing of metallic molds, especially to produce single-tier laser-induced periodic surface structures (LIPSS) and two-tier multiscale structures (MS). Then, these two LIPSS and MS masters were used to replicate them onto two thermoplastic substrates, namely polycarbonate and cyclic olefin copolymer, by using hot embossing. Finally, the LIPSS and MS surfaces of the replicas were infiltrated by silicone oils to prepare lubricant-impregnated surfaces (LIS). Droplet sliding tests revealed that the durability of the as-prepared LIS improved with the increase of the lubricant viscosity. Moreover, the single-tier LIPSS replicas exhibited longer-lasting lubricant conservation properties than the MS ones. Also, LIPSS-LIS replicas demonstrated an excellent optical transparency, better than the MS-LIS ones, and almost match the performance of the reference polished ones. Furthermore, the LIPSS-LIS treatment led to superior antifouling characteristics, i.e., regarding fogging, blood adhesion, protein adsorption, and microalgae attachment, and thus demonstrated its high suitability for treating endoscopic lenses. Finally, a proof-of-concept LIPSS-LIS treatment of endoscope lenses was conducted that confirmed their superior multifunctional response.

Effect of Texturing Environment on Wetting of Biomimetic Superhydrophobic Surfaces Designed by Femtosecond Laser Texturing

Inspired by Euphorbia leaves, micrometric pillars are designed on 316L stainless steel surfaces using a femtosecond laser to achieve superhydrophobicity. In this study, we focus on wetting behavior evolution as a function of time and chemical environment. Two types of texturing designs are performed: the laser texturing of micrometric square pillars, and the laser texturing of micrometric square pillars whose tops were irradiated using various fluences to obtain a different topography on the nanometric scale. Two laser texturing environments are considered in both cases: a CO₂ flow and ambient air. The main result is that 250 days after laser texturing, steady-state contact angles (SSCA) were above 130° no matter what the environment was. We also study the effect of regular wetting over time. Comparing the results of surfaces for which wetting over time was conducted and that of the undisturbed surfaces for 250 days demonstrates that performing wetting measurements when the surface is not stable led to major changes in droplet behavior. Our surfaces have a unique wettability in which droplets are in an intermediate state. Finally, using a CO₂ flow did not help reach higher SSCA, but it limited the effect of regular wetting measurements.

Cuprous Oxide Nanoparticles Decorated Fabric Materials with Anti-biofilm Properties

Considering the global spread of bacterial infections, the development of anti-biofilm surfaces with high antimicrobial activities is highly desired. This work unraveled a simple, sonochemical method for coating Cu2O nanoparticles (NPs) on three different flexible substrates: polyester (PE), nylon 2 (N2), and polyethylene (PEL). The introduction of Cu2O NPs on these substrates enhanced their surface hydrophobicity, induced ROS generation, and completely inhibited the growth of sensitive (Escherichia coli and Staphyloccocus aureus) and drug-resistant (MDR E. coli and MRSA) planktonic and biofilm. The experimental results confirmed that Cu2O-PE exhibited complete biofilm mass reduction ability for all four strains, whereas Cu2O-N2 showed more than 99% biomass inhibition against both drug-resistant and sensitive pathogens in 6 h. Moreover, Cu2O-PEL also indicated a 99.95, 97.73, 98.00, and 99.20% biomass reduction of MRSA, MDR E. coli, E. coli, and S. aureus, respectively. All substrates were investigated for time-dependent inhibitions, and the associated biofilm mass and log reduction were evaluated. The mechanisms of Cu2O NP action against the mature biofilms include the generation of reactive oxygen species (ROS) as well as electrostatic interaction between Cu2O NPs and bacterial membranes. The current study could pave the way for the commercialization of sonochemically coated Cu2O NP flexible substrates for the prevention of microbial contamination in hospitals and industrial environments.

