Contact Surface Research Articles

MODELING THE DEFORMATION PROCESS OF AN UNDERWATER GAS PIPELINE UNDER THE EXPLOSIVE LOADING

The process of deformation of an underwater two-layer gas pipeline during the explosion of a nearby octogen charge is simulated. For modeling, a specially developed proprietary software package is used to solve three-dimensional dynamic problems of interaction of elastoplastic structures with compressible media, based on a single Godunov scheme of increased accuracy for calculating the joint motion of gas, liquid, and elastoplastic media. The package uses an Eulerian-Lagrangian approach with explicit identification of moving contact surfaces between different media. For each environment, three types of computational grids are used. These are Lagrangian surface meshes in the form of a continuous set of triangles for specifying the initial geometry of bodies and accompanying them during the calculation process, as well as two types of three-dimensional volumetric meshes automatically generated during the calculation process. The charge, which has a spherical shape, is initiated at its center. To describe the process of propagation of steady-state detonation, the hydrodynamic theory of detonation is used. Shock waves generated during an explosion in the surrounding liquid interact with a fragment of a two-layer pipeline and a solid bottom. Wave processes are analyzed both in the steel pipe and in the concrete shell that weighs it down. Loads on the pipeline are estimated depending on the distance to the charge and the position of the pipeline relative to the bottom. The possible destruction of both steel and concrete weight shells in areas of tensile deformations that are formed in places of the maximum bending of the pipeline is shown. It is shown that the proximity of the bottom can significantly enhance the impact of explosive loading due to the action of shock waves reflected from the bottom.

Quantitative Assessment of Bony Fish Tropomyosin Using a Monoclonal Antibody Competitive ELISA.

Bony fish is one of the big-nine allergenic foods in the US. This study established a monoclonal antibody (mAb)-based indirect competitive enzyme-linked immunosorbent assay (ELISA) for the detection of bony fish tropomyosin (TM), a fish allergen. Immunoassay (Western blot and ELISA) was performed to characterize anti-TM mAb8F5 (target configuration, immunoaffinity, and species selectivity). Atlantic cod (Gadus morhua) tropomyosin (CTM) and mAb8F5 were used for assay development. The immunosignal was captured by two light sources, i.e., colorimetry (cELISA) and luminescence (lELISA). During assay validation, cELISA had a wider working range (1-250 ng/μL) than lELISA (0.5-62.5 ng/μL). However, lELISA showed better sensitivity because of its lower half-maximal inhibitory concentration (IC50, 8.8 ng/μL) than cELISA (37.1 ng/μL). The optimal cELISA was applied to measure CTM-equivalents in 21 bony fish samples (0.03-4.2 mg/g) and laboratory-spiked samples (recovery rates of CTM-spiked shrimp samples ranged from 104.7 to 120.8%). lELISA was used to quantify 5.25 μg CTM residues on four food contact surfaces (3.4-6.9 μg from CTM residues and 3.2-4.8 μg from Atlantic cod were detected). This immunoassay has the potential to surveil undeclared allergenic bony fish residues and validate the hygiene of food contact surfaces.

Effects of discrete fibre reinforcements on the wear resistance behaviour of polyamide-based spur gears

Abstract In many situations, the polymer gears are the perfect replacement for traditional metal gears. Compared to metal gears, the polymer gears will generate more heat at the gear tooth contact surface and more wear loss. Hence, this study aims to decrease the wear loss and increase the load-carrying capacity of the polymer gears. To achieve this, the reinforcement materials were added to the base polymer gear material. In this study, Nylon-66 was chosen as the polymer matrix material and an isolated glass fibre and steel grid were used as the reinforcement materials. Three different types of polymer spur gears such as Polyamide Gear (Nylon-66), Reinforced Polyamide Gear (Nylon-66+Glass Fibre), and Hybrid Glass Fiber Steel Grid Gear (Nylon-66+Glass Fibre+Steel Grid) named PG, RPG and HGFSGG were fabricated using injection moulding machine and each type of gears were compared for wear loss and specific wear rate under the similar testing conditions. The wear test was performed in the Forschungsstelle fur Zahnrader und Getriebebau (FZG) test rig at 1500 rpm with an applied load of 20 N for 12.5 hours continuously. From the test results, it was identified that HGFSGG polymer spur gears have exhibited a lower surface temperature and better wear properties compared to the other two types of spur gears. From the Scanning Electron Microscope (SEM) analysis, it was noticed that the PG spur gear exhibited deep and uniform wear at the gear tooth surface. In contrast, RPG spur gear exhibited glass fibre distortion and abrasive-type wear. The SEM micrograph of HGFSGG spur gear reveals the presence of very few surface flaws in the gear tooth surface.

