Search Results (8,592)

Analyses of rolling contact fatigue (RCF) problems require the use of multiaxial fatigue criteria, which take into account complex non-proportional stress conditions. One of the most often used criteria to analyse this phenomenon is the Dang Van criterion. However, this criterion is often criticised due to its overestimation of the influence of compressive stresses on fatigue strength, which leads to an underestimation of the equivalent fatigue stress. Due to the high popularity of this hypothesis, in this paper a few modifications of the Dang Van criterion based on the critical plane approach are compared. One of the investigated modifications is a new proposal in which it is assumed that compressive hydrostatic stresses are as unfavourable as tensile stresses. All variants are verified in three ways: (1) by means of the experimental results for the out-of-phase pulsating compression and alternating torsion; (2) by comparison with the results obtained by means of the Papadopoulos criterion (which provides the most accurate results for RCF issues); and (3) using the example of an RCF analysis of a roller bearing. Based on these investigations, it is confirmed that the original Dang Van criterion is not suitable for application to RCF problems. It is shown that the mere omission of compressive hydrostatic stresses is also insufficient. The highest agreement with the experimental results (relative error $\mathsf{\delta }$ = 0.77%), the Papadopoulos criterion ($\mathsf{\delta }=5.8\mathrm{\%}$) and, in the case of the practical application (roller bearing; $\mathsf{\delta }=1.1\mathrm{\%}$), is obtained for the proposed modification in which it is assumed that the compressive hydrostatic stress is an unfavourable for fatigue processes in the same way as the tensile hydrostatic stress. Full article

This comprehensive review aims to cover the surface tribology and triboelectric properties of additively manufactured (AM) natural biopolymers, including cellulose, chitosan (CS) and silk fibroin (SF), in biomedical interface engineering. While these sustainable materials exhibit innate biocompatibility and tribopositivity, their baseline triboelectric performance demands targeted surface engineering. We synthesize key physical mechanisms governing charge generation, emphasizing how controlled surface roughness, hierarchical porosity and nanoscale architectures maximize contact electrification. Furthermore, distinct dielectric and polarity modulation strategies are evaluated across the biopolymer families: cellulose relies heavily on chemical functionalization to overcome weak native polarity; chitosan utilizes ionic coordination and fillers to elevate its relatively low charge density; and silk fibroin achieves exceptional power outputs via highly porous three-dimensional nanocomposite aerogels. AM technologies afford unprecedented spatial control over these biointerfaces but introduce severe processing constraints. Techniques such as those based on extrusion impose strict shear-thinning rheology and rapid crosslinking for cellulose and chitosan, while SF frequently suffers from crystallization-induced nozzle clogging, necessitating photocurable derivatives. Full article

Hydroxygallium phthalocyanine type V (HOGaPc V) is an excellent photo generator and is applied in xerography. The material is only accessible as polycrystalline substances, and the crystal structure for an evaluation of the structure–property relationship cannot be determined from the few X-ray reflections available by powder X-ray pattern. A new method for crystal structure determination is introduced, utilizing molecular interactions. This proposed structure appears to be superior to the published one by the classical application of the Rietveld analysis. Hydrogen bonds are detected and explain the thermal stability, combined with high photosensitivity, and point towards favorable application in electrophotography. A triclinic two-molecule unit cell P-1 with a = 11.63 Å, b = 12.60 Å, c = 8.88 Å, α = 95.7°, β = 95.2°, γ = 69.1° was established close to the one verified by the Rietveld analysis. The structure obtained was successfully tested by a comparison of the observed contacts and the packing energy of known Pc single-crystal structures and by a similar X-ray residual R factor of the mostly overlapping reflections with other materials. The packing contacts of the crystal determined by the Rietveld analysis show too short contacts and too high packing energies. The molecular and crystal structure of HOGaPc V is represented and discussed. Full article

