Search Results (20)

Carbon-based materials have emerged as promising biomaterials due to their biocompatibility and inherent antibacterial properties. Carbyne, a unique allotrope of carbon, characterized by sp-hybridized carbons forming alternating single and triple bonds, exhibits exceptional toughness. Herein, we explore the potential of carbyne-enriched plasma coatings for antibacterial applications in conjunction with micro- and nano-textured polymeric surfaces. We investigate and characterize carbyne-enriched plasma coatings onto superhydrophilic or superhydrophobic poly (methyl methacrylate) (PMMA) plasma micro-nanotextured surfaces. Our analysis evaluates the wetting properties and durability of these surfaces, particularly in liquid immersion conditions. The integration of carbyne-enriched plasma coatings serves a dual purpose: it enhances the chemical bactericidal action and protects surface micro-nanostructures from deformation due to capillary forces thanks to the material’s innate toughness. The results show that the micro-nanotextured and carbyne-enriched coated PMMA surfaces exhibit a significant bactericidal activity as expressed by a bactericidal index of approximately 50%, owing to the combined effect of both the surface topography and the plasma-deposited carbyne coating. Full article

Polyethylene terephthalate (PET) is widely used in food packaging, biomedical, and optical applications, but its inherent wettability limitations can hinder its performance in extreme environments. To this end, several methods have been developed to improve PET wetting properties. Yet, most of the methods proposed are wet and involve the use of chemical reagents, whereas, in most of the dry-based methods, such as plasma-based methods, which can easily tune the wetting properties of polymeric materials such as PET, achieving long-term stability, especially in extreme wetting states (superhydrophilicity and superhydrophobicity), remains a challenge. In this work, oxygen plasma etching is used to micro-nanotexture thin and, therefore, flexible PET films (thickness: 50 μm) for three different time durations of 4, 6, and 12 min followed by a C₄F₈ plasma deposition of a hydrophobic film or a hydrophilic poly (ethylene glycol) coating depending on the wettability profile targeted. Using this dry and, therefore, “green” and simple two step method, durable superhydrophilic and superhydrophobic surfaces that last for at least one year have been successfully realized. Finally, it is also shown that wetting control can be achieved without significantly affecting the inherent optical properties of the PET film (texturing duration up to 6 min), highlighting the multifunctionality of the plasma micro-nanotextured PET film. Full article

The enhanced and direct immobilization of the enzyme horseradish peroxidase on poly(methyl methacrylate) (PMMA) microchannel surfaces to create a miniaturized enzymatic reactor for the biocatalytic oxidation of phenols is demonstrated. Enzyme immobilization occurs by physical adsorption after oxygen plasma treatment, which micro-nanotextures the PMMA surfaces. A five-fold enhancement in immobilized enzyme activity was observed, attributed to the increased surface area and, therefore, to a higher quantity of immobilized enzymes compared to an untreated PMMA surface. The enzymatic reaction yield reached 75% using a flow rate of 2.0 μL/min for the reaction mixture. Additionally, the developed microreactor was reused more than 16 times without affecting the enzymatic conversion yield. These results demonstrate the potential of microchannels with plasma micro/nanotextured surfaces for the rapid and facile fabrication of microfluidic enzymatic microreactors with enhanced catalytic activity and stability. Full article

The need for sustainable energy solutions is steering research towards green fuels. One promising approach involves electrocatalytic gas conversion, which requires efficient catalyst surfaces. This study focuses on developing and testing a hydrophobic octadiene (OD) coating for potential use in electrocatalytic gas conversion. The approach aims to combine a plasma-deposited hydrophobic coating with air-trapping micro- and nanotopographies to increase the yield of electrocatalytic reactions. Plasma polymerisation was used to deposit OD films, chosen for their fluorine-free non-polar properties, onto titanium substrates. We assessed the stability and charge permeability of these hydrophobic coatings under electrochemical conditions relevant to electrocatalysis. Our findings indicate that plasma-deposited OD films, combined with micro-texturing, could improve the availability of reactant gases at the catalyst surface while limiting water access. In the presence of nanotextures, however, the OD-coated catalyst did not retain its hydrophobicity. This approach holds promise to inform the future development of catalyst materials for the electrocatalytic conversion of dinitrogen (N₂) and carbon dioxide (CO₂) into green fuels. Full article

