Search Results (549)

Many low-temperature applications, such as rocket engines and liquefied natural gas (LNG) transport pumps, necessitate ultra-low-temperature operational environments. In these conditions, the properties of lubricating oils and greases are significantly influenced by temperature, leading to the widespread adoption of solid lubrication. Currently, there is no international research regarding the influence of bearing coatings on the subsurface stress distribution in raceways. The Lundberg–Palmgren (L-P) theory states that subsurface stress variations govern bearing lifespan. Therefore, this paper utilizes existing formulas and Python programming to calculate the subsurface stress field of the inner raceway in a MoS₂ solid-lubricated angular contact ball bearing. Furthermore, it analyzes the impacts of factors such as coating material properties, slide-to-roll ratio, traction coefficient, and load on its subsurface stress field. The results reveal that for solid-lubricated ball bearings, as the load increases, the maximum subsurface stress shifts closer to the center of the contact area, and the maximum subsurface shear stress becomes more concentrated. As the traction coefficient increases, the stress on the XZ-plane side increases and its position moves closer to the surface, while the opposite trend is observed on the other side. Additionally, the maximum value of the subsurface von Mises stress is approximately 0.64P₀, and the maximum value of the orthogonal shear stress component τ_yz in the subsurface is approximately 0.25P₀. Full article

Background/Objectives: Liquid biopsy is a minimally invasive alternative to tissue biopsy and is used to obtain information about a disease from a blood sample or other body fluids. In the context of cancer, circulating tumor cells (CTC) can be used as biomarkers to determine the nature of the tumor, its stage of progression, and the efficiency of the administered therapy through monitoring. However, the low concentration of CTCs in blood (1–10 cells/mL) is a challenge for their isolation. Therefore, a minimally invasive medical device (BMProbe™) was developed that isolates CTCs via antigen–antibody binding directly from the bloodstream. Current investigations focus on the process of detaching bound cells from the BMProbe™ surface for cell cultivation and subsequent drug testing to enable personalized therapy planning. Methods: This article presents two approaches for detaching LNCaP cells from anti-EpCAM coated BMProbes™: enzymatic detachment using TrypLE™ and detachment through enzymatic pretreatment with supplementary flow-induced shear stress. The additional shear stress is intended to increase the detachment efficiency. To determine the flow rate required to gently detach the cells, a computational fluid dynamics (CFD) simulation was carried out. Results: The experimental test results demonstrate that 91% of the bound cells can be detached enzymatically within 10 min. Based on the simulation, a maximum flow rate of 47.76 mL/min was defined in the flow detachment system, causing an average shear stress of 8.4 Pa at the probe edges. The additional flow treatment did not increase the CTC detachment efficiency. Conclusions: It is feasible that the detachment efficiency can be further increased by a longer enzymatic incubation time or higher shear stress. The influence on the integrity and viability of cells must, however, be considered. Full article

Hydroxyapatite (HA) has become a widely used material for bone grafting and surface modification of titanium-based orthopedic implants due to its excellent biocompatibility. Among various coating techniques, microplasma spraying (MPS) has gained significant industrial relevance. However, the clinical success of HA coatings also depends on their adhesion to the implant substrate. Achieving durable fixation and reliable biological integration of orthopedic implants remains a major challenge due to insufficient coating adhesion and limited osseointegration. This study addresses challenges in dental and orthopedic implantology by evaluating the microstructure, mechanical properties, and biological behavior of bilayer coatings composed of a zirconium (Zr) sublayer and an HA top layer, applied via MPS onto titanium alloy. Surface roughness, porosity, and adhesion were characterized, and pull-off and shear tests were used to assess mechanical performance. In vitro biocompatibility was tested using rat mesenchymal stem cells (MSCs) to model osteointegration. The results showed that the MPS-fabricated Zr–HA bilayer coatings achieved a pull-off strength of 28.0 ± 4.2 MPa and a shear strength of 32.3 ± 3.2 MPa, exceeding standard requirements. Biologically, the HA top layer promoted a 45% increase in MSC proliferation over three days compared to the uncoated titanium substrate. Antibacterial testing also revealed suppression of E. coli growth after 14 h. These findings support the potential of MPS-applied Zr-HA coatings to enhance both the mechanical integrity and biological performance of titanium-based orthopedic implants. Full article