The growing environmental plastic pollution triggered research for biodegradable and safe materials, among which biopolymer-based films stand as the most promising. Among these, chitosan has gained significant attention due to its biocompatibility, film-forming ability, and inherent antimicrobial properties. In this context, the use of fillers to design chitosan nanocomposite films has been shown to enhance the mechanical, barrier, thermal, optical, and antimicrobial properties of the resulting bioplastics. However, the fate and destiny of these fillers, as well as their impact on the biological properties and biodegradability of chitosan films, remain underexplored. We herein report a more comprehensive screening of a set of fillers, encompassing three clay variants (montmorillonite, sepiolite, and halloysite) and microcrystalline chitin. The films were systematically characterized to assess their antibacterial performance, cytocompatibility, hemocompatibility, and biodegradability. The highest antibacterial activity was observed for CS@MMT-f film towards Staphylococcus aureus and Escherichia coli. Importantly, all developed films demonstrated negligible hemolytic activity and low cytotoxicity, indicating their safety for potential biomedical or food-contact applications. Moreover, the selected films completely degrade within four to six weeks under soil burial conditions, demonstrating their potential as environmentally friendly packaging materials. Full article

We propose an integrated electrowetting-on-dielectric (EWOD) device incorporating a mesh-patterned heater to restore damaged hydrophobic coatings and evaluate its recovery performance. Hydrophobic degradation was induced under submersion and falling droplet conditions, and the damage and recovery mechanisms of the coating were examined. A damaged Cytop (CTL-809M) coating was thermally treated using the embedded heater at 200 °C for 24 h, successfully restoring its hydrophobicity. Coating properties before and after recovery were characterized by contact angle (CA) and contact angle hysteresis (CAH) measurements, evaluating EWOD performance and surface analyses using atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). After treatment, the reduced CA and increased CAH were recovered, and wetting/dewetting performance in EWOD operation also recovered to pre-damage levels. AFM and XPS analyses confirmed the simultaneous restoration of the surface morphology and chemical composition. These results demonstrate a practical approach for restoring hydrophobic coatings within EWOD devices and offering a promising solution for improving device reliability and lifetime in applications related to EWOD. Full article

Bone grafting remains limited, and the strategies to design even more structurally complex scaffolds—able to reproduce the hierarchical architecture of bone extracellular matrix—are rapidly growing. In this study, we report the fabrication of a hierarchically structured scaffold produced by layering poly(ε-caprolactone)/gelatin (PCL/Gt) or poly(lactic acid)/gelatin (PLA/Gt) electrospun nanofibers via coaxial electrospinning onto 3D-printed poly(lactic acid) (PLA) scaffolds via fused deposition modeling (FDM). After the printing process, PLA disks (10 × 1 mm, 20% infill, ~80% porosity, pore size ~1.57 mm) were coated with core/shell (PCL/Gt, PLA/Gt) fibers to investigate the in vitro interfacial response of osteoblasts in comparison with monocomponent fibrous coatings (PCL, PLA, Gt). SEM and TEM confirmed that core/shell fibers exhibited bead-free morphologies, with a significant reduction in fiber diameter (≈287–316 nm) and higher interfibrillar porosity compared to monocomponent fibers. FTIR and thermogravimetric analyses indicated the presence of hydrogen bonding between the polyester and gelatin, and the absence of residual solvent after deposition. At the same time, water contact angle measurements confirmed an increase in hydrophilic properties from 80–86° to 120° ascribable to the presence of gelatin. Accordingly, in vitro response of human fetal osteoblasts (hFOB 1.19) exhibited an evident improvement in the case of Gt-based fibrous coatings (i.e., PCL/Gt and PLA/Gt) in terms of early adhesion (4–24 h) and metabolic activity from 3 to 21 days, cell spreading into star-shaped morphologies, formation of extracellular matrix, and mineral phase deposition. In more detail, a remarkable increase in alkaline phosphatase activity was observed in Gt-based coaxial coatings from day 7 onward, with the highest values recorded for PLA/Gt. Overall, we demonstrated that the Gt-based coaxial fibrous coating provided a mix of topological and biochemical cues that synergistically promoted key osteoblast activities at the interface, supporting the regeneration of new bone tissue in highly tailored 3D-printed scaffolds, thus suggesting a promising strategy for personalized regenerative medicine. Full article

