Search Results (539)

Bigels (BGs) are promising biphasic systems for extrusion-based 3D food printing inks. In this study, BG inks were formulated by combining a 6% beeswax—4% monoglycerides oleogel (OG) with a 4% gelatin—1% guar gum hydrogel (HG). The BGs were formulated at OG:HG ratios of 10:90 up to 50:50. The effect of the OG:HG ratio on appearance, microstructure, extrusion, rheological and thermal characteristics was investigated to assess printability and shape fidelity. All formulations showed no signs of phase separation during storage, while changes in color were observed with increasing OG content, suggesting modifications in phase distribution and light-scattering behavior. Increasing the OG content induced a transition from OG-in-HG systems to a bicontinuous structure at a 50:50 ratio. All inks showed shear-thinning behavior (G′ > G″) and viscoelastic properties suitable for 3D printing. BG with intermediate OG contents displayed moderate extrusion forces (7.27–9.00 N) and improved structural recovery (up to ≈60%), consistent with desirable printability and appropriate yield/flow points to ensure shape fidelity after deposition. Thermal analysis further confirmed the coexistence of OG and HG phases, ensuring structural integrity at printing temperature. These findings demonstrate the potential of BG as tunable, fat-reduced inks for 3D food structuring. Full article

This paper investigates the linear stability of Navier–Stokes–Voigt (NSV) fluid flow in a channel filled with a homogeneous porous medium under general asymmetric slip boundary conditions. This study bridges the research gap between idealized theoretical models (uniform coating) and realistic engineering surfaces in superhydrophobic channels. In practice, manufacturing defects often lead to non-uniform slip distributions. By solving the generalized eigenvalue problem using the Chebyshev spectral collocation method, we quantify the sensitivity of the critical Reynolds number to symmetry breaking. The results reveal that symmetric slip achieves optimal stability, whereas symmetry breaking causes a significant destabilizing effect. Energy analysis clarifies the physical origin of this instability. Furthermore, we find that increasing the porous medium permeability parameter or the Voigt regularization parameter effectively counteracts the slip-induced instability. Specifically, flow stability can be restored even under highly asymmetric slip conditions if the porous damping or the viscoelastic regularization effect is sufficiently strong. This implies that inevitable manufacturing defects in engineering can be compensated for by optimizing the porous medium matrix. Full article

Although many studies have focused on the initial adhesion of bacteria, there have been few that looked at responses to changing environmental conditions. To more closely examine the viscoelastic nature of initial adhesion, surface-associated bacteria were quantified and monitored for their Brownian motion vibrations. This study used a flow chamber to observe the surface association of Enterobacter cloacae BS 1037, Staphylococcus aureus ATCC 12600, Klebsiella pneumoniae–1, Acinetobacter baumannii–1, Pseudomonas aeruginosa PA O1, and Enterococcus faecalis 1396 to glass under dynamic shear rates of 7–15–30 s⁻¹, 15–30–60 s⁻¹, and 30–15–7 s⁻¹. Comparing increasing and decreasing shear rates, information about retention and recovery became apparent. Coccoid bacteria primarily reacted to directional changes in shear rates with changes in either surface-associated bacterial densities or surface-associated strength independently. A. baumannii and E. faecalis did not change their associated strength, whereas S. aureus did not change its associated density. Bacillus bacteria demonstrated differences in both associations with directional changes in shear rates. We demonstrate that retention and recovery are different methods of adaptation to environmental conditions utilised by different bacterial species. These adaptations may form the basis of upregulation and downregulation responses used for survival. Full article

