Search Results (51)

This study looked at the performance requirements of repair materials for concrete structures in cold regions, systematically analyzing the effects of steel fiber dosage (0.7–2.1%), early-strength agent PRIORITY dosage (6–10%), and their coupling effects on the workability, interfacial bond strength, and freeze–thaw resistance of rapid-hardening ultra-high-performance concrete (UHPC). Through fluidity testing, bond interface failure analysis, freeze–thaw cycle testing, and pore analysis, the mechanism of steel fibers and early-strength agent on the multi-dimensional performance of fast-hardening UHPC was revealed. The results showed that when the steel fiber dosage exceeded 1.4%, the flowability was significantly reduced, while a PRIORITY dosage of 8% improved the flowability by 20.5% by enhancing the paste lubricity. Single addition of steel fibers decreased the interfacial bond strength, but compound addition of 8% PRIORITY offset the negative impact by optimizing the filling effect of hydration products. Under freeze–thaw cycles, excessive steel fibers (2.1%) exacerbated the mass loss (1.67%), whereas a PRIORITY dosage of 8% increased the retention rate of relative dynamic elastic modulus by 10–15%. Pore analysis shows that the synergistic effect of 1.4% steel fiber and 8% PRIORITY can reduce the number of pores, optimize the pore distribution, and make the structure denser. The study determined that the optimal compound mixing ratio was 1.4% steel fibers and 8% PRIORITY. This combination ensures construction fluidity while significantly improving the interfacial bond durability and freeze–thaw resistance, providing a theoretical basis for the design of concrete repair materials in cold regions. Full article

Both biosystems and engineering fields demand advanced friction-reducing and lubricating materials. Due to their hydrophilicity and tissue-mimicking properties, hydrogels are ideal candidates for use as lubricants in water-based environments. They are particularly well-suited for applications involving biocompatibility or interactions with intelligent devices such as soft robots. However, external environments, whether within the human body or in engineering applications, often present a wide range of dynamic conditions, including variations in shear stress, temperature, light, pH, and electric fields. Additionally, hydrogels inherently possess low mechanical strength, and their dimensional stability can be compromised by changes during hydration. This review focuses on recent advancements in using environmentally responsive hydrogels as lubricants. It explores strategies involving physical or structural modifications, as well as the incorporation of smart chemical functional groups into hydrogel polymer chains, which enable diverse responsive mechanisms. Drawing on both the existing literature and our own research, we also examine how composite friction materials where hydrogels serve as water-based lubricants offer promising solutions for demanding engineering environments, such as bearing systems in marine vessels. Full article

To investigate the lubrication mechanism of phytic acid (PA) solution, a “copper–PA solution–copper” confined model with varying concentrations was established. Molecular dynamics (MD) simulations were employed to model the behavior of compression and the confined shear process. By examining the variations in key parameters such as dynamic viscosity, compressibility, radial distribution function, relative concentration distribution, and velocity distribution of PA solutions under different normal loads or shear rates, we elucidated the lubrication mechanism of PA solutions at the molecular level. The results demonstrate that under standard loading conditions, higher PA concentrations facilitate the formation of denser hydrated layers with decreased compressibility compared to free water, thereby significantly enhancing the load-bearing capacity. The shear stress at the solution–copper interface exhibits a substantial increase as the shear rate rises. This phenomenon originates from shear-driven migration of PA to the copper interface, disrupting the hydration layers and weakening hydrogen bonds. Consequently, this reduction in PA–water interactions amplifies slip velocity differences, ultimately elevating interfacial shear stress. The load-bearing capacity of the PA solution and the interfacial shear stress between the PA and copper are critical factors that influence the lubrication mechanism at the PA/Cu interface. This study establishes a theoretical foundation for the design and application of PA solution as a water-based lubricant, which holds significant importance for advancing the development of green lubrication technology. Full article

Lubrication is a well-established strategy for reducing interfacial frictional energy dissipation and preventing surface wear. Various lubricants have been developed, including mineral oil materials, vegetable oil materials, polymer-based materials, and solid lubrication materials. Among these, polymer-based lubrication materials have gained significant interest due to their versatility, leading to the development of tailored strategies to meet diverse application demands. In load-bearing scenarios, polymer-based materials enhance interfacial hydration, exhibiting exceptional frictional properties, including extremely low friction coefficients, high load-bearing capacity, and superior wear resistance. In contrast, in non-load-bearing scenarios, polymer-based coatings improve interfacial hydrophobicity, promoting boundary slip and reducing frictional resistance at the solid–liquid interface (SLI), making them an important strategy for drag reduction. Despite substantial advancements in polymer-based lubrication and drag reduction (PBLDR), the underlying microscopic mechanisms remain incompletely understood. Therefore, this review aims to provide a comprehensive analysis of the fundamental principles governing PBLDR. The main topics covered will include the following: (1) the fundamentals of the surface forces and hydrodynamic force, (2) the mechanisms underlying hydration lubrication, (3) joint lubrication and polymer brush lubrication, (4) the friction tuning and interfacial drag reduction via polymer coating design, and (5) the potential and limitations of polymer-based materials. By summarizing recent advancements in PBLDR, this work will provide valuable contributions to future research and applications in related fields. Full article