As an emerging energy-saving approach, bio-inspired drag reduction technology has become a key research direction for reducing energy consumption and greenhouse gas emissions. This study introduces the latest research progress on bio-inspired microstructured surfaces in the field of underwater drag reduction, focusing on analyzing the drag reduction mechanism, preparation process, and application effect of the three major technological paths; namely, bio-inspired non-smooth surfaces, bio-inspired superhydrophobic surfaces, and bio-inspired modified coatings. Bio-inspired non-smooth surfaces can significantly reduce the wall shear stress by regulating the flow characteristics of the turbulent boundary layer through microstructure design. Bio-inspired superhydrophobic surfaces form stable gas–liquid interfaces through the construction of micro-nanostructures and reduce frictional resistance by utilizing the slip boundary effect. Bio-inspired modified coatings, on the other hand, realize the synergistic function of drag reduction and antifouling through targeted chemical modification of materials and design of micro-nanostructures. Although these technologies have made significant progress in drag reduction performance, their engineering applications still face bottlenecks such as manufacturing process complexity, gas layer stability, and durability. Future research should focus on the analysis of drag reduction mechanisms and optimization of material properties under multi-physical field coupling conditions, the development of efficient and low-cost manufacturing processes, and the enhancement of surface stability and adaptability through dynamic self-healing coatings and smart response materials. It is hoped that the latest research status of bio-inspired drag reduction technology reviewed in this study provides a theoretical basis and technical reference for the sustainable development and energy-saving design of ships and underwater vehicles. Full article

To meet the special needs of preventive maintenance for oil and gas well pipelines, this study conducts a geometric dissection of remora suckerfish based on bionics. It combines the biological features with fiberboard tape and uses the discrete element method to construct a particle model of solvent-free, epoxy-reinforced polymer materials, determining relevant parameters. The model accuracy is verified through volumetric density and drop tests, and the optimal parameter combination of the remora-inspired structure is obtained via multi-factor simulation analysis. Comparative tests confirm that the bionic structure enhances stability by approximately 43.29% compared to the original structure, effectively avoiding insufficient strength. It successfully addresses the gravitational segregation and fluid shear caused by uneven coating thickness, ensures stable and reliable interfacial properties of the composite structure during service, and provides strong support for the practical application of related materials in the preventive repair of oil and gas well pipelines. The findings promote the upgrade of oil and gas pipeline maintenance strategies from “passive response” to “active prevention”, laying the core technical foundation for the resilience of energy infrastructure. Full article

Soft body armor (SBA) remains an essential component of first responder protection. However, most SBA design concepts do not adequately address the unique performance, morphological, and psychological needs of women as first responders. In this review, female-specific designs of ballistic-resistant panels, material systems, and SBA performance testing are critically examined. The paper also explores innovations in shaping and design techniques, including darting, dartless shape construction, modular assembly, and body scanning with CAD integration to create contoured and structurally stable panels with improved coverage, reduced bulk, and greater mobility. In addition, the review addresses broadly used and emerging dry textile fabrics and fiber-reinforced polymers, considering various innovations, such as 3D warp interlock weave, shear thickening fluid (STF) coating, nanomaterials, and smart composites that improve energy dissipation and impact tolerance without sacrificing flexibility. In addition, the paper also examines various emerging ballistic performance testing standards and their revisions to incorporate gender-specific standards and measures their ability to decrease trauma effects and maintain flexibility and practical protection. Finally, it identifies existing challenges and areas of future research, such as optimizing multi-layer systems, addressing fatigue behavior, and improving multi-angle and low-velocity impact performance while providing avenues for future sustainable, adaptive, and performance-optimized body armor. Full article

