Shear-thinning Behavior Research Articles

Simvastatin-loaded gelatin-capped polycaprolactone nanoparticles for the post-operative management of breast cancer

Minimal residual disease at the tumor site after surgical ablation is a major cause for tumor recurrence and metastasis. The tropism of circulating tumor cells towards injured areas increases the risk of tumor recurrence. Recent studies have reported the inability of nanocarriers to penetrate the tumor site owing to short systemic half-life, high hydrostatic pressure, and inability to extravasate the tumor tissue. In this work, we developed simvastatin-loaded polycaprolactone - gelatin core-shell nanoparticles (SNP) for post-surgical management of breast cancer (BC). NP-loaded within the hyaluronic acid solution demonstrated shear thinning behavior (n = 0.3089). SNP demonstrated cytotoxic potential in the 2-D cell culture and 3-D tumoroids of MDA-MB-231 cell line in vitro. JC-1 and rhodamine-123 based assays demonstrated the ability of SNP to induce mitochondrial membrane damage. Further, cell cycle analysis revealed that the SNP prevented the progression of cell line from G0/G1 to S-phase. Simvastatin and SNP induced early apoptosis in the MDA-MB-231 cell line. Scratch, invasion, migration, and clonogenic assays demonstrated the ability of SNP to prevent cell invasion and clonal expansion. Immunocytochemistry revealed that both SIM and SNP reduced the expression of anti-apoptotic protein BCL-2 in metastatic cell line. Overall, the developed formulation demonstrates enormous potential for the post-surgery management of BC.

Overview of 37 Tear Substitutes in Europe Based on Various Physicochemical Parameters.

Dry eye disease (DED) is one of the most prevalent eye conditions worldwide, with artificial tears serving as a primary treatment option. Despite their wide availability on the European market, there is a lack of established classifications based on their physicochemical properties. The aim of our study was therefore (i) to develop an analytical method that measures the concentration and the molecular weight (MW) of the hyaluronic acid (HA) in commercialized products, and (ii) to propose an overview based on their various physicochemical parameters. The intrinsic viscosity and MW of the HA, as well as osmolarity, pH, rheological profile, and viscosity, were measured or determined. A specific method was developed to measure the average intrinsic viscosity and HA content using a liquid size-exclusion chromatography system. The MW was determined using the Mark-Houwink equation. Thirty-seven products commercialized in Europe were analyzed, with 21 of them containing HA. The HA MW was lowest (300kDa) for Thealose®, Thealoz Duo® Gel, and Hyabak®, and highest (1300kDa) for Vismed® Multi, Vismed® Gel, and Neovis® Gel. The pH values varied between 5.94 for Treovis® and 8.06 for Systane® Ultra. Osmolarity ranged between 148 mOsm/L and 325 mOsm/L for Neovis® and Treovis®, respectively. Viscosity was highly variable, ranging from 0.38 mPas·s for Hylolipid® to 337.47 mPas·s for Thealoz® Duo Gel. Finally, rheological profile analysis revealed different shear-thinning behaviors. While the perfect eye drop does not exist, a multitude of options are available to choose from. This study improves our understanding of the major tear substitutes available on the European market based on several physicochemical properties. A better understanding and awareness of these parameters is crucial in order to offer the best treatment for patients with DED.

Effect of chitosan and its derivatives on food processing properties of potato starch gel: Based on molecular interactions

Potato starch gel foods are appreciated for their distinctive taste; however, they face challenges such as high paste viscosity, susceptibility to aging, and poor cold-storage stability, limiting their industrial production. This study aimed to enhance potato starch characteristics by investigating the effects of alum, chitosan, carboxymethyl chitosan, and quaternized chitosan on its pasting, rheological, and textural properties. Results revealed that the addition of 1% chitosan, carboxymethyl chitosan, and quaternized chitosan significantly reduced the gelatinization viscosity of potato starch. Moreover, the addition of alum or chitosan provided better shear resistance and reduced shear-thinning behavior. The potato starch gel prepared with chitosan was harder than that prepared with alum. These findings highlight the influential roles of alum, chitosan, and their derivatives in potato starch and provide a theoretical foundation for their application in potato starch gel foods.