Characteristics of rolling interface lubrication considering contact surface textures in mixed lubrication

This study comprehensively utilizes the mixed lubrication theory and rolling deformation theory to establish a finite element stiffness contact model that considers the surface texture characteristics of the rolling interface. The dynamic explicit finite element analysis is used to obtain the deformed solid, and the turbulent equation is used to control the fluid boundary conditions. The bidirectional Fluid-Structure Interacton (FSI) ansysis is used to study the influence of surface roughness, surface textures, and rolling parameters such as rolling speed on the distribution of oil film pressure and contact characteristics during the rolling process. The results confirm that transverse texture reduces the friction coefficient and dynamic pressure by enhancing the trapping effect of rough peaks and facilitating the entrainment of the fluid film. Under the same textural conditions, the contact area decreases with increasing roughness while the friction coefficient increases. As the rolling speed increases, the rolling pressure decreases to a certain extent, and the contact area ratio will decrease; Lubricants with higher viscosity can effectively reduce the friction and rolling force at the rolling interface. We believe that the insights obtained from the numerical simulations provided in this reaserch will lay a theoretical foundation for subsequent research on plate shape control.

Microbiome dynamics and functional profiles in deep-sea wood-fall micro-ecosystem: insights into drive pattern of community assembly, biogeochemical processes, and lignocellulose degradation.

Wood-fall micro-ecosystems contribute to biogeochemical processes in the oligotrophic deep ocean. However, the community assembly processes and biogeochemical functions of microbiomes in wood fall remain unclear. This study investigated the diversity, community structure, assembly processes, and functional profiles of bacteria and fungi in a deep-sea wood fall from the South China Sea using physicochemical indices, amplicon sequencing, and metagenomics. The results showed that distinct wood-fall contact surfaces exhibit habitat heterogeneity. The bacterial community of all contact surfaces and the fungal community of seawater contact surface (SWCS) were affected by homogeneous selection. In SWCS and transition region (TR), bacterial communities were influenced by dispersal limitation, whereas fungal communities were affected by homogenizing dispersal. The Venn diagram visualization revealed that the shared fungal community between SWCS and TR was dominated by Aspergillaceae. Additionally, the bacterial community demonstrated a higher genetic potential for sulfur, nitrogen, and methane metabolism than fungi. The sediment contact surface enriched modules were associated with dissimilatory sulfate reduction and methanogenesis, whereas the modules related to nitrate reduction exhibited enrichment characteristics in TR. Moreover, fungi showed a stronger potential for lignocellulase production compared to bacteria, with Microascaceae and Nectriaceae identified as potential contributors to lignocellulose degradation. These results indicate that environmental filtering and organism exchange levels regulated the microbial community assembly of wood fall. The biogeochemical cycling of sulfur, nitrogen, and methane was mainly driven by the bacterial community. Nevertheless, the terrestrial fungi Microascaceae and Nectriaceae might degrade lignocellulose via the combined action of multiple lignocellulases.IMPORTANCEThe presence and activity of microbial communities may play a crucial role in the biogeochemical cycle of deep-sea wood-fall micro-ecosystems. Previous studies on wood falls have focused on the microbiome diversity, community composition, and environmental impact, while few have investigated wood-fall micro-ecosystems by distinguishing among distinct contact surfaces. Our study investigated the microbiome dynamics and functional profiles of bacteria and fungi among distinct wood-fall contact surfaces. We found that the microbiome community assembly was regulated by environmental filtering and organism exchange levels. Bacteria drive the biogeochemical cycling of sulfur, nitrogen, and methane in wood fall through diverse metabolic pathways, whereas fungi are crucial for lignocellulose degradation. Ultimately, this study provides new insights into the driving pattern of community assembly, biogeochemical processes, and lignocellulose degradation in the microbiomes of deep-sea wood-fall micro-ecosystems, enhancing our comprehension of the ecological impacts of organic falls on deep-sea oligotrophic environments.