This study systematically investigates how thiol–disulfide interactions influence the structure and mechanical properties of casein gels. Acid gels were prepared from suspensions of micellar casein (MC) powder that were heat-treated at 70 °C. Thiol groups were variably blocked with N-ethylmaleimide (NEM). The gels were characterized using stress–strain measurements, rheological analyses, and confocal microscopy. The stress–strain curves exhibited a biphasic behavior, with an initial linear elastic phase followed by a linear plastic region and a nonlinear failure zone. Compared to control samples, the addition of 100 mM NEM reduced the gel strength by 50%, while G′ and G″ increased by around 100%, unexpectedly. NEM-treated gels consist of uniformly sized building blocks coated with a whey protein layer. Strong physical interactions and dense packing enhance viscoelasticity under short deformations but reduce the compressive strength during prolonged loading. In contrast, control samples without NEM demonstrate weak viscoelasticity and increased compressive strength. The former is attributed to a broader particle size distribution from lower acid stability in the untreated gels, while the particularly high compressive strength of heat-treated gels additionally results from disulfide cross-links. The results show that thiol blocking and heating enable the targeted formation of acid casein gels with high shear stability but a low compressive strength. Full article

Anti-icing glass is particularly important for applications where ice formation can pose safety risks or impair functionality. The challenge of anti-icing modification for glass lies in maintaining water repellency while addressing the issue of transparency and durability. In this work, leveraging the robustness and wear resistance of inorganic/organic composite materials, a highly transparent coating, with strong adhesive properties to glass substrates and repellency to liquids has been developed. Briefly, 3-glycidoxypropyl polyhedral oligomeric silsesquioxane (GPOSS) is employed as a precursor to fabricate a high-strength, high-transparency coating through modification with acrylic acid and perfluorooctyl acrylate. The inorganic component imparts strength and wear resistance to the coating, while the organic component provides hydrophobic and near oleophobic features. Furthermore, a custom-built mechanical test instrument evaluated the absolute value of the de-icing shear force. The results reveal that at −20 °C, the fluorinated modified coating only exhibit a minimum de-icing pressure of 40.3 kPa, which is 75% lower than the unmodified glass substrate. As-prepared coating exhibits a transmittance of up to 99% and can endure a high-pressure water impact of 30 kPa for 1 min without cracking. Compared to existing anti-icing coating methods, the core innovation of the fluorinated GPOSS-based coating developed in this study lies in its inorganic/organic composite structure, which simultaneously achieves high transparency, mechanical durability, and enhanced anti-icing performance. Full article

Extracorporeal membrane oxygenation (ECMO) is a crucial life support therapy for patients with severe cardiac and respiratory failure. However, the complications associated with venoarterial ECMO (VA-ECMO), including thrombus formation, bleeding, and hemolysis, remain significant challenges that impact patient outcomes and healthcare costs. These complications primarily arise from blood–material interactions within the ECMO circuit, necessitating the development of biocompatible materials to optimize hemocompatibility. This review provides an updated overview of the latest advancements in VA-ECMO materials, focusing on cannula, oxygenators, and centrifugal pumps. Various surface modifications, such as heparin coatings, nitric oxide-releasing polymers, phosphorylcholine (PC)-based coatings, and emerging omniphobic surfaces, have been explored to mitigate thrombosis and bleeding risks. Additionally, novel oxygenator membrane technologies, including zwitterionic polymers and endothelial-mimicking coatings, offer promising strategies to enhance biocompatibility and reduce inflammatory responses. In centrifugal pumps, magnetic levitation systems and hybrid polymer-composite impellers have been introduced to minimize shear stress and thrombogenicity. Despite these advancements, no single material has fully addressed all complications, and further research is needed to refine surface engineering strategies. This review highlights the current progress in ECMO biomaterials and discusses future directions in developing more effective and durable solutions to improve patient safety and clinical outcomes. Full article