Regular Periodic Surface Structures on Indium Tin Oxide Film Efficiently Fabricated by Femtosecond Laser Direct Writing with a Cylindrical Lens

Regular laser-induced periodic surface structures (LIPSS) were efficiently fabricated on indium tin oxide (ITO) films by femtosecond laser direct writing with a cylindrical lens. It was found that randomly distributed nanoparticles and high spatial frequency LIPSSs (HSFL) formed on the surface after a small number of cumulative incident laser pulses per spot, and regular low spatial frequency LIPSSs (LSFL) appeared when more laser pulses accumulated. The mechanism of the transition was studied by real-time absorptance measurement and theoretical simulation. Results show that the interference between incident laser and surface plasmon polaritons (SPPs) excited by random surface scatterers facilitates the formation of prototype LSFLs, which in turn enhances light absorption and SPP excitation following laser pulses. The effects of scanning velocity and laser fluence on LSFL quality were discussed in detail. Moreover, large-area extremely regular LSFL with a diameter of 30 mm were efficiently fabricated on an ITO film by femtosecond laser direct writing with the cylindrical lens. The fabricated LSFLs on the ITO film demonstrate vivid structural color. During LSFL processing, the decrease of ITO film thickness leads to the increase of near-infrared optical transmittance.

Investigating Potential Effects of Ultra-Short Laser-Textured Porous Poly-ε-Caprolactone Scaffolds on Bacterial Adhesion and Bone Cell Metabolism

Developing antimicrobial surfaces that combat implant-associated infections while promoting host cell response is a key strategy for improving current therapies for orthopaedic injuries. In this paper, we present the application of ultra-short laser irradiation for patterning the surface of a 3D biodegradable synthetic polymer in order to affect the adhesion and proliferation of bone cells and reject bacterial cells. The surfaces of 3D-printed polycaprolactone (PCL) scaffolds were processed with a femtosecond laser (λ = 800 nm; τ = 130 fs) for the production of patterns resembling microchannels or microprotrusions. MG63 osteoblastic cells, as well as S. aureus and E. coli, were cultured on fs-laser-treated samples. Their attachment, proliferation, and metabolic activity were monitored via colorimetric assays and scanning electron microscopy. The microchannels improved the wettability, stimulating the attachment, spreading, and proliferation of osteoblastic cells. The same topography induced cell-pattern orientation and promoted the expression of alkaline phosphatase in cells growing in an osteogenic medium. The microchannels exerted an inhibitory effect on S. aureus as after 48 h cells appeared shrunk and disrupted. In comparison, E. coli formed an abundant biofilm over both the laser-treated and control samples; however, the film was dense and adhesive on the control PCL but unattached over the microchannels.

A two-phase and long-lasting multi-antibacterial coating enables titanium biomaterials to prevent implants-related infections

In clinical work, the main challenges for titanium (Ti) implantation are bacterial infection and aseptic loosening, which severely affect the survival rate of implants. The first 4 weeks post-operation is the infection peak phase of implants. Inhibiting implant infection caused by bacteria adhesion and proliferation during the early phase as well as promoting subsequent osteointegration is essential for implant success. Herein, we constructed a quaternary ammonium carboxymethyl chitosan (QCMC), collagen (COL Ⅰ) and hydroxyapatite (HAP) multilayers coating on Ti substrates via a modified layer-by-layer (LBL) technique and polymerization of dopamine. The QCMC/COL/HAP coating exhibited a multi-antibacterial property with a two-phase function: (1) At the first 4 weeks post-operation, the covalently bonded QCMC could be slowly degraded and demonstrated both contact-killing and release-killing properties during the infection peak phase; (2) At the second phase, osteogenesis and osseointegration-promotion capabilities were enhanced by HAP under the effective control of infection. The multifilm coating was degraded for more than 45 days under the action of collagenase Ⅰ, and displayed good biocompatibility in vivo and in vitro. Most importantly, the coating exhibited a long-lasting antibacterial activity for more than 3 months, against the main pathogenic bacteria of peri-implant infections. Both in vitro studies and in vivo animal models revealed a desirable osteogenic differentiation capacity of Ti-CCH. Therefore, our study reports a two-phase, long-lasting multi-antibacterial coating on Ti-CCH and indicates potential applications of the modified LBL strategy in orthopaedic fields, which is enlightening for developing practical implant and scaffold materials.

