Is Low Polydispersity Always Beneficial? Exploring the Impact of Size Polydispersity on the Microstructure and Rheological Properties of Graphene Oxide.

Graphene oxide (GO) is a promising material widely utilized in advanced materials engineering, such as in the development of soft robotics, sensors, and flexible devices. Considering that GOs are often processed using solution-based methods, a comprehensive understanding of the fundamental characteristics of GO in dispersion states becomes crucial given their significant influence on the ultimate properties of the device. GOs inherently exhibit polydispersity in solution, which plays a critical role in determining the mechanical behavior and flowability. However, research in the domain of 2D colloids concerning the effects of GO's polydispersity on its rheological properties and microstructure is relatively scant. Consequently, gaining a comprehensive understanding of how GO's polydispersity affects these critical aspects remains a pressing concern. In this study, we aim to investigate the dispersions and structure of GOs and clarify the effect of polydispersity on the rheological properties and yielding behavior. Using a rheometer, polarized optical microscopy, and small-angle X-ray scattering, we found that higher polydispersity in the same average size leads to overall improved rheological properties and higher flowability during yielding. Thus, our study can be beneficial in the employment of polydispersity in the processing of GO such as 3D printing and fiber spinning.

A bi-component model to assess the rheology of soft cellular aggregates probed using the micropipette aspiration technique.

The micro-pipette aspiration technique is a classical experiment used to characterize the physical properties of inert fluids and biological soft materials such as cellular aggregates. The physical parameters of the fluid, as viscosity and interfacial tension, are obtained by studying how the fluid enters the pipette when the suction pressure is increased and how it relaxes when the suction pressure is put to zero. A mathematical model representative of the experiment is needed to extrapolate the physical parameters of the fluid-like matter; however, for biological materials as cells or cell aggregates these models are always based on strong starting hypotheses that impact the significance of the identified parameters. In this article, starting from the bi-constituent nature of the cell aggregate, we derive a general mathematical model based of a Cahn-Hilliard-Navier-Stokes set of equations. The model is applied to describe quantitatively the aspiration-retraction dynamics of a cell-aggregate into and out of a pipette. We demonstrate the predictive capability of the model and highlight the impact of the assumptions made on the identified parameters by studying two cases: one with a non-wetting condition between the cells and the wall of the pipette (classical assumption in the literature) and the second one, which is more realistic, with a partial wetting condition (contact angle θs = 150°). Furthermore, our results provide a purely physical explanation to the asymmetry between the aspiration and retraction responses which is alternative to the proposed hypothesis of an mechano-responsive alteration of the surface tension of the cell aggregate. STATEMENT OF SIGNIFICANCE: Our study introduces a general mathematical model, based on the Cahn-Hilliard-Navier-Stokes equations, tailored to model micro-pipette aspiration of cell aggregates. The model accounts for the multi-component structure of the cell aggregate and its intrinsic viscoelastic rheology. By challenging prevailing assumptions, particularly regarding perfect non-wetting conditions and the mechano-responsive alteration of cell surface tension, we demonstrate the reliability of the mathematical model and elucidate the mechanisms at play, offering a purely physical explanation for observed asymmetries between the aspiration and retraction stages of the experiment.

Haematococcus pluvialis meets gellan gum: Rheological and thermal exploration of a new resource food and biomedical gel matrix.

The increasing interest in hydrogel matrices and their diverse applications has fueled extensive research. However, single-component gels have a limited adjustable performance range, and multi-component gels raise concerns about biological safety, hindering their widespread use. This study focuses on harnessing high-speed shearing and ultrasound-assisted methods to incorporate active natural Haematococcus pluvialis (HP), creating novel composite hydrogels in conjunction with biological macromolecule gellan gum, and eliminating the need for structural modifications or chemical crosslinking. Rich astaxanthin, proteins, polysaccharides, and other components in HP can fill and promote the formation of a unified functional network. The study aims to explore the potential of HP as a rheology regulator and investigate its impact on the rheological properties of the gels. Various rheological models, including Power-Law, Herschel-Bulkley, and Arrhenius, were employed for comparative analysis. This pioneering report on gellan/HP hydrogels holds significant importance as they exhibit optimized elasticity, thermal stability, enhanced injectability, and self-recovery, making them suitable for a wide range of applications in specialized medical food and biomedicine.

