Low Roughness Research Articles

Changes in the Transition Process of Roughness-Induced Crossflow Vortices due to Freestream Turbulence

AbstractLaminar-turbulent transitions in boundary layers are one of the major research topics in fluid dynamics. In this study, we focused on a three-dimensional boundary layer formed on a swept flat plate. In this boundary layer, the crossflow instability is dominant, and the instability induces crossflow vortices (CFVs). Many studies have focused on the dependency of the transition process on the intensities of steady or unsteady disturbances, which correspond to a roughness element and freestream turbulence (FST), respectively. On the other hand, the effects of the FST wavelength are still unclear. Moreover, there is a lack of knowledge about the transition processes caused by both steady and unsteady disturbances. We investigated how the transition process of a stationary structure caused by cylindrical roughness changes depending on the FST wavelength using direct numerical simulations. We classified transition processes into two types: processes in which stationary structures grow into CFVs and processes in which hairpin vortices are generated on the stationary structures. The former is further classified into four types depending on the presence or absence of FST and on the FST wavelength. We revealed the contributions of different FST wavelengths to the transition process changes. The short-wavelength FST provides hairpin vortices to the stationary structure at low roughness height conditions because of its high-frequency components. The long-wavelength FST changes the process due to unsteady fluctuations influencing the stationary structure. In summary, the transition processes undergo different mechanisms between short- and long-wavelength FST.

A Study of the Effect of Roughness on the Three-Body Wear Mechanism from a Microscopic Point of View: Asperity Peak Removal

The presence of particles leads to varying degrees of mass loss on a metal sealing surface, which severely affects the seal’s lifespan. Understanding the complex wear mechanism and optimizing the surface roughness morphology are particularly important in engineering. By characterizing the surface of the metal (SS 304) with different roughness parameters Ra, Rp, Rpk, Rpc and Rku, the variation mode of mass loss under abrasive wear conditions was revealed. Unlike traditional two-body wear, the involvement of abrasive particles significantly impacts surface Ra and other surface morphologies (asperity peak features). A contact model for metal rough surfaces, distinct from two-body contact, was established to clarify the changes in removal mechanisms. It was found that the change in the contact between the particle and the asperity peak led to a change in the mass loss and guided the appropriate metal roughness range: Ra 0.05 μm and Ra 0.6–0.8 μm. In addition, it was found that the removal of asperity peaks is holistic under low roughness, and only parts of asperity peaks are removed under high roughness. Notably, the metrological methods used in this study supplement existing roughness measurements. By exploring the complex removal mechanism of asperity peaks, micro-scale guidance for surface (texture) design, machining, and optimization is provided.

Rational design of static wetting on roughness-engineered heterogeneous surfaces

Surface roughness and chemical composition are crucial in controlling the static wetting properties of surfaces. Here, conventional surface structuring methods used in Si microfabrication are used as a reference to analyze the impact of precisely engineered surface roughness. The static wettability of rough chemically heterogeneous surfaces is experimentally studied through contact angle measurements and compared against computational simulations to categorize the wetting behavior of water droplets. Heterogeneous samples are observed to already show significant dependence on the surface fraction covered by each material. Furthermore, owing to the presence of a resist layer on top of the Si pillars, intermediate states between the Wenzel (W) and Cassie–Baxter (CB) models are observed. Consistent with these models, we find that local chemical modifications of microstructured surfaces are crucial for controlling their surface wettability properties. Additionally, a comparison of equivalent microstructures made of Si or polydimethylsiloxane (PDMS) reveals the quantitative impact of the hydrophilic/hydrophobic nature of the material on the evolution of the wetting properties with increasing roughness factors. While Si surfaces behave according to the W model, PDMS surfaces show intermediate wetting states at significantly lower roughness levels. Bubbles trapped beneath water droplets demonstrate the existence of intermediate states that cannot be defined by either the W or CB models. By combining experimental results with finite element simulations, we not only demonstrate wettability control through specific roughness and chemical modifications but also provide insight into how these parameters interact to accurately predict and adjust static wetting properties.