This paper reports the optimization of a two-step atmospheric pressure plasma process to modify the surface properties of a polyurethane (PU) foam and, specifically, to prepare a superhydrophobic/superoleophilic absorbent for the removal of oils and nonpolar organic solvents from water. In particular, in the first step, an oxygen-containing dielectric barrier discharge (DBD) is used to induce the etching/nanotexturing of the foam surfaces; in the second step, an ethylene-containing DBD enables uniform overcoating with a low-surface-energy hydrocarbon polymer film. The combination of surface nanostructuring and low surface energy ultimately leads to simultaneous superhydrophobic and superoleophilic wetting properties. X-ray photoelectron spectroscopy, scanning electron microscopy and water contact angle measurements are used for the characterization of the samples. The plasma-treated PU foam selectively absorbs various kinds of hydrocarbon-based liquids (i.e., hydrocarbon solvents, mineral oils, motor oil, diesel and gasoline) up to 23 times its own weight, while it completely repels water. These absorption performances are maintained even after 50 absorption/desorption cycles and after immersion in hot water as well as acidic, basic and salt aqueous solutions. The plasma-treated foam can remove mineral oil while floating on the surface of mineral oil/water mixtures with a separation efficiency greater than 99%, which remains unaltered after 20 separation cycles. Full article

Hydrophilic and nanotextured surfaces for dental implants have been reported as relevant properties for early osseointegration. However, these surface characteristics are quite sensitive to oral interactions. Therefore, this pilot study aimed to investigate the superficial alterations caused on hydrophilic nanotubular surfaces after early human saliva interaction. Titanium disks were treated using an anodization protocol followed by reactive plasma application in order to achieve nanotopography and hydrophilicity, additionally; surfaces were stored in normal atmospheric oxygen or wet conditioning. Following, samples were interacted with saliva for 10 min and analyzed regarding physical–chemical properties and cellular viability. Saliva interaction did not show any significant influence on morphological characteristics, roughness measurements and chemical composition; however, hydrophilicity was statistically altered compromising this feature when the samples were stored in common air. Cellular viability tested with pre-osteoblasts cell line (MC3T3-E1) reduced significantly at 48 h on the samples without wet storage after saliva contamination. The applied wet-storage methodology appears to be effective in maintaining properties such as hydrophilicity during saliva interaction. In conclusion, saliva contamination might impair important properties of hydrophilic nanotubular surfaces when not stored in wet conditions, suggesting the need of saliva-controlled sites for oral application of hydrophilic surfaces and/or the use of modified-package methods associated with their wet storage. Full article

The development and efficient production of effective bioplastics is a hot topic, required to face up to the issue of the difficult disposal of plastics derived from oil. Among the different natural sources of bioplastics, starch is one of the most promising. However, for most applications, the proper mastering of the surface properties of bioplastic is necessary. We report about the surface modification of extruded corn starch films by means of cold plasma based on helium (He) and hexamethyldisiloxane (HMDSO). The differently treated surfaces were functionally characterized in wettability and water absorption. The nanoscale morphology was assessed by scanning electron microscopy and atomic force microscopy. The obtained images were analyzed by advanced figures describing both texture and amplitude parameters, including fractal behavior. The combined treatment (He/HMDSO) resulted in more homogeneous films with smaller, better-distributed grains compared to the case wherein He was not used. Despite the different morphologies observed, starch coated by HMDSO alone and by He/HMDSO presented similar hydrophobic character, with contact angles higher than 110°. Plasma treatment with HMDSO and He/HMDSO resulted in a significant reduction of absorbed water content without reduction of water vapor permeability. The nanotexture of the films did not present statistically significant differences, in terms of spatial complexities, dominant spatial frequencies, homogeneous void distribution, and surface percolation. Full article

A new data transformation method for micro-manufacturing using a topological model for a micro-/nano-texture was proposed for a surface-decorated product. Femtosecond laser printing was utilized to form the micro-/nano-textures into the hardened thick layer of dies by plasma nitriding. At first, the plasma-nitrided AISI316L flat substrate was laser-printed as a punch to imprint the tailored nano-textures onto the AA1060 aluminum plate for its surface decoration with topological emblems. Second, the plasma-nitrided SKD11 cylindrical punch was laser-trimmed to form the nanostructures on its side surface. This nano-texture was imprinted onto the hole surface concurrently with piercing a circular hole into electrical steel sheet. The fully burnished surface had a shiny, metallic quality due to the nano-texturing. The plasma nitriding, the laser printing and the CNC (computer numerical control) imprinting provided a way of transforming the tailored textures on the metallic product. Full article