Unravelling the physicochemical features of allulose and kestose as sugar alternatives in chemically-leavened baked goods

The feasibility of two natural sweeteners (allulose and kestose) as sugar alternatives was evaluated in chemically-leavened baked products. Sucrose in muffins was replaced with allulose and kestose at two different levels (50 and 100 g/100 g) and their effects on the quality attributes of muffins were characterized primarily in terms of physical, rheological, tomographical, and sensory features. Regardless of the sweeteners, shear-thinning behaviors were clearly observed in the muffin batters. However, the batter samples with allulose showed relatively lower viscosity and less shear-thinning. The use of allulose raised the viscoelastic properties of the batters at temperatures higher than 70 °C, while the kestose batter showed a similar viscoelastic pattern to the sucrose sample. Kestose behaved similarly to sucrose in terms of browning, while allulose significantly contributed to the browning reaction during the baking process. The use of kestose for sucrose positively impacted the expansion of muffins and resulted in a softer texture. Furthermore, tomographical analysis revealed that, unlike allulose, the replacement of sucrose with kestose produced muffins with higher total porosity and larger pore size distribution. When half of the sucrose was replaced with kestose, similar sensory properties, except for sweetness, were distinctly observed.

Micromixing efficiency and enhancement methods for non-Newtonian fluids in millimeter channel reactors

Micromixing efficiency and enhancement methods for non-Newtonian fluids in millimeter channel reactors

Direct ink writing of WC-Co composite with flexible green bodies

Direct ink writing of 3D WC-Co with conformable green bodies was achieved benefiting from the highly flexible WC-Co paste with high solid loading. Rheology properties of the paste, microstructure of the 3D structure was investigated. Organic-based paste of WC-8Co with a high solid content of 91 wt% were prepared, which exhibited shear thinning behavior and had a high storage modulus, two key parameters for ensuring the smooth printing. After secondary molding, 3D WC-Co green bodies with overhanging structure and no cracks were confirmed through secondary treatment of twisting or bending. Sound 3D structures with uniform and dense microstructure were obtained after debinding and sintering in vacuum. This work showed a facile route for the fabrication of 3D bone cemented carbides by direct ink writing with flexible green bodies.

BEAD SIZE AND RHEOLOGICAL PROPERTIES OF SEBS-BASED ELASTIC BEADS

ABSTRACT Styrene–ethylene–butylene–styrene (SEBS) is a thermoplastic elastomer that has applications in robotics and shock absorption. Although SEBS as a bulk material as well as an additive to solid composites has been extensively studied, this work focuses on developing SEBS-based beads to enhance material elasticity. SEBS bead mixtures were developed by mixing SEBS elastomer, water, and surfactant (Triton X-100) at high temperature. Stability, rheology, and microscopy of SEBS bead mixtures were studied as a function of neat SEBS concentration in SEBS elastomer, SEBS elastomer concentration, and surfactant concentration. Resulting bead mixtures were classified as creamed, homogenous and stable, or aggregated based on the mixture’s tendency to separate into layers and its ability to disperse in excess water. Microscopic studies suggest that although bead mixtures exhibit size polydispersity, the average bead size is a strong function of neat SEBS, SEBS elastomer, and surfactant concentrations. Rheological studies suggest that all the bead mixtures exhibit shear thinning behavior, and the overall viscosity of a given bead mixture is a function of both SEBS elastomer and surfactant concentration. The developed SEBS elastic beads can be used as additives to enhance the viscoelastic properties of fluid-based systems such as magnetorheological and damping fluids.