Chlorine dioxide (ClO₂) is a neutral oxidant molecule with a short lifespan once in contact with electron donors (organic matter). ClO₂ solutions have antiviral, antibacterial, antifungal, anti-protozoan, anti-inflammatory, anticancer, and wound-healing activity and it was used at safe concentrations on patients from different countries during the COVID-19 pandemic. In Mexico, 1067 COVID-19 patients received compassionate treatments with ClO₂ during the 2020/2021 pandemic years. We describe the treatments and clinical reports of these patients, as it concerns the oxygen saturation (SpO₂) recovery, and provide a biochemical explanation. The number of healed patients was 1057, >99% of the total and SpO₂ showed a hyperbolic fast increase. This might happen because ClO₂ attracts one electron from the organic matter and produces a chlorite anion (${\mathrm{ClO}}_2^{-}$). This new molecule is known to exhibit metabolic activity in the blood stream. On the one hand, it will perform the aforementioned antibiotic and healing properties. On the other hand, it will also allow the production of oxygen (O₂) to be transported by the Oxyhemoglobin. This reaction is mediated by an intermediate state of a ferryl molecule (Fe=O) in the allosteric heme site of methemoglobin, which behaves as a reductase enzyme. This reaction can explain the rapid and steady increase in O₂ saturation in healed patients. Full article

Accurate prediction of Rate of Penetration (ROP) in carbonate formations remains constrained by the arbitrary selection of geomechanical input parameters in empirical drilling models. This study presents the first systematic field-based evaluation of sixteen geomechanical properties—grouped into three categories: strength parameters (uniaxial compressive strength (UCS), confined compressive strength (CCS), shear strength, thick-walled cylinder strength (TWC), friction angle, and cohesion), elastic moduli (Young’s modulus, shear modulus, bulk modulus, bulk compressibility, dynamic combined modulus (DCM), Poisson’s ratio, brittleness index), and in situ stress parameters (overburden pressure, minimum, and maximum horizontal stresses)—to identify optimal predictors for ROP modeling across PDC bit sizes of 12.25″ and 8.5″. Continuous wireline log data from two vertical carbonate wells in the Middle East (Well A: 1000–3370 m; Well B: 1945 to 3128 m; total intervals of 2370 m and 1183 m, respectively) penetrating formations comprising limestone, dolomite, sandstone, shale, anhydrite, and marly limestone were used. All sixteen geomechanical properties were computed using Interactive Petrophysics (IP) software with lithology-specific empirical correlations and validated against laboratory core measurements (R² = 0.79–0.95). Pearson and Spearman correlation analyses quantified parameter–ROP relationships, and the Al-Abduljabbar empirical model, recalibrated via multiple nonlinear regression, served as the evaluation framework. DCM consistently exhibited the strongest negative correlation with ROP across both bit sizes and achieved the highest model accuracy (R² = 0.54, AAPE = 25.33%), significantly outperforming the Bourgoyne and Young model (R² = 0.26, AAPE = 36.55%). A statistically validated scale-dependent effect was identified: Fisher’s Z-transformation tests confirmed that the correlation reversal between CCS and UCS across bit sizes is statistically significant (CCS: Z = −16.84, p < 0.001; UCS: Z = −6.75, p < 0.001), establishing CCS as the superior predictor at 12.25″ and UCS as the superior predictor at 8.5″—a finding not previously reported in the ROP literature. This reversal is attributed to the larger contact area of the 12.25″ bit, which promotes confinement-dominated rock failure better described by CCS, whereas the smaller bit produces localized stress concentration better represented by UCS. These results establish that (1) optimal geomechanical input selection is bit-size dependent, (2) nonlinear modeling outperforms linear frameworks for strength–ROP relationships, and (3) parameter relevance outweighs coefficient tuning in model robustness. DCM is recommended as the most operationally practical universal input, requiring only conventional compressional sonic and density logs. This study provides a systematic framework for geomechanical parameter selection with direct implications for drilling optimization in heterogeneous carbonate reservoirs. Full article