Effect of chairside polishing systems on the surface roughness of different CAD-CAM denture base materials

Adjusting and polishing a denture base affects surface roughness and, consequently, microbial adhesion. Since various computer-aided design and computer-aided manufacturing (CAD-CAM) denture base materials are available, the efficiency of chairside polishing systems to achieve a proper surface roughness should be investigated. The purpose of this in vitro study was to compare the surface roughness of milled and 3-dimensional (3D) printed denture base materials with that of heat-polymerized acrylic resin after the use of 2 different chairside polishing systems. Heat-polymerized (control), milled, and 3D printed denture base materials were tested. Laboratory polished and unpolished denture bases served as positive and negative controls. Specimens were divided into 2 chairside silicone polishing systems (AcryPoint system and Exa technique). Surface roughness was measured before and after polishing. Surface morphology of the unpolished and polished specimens was observed via scanning electron microscopy. The surface hardness of unpolished specimens was measured using a Vickers hardness tester. Stress-strain behavior of the silicone matrix and abrasive filler size of each polisher was assessed. The effects of denture base materials and polishing systems on surface roughness and hardness were evaluated using 1-way, 2-way, and repeated measures analyses of variance (ANOVA) (α=.05), along with Weibull proportional hazards regression to assess the likelihood of achieving clinically acceptable surface roughness. The Spearman correlation assessed the relationship between the hardness of unpolished denture bases and final surface roughness. The surface roughness of all denture bases decreased with increased polishing duration, reaching a plateau after 60 seconds. For the heat-polymerized and milled dentures, the Exa technique consistently yielded lower roughness than the AcryPoint system (P<.001). Conversely, both polishing systems produced comparable surface roughness on the 3D printed denture base. The Vickers hardness of the unpolished milled denture was significantly higher than of the others (P=.010). The stress-strain behavior of the polisher matrix revealed distinct characteristics between coarse or medium and fine polishers within each polishing system. The abrasive filler size of the AcryPoint coarse polisher was relatively larger than that of the Exa technique. Regardless of polishing protocols, the 3D printed denture base exhibited the highest surface roughness, followed by heat-polymerized and milled denture bases. The surface roughness of the polished denture was not related with the material hardness. For heat-polymerized and milled dentures, a chairside silicone polishing system can be used to attain a level of surface roughness similar to that of laboratory polishing, depending on the properties of the chairside silicone polishing system. The data that support the findings of this study are available upon request from the corresponding author.

Characterization of novel bio-plasticizer from Cissus quadrangularis linn. stem: A sustainable and cleaner material for futuristic applications

There is also an increase in demand for plasticizers derived from natural resources, which are biodegradable. In search of novel bio-plasticizers, Cissus quadrangularis linn. (CQL) plant identified serves as an ideal source for plasticizer from natural sources. In this context, plasticizer is extracted from Cissus quandrangularis linn. stem that are biodegradable and biocompatible. This research paper presents the extraction and characterization of plasticizers derived from Cissus quadrangularis linn. (CQL) stem as a substitute for synthetic plasticizers. Bio-Plasticizers from CQL stem are extracted through chemical processes: amination, alkalization, filtration and surface catalysis. Further to identify its plastic nature, different characterization techniques such as FTIR, Thermal analysis, XRD, density, micrographs from SEM, chemical composition from EDX surface texture from AFM are conducted. TGA results convey that the Cissus quadrangularis linn. plasticizers (CQLP) are thermally stable upto 2230 C and displays a lower glass transition temperature of 58.170 C and these results accomplish the desired thermal properties. Crystalline properties of CQLP are found to be good with values of Crystalline Index 72.95 % and Crystalline Size 2.32 nm and these results displays the crystalline nature of isolated plasticizers. Surface texture of CQLP identified from AFM is smooth and uniform with lower roughness values across horizontal and vertical directions. Results of characterization studies accomplishes that novel CQLP are biodegradable, compatible and possess good plasticizing effect. This research investigation shows that these novel CQLP proves as a reliable alternative to synthetic plasticizers.