Microstructure and mechanical property of high-density 7075 Al alloy by compression molding of POM-based feedstock

Metal injection molding of aluminium alloy (MIM-Al) attracts attention, owing to the lightweight, corrosion resistance and good thermal conductivity. However, it is hard to fabricate high-quality MIM-Al due to the hard-to-sinter powder and poor mechanical properties. Here, we report a facile compression molding process for fabricating high-density 7075Al alloy parts using polyformaldehyde (POM)-based feedstock. Pressureless sintering with a high nitrogen flow rate was adopted to promote sintering densification process. The wetting behavior, rheological properties, and morphology of the feedstock were characterized, showcasing the shear-thinning behavior and suitable viscosity for POM-PP-SA binder. Through controlling the compact pressure, mold temperature and holding time, green gear part with good shape retention and dense microstructure was achieved. Influence of process factors and sintering temperature on the microstructure and mechanical properties of 7075Al alloy are investigated. Remarkably, the aluminum alloy components sintered at 610 °C exhibited excellent performance, with a relative density reaching 97.6 % and a tensile strength of 214.8 MPa. This achievement provides a foundation for the industrial application of complex-shaped aluminum alloy components through the compression molding process.

Comparative analysis of carrageenan/ovalbumin and carrageenan oligosaccharide/ovalbumin complexes

The saccharides ι-carrageenan (ι-CG) and ι-carrageenan oligosaccharides (ι-CO) exhibit different molecular chain lengths and charge intensities, which are pivotal determinants of their interactions with ovalbumin (OVA). This study investigated the interaction mechanisms between OVA and ι-CG as well as between OVA and ι-CO using experimental methods and molecular docking. The results of zeta potential showed that the strongest electrostatic interaction occurred at an OVA/ι-CG ratio of 100:13 (−1.59 ± 0.41 mV) and an OVA/ι-CO ratio of 100:10 (−1.32 ± 0.30 mV). The OVA/ι-CG complexes showed higher turbidity (1.63 ± 0.08 cm−1). Furthermore, Fourier transform infrared spectroscopy showed that ι-CG significantly altered the secondary structure of OVA, whereas ι-CO did not affect it. Fluorescence spectroscopy also verified the interactions in the OVA/ι-CG and OVA/ι-CO complexes. Both complexes exhibited shear-thinning behaviour; the largest storage modulus (G′) and loss modulus (G″) were observed at 100:13 and 100:10 ratios for OVA/ι-CG OVA/ι-CO samples, respectively. ι-CG induced OVA to form more loosely clumped aggregates, whereas OVA and ι-CO formed compact granular aggregates when observed using confocal scanning laser microscopy. Molecular docking results showed that more salt bridges were formed between ι-CG and OVA than between ι-CO and OVA. A schematic model was established to elucidate the effects of ι-CG and ι-CO on OVA. This study provides instructions for designing innovative food systems based on different charge intensities and chain lengths of saccharides.

Development of a highly loaded zirconium carbide paste for material extrusion additive manufacturing

A highly loaded, aqueous-based zirconium carbide (ZrC) paste was developed for ceramic on-demand extrusion (CODE). Commercial ZrC powder was ball milled to reduce the particle size to ∼1 μm. Paste composition was determined by rheological characterization and observation of printing behavior; the final paste consisted of 46–47 vol% ZrC, 43.5 vol% distilled water, 8.1 vol% dispersant, and 1.6 vol% binder. Rheological characterization of the paste showed a yield stress of ∼8 Pa and shear thinning behavior (ΔG′/Δσ* = −55). The paste was printed using a 610 μm nozzle; a test print showed shape fidelity using the developed paste. A pressureless sintering study was performed; a sintering temperature of 2000°C with a 2-hour hold produced samples of 90 % relative density with 3.8 μm grains, which was consistent with literature. The developed paste, in combination with the pressureless densification results, adds a new, ultra-high temperature material to ceramic extrusion additive manufacturing.

Exploring the potential of browntop millet (Urochloa ramosa) starch: Physicochemical, morphological, thermal and rheological properties across four cultivars