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Developing a QCMC/COL/HAP multifilm coating via modified layer-by-layer technique and self-polymerization of dopamine.

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The QCMC/COL/HAP coating exhibited desirable mechanical properties and excellent biocompatibility.

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The release kinetics endowed the QCMC/COL/HAP coating with multi-antibacterial activity at the first phase after operation.

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The QCMC/COL/HAP coating could improve osseointegration at the second phase of post-operation.

Wettability and Surface Roughness Analysis of Laser Surface Texturing of AISI 430 Stainless Steel

Due to its wide applicability in industry, devising microstructures on the surface of materials can be easily implemented and automated in technological processes. Laser Surface Texturing (LST) is applied to modify the chemical composition, morphology, and roughness of surfaces (wettability), cleaning (remove contaminants), reducing internal stresses of metals (hardening, tempering), surface energy (polymers, metals), increasing the adhesion (hybrid joining, bioengineering) and decreasing the growth of pathogenic bacteria (bioengineering). This paper is a continuation and extension of our previous studies in laser-assisted texturing of surfaces. Three different patterns (crater array-type C, two ellipses at 90° overlapping with its mirror-type B and 3 concentric octagons-type A) were applied with a nanosecond pulsed laser (active medium Nd: Fiber Diode-pumped) on the surface of a ferritic stainless steel (AISI 430). Micro texturing the surface of a material can modify its wettability behavior. A hydrophobic surface (contact angle greater than 90°) was obtained with different variations depending on the parameters. The analysis performed in this research (surface roughness, wettability) is critical for assessing the surface functionality, characteristics and properties of the stainless steel surface after the LST process. The values of the surface roughness and the contact angle are directly proportional to the number of repetitions and inversely proportional to the speed. Recommendations for the use of different texturing pattern designs are also made.

Laser Direct Writing of Dual-Scale 3D Structures for Cell Repelling at High Cellular Density

The fabrication of complex, reproducible, and accurate micro-and nanostructured interfaces that impede the interaction between material's surface and different cell types represents an important objective in the development of medical devices. This can be achieved by topographical means such as dual-scale structures, mainly represented by microstructures with surface nanopatterning. Fabrication via laser irradiation of materials seems promising. However, laser-assisted fabrication of dual-scale structures, i.e., ripples relies on stochastic processes deriving from laser-matter interaction, limiting the control over the structures' topography. In this paper, we report on laser fabrication of cell-repellent dual-scale 3D structures with fully reproducible and high spatial accuracy topographies. Structures were designed as micrometric "mushrooms" decorated with fingerprint-like nanometric features with heights and periodicities close to those of the calamistrum, i.e., 200-300 nm. They were fabricated by Laser Direct Writing via Two-Photon Polymerization of IP-Dip photoresist. Design and laser writing parameters were optimized for conferring cell-repellent properties to the structures, even for high cellular densities in the culture medium. The structures were most efficient in repelling the cells when the fingerprint-like features had periodicities and heights of ≅200 nm, fairly close to the repellent surfaces of the calamistrum. Laser power was the most important parameter for the optimization protocol.

Superhydrophilic-Superhydrophobic Multifunctional Janus Foam Fabrication Using a Spatially Shaped Femtosecond Laser for Fog Collection and Detection

Fog collection is an effective method for addressing water shortages in arid areas. By constructing a Janus structure with asymmetric wettability on its two sides, flexible and efficient fog capture can be achieved. However, in situ detection and fog collection on a Janus surface are still challenging tasks. Herein, a novel method for producing a superhydrophilic-superhydrophobic Janus fog collector is proposed; the method utilizes a combined process in which a spatially shaped femtosecond laser treatment (superhydrophilic) is applied to one side of a copper foam and a chemical replacement reaction (superhydrophobic) is applied to the other side of the copper foam. Two configurations of the Janus structure were designed to study different water transport behaviors. Furthermore, the Au micro-nanoparticle prepared adhered to the Janus structure, indicating the effectiveness of surface-enhanced Raman spectroscopy detection. The Janus foam shows excellent sensitivity and stability on testing the fog mixed with rhodamine 6G. This surface allows for the simultaneous collection and detection of fog, which can provide insights into the preparation of Janus multifunction structures and how such structures can play a key role in the subsequent purification and usage of water resources.

