Search Results (1,658)

Background: A transdermal drug delivery system has significant benefits over conventional routes; however, its effectiveness is limited by the barrier properties of the stratum corneum. Dissolving microneedles (DMNs) have emerged as a minimally invasive strategy to enhance drug permeation while improving patient compliance. The integration of advanced fabrication techniques such as 3D printing enables precise control over microneedle geometry and reproducibility. Objective: This study aimed to fabricate and characterize pregabalin-loaded PVA/PVP dissolving microneedle arrays using a 3D-printing-assisted mold fabrication approach for efficient transdermal drug delivery. Methods: Microneedle master molds were fabricated using 3D printing, followed by replication using polydimethylsiloxane (PDMS) to obtain negative molds. Pregabalin-loaded bilayer microneedles were prepared using a micromolding technique with PVA/PVP polymers. The formulation was evaluated through rheological analysis, scanning electron microscopy (SEM), mechanical strength testing, insertion studies, swelling behavior, drug loading efficiency, Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), X-ray diffraction (XRD), and in vitro drug release studies. Results: The fabricated microneedles exhibited uniform geometry with sharp tips and no structural defects. Rheological analysis confirmed shear-thinning behavior suitable for mold filling. The microneedles demonstrated adequate mechanical strength (~3.3 N/needle) and efficient insertion into the parafilm model. Drug loading efficiency was high (92.4%), indicating effective encapsulation. FTIR analysis confirmed compatibility between drug and polymers, while DSC and XRD results indicated partial amorphization of pregabalin within the polymer matrix. The formulation showed a biphasic drug release profile with an initial burst followed by sustained release, achieving ~96.8% cumulative release over 24 h. Conclusions: The study successfully demonstrates a robust and reproducible 3D-printing-assisted approach for fabricating pregabalin-loaded dissolving microneedles. The developed system exhibited desirable mechanical, physicochemical, and drug release properties, highlighting its potential as an effective transdermal drug delivery platform. Full article

Chronic wounds, particularly those complicated by infection, present significant challenges in clinical management. The microenvironment of these wounds is typically characterized by the accumulation of reactive oxygen species (ROS) and abnormal local pH levels, both of which impede the healing process. Baicalin (BA), a natural flavonoid, exhibits anti-inflammatory activity, ROS-scavenging capability, and pro-healing effects. In this study, hydrogels were synthesized through photoinitiated radical polymerization of methacrylic anhydride (MAA) and dopamine (DA)-modified chondroitin sulfate (ChSMA-DA), grafting degrees of MA and DA were 58%, 23%, MPDA@MnO₂ nanoparticles (NPs), and methacrylated gelatin (GelMA). The gelation time, microtopography, swelling behavior, and water retention of the hydrogels were investigated, along with their degradation, rheological properties, and photothermal effects. The results indicate that swelling ratio (SR) and water retention (WR) of optimal HG-MPDA@MnO₂-M sample were 5.7, 82.42%, exhibited responsive behavior upon weakly acidic environment with pH 6.5 and elevated ROS levels, and exhibited a stable photothermal effect (photothermal conversion efficiency was 22.7%) under 808 nm near-infrared (NIR) light. Following the incorporation of the drug model BA, the cumulative release percentage over 24 h under the combined stimulation of pH 6.5, 1 mmol·L⁻¹ H₂O₂, and 808 nm NIR was 81.1%, significantly higher than either factor alone. These hydrogels show promise as an injectable dressing for chronic wounds, effectively integrating the internal microenvironment of the wound tissue with external NIR to modulate drug release. Full article