Effects of immersion in various beverages, polishing and bleaching systems on surface roughness and microhardness of CAD/CAM restorative materials

BackgroundThe aim of this study was to investigate the effect of an immune-boosting beverage with Sambucus nigra (SAM), an energy beverage (ENE), an in-office bleaching agent with a novel composition, and a fine-grain professional dental prophylaxis (PDP) paste on the surface roughness (Ra) and microhardness (MH) of CAD/CAM restorative materials over time.MethodsFeldspathic ceramic (FC) and polymer infiltrated ceramic network (PICN) specimens were prepared (N = 126). Glazing, polishing, bleaching and immersion in beverages groups were formed. Bleaching gel containing 25% Hydrogen Peroxide Superior was applied to the specimens with a bleaching pen. Ra and MH were measured at five time points of baseline, days 1, 14, 28 and after PDP. Scanning electron microscopy (SEM) images were taken after PDP. Statistics were performed by ANOVA and Bonferroni tests (α = 0.05).ResultsRa increased over time regardless of material type, polishing method, beverage type and bleaching (p < 0.0001). Glazed and polished FCs caused higher roughness than PICN, SAM and ENE than distilled water, and bleaching than no bleaching (p < 0.0001). For glazed or polished FCs, MH decreased slightly lower at all time points, but for PICN, MH increased until day 28, not changing after PDP. Beverages decreased the MH of ceramics at all time points, but PDP did not lead to a change for PICN (p < 0.0001). The MH decreased more in bleached specimens than in non-bleached specimens up to day 28 (p < 0.0001). According to the SEM images after PDP, the glazed FC had numerous crack marks, pores and detached particles. The polished FC had traces of mechanical polishing. The polymer part of the PICN had voids, but the ceramic part was better preserved.ConclusionsBoth energy beverages and immune-boosting beverages can increase roughness on FCs compared to PICNs. There was no significant difference between glazing and polishing in terms of lower roughness in FCs. PDP tended to slightly increase the roughness for ceramics, while it tended not to change it for PICN. Beverages decreased the microhardness of ceramics. PDP further decreased the microhardness in glazed ceramics, but increased it in polished ones. In PICN the microhardness increased over time, but decreased slightly after PDP.

Understanding the correlation between source and structural properties of chitin nanocrystals; insights from beetle (Cetonia aurata) skeletal segments

Chitin properties are known to vary depending on animal taxa, organismal source, and specific skeletal segments; However, the influence of these source-dependent variations on the physicochemical characteristics of chitin nanocrystals, particularly their Bouligand architecture, remains largely unexplored. Herein, chitin nanocrystals were isolated from seven different skeletal segments of C. aurata and characterized. Significant variation was observed in nanocrystal size, with wing-derived nanocrystals averaging 320 ± 127 nm and abdomen-derived nanocrystals 203 ± 104 nm, while surface charges ranged, with thorax-1 exhibiting the highest (45.68 ± 1.2 mV). All characteristic peaks were observed for both chitin and chitin nanocrystals, with the latter displaying sharper peaks and a slight increase in crystallinity, attributed to the removal of amorphous regions. Wing-derived chitin nanocrystals showed the highest thermal stability (372 °C), potentially due to lower surface area. Chitin nanocrystals-based films were produced to investigate the chiral behavior of isolated chitin nanocrystals. All the films displayed a unique helicoidal Bouligand structure with visible pitches, except those from thorax-1. The formation of mesophase (unclear pitch in Bouligand architecture) in thorax-1 films is likely due to nanocrystal dimensions and surface charges. This is further supported by the lower roughness and contact angle values observed in thorax-1 films.

Enhancing biosensor capabilities through laccase immobilization in nanostructured Langmuir-Blodgett films for phenol detection

Fabricating nanoscale structures combining various elements with specific functionalities is a pertinent strategy for enhancing sensor capabilities. In this study, we immobilized Laccase (Lac) in a biomimetic environment provided by a nanostructured Langmuir-Blodgett (LB) film of an amphiphilic material (octadecylamine, ODA), where poly(3-hexylthiophene-2,5-diyl) (P3HT) has been coimmobilized as the electron mediator. Tensiometry demonstrates that the enzyme is incorporated in the floating monolayers efficiently. The monolayers were transferred to solid substrates as LB films and characterized using UV–vis and infrared spectroscopies and Atomic Force Microscopy, exhibiting a quasi-ordered structure with low roughness. The films' ability to detect phenols was evaluated through enzymatic activity estimation using colorimetric and voltammetry measurements against vanillin, catechol, and pyrogallol. Our results demonstrate that the electrochemical response depends on the phenol's nature, with limits of detection for vanillin, catechol, and pyrogallol at 1.10.10−6, 2.13.10−7, and 2.07.10−7 mol.L−1, respectively. Additionally, the intensity of the response does not correlate with film thickness, confirming that the electrochemical reaction is a surface phenomenon for catechol and pyrogallol. We believe this study provides valuable insights into phenol detection in the food industry, which is crucial for ensuring food safety, quality, and authenticity by aiding in regulatory compliance, process optimization, and product preservation.