Enhancement of Bacterial Anti−Adhesion Properties on Robust PDMS Micro−Structure Using a Simple Flame Treatment Method

Biofilm-associated infections caused by an accumulation of micro-organisms and pathogens significantly impact the environment, health risks, and the global economy. Currently, a non-biocide-releasing superhydrophobic surface is a potential solution for antibacterial purposes. This research demonstrated a well-designed robust polydimethylsiloxane (PDMS) micro-structure and a flame treatment process with improved hydrophobicity and bacterial anti-adhesion properties. After the flame treatment at 700 ± 20 °C for 15 s, unique flower-petal re-entrant nano-structures were formed on pillars (PIL-F, width: 1.87 ± 0.30 μm, height: 7.76 ± 0.13 μm, aspect ratio (A.R.): 4.14) and circular rings with eight stripe supporters (C-RESS-F, width: 0.50 ± 0.04 μm, height: 3.55 ± 0.11 μm, A.R.: 7.10) PDMS micro-patterns. The water contact angle (WCA) and ethylene glycol contact angle (EGCA) of flame-treated flat-PDMS (FLT-F), PIL–F, and C–RESS-F patterns were (133.9 ± 3.8°, 128.6 ± 5.3°), (156.1 ± 1.5°, 151.5 ± 2.1°), and (146.3 ± 3.5°, 150.7 ± 1.8°), respectively. The Escherichia coli adhesion on the C-RESS-F micro-pattern with hydrophobicity and superoleophobicity was 42.6%, 31.8%, and 2.9% less than FLT-F, PIL-F, and Teflon surfaces. Therefore, the flame-treated C-RESS-F pattern is one of the promising bacterial anti-adhesion micro-structures in practical utilization for various applications.

Antibacterial Performance of Zr-BMG, Stainless Steel, and Titanium Alloy with Laser-Induced Periodic Surface Structures

A laser-induced periodic surface structure (LIPSS) was shown to have antibacterial adhesion properties in previous research. In this study, the antibacterial performance of LIPSS on traditional biometals (stainless steel and titanium alloy) and a potential biometal (zirconium-based bulk metallic glass, Zr-BMG) was investigated. A femtosecond laser was used to fabricate LIPSS on the specimens. Gram-negative Escherichia coli (E. coli) and Gram-positive Staphylococcus aureus (S. aureus) were used to examine the antibacterial behavior of the LIPSS samples. The bacterial adhesion force on each specimen was evaluated by an atomic force microscopy (AFM) cell probe. The results showed that the LIPSS on all three metal surfaces significantly lowered antibacterial adhesion compared to polished metal specimens. E. coli demonstrated a higher adhesion force but a lower surface adhesion rate compared to S. aureus. The Zr-BMG specimen with LIPSS has multiple antimicrobial mechanisms (physical antiadhesion and chemical elimination), while the traditional biometals (316L and TC4) mainly offer physical antiadhesion. Finally, an in vitro/vivo study showed that specimens with LIPSS surfaces did not significantly affect the biocompatibility of the specimens. This study reveals that the Zr-BMG specimen with femtosecond laser-processed LIPSS is an ideal choice for achieving an antibacterial surface.

Antibacterial surfaces: Strategies and applications

Antibacterial surfaces are surfaces that can resist bacteria, relying on the nature of the material itself. It is significant for safe food and water, human health, and industrial equipment. Biofilm is the main form of bacterial contamination on the material surface. Preventing the formation of biofilm is an efficient way to develop antibacterial surfaces. The strategy for constructing the antibacterial surface is divided into bacteria repelling and bacteria killing based on the formation of the biofilm. Material surface wettability, adhesion, and steric hindrance determine bacteria repelling performance. Bacteria should be killed by surface chemistry or physical structures when they are attached to a material surface irreversibly. Killing approaches are usually in the light of the cell membrane of bacteria. This review summarizes the fabrication methods and applications of antibacterial surfaces from the view of the treatment of the material surfaces. We also present several crucial points for developing long-term stability, no drug resistance, broad-spectrum, and even programable antibacterial surfaces.