The comparison of the ability of poly(phenylene sulfone) (PPSU), a recently introduced alternative membrane polymer, with established poly(ether sulfone) (PESU), both in combination with tailored amphiphilic block copolymer additives to improve ultrafiltration (UF) membrane separation and anti-fouling performance is the focus of this work. Different poly(alkylene oxide)-containing tri- and multiblock polymers with hydrophobic blocks analogous to the respective base polymer, PPSU or PESU, of varied length were used as additives in the casting solution. Membranes were subsequently prepared via film casting and a liquid non-solvent-induced phase separation (NIPS) process. The rheological properties and thermodynamic stability of the casting solutions were investigated. At the same mass concentration, PPSU-based casting solutions show overall higher viscosity that is also more sensitive to the presence of additives compared with PESU-based solutions. PPSU-based casting solutions also have lower tolerance to non-solvents. By adding certain block copolymers in ratios of up 10 wt.% relative to the base polymer, it is possible to increase the UF performance of the membranes of PPSU and PESU. An increase in the block length of the hydrophobic block of PESU leads to a reduction in pure water permeance (PWP), whereas for PPSU, PWP is increased by the addition of additives. Especially additives with shorter PESU or PPSU block length, i.e., with a larger fraction of poly(ethylene oxide) blocks in the casting solution, seem to act as additional pore-forming agents. The water contact angle can be decreased for both additive systems, indicating a more hydrophilic membrane surface. Finally, using flower soil extract as a model substance for surface water, interesting candidates of additives that enable fouling reduction with competitive UF performance were identified for PESU and PPSU membranes. Full article

Acrylate hot-melt adhesives (AHMAs) are widely used in medical dressings, electronic components, and automotive interiors due to their solvent-free nature and high bonding strength. However, their wetting behavior on porous fabric substrates under varying coating temperatures—a critical factor for interfacial adhesion—remains poorly understood. To investigate how coating temperature affects the wetting and adhesion of acrylic hot-melt adhesives on fabric substrates, the apparent surface tension and viscosity of the adhesive (130–160 °C) and the apparent surface energy of the substrate (20–160 °C) were measured. By combining these measurements with contact angle decay curves on steel plates, scanning electron microscopy of cold-brittle cross-sections, and mechanical property tests, the study analysed the effects of temperature on wetting and spreading, penetration depth, and adhesive performance. Results show that with increasing temperature, adhesive surface tension and viscosity decrease, while fluidity improves; substrate surface energy shows no temperature dependence. The penetration depth into the fabric increases from 16 μm to 25 μm, and penetration uniformity gradually improves. However, both peel strength and loop tack continuously decrease with rising temperature, with optimal adhesion at 130 °C. A penetration depth model based on the Washburn equation effectively predicts the penetration behavior. Viscosity accounts for more than 50% of the effect, whilst the wetting factor contributes to a lesser extent. This study provides a theoretical basis for optimizing the coating process of acrylic hot-melt adhesives on fabric substrates. Full article