Background: Endothelial dysfunction triggers atherosclerosis pathogenesis. This study aimed at developing a 3D scaffold model able to reproduce in vitro the human vascular intima and study the endothelial damage induced by oxidative low-density lipoproteins (ox-LDLs) and shear stress. (2) Methods: Three-dimensional sandwich-like scaffolds were fabricated using electrospinning technology, functionalized with type I collagen and laminin, and subsequently coated with methacrylated gelatin hydrogel (GelMa) to achieve the final composite structure. Human umbilical vein endothelial cells (HUVECs) were used as the cell model for testing the suitability of 3D supports for cell culture exposed to ox-LDL both under static and shear stress conditions. Cell viability, ultrastructural morphology, and nitric oxide (NO) levels were analyzed. (3) Results: Electrospun mats and their functionalization were optimized to reproduce the chemical and physical properties of the vascular intima tunica. The 3D supports were suitable for the cell culture. Ox-LDL did not affect the HUVEC behavior in the 3D models under a static environment. Conversely, high shear stress (500 µL/min, HSS) significantly decreased the cell viability, also under the ox-LDL treatment. (4) Conclusions: Endothelial cell cultures on electrospun supports exposed to HSS provide a candidate in vitro model for investigating the endothelial dysfunction in atherosclerosis research. Technical improvements to the experimental setting are necessary for validating and standardizing the suggested 3D model. Full article

The present work intends to assess the impact of trochoidal toolpath rounding radius loop adjustments on surface roughness, nose radius wear, and resultant cutting force during end milling of AISI D3 steel. Twenty experimental trials have been performed utilizing a face-centered central composite design through a response surface approach. Artificial Neural Network (ANN) models were built to forecast outcomes, utilizing four distinct learning algorithms: the Batch Back Propagation Algorithm (BBP), Quick Propagation Algorithm (QP), Incremental Back Propagation Algorithm (IBP), and Levenberg–Marquardt Back Propagation Algorithm (LMBP). The efficacy of these models was evaluated using RMSE, revealing that the LMBP model yielded the lowest RMSE for surface roughness (Ra), nose radius wear, and resultant cutting force, hence demonstrating superior predictive capability within the trained dataset. Additionally, a Genetic Algorithm (GA) was employed to ascertain the optimal machining settings, revealing that the ideal parameters include a cutting speed of 85 m/min, a feed rate of 0.07 mm/tooth, and a rounding radius of 7 mm. Moreover, the detachment of the coating layer resulted in alterations to the tooltip cutting edge on the machined surface as the circular loop distance increased. The initial arc radius fluctuated by 33.82% owing to tooltip defects that alter the edge micro-geometry of machining. The measured and expected values of the surface roughness, resultant cutting force, and nose radius wear exhibited discrepancies of 6.49%, 4.26%, and 4.1%, respectively. The morphologies of the machined surfaces exhibited scratches along with laces, and side flow markings. The back surface of the chip structure appears rough and jagged due to the shearing action. Full article

Cultural Heritage is a vital socioeconomic driver that must contend with works of art continuously exposed to degradation processes, which are further exacerbated by climate change. Aged coatings, varnishes, and soil can compromise the appearance of artworks, preventing their preservation and valorization. In response, soft matter and colloidal systems, such as nanostructured cleaning fluids (NCFs), have proved to be valuable solutions for safely and effectively cleaning works of art. Here, a novel cleaning system is proposed, for the first time employing microgels of poly(N-isopropylacrylamide) (PNIPAM) with surface chains of oligoethylene glycol methyl ether methacrylate (OEGMA) to favor shear deformation by lubrication. These microgels are loaded with NCFs featuring “green” solvents and different kinds of bio-derived or petroleum-based surfactants (non-ionic, zwitterionic). Rheological characterization of the combined systems highlighted a sharp transition from solid to liquid-like state in the 21–24 °C range when the zwitterionic surfactant dodecyldimethylamine oxide was used; the system displays a solid-like behavior at rest but flows easily at intermediate strains. At slightly higher temperature (>24 °C), an inversion of the G′, G″ values was observed, leading to a system that behaves as a liquid. Such control of rheological behavior is significant for feasible and complete removal of soiled polymer coatings from textured ceramic surfaces, which are difficult to clean with conventional gels, without leaving residues. These results position the PNIPAM-OEGMA microgels as promising cleaning materials for the conservation of Cultural Heritage, with possible applications also in fields where gelled systems are of interest (pharmaceutics, cosmetics, detergency, etc.). Full article