This comprehensive research explores the starch isolated from four browntop millet cultivars to determine physicochemical, thermal, morphological, powder flow, pasting, and rheological properties. Significant variations (p ≤ 0.05) were observed among the cultivars. Aerated bulk density (ABD) and Tapped bulk density (TBD) values ranged from 0.476 g/mL (BTM4) to 0.591 g/mL (BTM1), and 0.591 g/mL (BTM1) to 0.476 g/mL (BTM4). Amylose content varied from 22.55% (BTM4) to 25.86% (BTM3), influencing gelling strength and film-forming properties. Water absorption capacity ranged from 1.78 g/g to 1.92 g/g, while oil absorption capacity varied from 2.20 g/g to 2.47 g/g. DSC analysis showed gelatinization temperatures (Tp, and Tc) ranging from 85.44–91.61 °C, and 147.08–154.21 °C, respectively. X-ray diffraction (XRD) patterns revealed A-type crystalline patterns, with relative crystallinity ranging from 22.66% (BTM3) to 27.81% (BTM2). Pasting properties exhibited variations among cultivars, with peak viscosity ranging from 2480 c P to 3119 cP, and pasting temperature from 77.50 °C to 82.35 °C. Rheological analysis indicated shear-thinning behavior. The findings offer insights into the diverse properties of browntop millet starch, contributing to its potential applications in various industries and potentially guiding future studies on browntop millet starch modifications and novel utilization.

Rheological and tribological properties of xanthan gum-fucoidan mixture: Effect of NaCl, KCl, and CaCl2

This study endeavored to investigate the effects of salts (NaCl, KCl, and CaCl2) on the rheological and tribological properties of xanthan gum (XG)-fucoidan mixtures. With increasing salt concentrations, the intrinsic viscosity (56.1–30.9 dL/g) of mixtures decreased, with pronouncedly lower values (30.9–35.8 dL/g) observed with CaCl2 addition compared to monovalent salts addition (36.4–46.6 dL/g). This indicates a contraction of hydrodynamic size of the polymers due to the charge screening effect of cations and the formation of a more compact conformation in the presence of CaCl2 than with either NaCl or KCl addition. FTIR analysis revealed changes in the interaction between the two polymers in the presence of each salt. All samples exhibited shear-thinning behavior, and their thixotropic behavior increased as the salt concentration increased. The apparent viscosity and viscoelastic moduli decreased in the presence of monovalent salts but were increased in the presence of CaCl2. This was attributed to the crosslinking effect of Ca2+; Na+ and K+ did not induce crosslinking. In addition, the friction coefficient (μ) of mixtures containing salts reached the maximum at a lower entrainment speed (0.08–0.17 mm·s−1) than that without salt (1.54 mm·s−1), and the mixtures containing salts exhibited lower maximum μ values (0.28–0.62) compared to that without salt (0.83), indicating an improvement in the lubricant properties of XG-fucoidan mixtures. Our findings may help broaden the application of fucoidan in the food industry.

Development of Oleogel-in-Water High Internal Phase Emulsions with Improved Physicochemical Stability and Their Application in Mayonnaise.

Egg-free mayonnaise is receiving greater attention due to its potential health benefits. This study used whey protein isolate (WPI) as an emulsifier to develop high internal phase emulsions (HIPEs) based on beeswax (BW) oleogels through a simple one-step method. The effects of WPI, NaCl and sucrose on the physicochemical properties of HIPEs were investigated. A novel simulated mayonnaise was then prepared and characterized. Microstructural observation revealed that WPI enveloped oil droplets at the interface, forming a typical O/W emulsion. Increase in WPI content led to significantly enhanced stability of HIPEs, and HIPEs with 5% WPI had the smallest particle size (11.9 ± 0.18 μm). With the increase in NaCl concentration, particle size was increased and ζ-potential was decreased. Higher sucrose content led to reduced particle size and ζ-potential, and slightly improved stability. Rheological tests indicated solid-like properties and shear-thinning behaviors in all HIPEs. The addition of WPI and sucrose improved the structures and viscosity of HIPEs. Simulated mayonnaises (WE-0.3%, WE-1% and YE) were then prepared based on the above HIPEs. Compared to commercial mayonnaises, the mayonnaises based on HIPEs exhibited higher viscoelastic modulus and similar tribological characteristics, indicating the potential application feasibility of oleogel-based HIPEs in mayonnaise. These findings provided insights into the development of novel and healthier mayonnaise alternatives.

Rheological Behavior of SiO2 Ceramic Slurry in Stereolithography and Its Prediction Model Based on POA-DELM.