Wear in microscale material removal is difficult to predict because material loss can proceed through several distinct pathways, including plastic deformation, adhesion, atom-by-atom attrition, tribochemical reactions, oxidation-assisted removal, and fracture. Since these mechanisms operate under different contact and environmental conditions, no single wear law is reliable across all cases. This review examines the main quantitative wear models used in microscale material removal, from classical Archard-type and Reye-type relations to atomistic Arrhenius-type descriptions and models developed for adhesive, tribochemical, oxidation-related, and fracture-dominated wear. Attention is given to the assumptions behind these models, the regimes in which they remain useful, and the conditions under which their predictions begin to fail. The discussion also considers how material properties, tool characteristics, operating conditions, and environmental factors act alone and in combination to influence wear behavior and the reliability of different models. Across the literature, a consistent conclusion is that model selection is most reliable when it is based on the active wear mechanism and the evolving contact state. On this basis, practical guidelines are outlined for different classes of contacts, and current limitations are discussed, including poor treatment of regime transitions, difficulty in parameter identification, and the gap between atomistic models and engineering use. Future progress will depend on multi-regime modeling, better treatment of coupled effects, and improved in situ characterization under realistic operating conditions. Full article

The wettability of dust is fundamental to its dispersion and control in mining operations. Current research, however, focuses largely on isolated properties, leaving the synergistic mechanisms of multi-scale factors-such as particle size, morphology, and surface chemistry-poorly understood. This study integrates field measurements, laboratory characterization, and theoretical analysis to investigate the spatial distribution and wetting behavior of dust in fully mechanized mining faces. The results show that respirable dust preferentially accumulated in mechanically disturbed and personnel-exposure zones. At the shearer operator’s station, respirable dust concentrations reached 328.6 mg/m³ in Mine A and 278.4 mg/m³ in Mine B, which were 1.8 and 1.6 times higher than those at the shearer cutting point, respectively. Mine A dust also showed poorer wettability, with a higher water contact angle of 148.9° ± 2.1° compared with 134.7° ± 1.8° for Mine B, mainly due to its larger agglomerates, rougher surface morphology, and more hydrophobic surface chemistry. Accordingly, targeted development pathways for spray and foam technologies are outlined, including compound wetting agents and micro-nano enhanced foaming systems. The integrated multi-scale framework linking concentration, particle size, morphology, surface chemistry, and wettability provide an application-oriented basis for understanding coal mine dust behavior and for supporting more precise and intelligent dust-control strategies. Full article

In this study, La-doped TiO₂-SiO₂ composite films were deposited on glass substrates by radio-frequency magnetron sputtering. The evolution of microstructure and macroscopic properties was systematically investigated across an annealing temperature range of 350–650 °C. The results show that the La-doped TiO₂-SiO₂ composite structure effectively suppresses abnormal grain growth and delays the anatase-to-rutile phase transition, thereby improving the films’ high-temperature structural stability. Notably, the composite film annealed at 550 °C (LS-550) exhibits the highest anatase crystallinity and forms a dense, smooth (RMS = 1.37 nm), crack-free nanocrystalline network. In terms of wettability, the improved hydrophilicity is attributed to the combined effects of La incorporation and hydrophilic silanol (Si-OH) groups in the amorphous SiO₂ phase. As a result, the water contact angle of the LS-550 film decreases dramatically to 28.0°, indicating excellent hydrophilicity. Moreover, the LS-550 film demonstrates an optimal photocatalytic degradation efficiency of approximately 76% for methylene blue, significantly outperforming the pure TiO₂ film. Furthermore, the enhanced mechanical performance is associated with the combined effects of the SiO₂-containing amorphous phase and the finer microstructure induced by La incorporation. Consequently, the critical load (Lc) of the LS-550 film reaches 75.64 mN, significantly exceeding that of the pure TiO₂ film annealed at the same temperature (61.25 mN). In summary, the composite film annealed at 550 °C concurrently achieves high crystallographic thermal stability, robust interfacial mechanical durability, excellent surface hydrophilicity, and enhanced photocatalytic activity, thereby offering practical guidance for developing TiO₂-based coatings with self-cleaning potential for high-rise building curtain walls. Full article