To address the insufficient bonding performance between TC4 (Ti-6Al-4V) coating and carbon fiber-reinforced thermoplastic (CFRP) matrices that limits engineering applications of composite structures, TC4 coatings were fabricated on CFRP polymer composites via laser cladding and analyzed using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) to examine the interface morphology, microstructure, and phase composition. The influence of laser processing parameters on the cladding quality was assessed based on the mechanical performance of the TC4 coating. The findings revealed that insufficient laser power (<230 W) or excessive scanning speed (>1.4 m/min) led to incomplete melting of TC4 powder, preventing the formation of intermetallic compound (IMC) layers. Conversely, excessive laser power (>270 W) or a low scanning speed (<1.0 m/min) caused thermal decomposition of the CFRP due to its limited thermal resistance, leading to interfacial defects such as cracks and pores. The interface between the CFRP and TC4 coating primarily comprised granular TiC and acicular α′ martensite, with minor TiS₂ detected. Optimal mechanical performance was achieved at a laser power of 250 W and a scanning speed of 1.2 m/min, yielding a maximum interfacial shear strength of 18.5 MPa. These findings provide critical insights for enhancing the load-bearing capacity of TC4/CFRP aeronautical composites, enabling their reliable operation in extreme aerospace environments. Full article

Submicron particles are widely used in industrial applications due to their unique physical and mechanical properties that enhance the performance of composite materials. In particular, boron carbide particles are valued for their exceptional hardness and high wear resistance and are especially valuable in protective coatings and aerospace applications. However, these particles can agglomerate, significantly impairing their effectiveness. When this occurs during the development of composite materials, physical and mechanical properties are negatively affected. In this paper, a chemical-free method using a non-destructive, open-system dry mechanical deagglomeration technique is developed, leaving the primary particles unaltered, while breaking up strong adhesions between primary particles resulting from the manufacturing process. This method was tested for the deagglomeration of as-received boron carbide submicron particles, with an average primary particle diameter of d₅₀ = 300 nm, and its effect on particle size distribution is presented. Furthermore, X-ray diffraction and true density measurements were carried out on the raw powder. Submicron particles in the dry and as-received state were poured into an experimental mold without a dispersing agent or a protective atmosphere. Static pressure was applied up to 141 MPa to produce tablets at room temperature, finding that 70 MPa yielded the best results in terms of homogeneity, dispersibility, and reproducibility. In order to break apart the densified pressed tablets, ultrasonication was applied before running particle size measurements in the wet dispersed state. Using a tri-laser diffraction light scattering technique, it was determined that particle size distribution followed a Gaussian curve, indicating that this method is suitable to regain the primary submicron particles with uniform properties. It is also shown that applying ultrasound on the as-received powder alone failed to cause the complete deagglomeration of strongly adhering primary particles. These findings suggest that there is no significant wear on the primary particles and no alteration of their surface chemistry, due to the lack of any chemically supported mechanisms such as the alteration of surface charge or the adsorption of surfactants. Furthermore, as the static pressure exerts an immediate impact on all particles in the mold, there is a clear economical advantage in terms of a shorter processing time over other deagglomeration methods such as high shear mixing. Full article

Composite edible coatings based on arabic gum with mango peel hydrocolloids and mango seed extracts were prepared and used to evaluate grape conservation. Hydroethanolic solutions were used for the obtention of mango seed extracts, by microwave-assisted extraction, with total phenolic compounds (5.48 and 9.85 GAE/g of extract) and antioxidant activity (<13.03 µmol Trolox/g of extract). The extracts were selected for the development of edible coatings. The rheological properties of edible coating solutions present a non-Newtonian behavior-type shear thinning fluid; the addition of extracts improves their viscoelastic properties, favoring their application into grapes. The coated grapes maintained physicochemical parameters, such as weight, pH, acidity, soluble solids, and color during the 15 days of storage. The results of this research offer the possibility of using by-products from fruit industries, especially mango, to obtain functional ingredients and their application in food systems, taking advantage of their biological activity. Full article