Conventional hydrochloric acid (HCl) acidizing in carbonate reservoirs is often limited by excessively rapid acid–rock reactions and preferential flow through high-permeability paths, resulting in shallow penetration and inefficient stimulation. Viscoelastic surfactant (VES)-based diverting acids have been widely applied to address these challenges; however, the intrinsic relationship between reaction retardation and diversion efficiency, particularly under varying shear conditions, remains insufficiently clarified. In this study, a VES-based diverting acid system formulated with erucamidopropyl hydroxysultaine (EH50) was systematically investigated through multiscale experiments, including rotating disk reaction kinetics, rheological characterization, porous core flooding, and fracture-scale plate flow tests. The results reveal a pronounced shear-dependent transition in the governing mechanism of the system. Under low-shear conditions, the VES system significantly reduces the apparent acid–rock reaction rate, with a maximum reduction of 77.3%, and exhibits a synergistic retardation effect in the presence of Ca²⁺, indicating mass transfer limitation. However, under high-shear porous media flow, the intrinsic retarding effect is substantially weakened due to partial disruption of the viscoelastic structure. Despite this attenuation of chemical retardation, effective diversion performance persists under dynamic flow conditions, manifested by pressure plateau behavior, enhanced flow redistribution, more distributed wormhole networks, and greater overall dissolution. Fracture-scale experiments further demonstrate that the diversion acid suppresses excessive inlet etching and promotes spatially distributed etching patterns favorable for fracture conductivity maintenance. These findings clarify that reaction retardation and diversion are distinct yet dynamically coupled mechanisms, whose relative dominance depends on shear intensity and ionic environment. The proposed shear-responsive mechanism framework provides new insight into the design and optimization of VES diverting acid systems for carbonate reservoir stimulation. Full article

While anisotropic extrudate swell in polymer processing is fundamentally driven by physical viscoelastic recovery, this paper proposes a theoretical framework to explicitly isolate and map the purely geometric and kinematic components of this phenomenon. Serving as a mathematical proof-of-concept, a multi-velocity-centre hypothesis is proposed. By introducing a semi-empirical, lumped material-flow calibration parameter, the macroscopic diameter swell ratio is mathematically extended to the discrete local flow field of a rectangular slit die. To evaluate its validity, the analytical framework is subjected to a numerical test for kinematic consistency utilizing isothermal, inelastic power-law fluid CFD simulations, thereby separating geometric mapping from complex viscoelastic stress relaxation. Results indicate that analytical predictions show good agreement with CFD data (error < 5%) strictly within the core zone of high-aspect-ratio dies. However, due to the infinite-slit assumption, 3D flow kinematics near die edges induce velocity decay, leading to local deviations that require future empirical corrections. Although comprehensive physical extrusion experiments and non-isothermal viscoelastic coupling are required for industrial deployment, this semi-empirical kinematic mapping provides a foundational mathematical basis that could potentially inform future inverse die-profile design and shape distortion compensation. Full article

This paper deals with a boundary control problem for the Darcy–Brinkman–Jeffreys system describing 3D (or 2D) steady-state flows of an incompressible viscoelastic fluid through a porous medium. Applying the elliptic regularization method and arguments from the topological degree theory, we prove a theorem about the weak solvability of the corresponding boundary value problem under an inhomogeneous Dirichlet boundary condition. Using this theorem, we obtain sufficient conditions for the existence of optimal weak solutions minimizing a given cost function. Moreover, it is shown that the set of all optimal weak solutions is bounded and sequentially weakly closed in an appropriate function space. Full article

The mechanisms driving the uplift and outward expansion of the Tibetan Plateau remain debated. The Qinghai Lake region at the plateau front, characterized by pronounced basin–range differential uplift, provides a key natural laboratory. Here, we first predict vertical deformation induced by the horizontal GPS velocity field and then construct a three-dimensional (3D) viscoelastic finite-element model to evaluate how lithospheric rheology shapes present-day 3D deformation. Horizontal GPS velocities predict higher uplift in the Songpan–Ganzi Terrane and the Qilian Orogen and lower values in the intervening basins, capturing the first-order basin–range pattern; the predicted uplift in the Qilian Orogen is ~1.0 mm/yr and agrees with observations, indicating that its dominant mechanism is crustal shortening and thickening. However, horizontal constraints alone leave vertical-velocity residuals of ~0.8–1.5 mm/yr in several localized areas, including the West Qinling Orogen, the southern Elashan region, the Qinghai–Nanshan region, and areas south of the Lenglongling Fault. Lateral rheological heterogeneity in the mid–lower crust, acting under mantle-flow drag, can better account for these residuals and more accurately reproduce the present 3D velocity field in the basin–range system. We further propose northeastward mid–lower crustal flow along a weak channel; when the flow is impeded by rigid domains (e.g., the Gonghe Basin and the Qinghai Lake Basin), it promotes material accumulation and localized deformation. These results support a hybrid mechanism that combines crustal shortening and mid–lower crustal flow for the Qinghai Lake basin–range system. Full article