Fluorine-Free Superhydrophobic Coating with Antibiofilm Properties Based on Pickering Emulsion Templating

This study presents antibiofilm coating formulations based on Pickering emulsion templating. The coating contains no bioactive material because its antibiofilm properties stem from passive mechanisms that derive solely from the superhydrophobic nature of the coating. Moreover, unlike most of the superhydrophobic formulations, our system is fluorine-free, thus making the method eminently suitable for food and medical applications. The coating formulation is based on water in toluene or xylene emulsions that are stabilized using commercial hydrophobic silica, with polydimethylsiloxane (PDMS) dissolved in toluene or xylene. The structure of the emulsions and their stability was characterized by confocal microscopy and cryogenic-scanning electron microscopy (cryo-SEM). The most stable emulsions are applied on polypropylene (PP) surfaces and dried in an oven to form PDMS/silica coatings in a process called emulsion templating. The structure of the resulting coatings was investigated by atomic force microscopy (AFM) and SEM. The surface of the coatings shows a honeycomb-like structure that exhibits a combination of micron-scale and nanoscale roughness, which endows it with its superhydrophobic properties. After tuning, the superhydrophobic properties of the coatings demonstrated highly efficient passive antibiofilm activity. In vitro antibiofilm trials with E. coli indicate that the coatings reduced the biofilm accumulation by 83% in the xylene-water-based surfaces and by 59% in the case of toluene-water-based surfaces.

Biomimetic Hierarchical Structuring of PLA by Ultra-Short Laser Pulses for Processing of Tissue Engineered Matrices: Study of Cellular and Antibacterial Behavior

The influence of ultra-short laser modification on the surface morphology and possible chemical alteration of poly-lactic acid (PLA) matrix in respect to the optimization of cellular and antibacterial behavior were investigated in this study. Scanning electron microscopy (SEM) morphological examination of the processed PLA surface showed the formation of diverse hierarchical surface microstructures, generated by irradiation with a range of laser fluences (F) and scanning velocities (V) values. By controlling the laser parameters, diverse surface roughness can be achieved, thus influencing cellular dynamics. This surface feedback can be applied to finely tune and control diverse biomaterial surface properties like wettability, reflectivity, and biomimetics. The triggering of thermal effects, leading to the ejection of material with subsequent solidification and formation of raised rims and 3D-like hollow structures along the processed zones, demonstrated a direct correlation to the wettability of the PLA. A transition from superhydrophobic (θ > 150°) to super hydrophilic (θ < 20°) surfaces can be achieved by the creation of grooves with V = 0.6 mm/s, F = 1.7 J/cm2. The achieved hierarchical architecture affected morphology and thickness of the processed samples which were linked to the nature of ultra-short laser-material interaction effects, namely the precipitation of temperature distribution during material processing can be strongly minimized with ultrashort pulses leading to non-thermal and spatially localized effects that can facilitate volume ablation without collateral thermal damage The obtained modification zones were analyzed employing Fourier transform infrared (FTIR), X-ray photoelectron spectroscopy (XPS), Energy dispersive X-ray analysis (EDX), and optical profilometer. The modification of the PLA surface resulted in an increased roughness value for treatment with lower velocities (V = 0.6 mm/s). Thus, the substrate gains a 3D-like architecture and forms a natural matrix by microprocessing with V = 0.6 mm/s, F = 1.7 J/cm2, and V = 3.8 mm/s, F = 0.8 J/cm2. The tests performed with Mesenchymal stem cells (MSCs) demonstrated that the ultra-short laser surface modification altered the cell orientation and promoted cell growth. The topographical design was tested also for the effectiveness of bacterial attachment concerning chosen parameters for the creation of an array with defined geometrical patterns.