Background/Objectives: Carprofen (CP) is a potent non-steroidal anti-inflammatory drug whose clinical use is limited by systemic adverse effects associated with oral administration. The aim of this study was to develop and evaluate a CP-loaded nanoemulsion (CP-NE) as a topical formulation for the management of post-surgical inflammation in veterinary applications. Methods: CP-NE was physicochemically characterized in terms of droplet size, polydispersity index, morphology, pH, rheological behavior, spreadability, and stability. Biopharmaceutical performance was assessed through in vitro drug release and ex vivo permeation studies using porcine ear skin. Safety was evaluated using in vitro cytotoxicity assays in HaCaT keratinocytes, histological analysis of ex vivo porcine skin, and assessment of biomechanical skin parameters in mice. Finally, anti-inflammatory efficacy was investigated in a murine model. Results: CP-NE showed a mean droplet size of approximately 140 nm, low polydispersity, spherical morphology, and Newtonian flow behavior with good spreadability. Stability studies confirmed the absence of significant physical destabilization and acceptable chemical stability under refrigerated and room temperature conditions. Release studies demonstrated sustained drug release, while permeation assays revealed low systemic exposure and high drug retention within the skin. Safety evaluations indicated good biocompatibility with no cytotoxicity, no histological alterations in skin tissue, and no alteration of the skin’s biomechanical properties in volunteers. In vivo efficacy studies showed that CP-NE significantly reduced post-surgical inflammation, promoting faster restoration of skin architecture and improved wound appearance. Conclusions: These findings suggest that CP-NE represents a promising topical delivery system for localized anti-inflammatory therapy following surgical procedures, offering significant potential for veterinary applications. Full article

Weld-bonded joints combine localized metallic welding with structural adhesives and are increasingly used in lightweight multi-material structures. Although numerous studies have examined individual weld-bonding processes, the available literature remains fragmented with respect to process classification, adhesive–weld interaction and mechanical performance. This paper presents a critical review of hybrid weld-bonded joints published between 2000 and 2026, with emphasis on welding-based joining processes and their influence on joint behavior. The main weld-bonding techniques, including resistance spot weld-bonding (RSWB), friction stir weld-bonding (FSWB), friction stir spot weld-bonding (FSSWB) and laser weld-bonding (LWB), are systematically compared in terms of heat input, adhesive stability, load transfer mechanisms and mechanical performance. The analysis indicates that processes with lower heat input, such as FSWB and FSSWB, provide improved adhesive preservation and fatigue performance, whereas RSWB remains the most industrially established solution. The influence of different adhesive families (epoxy, polyurethane, acrylic and thermoplastic) is evaluated with respect to thermal resistance, rheological behavior during welding and long-term durability. Mechanical performance under static, fatigue and impact loading is critically assessed, highlighting typical strength improvements compared with purely welded joints and identifying dominant failure modes. In addition, numerical modeling approaches, including finite element and cohesive zone methods, are reviewed in terms of their ability to capture coupled thermomechanical and damage phenomena. The review further outlines key industrial applications, current technological limitations and future research directions, including advanced adhesive systems, low-heat-input processes, non-destructive testing and digital-twin-based optimization. Full article

Nanomaterials such as cellulose nanocrystals and fumed silica are emerging as excellent thickeners for liquids in a variety of practical applications. Surfactants are often incorporated into the thickening fluids to provide stabilizing components and to control the surface activity of fluids. To develop new thickening materials with desired surface-active properties, it is important to understand the interactions between surfactants and nanoparticles in suspensions. In this work, the interactions between surfactants and nanocrystals/nanoparticles were investigated. Two surfactants, anionic sodium lauryl sulfate-based surfactant (referred to as Stepanol) and cationic hexadecyltrimethylammonium bromide (referred to as HTAB), were studied. Cellulose nanocrystals (referred to as NCC) and fumed-silica nanoparticles (referred to as N20) were used as nanomaterials. The unique feature of this study is that it simultaneously measures rheology, surface activity, and electrical conductivity to determine the influence of ionic surfactants on the behavior and properties of cellulose nanocrystal and fumed silica nanoparticle suspensions. Furthermore, the interactions are observed in the low surfactant concentration range of 0 to 500 ppm. The NCC concentration of NCC–surfactant mixtures was fixed at 1 wt%. Two concentrations of N20 (2 and 5 wt%) were used for N20–surfactant mixtures. The influence of Stepanol was found to be weak whereas HTAB had a strong influence on the rheology of NCC and N20 suspensions. The NCC suspension and surfactant–NCC suspensions were highly non-Newtonian shear-thinning. The N20 suspensions and N20-Stepanol mixtures were nearly Newtonian. The N20-HTAB mixtures were shear-thinning at high HTAB concentrations. The power law model described the rheological behavior of non-Newtonian systems adequately. The consistency and flow behavior indices varied only marginally with the addition of the anionic surfactant Stepanol to NCC and N20 suspensions. With the addition of cationic surfactant HTAB to NCC and N20 suspensions, however, a large increase (20- to 70-fold) in consistency index was observed at high surfactant concentrations. The critical surfactant concentrations where sharp transitions in the rheological properties took place were identified using break points in surface tension and electrical conductivity plots. This study offers valuable insights into tailoring surfactant–nanoparticle systems for practical applications, where precise control of rheological and interfacial properties may be required. Full article