Concentrated solutions of polycarbosilane (PCS) are critically important for the development of continuous SiC precursor fibers, where solvent–polymer interactions govern rheology, viscoelastic stability, and spinnability. In this work, PCS solutions in two nonpolar hydrocarbon solvents with different molecular architectures as linear n-heptadecane and bicyclic decalin were systematically investigated over a wide concentration range, with emphasis on the semi-dilute entangled and concentrated regimes relevant to solution-based fiber spinning. A combined experimental approach involving steady and oscillatory rheometry and Fourier transform infrared (FTIR) spectroscopy was used to elucidate the influence of solvent structure on solvation, viscoelastic response, microstructural organization, and local intermolecular interactions. Despite similar dilute-solution interaction parameters, the concentrated regimes exhibit pronounced solvent-dependent differences in elasticity and flow behavior. For the first time, linear heptadecane is identified as a viable and technologically promising solvent for PCS, enabling the formation of thermostable homogeneous concentrated solutions with enhanced deformability. This behavior opens a realistic pathway toward a new solution-based fiber-spinning route based on elasticity-controlled processing. The results demonstrate that solvent molecular geometry governs the structure–rheology–processability relationship of concentrated PCS systems rather than solubility parameters alone, providing a new framework for solvent selection in SiC precursor fiber technologies. Full article

To address the lack of systematic comparison regarding rheological properties and the unclear structure–property relationships among three core fracturing fluid materials including synthetic polymers, vegetable gums, and microbial polysaccharides, this study selected acrylamide-based polymers, hydroxypropyl guar gum and xanthan gum as the representative systems. The steady-state viscosity, rheological curves, thixotropy, viscoelasticity, and temperature-shear resistance of the three samples were systematically characterized at concentrations ranging from 0.1 to 0.7 wt% using an MCR301 rotational rheometer. The outcomes indicate that the structural strength values of all three materials increase with rising concentration, but their rheological behaviors and stability differ significantly due to distinct molecular structures. The acrylamide-based copolymer forms a temporary network via weak hydrogen bonds (amide-carboxyl or amide-amide) and physical entanglements, exhibiting thixotropy and a stress pre-elastic response. The most significant effects occur at 0.7 wt%, with a thixotropic loop area of 2.874 Pa·s⁻¹ and a stress overshoot of 4.97 Pa.; hydroxypropyl guar gum has insufficient thermal stability and poor heat resistance. Its viscosity retention rate is as low as 31%, and it always exhibits a solution-type rheological property of G′ < G″; the xanthan gum exhibits elastic gel properties with tanδ < 1 due to its double-helix molecular structure. It has excellent temperature shear tolerance and the viscosity retention value can reach up to 98.6 mPa·s. Two mathematical models were established and demonstrated strong applicability: a modified Carreau model for flow curve fitting yielded a coefficient of determination (R²) greater than 0.95, enabling accurate description of fluid-type transitions; a four-parameter equation for temperature–shear resistance curves also achieved an R² above 0.95, effectively characterizing viscosity evolution with temperature. Full article