Lubricity performance of Jatropha oil incorporated PTFE and h-BN as additives for electric vehicles transmission lubrication

Purpose Concerns over the pollution caused by internal combustion vehicles have increased owing to population and industrialization increment. Addressing the confrontations, the demand for electric vehicles (EVs) as a combustion engine substitute became necessary in responding to environmental worries from internal combustion. The development of bio lubricant in lubricating the sliding parts of EVs is required to maintain the sustainability idea and to improve the system performance, which this research tends to explore. Design/methodology/approach In this research, the enhancement of base Jatropha oil was done using polytetrafluoroethylene (PTFE) and hexagonal boron nitrate (h-BN) as additives. Different characterization was conducted on the new formulation to ascertain its anticorrosion tendency. The wear and friction behavior of the formulations on the tribo-pairs surfaces in contact were investigated using ball on flat tribometer to determine their tribological responsiveness as mineral lubricant alternative. To explore the surface topography, surface profilometer, scanning electron microscope and energy dispersive X-ray investigations were PTFE, lubrication and EV carried out. Findings The test’s input parameters were EVs’ usual load and sliding speed, and the addition concentrations for PTFE were 0.3 Wt.%, 0.4 Wt.%, 0.5 Wt.% and 0.6 Wt.%, whereas h-BN were 0.4 Wt.%, 0.8 Wt.% and 1.2 Wt.%, respectively. The study on corrosion demonstrated resistance when applied PTFE and h-BN additives in Jatropha oil. The analysis revealed that 0.5 Wt.% PTFE + 0.8 Wt.% h-BN concentrations significantly improved the tribological characteristics when compared to the base Jatropha oil. The application of formulations yielded percentage reduction of 8.67%, 10.98%, 7.34% and 7.35%, respectively, for 0.5% poly + 0.5% h-BN, 0.5% poly + 0.6% h-BN, 0.5% poly + 0.7% h-BN, 0.5% poly + 0.8% h-BN against base Jatropha oil under 20 N. Originality/value The formulation of PTFE and h-BN for electric transmission with wear and friction effects was accomplished in this paper. The mechanism of particle diffusing at the sliding contact on tribological behavior could be examined based on the created model of operation. Peer review The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-07-2023-0235/

Improvement of contact lens-associated dry eye disease with the use of hydrogen peroxide.

The dropout rate of contact lens users has not decreased significantly over the years. Despite continuous improvements in contact lens (CL) designs, materials and surface treatments, the number of CL users who drop out remains similar to the number of new CL users. The aim of this study is to analyse the improvement in contact lens-associated dry eye disease (CLADE), quantified with the OSDI questionnaire when changing maintenance system solution from multipurpose solution to hydrogen peroxide. This study included contact lens users for over a year as the multipurpose solution for the maintenance system, suffering from CLADE, and those who scored over 13 in the ocular surface disease index questionnaire, and did not manifest any clinical signs over 3 in the EFRON scale. The non-parametric data distribution was verified with the Kolmogorov-Smirnov test and Wilcoxon signed-rank test, which was used to compare the visual acuity (VA), OSDI score and bulbar redness (EFRON scale) of the follow-up visit against the baseline value. Thirty-eight patients were included. Analysing the clinical parameters between the initial and final visit after one month of hydrogen peroxide use, a statistically significant improvement was found in the VA, bulbar hyperemia, OSDI scale and their subscales of the total sample (P<0.04). This study is intended as a first step towards a standardised protocol of actions to improve CLADE in an attempt to reduce contact lens dropout using OSDI as a tool for detection.

Structures of KEOPS bound to tRNA reveal functional roles of the kinase Bud32

The enzyme complex KEOPS (Kinase, Endopeptidase and Other Proteins of Small size) installs the universally conserved and essential N6-threonylcarbamoyl adenosine modification (t6A) on ANN-decoding tRNAs in eukaryotes and in archaea. KEOPS consists of Cgi121, Kae1, Pcc1, Gon7 and the atypical kinase/ATPase Bud32. Except Gon7, all KEOPS subunits are needed for tRNA modification, and in humans, mutations in all five genes underlie the lethal genetic disease Galloway Mowat Syndrome (GAMOS). Kae1 catalyzes the modification of tRNA, but the specific contributions of Bud32 and the other subunits are less clear. Here we solved cryogenic electron microscopy structures of KEOPS with and without a tRNA substrate. We uncover distinct flexibility of KEOPS-bound tRNA revealing a conformational change that may enable its modification by Kae1. We further identified a contact between a flipped-out base of the tRNA and an arginine residue in C-terminal tail of Bud32 that correlates with the conformational change in the tRNA. We also uncover contact surfaces within the KEOPS-tRNA holo-enzyme substrate complex that are required for Bud32 ATPase regulation and t6A modification activity. Our findings uncover inner workings of KEOPS including a basis for substrate specificity and why Kae1 depends on all other subunits.