Aspect ratio of nano/microstructures determines Staphylococcus aureus adhesion on PET and titanium surfaces

AIMS

Joint infections cause premature implant failure. The avoidance of bacterial colonization of implant materials by modification of the material surface is therefore the focus of current research. In this in vitro study the complex interaction of periodic structures on PET and titanium surfaces on the adhesion of Staphylococcus aureus is analysed.

METHODS AND RESULTS

Using direct laser interference patterning as well as roll-to-roll hot embossing methods, structured periodic textures of different spatial distance were produced on surfaces and S. aureus were cultured for 24 h on these. The amount of adhering bacteria was quantified using fluorescence microscopy and the local adhesion behaviour was investigated using scanning electron microscopy. For PET structures, minimal bacterial adhesion was identified for an aspect ratio of about 0·02. On titanium structures, S. aureus adhesion was significantly decreased for profile heights of < 200 nm. Our results show a significantly decreased bacterial adhesion for structures with an aspect ratio range of 0·02 to 0·05.

CONCLUSIONS

We show that structuring on surfaces can decrease the amount of S. aureus on titanium and PET as common implant materials.

SIGNIFICANCE AND IMPACT OF THE STUDY

The study highlights the immense potential of applying specific structures to implant materials to prevent implant colonization with pathogen bacteria.

Significantly enhanced electrocatalytic activity of copper for hydrogen evolution reaction through femtosecond laser blackening

In this work, we report on the creation of a black copper via femtosecond laser processing and its application as a novel electrode material. We show that the black copper exhibits an excellent electrocatalytic activity for hydrogen evolution reaction (HER) in alkaline solution. The laser processing results in a unique microstructure: microparticles covered by finer nanoparticles on top. Electrochemical measurements demonstrate that the kinetics of the HER is significantly accelerated after bare copper is treated and turned black. At -0.325 V (v.s. RHE) in 1 M KOH aqueous solution, the calculated area-specific charge transfer resistance of the electrode decreases sharply from 159 Ω cm2 for the untreated copper to 1 Ω cm2 for the black copper. The electrochemical surface area of the black copper is measured to be only 2.4 times that of the untreated copper and therefore, the significantly enhanced electrocatalytic activity of the black copper for HER is mostly a result of its unique microstructure that favors the formation and enrichment of protons on the surface of copper. This work provides a new strategy for developing high-efficient electrodes for hydrogen generation.

Implication of Surface Properties, Bacterial Motility, and Hydrodynamic Conditions on Bacterial Surface Sensing and Their Initial Adhesion

Biofilms are structured microbial communities attached to surfaces, which play a significant role in the persistence of biofoulings in both medical and industrial settings. Bacteria in biofilms are mostly embedded in a complex matrix comprised of extracellular polymeric substances that provide mechanical stability and protection against environmental adversities. Once the biofilm is matured, it becomes extremely difficult to kill bacteria or mechanically remove biofilms from solid surfaces. Therefore, interrupting the bacterial surface sensing mechanism and subsequent initial binding process of bacteria to surfaces is essential to effectively prevent biofilm-associated problems. Noting that the process of bacterial adhesion is influenced by many factors, including material surface properties, this review summarizes recent works dedicated to understanding the influences of surface charge, surface wettability, roughness, topography, stiffness, and combination of properties on bacterial adhesion. This review also highlights other factors that are often neglected in bacterial adhesion studies such as bacterial motility and the effect of hydrodynamic flow. Lastly, the present review features recent innovations in nanotechnology-based antifouling systems to engineer new concepts of antibiofilm surfaces.

Nanotechnology-Based Antimicrobial and Antiviral Surface Coating Strategies

Biocontamination of medical devices and implants is a growing issue that causes medical complications and increased expenses. In the fight against biocontamination, developing synthetic surfaces, which reduce the adhesion of microbes and provide biocidal activity or combinatory effects, has emerged as a major global strategy. Advances in nanotechnology and biological sciences have made it possible to design smart surfaces for decreasing infections. Nevertheless, the clinical performance of these surfaces is highly depending on the choice of material. This review focuses on the antimicrobial surfaces with functional material coatings, such as cationic polymers, metal coatings and antifouling micro-/nanostructures. One of the highlights of the review is providing insights into the virus-inactivating surface development, which might particularly be useful for controlling the currently confronted pandemic coronavirus disease 2019 (COVID-19). The nanotechnology-based strategies presented here might be beneficial to produce materials that reduce or prevent the transmission of airborne viral droplets, once applied to biomedical devices and protective equipment of medical workers. Overall, this review compiles existing studies in this broad field by focusing on the recent related developments, draws attention to the possible activity mechanisms, discusses the key challenges and provides future recommendations for developing new, efficient antimicrobial and antiviral surface coatings.