Ceramic slurry is the raw material used in stereolithography, and its performance determines the printing quality. Rheological behavior, one of the most important physical factors in stereolithography, is critical in ceramic printing, significantly affecting the flow, spreading, and printing processes. The rheological behavior of SiO2 slurry used in stereolithography technology is investigated in the current research using different powder diameters and temperatures. The results present the apparent non-Newtonian behavior. The yielding characteristics occur in all cases. For single-powder cases, the viscosity decreases when the powder diameter is increased. When the nano-sized and micro-sized powders are mixed in different proportions, a more significant proportion of micron-sized powders will decrease the viscosity. With an increase in the nano-sized powders, the slurry exhibits the shear thinning behavior; otherwise, the shear thickening behavior is observed. Thus, the prediction model is built based on the use of the pelican optimization algorithm-deep extreme learning machine (POA-DELM), and the model in then compared with the fitted and traditional models to validate the effectiveness of the method. A more accurate viscosity prediction model will contribute to better fluid dynamic simulation in future work.

Structure-property correlations study in biochar-enhanced polyamide composites for sustainable materials development

This study explores the synthesis and characterization of polyamide/biochar composites via in situ polymerization of 12-aminolauric acid with varying biochar concentrations. The motivation behind this research is to enhance the properties of polyamide 12 (PA12) by integrating biochar, a sustainable material derived from biomass, to improve both performance and environmental impact. A detailed structure-property correlation analysis was conducted to assess the effects of biochar on PA12's morphology, mechanical behavior, crystallinity, thermal stability, viscoelastic performance, and environmental sustainability. Key findings include successful PA12 synthesis, confirmed by FTIR and 1H NMR spectroscopy. Increased biochar content led to a decrease in molecular weight and an increase in crystallinity from 27 % to 38 %, suggesting enhanced nucleation effects. SEM analysis showed excellent dispersion and compatibility of biochar within the PA12 matrix, leading to significant improvements in tensile strength (from 38 ± 1 MPa to 54 ± 2 MPa) and modulus (from 745 ± 30 MPa to 2055 ± 65 MPa). Rheological tests demonstrated shear-thinning behavior, facilitating effective extrusion-based 3D printing of a complex object with 50 wt% biochar. A life cycle assessment revealed substantial environmental benefits, including a net reduction of 1.83 kg·CO₂ equiv.·kg⁻1 due to the use of biochar derived from wood pyrolysis. These findings highlight the potential of PA12/biochar composites as environmentally sustainable structural materials, combining enhanced functional properties with significant ecological advantages.

Rheological behavior analysis of emulsified cutback composite cold-mixed epoxy asphalt binder based on apparent viscosity

In this paper, a composite cold-mixed epoxy asphalt binder (CCEAB) is made using diluted epoxy resin (DER) and cold-mixed solvent (CMS). The rheological behavior of CCEAB is analyzed by rotary viscosimeter at different temperatures, curing times, shear rates, DER and CMS contents. The fluid type of the CCEAB is identified, and its flow curve is modeled. The parallel phenomenon of apparent viscosity curves is revealed, and the shift factor is analyzed. The results showed that temperature, CMS content and shear rate are negatively correlated with viscosity, while time and DER content are positively correlated with it. CCEAB has typical shear thinning behavior and is a pseudoplastic fluid without yield stress. When the shear rate is greater than 18.6 s−1, the viscosity curves trend stable, and the final viscosity is about 60 % of the initial viscosity. The 5 variables have been added to the power law model to establish the flow curve of CCEAB, whose parameters are identified by the generalized inverse matrix. The parallel of viscosity curves follows the time-temperature superposition, and the shift factor function with 4 variables describes the conversion of viscosity curves. The flow curve of CCEAB has the same form and essence as the shift factor function, meaning the flow curve also describes the parallel. If the shift factor is regarded as a viscosity prediction method, it is not as accurate as the flow curve.