Experimental investigation of the influence of surface topographic parameters on fluid leakage through static metallic seals

Purpose The purpose of this paper is to monitor leakage in the static sealing interface, using three-dimensional and two-dimensional surface topography parameters as indicators. Design/methodology/approach This study involved developing a test rig for examining fluid leakage in metallic seals. Leakage of water through the interface of the metallic valve and valve seats was measured. The analysis focused on the combined effect of roughness, waviness and form error of metallic seal surfaces on leakage, with a detailed emphasis on the significance of form errors through harmonic analysis. Findings The findings suggest that three-dimensional or areal surface texture parameters have more predictive control over leakage compared to two-dimensional or profile parameters, as they provide information about micro-leak channels in all directions. Moreover, it was observed that average amplitude parameters of surface topography, particularly the form error of metallic valves, are strongly correlated with leakage values compared with the roughness and waviness of the contact surface. In addition, the leakage in metallic seals is profoundly influenced by lower-order harmonics, with a corresponding increase as the average undulation number of the flatness profile rises. Originality/value This research contributes to the understanding of the relationship between surface topography and sealing performance, particularly in metallic seals. By emphasizing the importance of form errors and using advanced surface texture analysis techniques, the study offers insights that can aid in optimizing the design and performance of static seals in industrial applications. Peer review The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-05-2024-0186/

Analysis and numerical treatment of a thermo-electro-visoplastic frictional contact problem with adhesion and internal states variable

We consider a frictional contact problem between a thermo-electro-viscoplastic body and a conductive foundation. The contact is frictional; it is modeled with normal compliance, and the adhesion of the contact surfaces is taken into account. The material has internal state variables. We derive a variational formulation for the model and prove the existence of a unique weak solution to the problem. The proof is based on results for elliptic variational inequalities, differential equations, and fixed-point theory. Finally, we present a finite element algorithm to approximate solutions to our problem and provide an error estimate for these approximations.

Study on vibration characteristics of anisotropic vehicle rubber bushings by conformal contact force analysis

For ride comfort and handling performance design of vehicles, anisotropic rubber bushings are used as the connection between lower arms and body frames. The nonlinear vibration performance with the deformation amplitude is advantageous to minimise vibration transmission at low magnitude responses and to reduce deformation at large excitations. During transient deformation, the area under the force-deformation curve serves as an indicator for evaluating vibration reduction and isolation performance. The elastomer geometric variables such as the relative radius between the inner and outer contact surfaces are effective design parameters for controlling bushing dynamic behaviour. This study presents a dynamic model to understand the nonlinear stiffness by the contact theory after addressing the actions between elastomer surfaces. The proposed model was confirmed by the measured dynamics stiffness and damping performance. Their influence on the vehicle ride comfort was investigated.

Numerical investigation of bolted rock joints under varying normal stress and joint roughness coefficient conditions

Rock masses are formed through long-term, complex geological processes, and the presence of joints significantly reduces their strength and increases their deformation. Rock bolts effectively enhance the strength and stability of rock masses and are extensively utilized for reinforcement. According to field investigations, a significant portion of the damage to bolted rock masses stems from shear deformation at joint surfaces. Moreover, roughness affects friction and surface contact, thus influencing the shear behavior between rock and rock bolts. This study considers two crucial factors affecting the shear characteristics of bolted rock joints: joint surface roughness and normal stress. Using the Particle Flow Code discrete element numerical method, the Barton standard joint profile lines were input to establish numerical models of both unbolted and bolted rock joints for direct shear tests. Results reveal that the peak shear stress and stiffness of both unbolted and bolted rock joints increase with rising normal stress and joint roughness coefficient. The peak shear stress and stiffness of bolted rock joints are notably higher than those of unbolted ones, with a maximum increase of 17.5%. Crack development in bolted rock joints occurs in stages of rapid, slow, and stable development, whereas no distinct slow development stage is observed in unbolted rock joints. Additionally, micro cracks in both unbolted and bolted rock joints are primarily tensile cracks, originating around the joint surface and extending outward with increasing shear displacement. These findings offer valuable insights into the microscopic shear mechanics of bolted rock joints and provide practical references for engineering design and applications in rock reinforcement projects.