Influence of crystal orientation and incident plane on n-type 4H-SiC wafer slicing by using picosecond laser

Laser slicing has been considered as the most efficient technique for slicing SiC wafers with the advantages of small kerf width (loss) and crack, low roughness on cleaved surface, high quality and efficiency, etc. Here, laser slicing of n-type 4H-SiC was demonstrated by using a homemade 1064 nm picosecond laser combined with mechanical stretch stripping. The influence of laser processing along [11 2¯ 0] and [1 1¯ 00] crystal orientations on Si-face and C-face of n-type 4H-SiC, specifically on the internal laser ablation lines and cracks, the peeling tensile strength, and the surface roughness of the peeled surfaces was investigated. The semi-insulating 4H-SiC wafer laser slicing was conducted for comparison. Under the same laser conditions, laser slicing of semi-insulating 4H-SiC was easier than that of n-type. The laser modification quality along [1 1¯ 00] orientation was better than that along [11 2¯ 0] orientation for both the semi-insulating and n-type 4H-SiC and the reasons were explained. The results indicated that the optimal laser slicing scheme detailed laser scanning along [1 1¯ 00] orientation and incidence from the C-face. Finally, a 6-inch, 420.36 µm-thick n-type 4H-SiC wafer was successfully sliced.

UV-curable polymer-treated polydimethylsiloxane substrate for ultrahigh-efficient flexible organic light-emitting diodes

Flexible organic light-emitting diodes (FOLEDs) have developed rapidly and have been successfully implemented in the technology of foldable smartphones. As one of the most promising flexible substrates, polydimethylsiloxane (PDMS) suffers from the drawbacks of low thermal stability and weak interfacial adhesion with the low-cost solution-processed poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) film electrodes. In this work, a UV-curable polymer, Norland Optical Adhesive 63 (NOA63), is proposed to enhance the thermal stability and interfacial adhesion, as well as facilitating the light extraction of PDMS substrate. The PEDOT:PSS electrode film on the NOA63 modified PDMS substrate performs a uniform and smooth surface morphology with a low roughness of 3.1 nm, a high transmittance of 94.7 % at 550 nm wavelength, a low sheet resistance of 160 Ω/sq, and superior mechanical durability even after 18,000 bending cycles. The outstanding characteristics of the PDMS/NOA63 substrate enables the fabrication of an ultrahigh-efficient FOLED with a maximum current efficiency, power efficiency and external quantum efficiency of 230.6 cd/A, 144.9 lm/W and 65 %, respectively. This study paves the way to realize high-performance FOLEDs for wearable electronics in the future.

On the Effect of Randomly Oriented Grain Growth on the Structure of Aluminum Thin Films Deposited via Magnetron Sputtering

The microstructure of aluminum thin films, including the grain morphology and surface roughness, are key parameters for improving the thermal or electrical properties and optical reflectance of films. The first step in optimizing these parameters is a thorough understanding of the grain growth mechanisms and film structure. To investigate these issues, thin aluminum films with thicknesses ranging from 25 to 280 nm were coated on SiOx/Si substrates at ambient temperature under high-vacuum conditions and a low argon pressure of 3 × 10−3 mbar (0.3 Pa) using the radio frequency magnetron sputtering method. Quantitative analyses of the surface roughness and nanograin characteristics were conducted using atomic force microscopy (AFM), transmission electron microscopy (TEM), and X-ray diffraction. Changes in specular reflectance were measured using ultraviolet–visible and near-infrared spectroscopy. The low roughness values obtained from the AFM images resulted in high film reflectivity, even for thicker films. TEM and AFM results indicate monomodal, randomly oriented grain growth without a distinct columnar or spherical morphology. Using TEM cross-sectional images and the dependence of the grain size on the film thickness, we propose a grain growth mechanism based on the diffusion mobility of aluminum atoms through grain boundaries.