Tight conglomerate reservoirs exhibit strong pore-scale heterogeneity and extremely low permeability, in which spontaneous imbibition is primarily governed by capillary and viscoelastic effects. In this study, the imbibition dynamics of four representative fracturing fluid systems, including slickwater, 3% potassium chloride (KCl) brine, hydrolyzed polyacrylamide (HPAM) viscoelastic fluid, and a nanoemulsion (NE), were investigated using a temperature-controlled nuclear magnetic resonance (NMR) monitoring system. This approach enables real-time quantification of fluid uptake and pore-scale redistribution through time-resolved T₂ spectral analysis. The experimental results reveal a three-stage imbibition process consisting of rapid capillary-driven uptake, viscoelastic-retarded transition, and final equilibrium. Among the four fracturing fluid systems, the nanoemulsion exhibits the lowest interfacial tension (1.72 mN/m), the strongest wettability alteration, and the highest equilibrium recovery (0.76), which is nearly 80% greater than that of slickwater. Based on these observations, a multiscale capillary–viscoelastic coupling model was developed by extending the Lucas–Washburn framework to incorporate pore-size distribution, time-dependent wettability evolution, and viscoelastic damping. The model fits the experimental data well (R² > 0.90) and identifies viscosity as the most influential parameter controlling the imbibition rate (sensitivity = 0.78). Energy analysis further indicates that capillary energy dominates the early stage, whereas viscoelastic energy storage sustains fluid transport during the later stage. SEM observations were further used to qualitatively corroborate pore heterogeneity and pore–mineral associations, supporting the NMR-based pore-scale interpretation. This study provides a quantitative framework for describing non-Newtonian capillary flow in tight conglomerate rocks and enhances the understanding of capillary–viscoelastic interactions relevant to multiphase fluid migration. Full article

This research focused on the systematic engineering of processing parameters to obtain novel hydrocolloids from cassava (Manihot esculenta), specifically investigating how extraction pH controls their functional and physicochemical properties. Hydrocolloids were obtained across a range of pH conditions, followed by rigorous analysis of their chemical composition, flow behavior, viscoelasticity, and technological capacity, including water and oil holding capacity (WHC and OHC). The study established that hydrocolloids yield can be decoupled from extreme pH constraints, as high yields were successfully attained in both acidic and alkaline environments, thereby identifying a critical and flexible processing window for scalable production. Compositionally, the extracts confirmed their potential as functional additives due to a high carbohydrate content and minimal fat. Crucially, the extracted hydrocolloids exhibited strong structural performance, displaying high water and oil retention capacity—metrics essential for emulsion stability and shelf life—while consistently confirming desirable shear-thinning behavior across all effective extraction conditions. In conclusion, these results demonstrate that hydrocolloids derived from cassava are versatile stabilizers whose robust structural performance is maintained across varying processing pH levels, positioning them as promising, cost-effective alternatives for developing resilient, stable food matrices. Full article

The development of photocurable hydrogel biomaterial inks with suitable rheology, low cytotoxicity, and tuneable mechanical properties is essential for reliable biofabrication. This study aimed to formulate PEGDA–gelatine–collagen inks using lithium phenyl-2,4,6-trimethylbenzoylphosphinate (LAP) as photoinitiator. Rheological characterisation and flow-model fitting were performed, mechanical stiffness modulation under different light intensities was evaluated, complex structures were printed using direct extrusion and FRESH methodologies, and PEGDA/LAP extractables were quantified by NMR after controlled washing procedures. In vitro assays assessed cell viability and proliferation on the resulting scaffolds. The Herschel–Bulkley model best described the flow behaviour across formulations; while viscoelastic measurements showed that increasing light intensity progressively enhanced hydrogel stiffness, enabling fine control over final mechanical properties. NMR analysis showed that washing removed a substantial fraction of residual LAP, in agreement with the biological findings: fibroblasts failed to survive on unwashed scaffolds but exhibited robust proliferation and recovered their characteristic elongated morphology on washed constructs. Among all inks, PeGeCol_10_2 provided the best combination of shear-thinning behaviour, structural integrity, low residual photoinitiator, and tuneable mechanics. Using this formulation, we successfully printed large anatomical models with high fidelity and excellent handling properties, underscoring its potential for soft-tissue prosthetics and broader tissue-engineering applications. Full article