The management of fine bauxite tailings, rich in clay minerals, represents an environmental and operational challenge for the aluminum industry. This study (Part 1) presents a pilot-scale investigation into the dewatering of these ultrafine tailings using a decanter centrifuge, 0.62 m in diameter, as an alternative to conventional wet storage. Tests were conducted at three bowl speeds, 1600 rpm, 1700 rpm, and 1800 rpm, corresponding to G-forces of 888, 1003, and 1124 G. The feed slurry behaved as a non-Newtonian, yield-pseudoplastic fluid, as confirmed by rheology tests. A comprehensive mass balance and performance analysis were conducted. The results demonstrated a monotonic improvement in key performance metrics with increasing bowl speed. Accordingly, increasing the G-force from 888 G to 1124 G improved the final cake solid content from 66.3% to 71.5% (by weight), together with an increase in the average solid recovery from 40.0% to 56.2%. Partition curve analysis revealed the primary limitation: while recovery of particles coarser than 20 µm was very high (>98%), recovery of particles finer than 20 µm remained low, ranging from 22.0% to 35.1%. Partition curve analysis using the Whiten model identified a mechanical cut size (d_50c) ranging from 9.72 µm to 12.0 µm. Hydraulic bypass increased from 8.35% to 14.9% with increasing bowl speed, indicating a significant non-size-selective component of separation. Rheological analysis further showed that the apparent viscosity at 100 s⁻¹ decreased from 0.332 to 0.111 Pa·s across the tested conditions, confirming enhanced slurry mobility and its contribution to increased ultrafine bypass. While overall solid recovery reached 56.2% at 1124 G, the mechanical capture of the ultrafine fraction (<5 µm) remains the primary bottleneck for industrial viability. It is concluded that while the decanter centrifuge is mechanically viable for producing a high-solid cake, the limited recovery of fines would create an unsustainable circulating load in an industrial plant. These results demonstrate that G-force alone, within the tested range, is insufficient to manage these tailings and provide the basis for the mathematical modeling required to design the process, as described in Part 2 of this investigation. Full article

Designing ultra-high-performance concrete (UHPC) mixtures requires balancing multiple, often conflicting, performance criteria, particularly mechanical strength and rheological behavior. However, the limited availability of publicly accessible datasets containing synchronized multi-property measurements, together with cross-source heterogeneity, poses a major challenge for robust data-driven modeling under small-sample conditions. To address this issue, this study proposes an integrated framework combining cross-source data harmonization, Variational Autoencoder (VAE)-based latent-space augmentation, multi-output deep learning, interpretability analysis, and Genetic Algorithm (GA)-driven inverse design. A dataset comprising 139 valid UHPC records was curated from 22 peer-reviewed studies and expanded to 2780 samples through VAE-based augmentation. Using the augmented dataset, a multi-output deep neural network was developed to jointly predict compressive strength, flexural strength, yield stress, and plastic viscosity. On the independent test set, the model achieved R² values of 0.8601, 0.9212, 0.8464, and 0.6603, respectively. Comparative benchmarks and augmentation ablation analyses further showed that VAE-based augmentation consistently improved predictive performance and generalization, especially under small-sample conditions. SHAP and partial dependence analyses identified curing age, steel fiber content, water-to-binder ratio, and superplasticizer dosage as the dominant factors governing UHPC performance. Finally, the trained surrogate model was coupled with a GA for multi-objective inverse optimization, and experimental validation of three candidate mixtures confirmed good agreement between predicted and measured values. This study provides a transparent and engineering-oriented methodology for the integrated prediction, interpretation, and optimization of UHPC mixtures. Full article