Film Properties of Heparin Cross-Linked with Epichlorohydrin in Absence or Presence of Imidazole

We cross-linked unfractionated heparin (H) using epichlorohydrin (E), in the absence or presence of imidazole (I), using various ratios of H, E, and I substances. The objectives and goals were to use the reaction for the preparation of medical materials suitable for blood sample applications. Nuclear magnetic resonance indicated the involvement of an H-end sequence [H-(1→4)-β-D-GlcA-(1→3)-β-D-Gal-(1→3)-β-D-Gal-(1→4)-β-D-Xyl-α-Ser] in the linkage with the 2-hydroxypropyl bridge. The yields of the individual experiments were found to increase in the following ratios: 1H/1E/3I (24%) &lt; 1H/1E/2I (32%) &lt; 1H/3E (42%) &lt; 1H/1E/1I (46%) &lt; 1H/2E (64%) &lt; 1H/1E (77%). According to size-exclusion chromatography with multiple-angle light scattering (SEC-MALS) analysis, the mass at the peak increased in the following order: H (9292 g/mol) &lt; 1H/1E (9294 g/mol) &lt; 1H/2E (9326 g/mol) &lt; 1H/3E (9708 g/mol) &lt; 1H/1E/2I (11,212 g/mol) &lt; 1H/1E/3I (12,301 g/mol) &lt; 1H/1E/1I (13,800 g/mol) and in the reverse order with the increase in amount of epichlorohydrin and imidazole, i.e., 1H/1E &gt; 1H/2E &gt; 1H/3E and 1H/1E/1I &gt; 1H/1E/2I &gt; 1H/1E/3I. X-ray diffraction revealed that all prepared films were amorphous. An evaluation of the surface morphology using atomic force microscopy (AFM) confirmed a relatively low films roughness (~0.9–3.6 nm). The surface reduced elastic modulus, determined by the PeakForce quantitative nanomechanical mapping (PF-QNM) technique, was found to increase by up to ~63% for films cross-linked with E in the absence of I when compared with the results for the H substrate. A negligible change in modulus was, however, observed for films cross-linked in the presence of I, or was even reduced by ~15% (1H/1E/3I) compared to that for the H substrate. This could be explained by the parallel cross-linking of H only with E within its serine end unit and in competition with only one nitrogen of I. According to the highest yield (77%) of 1H/1E, the preferred product is the following: H-(1→4)-β-D-GlcA-(1→3)-β-D-Gal-(1→3)-β-D-Gal-(1→4)-β-D-Xyl-α-Ser-CH2-CH(OH)-CH2-OH. For the 1H/1E/1I (46% yield), 1H/1E/2I (32%), and 1H/1E/3I (24%) products, the cross-linked motif was the same, and the difference represented the surplus amount of the imidazolium cation ionically bound to the heparin anionic groups.

Combination of cryo-mediated and salt-assisted liquid-phase exfoliation for GaSe nanosheets preparation with absorption coefficient estimation via Raman signal attenuation

In this study, a novel preparation method combining cryo-mediated method and salt-assisted liquid-phase exfoliation is presented for the preparation of Gallium Selenide (GaSe) nanosheets and the absorption coefficient are estimated by the Raman signal attenuation method on silicon substrates.It was found that Potassium citrate (C6H5K3O7·H2O) as an accelerator increased the lateral size of GaSe nanosheets, while employing liquid nitrogen as a cryo-mediation significantly reduced the surface roughness of the nanosheets. Furthermore, a correlation exists between the duration of cryo-pretreatment and the thickness distribution of GaSe nanosheets.Using the absorption overlayer model, the study experimentally determined more accurate absorption coefficient of 2D GaSe nanosheets by analyzing the changes in Raman signal intensity on a silicon substrate induced by GaSe nanosheets with varying thicknesses, resulting in an average absorption coefficient of 5.68×104 cm−1.This study introduces a novel approach to prepare GaSe and other two-dimensional (2D) material nanosheets with large size and low roughness, based on which the absorption coefficient of GaSe nanosheets are also determined in a more precise way.