Enhanced oil recovery (EOR) in fractured reservoirs presents significant challenges due to fluid channeling and poor sweep efficiency. In this study, a synergistic EOR system was developed with polymer-based weak gel as the primary component and foam as the auxiliary enhancer. The system utilizes a low-concentration polymer (1000 mg·L⁻¹) that forms a weakly cross-linked three-dimensional viscoelastic gel network in the aqueous phase, inheriting the core functions of viscosity enhancement and profile control from polymer flooding. Foam acts as an auxiliary component, leveraging the high sweep efficiency and strong displacement capability of gas in fractures. These two components synergistically create a multiscale enhancement mechanism of “bulk-phase stability control and interfacial-driven displacement.” Systematic screening of seven foaming agents identified an optimal formulation of 0.5% SDS and 1000 mg·L⁻¹ polymer. Two-dimensional visual flow experiments demonstrated that the polymer-induced gel network significantly improves mobility control and sweep efficiency under various injection volumes (0.1–0.7 PV) and gravity segregation conditions. Numerical simulation in a 3D fractured network model confirmed the superiority of this enhanced system, achieving a final oil recovery rate of 75%, significantly outperforming gas flooding (65%) and water flooding (59%). These findings confirm that weakly cross-linked polymer gels serve as the principal EOR material, with foam providing complementary reinforcement, offering robust conformance control and enhanced recovery potential in fracture-dominated reservoirs. Full article

Mechano-Organ-on-Chip (Mechano-OoC) platforms are emerging as powerful microphysiological systems that place mechanical cues at the center of tumor modeling, providing a scalable and human-relevant approach to recapitulate the biophysical complexity of the tumor microenvironment. Mechanical factors such as matrix stiffness, viscoelasticity, solid stress, interstitial flow, confinement, and shear critically regulate cancer progression, metastasis, immune interactions, and treatment response, yet remain poorly captured by conventional in vitro models and are often studied separately in tumor-on-chip and mechanobiology research. In this review, we summarize recent advances in mechano-OoC technologies for cancer research, highlighting strategies that integrate engineered mechanical cues with microfluidics, tunable extracellular matrices, vascular and stromal interfaces, and dynamic loading to model tumor invasion, vascular transport, immune trafficking, and drug delivery. We also discuss emerging approaches for real-time, multimodal readouts, including sensor-integrated platforms and artificial intelligence-assisted data analysis, and outline key challenges that limit translation, such as device complexity, limited throughput, insufficient standardization, and inadequate validation against in vivo and clinical data. By organizing progress across platform engineering, sensing and readout, data standardization, and AI-driven analytics, this review provides a unified framework for advancing mechanobiology-aware tumor models and guiding the development of predictive preclinical platforms for precision cancer therapy. Full article

The flow behavior of fluids can be characterized by rheology and is especially used in the field of polymeric materials. This study focused on characterizing cerebrospinal fluid (CSF) of patients who developed hydrocephalus after subarachnoid hemorrhage (SAH) with rheology. Samples were drawn from an external ventricular drainage (EVD) at four pre-defined time points after the initial hemorrhage. The CSF samples were analyzed using a rotational rheometer with a double gap geometry. In addition to the characterization of viscoelastic parameters, the cumulative storage factor was calculated to determine the interactions in the fluid. In order to investigate the temperature dependence of the CSF properties, the oscillatory measurements were implemented at certain temperatures that simulated specific conditions, such as 5 °C, at which temperature the CSF samples were stored; 35 °C for hypothermic conditions; 37 °C for physiologic conditions; and 40 °C for elevated body temperature. The overall goal was to evaluate whether rheology-based parameters may help in the prediction of shunt dependence for post-hemorrhagic hydrocephalus patients. For this aim, rheological parameters were correlated to certain laboratory parameters, such as erythrocyte and leukocyte count, glucose, lactate, and total protein concentration. Full article