This study aimed to develop antibacterial polyphenol–chitosan hydrogel dressings and, more importantly, to compare how three structurally distinct low-cost natural polyphenols—protocatechuic acid (PCA), gallic acid (GA), and tannic acid (TA)—regulate hydrogel performance within the same chitosan platform. PCA, GA, and TA were incorporated into chitosan to obtain the corresponding hydrogels, denoted CS-PCA, CS-GA, and CS-TA. Scanning electron microscopy confirmed that all formulations possessed a three-dimensional porous network. Rheological characterization revealed favorable viscoelastic behavior for all polyphenol-containing hydrogels, with CS-TA showing the highest mechanical strength in the present system. The hydrogels also exhibited pH-responsive swelling, good tissue adhesion, self-healing ability, and injectability. In vitro antibacterial assays demonstrated activity against both Gram-positive and Gram-negative microorganisms, with CS-TA showing the most favorable overall antibacterial performance under the tested conditions. In a rat full-thickness wound model, hydrogel treatment accelerated wound closure, while H&E staining indicated enhanced granulation tissue formation, collagen deposition, and reduced inflammatory cell infiltration. Collectively, these findings support the use of polyphenol–chitosan composite hydrogels as promising wound-dressing candidates and highlight the value of a side-by-side comparison of PCA, GA, and TA for understanding structure–property–function relationships in this class of materials. Full article

Understanding the dynamics of gas bubbles in viscoelastic media is crucial for applications involving stable cavitation under ultrasound, such as drug delivery, materials processing, and biomedical imaging. The Rayleigh-Plesset equation formulated in terms of bubble volume variation, incorporating viscoelastic effects via the linear Kelvin–Voigt model, is extended here to a fourth-order approximation. This formulation allows a more accurate description of nonlinear bubble dynamics at finite acoustic amplitudes. The resulting equation is solved numerically under various acoustic conditions, with particular emphasis on driving frequencies near the bubble’s resonance and differences between Newtonian and viscoelastic media. To identify the physical conditions under which higher-order nonlinearities become necessary, a decision-tree classification analysis is performed. The results show that the proximity to resonance and the excitation amplitude are the primary determinants of higher-order nonlinear effects, while rheological properties act as modulators, with viscosity exerting a stronger influence than elasticity within the explored ranges. This work provides a physically interpretable criterion for selecting the appropriate model order, improving the prediction and control of nonlinear bubble oscillations under ultrasound excitation in viscoelastic media. 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

Native Andean potatoes (Solanum tuberosum subsp. andigenum) are a valuable phytogenetic resource due to their compositional diversity and adaptation to high-altitude environments. Their starch is a key functional polysaccharide widely used in food systems; however, information on the kinematic viscosity of dilute gels under moderate thermal conditions remains limited. This study evaluated the effects of temperature (26, 36, and 46 °C) and starch concentration (1–3% w/v) on the kinematic viscosity of gels from three Andean potato varieties: Imilla Negra, Compis, and Peruanita. Starch was extracted from fresh tubers (Puno, Peru) using a wet extraction method, and gels were prepared by heating dispersions at 85 °C for 5 min under controlled conditions. Viscosity (0.61–34.47 cSt) decreased with increasing temperature and increased with concentration, confirming the sensitivity of these systems to thermal and compositional factors. The Arrhenius model adequately described temperature dependence, with activation energies of 15.19–29.75 kJ·mol⁻¹, showing an increasing trend with concentration. At 3% and 26 °C, viscosity followed Compis > Imilla Negra > Peruanita, indicating varietal differences in thickening capacity. These results provide useful rheological data for the design and optimisation of food processes involving dilute Andean potato starch dispersions. Full article

Cemented backfill material is an important technical means for improving the safety, efficiency, and environmental sustainability of underground mining. In tailings-free mining conditions, however, suitable aggregates for cemented backfill are often limited, making it necessary to identify alternative aggregates and optimize their mix proportions. To address this issue, clay-bearing crushed stone was selected as the primary aggregate for a tailings-free bauxite mine, and its effects on the mechanical properties, slurry stability, and rheological properties of cemented backfill material were systematically investigated. Crushed stone ratio, mass concentration, and fly ash ratio were used as experimental factors, and 24 experimental mixes were designed to determine the 3-day compressive strength, bleeding rate, and yield stress. Based on the experimental results, response surface regression models were established, and multi-objective optimization was performed using cost analysis, NSGA-II, and entropy-weighted TOPSIS. The results showed that the system containing clay-bearing crushed stone exhibited better stability than the clay-free crushed stone system. The response surface models for 3-day compressive strength, bleeding rate, and yield stress were all significant, with p-values below 0.0001 and R² values of 0.9658, 0.9306, and 0.8704, respectively. Comprehensive optimization gave the optimal mix proportions as a crushed stone ratio of 6.9721, a mass concentration of 0.82, and a fly ash ratio of 1, corresponding to a predicted 3-day compressive strength of 0.9629 MPa, a bleeding rate of 3.73%, and a cost of 68.225 RMB/t. For engineering application, the recommended mix proportions were adjusted to X₁ = 7, X₂ = 0.82, and X₃ = 1. Parallel tests gave a 3-day compressive strength of 0.99 MPa and a bleeding rate of 3.52%, both within the 95% prediction interval. These results demonstrate that clay-bearing crushed stone can serve as a feasible alternative aggregate for cemented backfill material under tailings-free conditions and that the proposed method combining response surface modeling with multi-objective optimization can effectively balance early strength, slurry stability, and material cost. Full article