Elucidating the formation pattern and mechanism of biofouling layer regulated by pre-deposition of powdered activated carbon in gravity-driven membrane systems

Powdered activated carbon (PAC) pre-deposition promotes pollutant removal in gravity driven membrane (GDM) but diversely affects flux. This study evaluated the effects of one-time deposition (GDM 1), batch deposition (GDM 2) and no deposition (GDM 3) of PAC on the biofouling layer formation mechanism and the GDM performance. The results showed that PAC particles effectively promoted the removal of dissolved organic carbon, ammonia nitrogen and fluorescent pollutants, while also significantly reducing the concentration of extracellular polymeric substances in the biofouling layer. The stable flux in GDM 1–3 were 6.58, 7.88 and 8.61 LMH respectively. One-time deposition of PAC compromised the structure of the biofouling layer and prevented its reverse relaxation. Pollutant floc particles continuously accumulated in the space between the PAC particles, forming a dense layer with low porosity and roughness. In GDM 2, the limited amount of PAC deposited each time helped to partially maintain the intact structure of the biofouling layer, which alleviated the decline in flux. The reverse relaxation of the intact biofouling layer in GDM 3 resulted in increased porosity, which positively influenced the flux. Additionally, the abundance of Bdelloidea significantly decreased in GDM 1 and GDM 2, and more predators with low agility showed limited modification on the biofouling layer, resulting in a dense biofouling layer. In conclusion, batch deposition of PAC is more recommended as the continuously renewed PAC promote pollutant removal, and compared with one-time deposition of PAC, the reduction in biofouling layer disturbance mitigates the flux decline.

Revealing the Role of Mo Leaching in the Structural Transformation of NiMo Thin Film Catalysts upon Hydrogen Evolution Reaction.

NiMo alloys are considered highly promising non-noble Hydrogen Evolution Reaction (HER) catalysts. Besides the synergistic effect of alloying elements, recent attention is drawn to the Mo leaching from the catalyst. This work investigates the role of Mo in NiMo alloys during HER, aiming to understand the interplay between compositional, structural, and electronic factors on the activity, and their effects on the electrode material and catalyst properties. For this purpose, sputter-deposited low roughness NixMo100-x thin films are produced. The investigation of catalyst performance depending on their chemical composition shows a volcano-shaped plot, peaking for the Ni65Mo35 alloy with the highest intrinsic activity in alkaline HER. A comprehensive electrode surface analysis combining transmission electron microscopy, X-ray photoelectron spectroscopy and atomic force microscopy identifies the leaching of Mo on a structural level and indicates the formation of a Ni(OH)2-rich surface area. The ultimate surface characteristics of the NiMo catalysts depend on the initial composition and the electrochemical procedure. Based on the findings, it conclude that the observed catalytic properties of NiMo alloys in HER are determined by a complex interplay of increasing roughness, available surface species and their synergies. The leaching of Mo has a proven structural effect and is considered one of several factors contributing to the enhanced catalyst activity.

Contact Simulation of Measured Surfaces with Low Roughness and Large Area Using the Elastoplastic Boundary Element Method

Contact Simulation of Measured Surfaces with Low Roughness and Large Area Using the Elastoplastic Boundary Element Method

Effect of lubricated polishing and repolishing on gloss, roughness and material loss of nanoparticle resin composite

Aim: The study examined how different dry and lubricated polishing protocols impact the gloss, roughness, and material loss of nanoparticle resin composites, before and after simulated toothbrushing. Methods: One hundred cylindrical resin composite specimens were prepared and divided into an unpolished group and three test groups: Dimanto (DIM), Sof-Lex Pop-On (SOF), and Astrobrush (ASTRO). These groups underwent polishing dry, with water, or with or petroleum jelly. Surface parameters including gloss (Novo-Curve – Rhopoint TM, England), roughness, and material loss (MaxSurf XT 20, MahrGoettingen, Germany) were evaluated at four stages: baseline, polishing, simulated toothbrushing, and repolishing. Data were submitted to repeated measures ANOVA (P&lt;0.05). Results: Lubrication did not affect the studied parameters after polishing with DIM. SOF showed improved performance without lubricants, whereas ASTRO achieved higher gloss and lower roughness when lubricated. In terms of surface material loss, DIM exhibited less material loss when used with petroleum jelly, SOF had reduced material loss when used with water, and ASTRO showed the most material loss when lubricated with petroleum jelly. Conclusion: The gloss, roughness, and surface material loss of the nanoparticle resin composite are influenced by the type of polisher used and the choice of lubricant. However, none of the differences observed surpassed the established thresholds for roughness or gloss perception, suggesting that these protocols are potentially viable for clinical application. Despite detectable differences among the polishing systems and lubricant combinations, all tested options are clinically acceptable. None of them exceeded the thresholds for biofilm accumulation or perceptible differences in surface gloss.