Research on water flow characteristics and stress around bridges during floods

ABSTRACT Due to the frequent threat of floods to structures and engineering constructions near rivers, this study examines the impact characteristics of river hydrodynamics on structures under excessive flow during floods, using Jiefang Bridge as an example. We employ the fluid volume two-phase flow model (volume of fluid) in computational fluid dynamics, combined with advanced geometric reconstruction techniques such as the isoAdvector method, to simulate the dynamic changes of the gas–liquid interface in the river. On the premise of ensuring grid independence, high-precision structural grids were used to finely divide the study area and numerical simulations were conducted. The research results indicate that when a flood contacts a bridge, the force on the bridge rapidly increases and fluctuates, reaching a significant peak of over 6,000,000 N. Bridge piers have a significant hindering effect on floods and their impact gradually expands over time. Vorticity and turbulence energy analysis indicate the presence of strong flow disturbances around the bridge pier. In addition, the characteristics of the contact surface between water flow and bridges also significantly affect the stress and flow characteristics of bridges. Especially at a 45° angle of attack, the force on the bridge decreases, but the wake velocity increases.

A green, versatile, and facile strategy for anti-biofouling surface with ultra-high graft density polyethylene glycol

Implantable catheters are susceptible to severe complications due to non-specific protein adhesion on their surfaces. Polyethylene glycol (PEG) coatings, the gold standard for resistance to non-specific protein adhesion, present a challenge in achieving high-density grafting, which significantly restricts their use as anti-biofouling coatings. Herein, we exploited the strong interaction between polyphenols (PCs) and polycations (K6-PEG) to graft PEG onto the surface of PC-Cu (A network of metal polyphenols composed of proanthocyanidins and metal copper ions, with expectation for the coating with excellent resistance to non-specific protein adhesion (PC-Cu@K6-PEG). The introduction of K6-PEG resulted in enhanced stability and modulus of PC-Cu, as well as a reduction in the surface adhesion energy and contact angle of PC-Cu. In contrast to previously reported PEG coatings, PC-Cu@K6-PEG exhibited a markedly elevated grafting density of PEG (4.06 chains/nm²), which was more than double the highest value previously reported (1.9 chains/nm²), due to the diffusing ability of K6-PEG throughout the PC-Cu networks. PC-Cu@K6-PEG displays robust resistance to a variety of proteins, microbials, and platelet attachment, thereby preventing thrombosis. The coating ability of PC-Cu onto diverse substrates, combined with the simple, straightforward and environmentally benign process of fabricating PC-Cu@K6-PEG, suggests that this strategy has significant potential for use in anti-biofouling surfaces.

Measurement of surface tension and contact angle of solar salt at high temperature with axisymmetric drop-shape analysis

As interfacial properties of common materials enabled many practical applications, those for molten salts would do the same. While their properties are important for the safety and design of thermal energy storage and modular nuclear reactors, they are hard to obtain because of the measurements done in confined spaces inside a furnace at high temperatures. Moreover, a small amount is preferred due to the high cost of salts. To overcome these limitations, an accurate method to measure surface tension, γ, and contact angles, θ, of molten salts were sought. As a steppingstone toward using more complex salts, solar salt was used because of safety and availability. Because molten salts typically show low θ, they provide large errors by incorrectly predicting volume and/or geometry. Therefore, various solid materials on which solar salts show high θ were sought and boron nitride was identified to provide θ > 60°. Later, solar salt sessile droplets were analyzed with the axisymmetric drop-shape analysis (ADSA) method to measure γ over a temperature range, which showed a good agreement with literature. Thus, this paper sets an experimental protocol that can be possibly used for other complex and hazardous salts that are scarcer and hard to handle. This paper extends the current knowledge by identifying solid surfaces on which the salts show low wettability for accurate measurements. Compared to other accurate methods, such as maximum bubble pressure method, this method used a small amount of salt (< 100 μL) while keeping a high accuracy.