Origins of complexity in the rheology of Soft Earth suspensions

When wet soil becomes fully saturated by intense rainfall, or is shaken by an earthquake, it may fluidize catastrophically. Sand-rich slurries are treated as granular suspensions, where the failure is related to an unjamming transition, and friction is controlled by particle concentration and pore pressure. Mud flows are modeled as gels, where yielding and shear-thinning behaviors arise from inter-particle attraction and clustering. Here we show that the full range of complex flow behaviors previously reported for natural debris flows can be reproduced with three ingredients: water, silica sand, and kaolin clay. Going from sand-rich to clay-rich suspensions, we observe continuous transition from brittle (Coulomb-like) to ductile (plastic) yielding. We propose a general constitutive relation for soil suspensions, with a particle rearrangement time that is controlled by yield stress and jamming distance. Our experimental results are supported by models for amorphous solids, suggesting that the paradigm of non-equilibrium phase transitions can help us understand and predict the complex behaviors of Soft Earth suspensions.

Cardamom Pickering emulsions stabilized by cellulose nanostructures as disinfection agents against bacteria and SARS-CoV-2

This study introduces a new disinfectant agent utilizing cardamom essential oil stabilized by cellulose nanomaterials (CN). The Pickering emulsion technique prevented oil degradation and extended its storage duration. Cellulose nanocrystals (CNC) or cellulose nanofibers (CNF) were utilized as stabilizers, and the emulsions were evaluated for surface tension, rheology, morphology, antimicrobial and antiviral activity against S. enterica, S. aureus, P. aeruginosa, E. coli, and SARS-CoV-2. Surface tension measurements indicated an electrostatic stabilization mechanism in CNC emulsions, exhibiting fluid behavior confirmed by rheological tests. On the other hand, CNF emulsions displayed drop packaging, characteristic of shear-thinning behavior, as confirmed by the Ostwald-de-Waele model. The emulsions exhibited antibacterial activity against S. aureus and P. aeruginosa, particularly the CNC samples, suggesting that nanocellulose alters the regulation of oil migration into the medium. Testing against SARS-CoV-2 revealed that cardamom essential oil required 30 min of contact for viral protein denaturation, while CNC and CNF emulsions took 60 and 50 min, respectively. This indicates that CN acts as an encapsulating agent, prolonging the oil’s release time and necessitating longer contact periods with the virus. These findings demonstrate the potential of these emulsions in developing new antimicrobial and antiviral products.

Exploring exudate viscosity: A rheological analysis of wound exudates.

Exudate and its viscosity are critical in wound healing. Changes in viscosity can interfere with dressings properties as well as affect the diffusion of immune cells, nutrients, oxygen and bacteria. Current international standards for laboratory testing of wound dressings use a single low-viscosity solution, named as 'Test Solution A', which fails to simulate the diverse range of exudates encountered clinically. This study employs rheological analysis to characterise exudates viscosity, comparing cattle-derived samples to the test solution A. Results reveal non-Newtonian, shear-thinning behaviour in exudates, contrasting with the Newtonian behaviour of the test solution A. Although clinically classified as 'seropurulent', three exudate samples analysed at 37°C present with different viscosity at various shear rates, ranging from 30.8 (±14.7) to 6.5 (±1.9) mPas. Findings show that the current tests on dressings employing Test Solution A are missing the complexity of real exudates.

The rheological behavior of aqueous magnetic fluids over a wide range of shear rates

Abstract A rheological measurement system was constructed to investigate the rheological behavior of magnetic fluids under a wide range of shear rates, and its feasibility was verified. The system is capable of measuring a shear rate range spanning five orders of magnitude, with a maximum shear rate of 106 s−1. It was utilized to study the time required for aqueous magnetic fluids in a magnetic field to reach a steady state, taking into account the coupling effect of the flow field and magnetic field. Additionally, the time needed for the magnetic fluids to return to their initial state after demagnetization was also measured. Based on these measurements, the rheological behavior of magnetic fluids with varying concentrations and magnetic field directions was studied. Results indicate that the residence time of the magnetic fluids in the magnetic field and the de-magnetization time have almost no effect on their viscosity. When the magnetic field direction is perpendicular to the flow direction, regardless of concentration, aqueous magnetic fluids exhibit shear thinning behavior; when it is parallel to the flow direction, high-concentration aqueous magnetic fluids show shear thickening, while low-concentration ones behave as Newtonian fluids. In this study’s shear rate range, no Newtonian regions were found in either high- or low-shear rate regions.