Background: Postoperative abdominal adhesion is a prevalent complication following abdominal surgery, with the incidence of adhesion reaching up to 90%, which may precipitate a range of adverse outcomes. Although fibrous membranes loaded with various anti-inflammatory or other drugs have been proposed for anti-adhesion, most of them suffer from drug-induced adverse effects. Methods: In this study, a lecithin-based electrospun polylactic acid (PLA) nanofibrous membrane (L/P-NM) was developed for the prevention of postoperative abdominal adhesion, utilizing the hydration lubrication theory. The loaded zwitterionic lecithin allows the nanofiber surface to strongly bind water molecules to create a hydration lubrication interface. Results: As the TGA results show, the content of bound water in the nanofibers increased significantly with the increase in the lecithin content. Tribological test results show that L/P-NM reached a minimum coefficient of friction (COF) of about 0.112. Additionally, the developed nanofibrous membranes possess favorable tensile property and biocompatibility. Rat postoperative abdominal adhesion model evaluation results demonstrated that L/P-NM possesses significant anti-adhesive performance, with an adhesion score of only 1. Conclusions: Therefore, this study offers a promising strategy for efficiently preventing abdominal adhesion. Full article

The low viscosity of water-lubricated films compromises their load-bearing capacity, posing challenges for practical application. Enhancing the lubrication stability of these films under load is critical for the successful use of seawater-lubricated bearings in engineering. Polydopamine (PDA) shows great potential to address this issue due to its strong bio-inspired adhesion and hydration lubrication properties. Thus, PDA nanoparticles and seawater suspensions were synthesized to promote adhesive lubricating film formation under dynamic friction. The lubrication properties of PDA suspensions were evaluated on Cu ball and ultra-high molecular weight polyethylene (UHMWPE) tribo-pairs, with a detailed comparison to seawater. The results show PDA nanoparticles provide excellent adhesion and lubrication, enhancing the formation of lubricating films during friction with seawater. Under identical conditions, PDA suspensions demonstrated the lowest friction coefficient and minimal wear. At 3 N, friction decreased by 56% and wear by 47% compared to distilled water. These findings suggest a novel strategy for using PDA as a lubricant in seawater for engineering applications. Full article

With the gradual improvement and implementation of unconventional wells drilling and environmental regulations, there is an urgent need for high-performance and more environmentally friendly lubricants for water-based drilling fluids (WD). Developing green oilfield chemicals from natural products is a shortcut. In this work, Abelmoschus esculentus (L.) Moench/okra has been studied as the lubricant in WD. The green drilling fluid lubricant developed demonstrates excellent lubrication performance, as well as good filtration loss reduction and inhibition of bentonite hydration expansion. The results show that with the addition of 2.5% okra slurry to water-based drilling fluid, the coefficient of friction decreased by 51.68%, the apparent viscosity (AV) increased by 51.32%, the plastic viscosity (PV) increased by 42.99%, and the fluid loss decreased by 39.88%. Moreover, through TGA, SEM, FT-IR, particle distribution tests, and contact angle tests, the lubrication mechanism of okra slurry was discussed. Finally, the economic feasibility of using okra as an environmentally friendly lubricant for drilling fluids was analyzed. This work combines agricultural products with industrial production, which not only solves industrial problems but also enhances the added value of agricultural products, providing a reference for the coordinated development of industry and agriculture. Full article

This paper presents a novel low-carbon binder formulated from fly ash (FA), ground granulated blast furnace slag, steel slag, and desulfurization gypsum as a quaternary solid waste-based material. It specifically examines the influence of FA content on the mechanical properties and hydration reactions of the quaternary solid waste-based binder. The mortar test results indicate that the optimal FA content is 10%, which yields a 28-day compressive strength 11.28% higher than that of the control group without FA. The spherical particles of fly ash reduce the overall water demand and provide a “lubricating” effect to the paste due to their continuous gradation, improving the fluidity of the slag-steel slag-gypsum cementitious materials. The micro test results indicate that fly ash has minimal effect on the early hydration products and process of the solid waste-based cementitious materials, but after 7 days, it continuously dissolves silicon-oxygen tetrahedrons or aluminum-oxygen tetrahedrons, consuming Ca²⁺ and OH⁻ in the system. After 28 days, the amount of ettringite and C-(A)-S-H gel generated increases significantly. The pozzolanic activity of fly ash is mainly stimulated by the Ca(OH)₂ from steel slag in the later hydration stage. Additionally, spherical fly ash particles can fill the voids in the hardened paste, reducing the formation of cracks and weak zones, and thereby contributing to a denser overall structure of the hydrated binder. The findings of this paper provide data support for the development of low-carbon cement-free binders using fly ash in conjunction with metallurgical slags, thereby contributing to the low-carbon advancement of the construction materials industry. Full article