Surface birefringence of regular periodic surface structures produced on glass coated with an indium tin oxide film using a low-fluence femtosecond laser through a cylindrical lens

Large-area regular laser-induced periodic surface structures (LIPSSs) with a birefringence effect were efficiently produced on a glass surface coated with an indium tin oxide (ITO) film, through irradiation by a femtosecond laser (800 nm, 50 fs, 3 mJ, 1 kHz) focused with a cylindrical lens. The laser fluence of 0.44 J/cm² on the coated glass was only one-tenth of that on bare glass, which significantly reduced the thermal effect. Moreover, regular LIPSSs with a period as short as 100 nm could be produced efficiently. The retardance of the fabricated LIPSSs was measured to be up to 44 nm, which is eight times that of LIPSSs fabricated on bare glass. The mechanisms of such a large difference of retardance were studied by measuring the nanostructures and the concentration of In³⁺ ions on the cross section of nano-corrugated surface layer on bare glass and ITO-coated glass.

Comparative study of femtosecond laser-induced structural colorization in water and air

The study of femtosecond laser structural coloring has recently attracted a great amount of research interest. These studies, however, have only been carried out in air. At the same time, laser ablation has also been actively studied in liquids as they provide a unique environment for material processing. However, surprisingly, structural coloring has never been performed in liquids. In this work, we perform the first study of metal structural coloring in liquid and compare the results to metal structural coloring in air. Colors created in liquid are formed by nanoparticle-induced plasmonic absorption and result in a range of colors transitioning from purple to orange. Surface structures formed in liquid are less hierarchical and more uniform than those formed in air, producing a surface with a much higher reflectance due to reduced light trapping, resulting in a more vibrant color. However, colorization formed in water suffers from less uniform colorization due to turbulence at the air-water and water-target interfaces, resulting in slight changes to the laser beam's focus during processing. Finally, finite-difference-time-domain simulation based on the measured surface structures is used to understand the role of plasmonic resonance in colorization.

Anti-Biofouling Properties of Femtosecond Laser-Induced Submicron Topographies on Elastomeric Surfaces

Antibacterial coatings are often employed to elastomer surfaces to inhibit bacterial attachment. However, such approaches could lead to increased antibiotic resistance. Surface micro-/nanotexturing is gaining significant attention recently, as it is a passive approach to reduce bacterial adhesion to surfaces. To this end, this work aims to assess the anti-biofouling functionality of femtosecond laser-induced submicron topographies on biomedical elastomer surfaces. Femtosecond laser processing was employed to produce two types of topographies on stainless-steel substrates. The first one was highly regular and single scale submicron laser-induced periodic surface structures (LIPSS) while the second one was multiscale structures (MSs) containing both submicron- and micron-scale features. Subsequently, these topographies were replicated on polydimethylsiloxane (PDMS) and polyurethane (PU) elastomers to evaluate their bacterial retention characteristics. The submicron textured PDMS and PU surfaces exhibited long-term hydrophobic durability up to 100 h under immersed conditions. Both LIPSS and MS topographies on PDMS and PU elastomeric surfaces were shown to substantially reduce (>89%) the adhesion of Gram-negative Escherichia coli bacteria. At the same time, the anti-biofouling performance of LIPSS and MS topographies was found to be comparable with that of lubricant-impregnated surfaces. The influence of physical defects on textured surfaces on the adhesion behavior of bacteria was also elucidated. The results presented here are significant because the polymeric biomedical components that can be produced by replication cost effectively, while their biocompatibility can be improved through femtosecond surface modification of the respective replication masters.