Passivation of titanium alloy dental meshes cleans their surface and forms a thin layer of protective oxide (TiO₂) on the surface of the material to improve resistance to corrosion and prevent release of ions to the physiological environment. The most common chemical agent for the passivation process of titanium meshes is hydrochloric acid (HCl). In this work, we introduce the use of Piranha solution (H₂SO₄ and H₂O₂) as a passivating and bactericidal agent for metallic dental meshes. Meshes of grade 5 titanium alloy (Ti6Al4V) were tested after different treatments: as-received control (Ctr), passivated by HCl, and passivated by Piranha solution. Physical-chemical characterization of all treated surfaces was carried out by scanning electron microscopy (SEM), confocal microscopy and sessile drop goniometry to assess meshes’ topography, elemental composition, roughness, wettability and surface free energy, that is, relevant properties with potential effects for the biological response of the material. Moreover, open circuit potential and potentiodynamic tests were carried out to evaluate the corrosion behavior of the differently-treated meshes under physiological conditions. Ion release tests were conducted using Inductively Coupled Plasma mass spectrometry (ICP-MS). The antibacterial activity by prevention of bacterial adhesion tests on the meshes was performed for two different bacterial strains, Pseudomonas aeruginosa (Gram-) and Streptococcus sanguinis (Gram+). Additionally, a bacterial viability study was performed with the LIVE/DEAD test. We complemented the antibacterial study by counting cells attached to the surface of the meshes visualized by SEM. Our results showed that the passivation of titanium meshes with Piranha solution improved their hydrophilicity and conferred a notably higher bactericidal activity in comparison with the meshes passivated with HCl. This unique response can be attributed to differences in the obtained nanotextures of the TiO₂ layer. However, Piranha solution treatment decreased electrochemical stability and increased ion release as a result of the porous coating formed on the treated surfaces, which can compromise their corrosion resistance. Framed by the limitations of this work, we conclude that using Piranha solution is a viable alternative method for passivating titanium dental meshes with beneficial antibacterial properties that merits further validation for its translation as a treatment applied to clinically-used meshes. Full article

Oxygen plasma micro-nanostructured poly(methyl methacrylate) (PMMA) slides were modified through silver microparticle deposition to create microarray substrates that enhance the emitted fluorescence intensity. Silver deposition relied on a commercially available reagent and was completed in two 30-min incubation cycles of the substrate with the reagent. The fluorescence enhancement achieved using these substrates over flat PMMA slides was determined through the development of a microarray for the multiplexed detection of four mycotoxins, aflatoxin B1, ochratoxin A, fumonisin B1, and deoxynivalenol. It was shown that the implementation of silver-plated oxygen plasma micro-nanotextured PMMA substrates increased the signals obtained for aflatoxin B1 and ochratoxin A by approximately 2.8 times, 5.6 times for deoxynivalenol, and 16-times for fumonisin B1, compared to flat PMMA substrates. Most notably, this signal increase was not accompanied by a significant increase in the non-specific signal. In addition, the spot repeatability both across a single slide as well as between different slides was high, with coefficients of variation lower than 12%. The slides were also stable for at least three months, thus offering a microarray substrate with improved properties compared to standard glass slides, regarding both the absolute spot fluorescence intensity and between spots repeatability. Full article

The formation of gallium nitride (GaN) semi-polar and non-polar nanostructures is of importance for improving light extraction/absorption of optoelectronic devices, creating optical resonant cavities or reducing the defect density. However, very limited studies of nanotexturing via dry etching have been performed, in comparison to wet etching. In this paper, we investigate the formation and morphology of semi-polar ($11\overline{2}2$) and non-polar ($11\overline{2}0$) GaN nanorods using inductively coupled plasma (ICP) etching. The impact of gas chemistry, pressure, temperature, radio-frequency (RF) and ICP power and time are explored. A dominant chemical component is found to have a significant impact on the morphology, being impacted by the polarity of the planes. In contrast, increasing the physical component enables the impact of crystal orientation to be minimized to achieve a circular nanorod profile with inclined sidewalls. These conditions were obtained for a small percentage of chlorine (Cl₂) within the Cl₂ + argon (Ar) plasma combined with a low pressure. Damage to the crystal was reduced by lowering the direct current (DC) bias through a reduction of the RF power and an increase of the ICP power. Full article