Purpose: An innovative eyedrop formulation based on a combination of 0.2% hyaluronic acid and 0.001% hydrocortisone sodium phosphate (Idroflog^®, Alfa Intes, Italy; HAC eyedrops) was granted a European Patent in 2016 and has been available on the market since 2019 in Europe and in other countries around the world. HAC eyedrops aim to synergize the moisturizing effects of hyaluronic acid with the mild anti-inflammatory properties of low-dose hydrocortisone, offering a more effective and safer alternative for treating dry eye disease (DED), targeting both tear film instability and dysfunctional para-inflammation. The activity of HAC eyedrops has been explored in different post-marketing clinical trials, in addition to preclinical studies. In this narrative review, we explored the available evidence on the use of HAC eyedrops for the management of para-inflammation in DED patients to provide a comprehensive overview of efficacy and safety data related to the use of this medical device in routine clinical practice. Methods: A literature search for preclinical and clinical data involving treatment with HAC eyedrops was conducted using PubMed/MEDLINE, considering only original research articles published in English, without time restrictions. Results: One preclinical and four clinical papers were retrieved. Preclinical evidence suggests that 0.001% hydrocortisone is able to control the expression of inflammatory markers, and this, together with the hydrating and lubricating properties of hyaluronic acid, leads to improvements in DED clinical signs, such as tear volume and the stability of the tear film. The results of clinical trials demonstrate that HAC eyedrops are able to improve the signs and symptoms of DED and that 0.001% low-dosage hydrocortisone can be helpful in preventing the progression to chronic stages of DED. Conclusions: HAC eyedrops represent a promising therapeutic strategy for the management of dysfunctional para-inflammation and offer a valuable addition to the armamentarium of treatments for DED. Full article

Poly[2-(methacryloyloxy)ethyl phosphorylcholine] liposomes (pMPC liposomes) gained attention during the last few years because of their potential use in treating osteoarthritis. pMPC liposomes that serve as boundary lubricants are intended to restore the natural lubrication properties of articular cartilage. For this purpose, it is important that the liposomes remain intact and do not fuse and spread as a lipid film on the cartilage surface. Here, we investigate the stability of the liposomes and their interaction with two types of solid surfaces, gold and carbon, by using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). With the aid of a hydrophilic species used as an electroactive probe in the solution, the charge transfer characteristics of the electrode surfaces are obtained. Additionally, from EIS, the capacitance characteristics of the surfaces are derived. No decrease of the peak currents and no displacement of the peak potentials to greater overpotentials are observed in the CV experiments. No decrease in the apparent capacitance and increase in the charge transfer resistance is observed in the EIS experiments. On the contrary, all parameters in both CV and EIS do change in the opposite direction. The obtained results confirm that there is only physical adsorption without fusion and spreading of the pMPC liposomes and without the formation of lipid films on the surfaces of both gold and carbon electrodes. Full article

The luminal surface of the intestinal epithelium is protected by a vital mucus layer, which is essential for lubrication, hydration, and fostering symbiotic bacterial relationships. Replicating and studying this complex mucus structure in vitro presents considerable challenges. To address this, we developed a hydrogel-integrated millifluidic tissue chamber capable of applying precise apical shear stress to intestinal models cultured on flat or 3D structured hydrogel scaffolds with adjustable stiffness. The chamber is designed to accommodate nine hydrogel scaffolds, 3D-printed as flat disks with a storage modulus matching the physiological range of intestinal tissue stiffness (~3.7 kPa) from bioactive decellularized and methacrylated small intestinal submucosa (dSIS-MA). Computational fluid dynamics simulations were conducted to confirm a laminar flow profile for both flat and 3D villi-comprising scaffolds in the physiologically relevant regime. The system was initially validated with HT29-MTX seeded hydrogel scaffolds, demonstrating accelerated differentiation, increased mucus production, and enhanced 3D organization under shear stress. These characteristic intestinal tissue features are essential for advanced in vitro models as they critically contribute to a functional barrier. Subsequently, the chamber was challenged with human intestinal stem cells (ISCs) from the terminal ileum. Our findings indicate that biomimicking hydrogel scaffolds, in combination with physiological shear stress, promote multi-lineage differentiation, as evidenced by a gene and protein expression analysis of basic markers and the 3D structural organization of ISCs in the absence of chemical differentiation triggers. The quantitative analysis of the alkaline phosphatase (ALP) activity and secreted mucus demonstrates the functional differentiation of the cells into enterocyte and goblet cell lineages. The millifluidic system, which has been developed and optimized for performance and cost efficiency, enables the creation and modulation of advanced intestinal models under biomimicking conditions, including tunable matrix stiffness and varying fluid shear stresses. Moreover, the readily accessible and scalable mucus-producing cellular tissue models permit comprehensive mucus analysis and the investigation of pathogen interactions and penetration, thereby offering the potential to advance our understanding of intestinal mucus in health and disease. Full article