Effect of ultrasonic surface rolling process by disparate static pressure on a carburized layer of 17CrNiMo6 steel

Considering the elevated application requirements for transmission gears in terms of wear and corrosion resistance, this study investigates the impact of different static pressures (0.4 MPa, 0.6 MPa, 0.8 MPa) on the structure and protective properties of vacuum-carburized USRP layers, leveraging the technical advantages offered by vacuum carburizing and USRP. The findings demonstrate that using USRP facilitates fine-grained strengthening, and the thickness of the grain refinement layer increases proportionally with static pressure. The 0.6 MPa static pressure exhibits the most pronounced positive impact on grain refinement. The application of varying static pressures results in different surface integrity and microhardness levels within the carburized layer, thereby impacting the layer's wear and corrosion resistance. The coating exhibits the highest hardness and lowest roughness at a static pressure of 0.6 MPa, thereby demonstrating superior wear resistance. In addition, the 0.6 MPa layer with the lowest roughness has the best corrosion resistance.

Surface wettability affects attachment of male bed bugs Cimex lectularius to rough Perspex substrates

AbstractInsects attach to various surfaces that differ, among others, in roughness and wettability. Identifying surface characteristics that allow or prevent insects from attaching are an important research avenue of pest control. Here we take an experimental approach to analyse the attachment of common bed bugs, Cimex lectularius Linnaeus (1758), to Perspex (PMMA) substrates. We construct a reliable centrifuge device that allows the measurement of attachment forces at substrate roughnesses, Ra, between 0.02 and 1.3 μm and at two wettabilities. Our results suggest that bed bug attachment to surfaces is minimal at a substrate roughness of 0.2 and 0.4 μm on normal PMMA, where the lowest attachment force was 0.8 mN and the safety factor 15. At lower and higher roughness, attachment forces were higher and the safety factor increased to a maximum of 133. On PMMA that was made superhydrophobic by spray‐coating, attachment was lowest (0.2 mN) at the lowest roughness and continuously increased with increasing roughness, reaching 2.5 mN and a safety factor of 46. For every roughness, attachment forces were lower on superhydrophobic than on normal PMMA. This knowledge may inspire the development of repelling substrates for bed bug control.

Development of Functionalized Polylactide Thin Films Using Poly(methylhydrogenosiloxane) Sol-Gel Process with Improved Antifouling Properties.

Biobased polylactide (PLA) films were modified with low reticulate polysiloxane gel acting as a scalable platform for the hydrophilization of polymeric film surface. The PLA thin film was first coated with poly(methylhydrogenosiloxane) (PMHS) by the sol-gel transition via the condensation of diethoxymethylsilane (DH) and triethoxysilane (TH) using trifluoromethanesulfonic acid as a catalyst. Then, hydrosilylation of Si-H bonds in the presence of Karstedt's catalyst allowed the covalent grafting of hydrophilic alkene-containing molecules, i.e., triethylene glycol monomethyl allyl (TEGMEA) and a new zwitterionic allylcarboxybetaine (ACB) synthesized for the first time by the quaternization of dimethyl allyl amine (DMAA) with β-propiolactone. PMHS coating on the PLA film was evidenced by Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS). The observation by atomic force microscopy (AFM) revealed a homogeneous coating with low roughness (RMS = 0.29 nm). The hydrophilicity of functionalized PLA films was determined by water contact angle (WCA) measurements using the captive bubble method. A large increase in wettability properties was observed for both grafting with TEGMEA (WCA = 38°) and ACB (WCA = 42°) in comparison with the native PLA film (WCA = 80°). Moreover, the biocompatibility and antifouling efficiency of functionalized PLA films were evaluated by protein adsorption, bacterial adhesion, and cytotoxicity tests. The results indicate that the grafting of the two types of hydrophilic compounds does not affect the biocompatibility of PLA while significantly reducing protein adsorption and bacterial adhesion, thus showing the great potential of this surface functionalization strategy for applications in the medical field.