Development and validation of hydrophobic molded pulp nursery pots made of hemp hurd

Biodegradable nursery pots (BNPs) composed of 50 % hemp hurd and 50 % recycled cardboard fibers (w/w dry basis) were produced using a custom-built handheld molded pulp device. Milling followed by sequential peracetic acid and sodium hydroxide delignification treatment reduced lignin content of hemp hurd from 23.76 % to 2.39 %, liberating cellulose and hemicellulose fibers for enabling the formation of interfiber interactions in molded pulp formulations. Beeswax and precipitated calcium carbonate based hydrophobic coating at ~10 μm thickness significantly enhanced hydrophobicity of the BNPs, as indicated by the surface contact and sliding angle of 116.25° and 34.82°, respectively. Anaerobic biodegradability of BNP was confirmed via carbon dioxide and methane gas accumulation measurements. Developed BNPs were successfully validated through an eleven week greenhouse planting trial. This study introduced a new biodegradable molded pulp formulation made from hemp hurd and validated its application as an alternative to single use plastic nursery pots for growing seedlings.

Understanding the antibacterial mechanism of metal surfaces

Bacterial inactivation on antibacterial metal surfaces has been widely used in medicine and daily life to inhibit infection caused by surface contact. However, the underlying antibacterial mechanism of metal surfaces has remained elusive due to a lack of comprehensive theoretical perspectives and direct evidence. Here, we propose a universal understanding of the bacteria-inactivation mechanism of metal surfaces and reveal the changes in bacterial survival behavior with time and spatial location. In terms of bacterial survival over time, we established a quantitative ion influx model and predicted four bacterial survival behaviors based on osmotic pressure changes and ion release. To demonstrate the spatial distribution of bacterial survival, we consider variations in metal antibacterial properties and electrode potentials and design five corrosion galvanic couples to cover all possible metal combinations. The results on the bacterial survival behavior over time confirm our theoretical predictions, exhibiting a dependence of bacterial viability on environmental humidity and metal toxicity. In addition, on the surfaces of galvanic couples, bacteria will experience the most pronounced decrease in viability at anodes, irrespective of the location of the antibacterial metals. This abnormal distribution pattern can be fundamentally attributed to the highest toxic-ion concentration resulting from a low pH at anodes. The consistency between our predictions and observed bacterial survival rates supports the notion that the antibacterial mechanism follows surface ion release and subsequent free-ion influx into the cytoplasm, leading to lethal biochemical reactions in bacteria. STATEMENT OF SIGNIFICANCE: Numerous studies have been conducted on developing antibacterial metals, alloys, and their related applications. However, the underlying antibacterial mechanism of metal surfaces has remained elusive. This work is the first to propose a general understanding of the antibacterial mechanism of metal surfaces, including the temporal and spatial characteristics of bacterial survival behavior. By building a theoretical model, we predicted and confirmed the shapes of the four bacterial survival curves over time. In addition, we found that bacteria have the worst viability loss at the alloy anode, even if non-antibacterial metals occupy this position. The conclusions can provide theoretical support for the antibacterial behavior of metal surfaces, including but not limited to Ag, Cu, Zn, and their corresponding alloys.

Construction of ultra-smooth and void-free buried interface via bilateral chemical bridging for efficient and hysteresis-suppressed perovskite solar cells

The surface properties are vital aspects in improving photovoltaic performance of perovskite solar cells (PSCs). Except for the upper surface of perovskite, the hidden buried interface which supports the beginning of perovskite film crystallization is of equal great importance for the construction of high-efficiency PSCs. Herein, we use urea phosphate (UPP) to build a bilateral chemical bridge in the buried interface under perovskite layer, to simultaneously improve the properties of SnO2 ETL and the upper perovskite. On one hand, the interaction between UPP and SnO2 passivates the defects of the SnO2 and facilitates the formation of ultra-smooth surface for superior interfacial contact. On the other hand, the chemical interaction between UPP and perovskite contributes to the optimization of crystal nucleation and growth, which improves the crystalline quality of perovskite, inhibits the formation of voids at the buried interface and reduces the defects of the grain boundary. Benefiting from the optimized buried interfacial contact, suppressed defects, accelerated charge extraction and modified energy level alignment, the UPP-processed device delivers an improved power conversion efficiency of 24.54 %, with effective suppression of hysteresis. Moreover, the stability of device is also improved owing to the reduction of trap defects. This work provides a feasible strategy to tune the buried interface between the charge transfer layer and perovskite layer for fabrication of efficient and stable PSCs.