Supercritical carbon dioxide (SC-CO₂) fracturing has emerged as an environmentally friendly alternative to conventional water-based hydraulic fracturing; however, its inherently low viscosity restricts proppant-carrying efficiency and reduces fracture conductivity. To address this limitation, this study systematically investigates the rheological behavior and sand-carrying mechanisms of CO₂ dry fracturing fluid under various thermodynamic and compositional conditions. Rheological measurements were conducted to evaluate the effects of thickener concentration, temperature, and pressure on viscosity, while visualized experiments were performed to examine the influence of injection rate, sand ratio, thickener concentration, and temperature on proppant migration and deposition. A numerical model developed in Fluent was further employed to simulate the temporal evolution of proppant transport within the fracture. The results show that higher thickener concentrations and injection rates significantly enhance proppant transport distance and uniformity, whereas elevated temperature and sand ratio promote localized settling. The simulation results agree well with the experimental observations, validating the model’s reliability. This study elucidates the coupled effects of rheology and operating parameters on CO₂ dry fracturing behavior and provides theoretical and experimental guidance for optimizing CO₂-based fracturing fluids in low-permeability reservoirs. Full article

Real-Time In-Line Monitoring (RTIM) of rheological properties such as slurry yield stress is important in different industries for its various benefits such as significant time savings and increased safety/efficiency of processes while reducing secondary waste due to sampling or inaccurate procedures. This paper discusses two methods for characterizing yield stress in real time: the Pressure Loss method and the Liquid Rise method. The Liquid Rise method uses the height of the slurry in a vertical column and the pressure difference to quantify the yield stress. The Pressure Loss method uses the drop of pressure in a laminar flow of slurry to determine the yield stress. Kaolin–water slurry is used as a simulant of the non-Newtonian fluid. An experimental setup is built to demonstrate the methods, and data obtained from the experimental setup is compared with the yield stress obtained from a conventional table-top rheometer (baseline rheology). The results show a good agreement between the experimental yield stress and baseline rheology. Full article

The present study provides a comprehensive investigation into the hydrodynamic performance of grooved rubber journal bearings (GRJBs) employed as shaft supports in various rotating systems, with particular emphasis on marine applications. These bearings are lubricated with non-Newtonian fluids such as modern oil containing additives and viscoelastic water-based lubricant, which—owing to its complex composition including hydrocarbon chains, metal oxides, and impurity particles and contaminants such as salts, organic substances, microalgae, biopolymers, and microorganisms—deviates from the ideal Newtonian fluid model and demonstrates non-Newtonian rheological behavior. By examining various theories used in the analysis of non-Newtonian fluid behavior, the power-law model, which has a high degree of generality, has been employed in the present study. Also, to improve modeling accuracy, the elastic deformation of the rubber bush in this study is characterized using the Winkler foundation approach and analyzed via the finite element method (FEM). This advanced mechanical formulation, integrated with non-Newtonian lubrication modeling of lubricant using the power-law fluid model, and the parametric assessment of groove number and dimensions on steady-state bearing performance parameters, constitutes the core of this research. The investigation focuses on groove configurations of 4, 6, 8, and 10 channels. The findings indicate that increasing the groove count partitions the convergent pressure film zone into discrete segments, thereby reducing the maximum hydrodynamic pressure while intensifying the overall energy dissipation within the bearing. Additionally, the influences of rheological properties of the fluid—namely the power-law index (n) and the consistency index (m)—on key performance characteristics are thoroughly examined. An increase in both parameters enhances the effective viscosity and load carrying capacity; however, the exponential amplification due to the power-law index exhibits a more pronounced effect on load capacity and peak pressure compared to the consistency index. Full article