The AISI316 austenitic stainless steel die was prepared and nitrided at 673 K for 14.4 ks. Through this low temperature plasma nitriding, the AISI316 die was homogeneously hardened up to 1400 HV within its surface layer of 50 μm. This nitrided AISI316 die was utilized to print the tailored micropattern with nanotextures onto its surface by the femtosecond laser processing. Each micropattern consisted of the tailored segments to have unidirectional nanotextures with different orientations. Each segment was recognized by its intrinsic surface plasmonic brilliance to tailored nanotextures. The CNC (Computer Numerical Control) stamping system was used to coin these micropatterns with nanotextures onto the AA1060 aluminum plates with the thickness of 1 mm. SEM (Scanning Electron Microscopy) and optical microscopy were employed to characterize the original micro-/nano-textures on the AISI316 die as well as the coined nanotextured patterns on the AA1060 plate surfaces. Full article

Over the last years, polymers have gained great attention as substrate material, because of the possibility to produce low-cost sensors in a high-throughput manner or for rapid prototyping and the wide variety of polymeric materials available with different features (like transparency, flexibility, stretchability, etc.). For almost all biosensing applications, the interaction between biomolecules (for example, antibodies, proteins or enzymes) and the employed substrate surface is highly important. In order to realize an effective biomolecule immobilization on polymers, different surface activation techniques, including chemical and physical methods, exist. Among them, plasma treatment offers an easy, fast and effective activation of the surfaces by micro/nanotexturing and generating functional groups (including carboxylic acids, amines, esters, aldehydes or hydroxyl groups). Hence, here we present a systematic and comprehensive plasma activation study of various polymeric surfaces by optimizing different parameters, including power, time, substrate temperature and gas composition. Thereby, the highest immobilization efficiency along with a homogenous biomolecule distribution is achieved with a 5-min plasma treatment under a gas composition of 50% oxygen and nitrogen, at a power of 1000 W and a substrate temperature of 80 °C. These results are also confirmed by different surface characterization methods, including SEM, XPS and contact angle measurements. Full article

Bacterial attachment and colonization to hygiene sensitive surfaces, both public and nosocomial, as well as in food industry areas, poses a serious problem to human healthcare. Several infection incidents are reported, while bacterial resistance to antibiotics is increasing. Recently, novel techniques for the design of antibacterial surfaces to limit bacterial spreading have emerged, including bifunctional antibacterial surfaces with antifouling and bactericidal action. In this context, we have recently developed smart, universal, metal-sputtered superhydrophobic surfaces, demonstrating both bacterial repulsion and killing efficacy. Herein, we present the optimization process that led to the realization of these “hybrid” antibacterial surfaces. To this end, two bactericidal agents, silver and copper, were tested for their efficiency against Gram-negative bacteria, with copper showing a stronger bactericidal action. In addition, between two low surface energy coatings, the fluorinated-alkyl self-assembled chlorosilane layer from perfluorinated octyltrichlorosilane (pFOTS) solution and the fluorocarbon layer from octafluorocyclobutane (C₄F₈) plasma were both approved for their anti-adhesive properties after immersion in bacterial solution. However, the latter was found to be more efficient when engrafted with the bactericidal agent in shielding its killing performance. Furthermore, the thickness of the plasma-deposited fluorocarbon layer was optimized, in order to simultaneously retain both the superhydrophobicity of the surface and its long-term bactericidal activity. Full article

Nano-texturing of polymers offers the possibility to drive important surface properties such as wettability and anti-reflectivity. Interestingly, plasma can lead to the desired characteristic of nanofeatures through a one step process based onto dry plasma etching. In this work, the literature concerning such plasma nano-texturing will be reviewed for different polymers, and in particular, for applications based upon wettability control. Then the mechanism of such processes will be commented upon, with a glance to the different characteristics of the polymers. Finally, some hints onto a feasible approach to plasma nano-texturing of the different polymers will be given. Full article