Hydration, interfacial interactions, and matrix stability are critical determinants of the mucoadhesive behavior of cellulose-based polymers. In this study, we investigated the physicochemical and mucoadhesive behavior of hydroxypropyl methylcellulose (HPMC), Carbopol 974P NF, and Kollidon VA 64, along with their binary blends (1:1, w/w) in the context of oral mucosal drug delivery. Wettability, surface free energy, mucoadhesion, and hydration-induced morphological changes were systematically evaluated using contact angle measurements, adhesion and water uptake studies, and real-time surface dissolution imaging (SDi2). The investigated systems displayed markedly different water contact angles: HPMC 103.4 ± 2.7°, Carbopol 47.2 ± 2.3°, Kollidon 36.0 ± 1.8°, HPMC:Carbopol 51.3 ± 2.8°, and HPMC:Kollidon 53.9 ± 3.4°. The corresponding surface free energy (SFE) values ranged from 12.0 mJ/m² for HPMC to 70.5 mJ/m² for Kollidon. Experiments were performed under saliva-mimicking conditions containing 0.1% (w/v) mucin. The HPMC:Carbopol blend exhibited superior mucoadhesive performance and mechanical stability compared with HPMC alone or with the HPMC:Kollidon blends. In 2% (w/v) mucin, the HPMC:Carbopol blend reached a mucoadhesive force of approximately 1.35 N, whereas HPMC and HPMC:Kollidon showed lower values of approximately 0.5–0.75 N and 0.60 N, respectively. After 96 h at 85% RH, the swelling index increased from 14.8 ± 0.5% for HPMC to 29.4 ± 0.3% for HPMC:Carbopol. The incorporation of Carbopol increased the polar contribution to the surface free energy of HPMC-based blends and promoted stable gel layer formation, whereas Kollidon-containing systems underwent rapid disintegration and asymmetric deformation. SDi2 imaging showed that the HPMC disk changed proportionally by approximately 18% in both height and width during 12 h, whereas the HPMC:Kollidon disk almost completely dissolved after approximately 6 h. These results demonstrate that rational selection and combination of cellulose-based polymers can be used to control hydration, interfacial properties, and mucoadhesion, with HPMC:Carbopol blends showing strong potential for oral mucosal drug delivery. Full article

This study presents the synthesis and use of a novel bamboo-derived magnetic activated carbon (BMAC) for the effective removal of cationic and anionic dyes, specifically methylene blue (MB), methyl orange (MO), and sunset yellow (SY), from aqueous solutions. The adsorbent was synthesized using thermal carbonization and subsequent inclusion of magnetic oxide, yielding a porous structure with improved adsorption and magnetic separation properties. Thorough characterization utilizing SEM, EDX, BET, FTIR, XRD, and TGA/DTA validated the creation of a highly porous material including uniformly dispersed magnetic particles and several surface functional groups. Batch adsorption tests were performed to examine the influences of contact time, adsorbent dosage, initial dye concentration, pH, and temperature. The findings indicated rapid adsorption kinetics, with equilibrium reached in around 60–70 min, and adsorption capacity ranked as MB > MO > SY. Augmenting adsorbent dosage enhanced removal efficiency but diminished adsorption capacity per unit mass due to site unsaturation. The maximum adsorption capacities (q_m) of BMAC were 58.9, 56.3, and 32.7 mg/g for MB, MO, and SY, respectively, as determined from the Langmuir isotherm model, indicating superior performance compared with other reported magnetic activated carbon. The adsorption process was determined to be exothermic and spontaneous, as evidenced by thermodynamic characteristics. The equilibrium data were optimally characterized by the Langmuir isotherm model, indicating monolayer adsorption, whereas the kinetic studies conformed to the pseudo-second-order model, signifying that chemisorption is predominant. The adsorption mechanism encompasses electrostatic interactions, π–π stacking, hydrogen bonding, van der Waals forces, pore filling, and surface complexation with magnetic oxides. The findings indicate that BMAC is an efficient, sustainable, and magnetically recoverable adsorbent for the elimination of both cationic and anionic dyes from wastewater. Full article