This study introduces a novel organosilicon-modified polysaccharide (Si-AP) synthesized via grafting and comprehensively evaluates its performance in water-based drilling fluids (WBDFs). The molecular structure of Si-AP was characterized using Fourier-transform infrared spectroscopy (FTIR) and ¹H-NMR experiments. Thermalgravimetric analysis (TGA) confirmed the good thermal stability of Si-AP up to 235 °C. Si-AP significantly improves the rheological properties and fluid loss performance of WBDFs. With increasing Si-AP concentration, system viscosity increases, API filtration rate decreases, clay expansion is inhibited, and drilling cuttings hydration dispersion is suppressed, especially under high-temperature conditions. Additionally, mechanistic analysis indicates that the introduction of siloxane groups can effectively inhibit the thermal degradation of AP chains and enhance their high-temperature resistance. Si-AP can form a lubricating film by adsorbing on the surface of clay particles, improving mud cake quality, reducing the friction coefficient, and significantly enhancing the lubricating performance of WBDFs. Overall, Si-AP exhibits a higher temperature-resistance limit compared to AP and more effectively optimizes the lubrication, inhibition, and control of the filtration rate of WBDFs under high-temperature conditions. While meeting the requirements of drilling fluid systems under high temperatures, Si-AP also addresses environmental concerns and holds promise as an efficient solution for the exploitation of deep-seated oil and gas resources. Full article

With the development of the shipbuilding industry, it is necessary to improve tribological properties of polyether ether ketone (PEEK) as a water-lubricated bearing material. In this study, the sulfonated PEEK (SPEEK) with three distinct chemical structures was synthesized through direct sulfonated polymerization, and high fault tolerance and a controllable sulfonation degree ensured the batch stability. The tribological and mechanical properties of SPEEK with varying side groups (methyl and tert-butyl) and rigid segments (biphenyl) were compared after sintering in a vacuum furnace. Compared to the as-made PEEK, as the highly electronegative sulfonic acid group enhanced the hydration lubrication, the friction coefficient and wear rate of SPEEK were significantly reduced by 30% and 50% at least without affecting the mechanical properties. And lower steric hindrance and entanglement between molecular chains were proposed to be partially responsible for the lowest friction behavior of SPEEK with methyl side groups, making it a promising and competitive option for water-lubricated bearings. Full article

The outstanding lubrication of articular cartilage in the major synovial joints such as hips and knees, essential for the joint well-being, has been attributed to boundary layers of lipids at the outer cartilage surfaces, which have very low friction mediated by the hydration lubrication mechanism at their highly hydrated exposed headgroups. However, the role of spontaneously present lipid splays—lipids with an acyl tail in each of the opposing bilayers—in modulating the frictional force between lipid bilayers has not, to date, been considered. In this study, we perform all-atom molecular dynamics simulations to quantitatively assess the significance of splayed molecules within the framework of lubricating lipid bilayers. We demonstrate that, although transient, splayed molecules significantly increase the inter-membrane friction until their retraction back into the lamellar phase, with this effect more steadily occurring at lower sliding velocities that are comparable to the physiological velocities of sliding articular cartilage. Full article

Emollients are valued ingredients of many cosmetic products and medical devices used to support the treatment and prevention of many skin diseases. Despite the fact that they are one of the oldest cosmetic ingredients, raw materials as well as new recipe solutions are constantly being sought, the main goal of which is to obtain products with the most favorable physicochemical properties while improving the hydration of the stratum corneum and softening and smoothing the skin. It should be noted that there are few scientific articles on the effect of emollients on the physicochemical and usable properties of emollient preparations of the body-oils type. The obtained formulations were subjected to physicochemical tests (dynamic viscosity, surface tension, contact angle, and color evaluation), and the degree of skin hydration and lubrication after application of the developed cosmetic oils was evaluated. Cosmetic oils based on natural emollients were characterized by weaker spreading abilities, which was confirmed by their higher viscosity, surface tension, and contact-angle results relative to those obtained for cosmetic oils based on synthetic emollients. In addition, it was found that the use of both groups of cosmetic oils based on natural and synthetic emollients leads to an increase in the degree of hydration of the skin and an increase in its oiliness. However, a higher increase in the degree of hydration and a lower decrease in the level of skin lubrication are observed after the application of body oils based on natural emollients. Full article