Ti3C2Tx and Mo2TiC2Tx MXenes as additives in synovial fluids - towards an enhanced biotribological performance of 3D-printed implants

Synovial joints, critical for limb biomechanics, rely on sophisticated lubrication systems to minimize wear. Disruptions, whether from injury or disease, often necessitate joint replacements. While additive manufacturing offers personalized implants, ensuring wear resistance remains a challenge. This study delves into the potential of Ti3C2Tx and Mo2TiC2Tx nanosheets in mitigating wear of additively manufactured cobalt-chromium tungsten alloy substrates when incorporated as additives into synovial fluid. The colloidal solutions demonstrate an excellent stability, a crucial factor for reproducible assays and potential clinical applicability. Analysis of contact angles and surface tensions reveals MXene-induced alterations in substrate wettability, while maintaining their general hydrophilic character. Viscosity analysis indicates that MXene addition reduces the dynamic viscosity, particularly at higher concentrations above 5 mg/mL, thus enhancing dispersion and lubrication properties. Friction and wear tests demonstrate a dependency on the MXene concentration, while Ti3C2Tx exhibits stable friction coefficients and up to 77 % wear reduction at 5 mg/mL, which was attributed to the formation of a wear-protecting tribo-film (amorphous carbon and MXene nano-sheets). Our findings suggest that Ti3C2Tx, when supplied in favorable concentrations, holds promise for reducing wear in biotribological applications, offering avenues for future research into optimizing MXene utilization in load-bearing joint replacements and other biomedical devices.

Preparation of dental resin composites with anti-bacterial adhesion against Streptococcus mutans using fluorinated and silicon containing dimethacrylates

ObjectiveThe purpose of this study was to enhance the anti-bacterial adhesion effect against Streptococcus mutans (S. mutans) of fluorinated dimethacrylate (DF MA) based dental resin composites (DRCs) by using silicone dimethacrylate (SMA-MEO). MethodThe SMA-MEO was added into mixture of DFMA and tricyclo (5.2.1.0) decanedimethanol diacrylate (SR833s) (DFMA/SR833s = 50 wt./50 wt.) with mass ratios of 10 wt% and 20 wt% to form resin matrix both with fluorinated and silicon containing dimethacrylates, and then DRCs named DS+ 10 %SMA-MEO and DS+ 20 %SMA-MEO were prepared by mixing the resin matrix with silaned BaAlSiO2 filler particles at a mass ratio of 30 wt./70 wt. Double bond conversion, volumetric shrinkage and shrinkage stress, flexural strength and modulus, water sorption and solubility, contact angle and surface free energy, anti-bacterial adhesion effect against Streptococcus mutans (S. mutans), and cytotoxicity of prepared DRCs were investigated according to standard or referenced methods. Fluorinated dimethacrylate (DFMA) based DRC named DS and 2,2-bis[4-(2-hydroxy-3-methacryloy-loxypropyl)-phenyl]propane (Bis-GMA) based DRC named BT were used as controls. ResultsAdding SMA-MEO into DFMA based DRC could lead to higher double bond conversion (p < 0.05), higher hydrophobicity (p < 0.05), and lower surface free energy (p < 0.05). Only DS+ 10 %SMA-MEO had better anti-bacterial adhesion effect against S. mutans than DS (p < 0.05). The SMA-MEO had no influence on volumetric shrinkage, shrinkage stress, flexural modulus, water sorption and solubility of DRC (p > 0.05), but could reduce flexural strength of dry DRC (p < 0.05). After water immersion, SMA-MEO containing DRCs had comparable flexural strength as DS (p > 0.05). Compared with BT, DS and SMA-MEO containing DRCs had better or comparable physicochemical properties, and lower amount of adherent S. mutans. All of DRCs had comparable cytotoxicity (p > 0.05). SignificanceDRCs with both DFMA and SMA-MEO could have better anti-bacterial adhesion effect against S. mutans than DRC only with DFMA due to increased hydrophobicity and decreased Surface free energy, and the optimal mass fraction of SMA-MEO in DFMA based resin matrix was 10 wt%.