Lateral Assessment of Mucomimetic Hydrogels to Evaluate Correlation between Microscopic and Macroscopic Properties.

A major limitation in the development of mucosal drug delivery systems is the design of in vitro models that accurately reflect in vivo conditions. Traditionally, models seek to mimic characteristics of physiological mucus, often focusing on property-specific trial metrics such as rheological behavior or diffusion of a nanoparticle of interest. Despite the success of these models, translation from in vitro results to in vivo trials is limited. As a result, several authors have called for work to develop standardized testing methodologies and characterize the influence of model properties on drug delivery performance. To this end, a series of trials is performed on 12 mucomimetic hydrogels reproduced from literature. Experiments show that there is no consistent correlation between barrier performance and rheological or microstructural properties of the tested mucomimetic hydrogels. In addition, the permeability of both mucopenetrating and mucoadhesive nanoparticles is assessed, revealing non-obvious variations in barrier properties such as the relative contributions of electrostatic and hydrophobic interactions in different models. These results demonstrate the limitations of predicting mucomimetic behavior with common characterization techniques and highlight the importance of testing barrier performance with multiple nanoparticle formulations.

Novel high-protein dairy product based on fresh white cheese and whey protein isolate.

The aim of the study was to obtain hard cheese similar to the rennet hard cheese starting from the fresh white cheese (low and full-fat). This was accomplished with adding a powdered whey protein isolate to the fresh white cheese and heating. Fresh white cheese was produced from full or skim milk and ground with the whey protein isolate powder. The obtained mixture was heated at different temperatures. The increased heating temperature resulted in a more compact product characterized by higher hardness and elasticity compared with the full-fat product. The product approved by the organoleptic analysis panel was obtained by heating the mixed fat white cheese and the powdered whey protein isolate at 80°C for 30 min. The most significant achievement was to obtain in ca. one hour a product similar to that produced in ca. one year that is the hard rennet cheese. It contained ca. 39% wt/wt of protein and can be an interesting offer for dairy industry.

Structural and property characterization of low-molecular-weight novel reuterans synthesized from pea starch by Limosilactobacillus reuteri N1 GtfB with 4,6-α-glucanotransferase II activity.

Promising novel α-glucanotransferases with starch-converting activity have recently emerged from the CAZy GH70 GtfB subfamily. In this study, we thoroughly investigated and elucidated the impact of the newly characterized 4,6-α-glucanotransferase II Limosilactobacillus reuteri N1 GtfB (LrN1 GtfB), which was capable of synthesizing linear (α1 → 6) and branched (α1 → 4,6) linkages, on the fine structure, rheology, and retrogradation properties of pea starch (PS). The results revealed that as the reaction time increased, the total (α1 → 6) linkages in linear chains and branching points of PS increased from 5.6 % to 18.7 %, the molecular weight decreased from 7.3 × 106 g/mol to 7.4 × 104 g/mol, and the percentage of short chains (DP ≤ 12) increased from 47.4 % to 92.7 %, thereby producing low-molecular-weight, short-clustered novel reuterans with new (α1 → 6) linkages in both linear chains and branches. Additionally, LrN1 GtfB-modified PS exhibited lower storage/loss modulus and weaker creep property, indicating a significant attenuation of the strength and rigidity of the modified gel structure. Moreover, products derived from pea starch and LrN1 GtfB exhibited notably low retrogradation properties. These findings provide insights into the potential application of GtfB-type α-glucanotransferases in starch-based products, thereby producing unique-structured α-glucans with versatile properties from starch.

Recommendations for defining disturbed flow as laminar, transitional, or turbulent in assays of hemostasis and thrombosis: Communication from the ISTH SSC Subcommittee on Biorheology.

Blood flow is vital to life, yet disturbed flow has been linked to atherosclerosis, thrombosis, and endothelial dysfunction. The commonly used hemodynamic descriptor 'disturbed flow' found in disease and medical devices is not clearly defined in many studies. However, the specific flow regime: laminar, transitional, or turbulent, can have very different effects on hemostasis, thrombosis, and vascular health. Therefore, it remains important to clinically identify turbulence in cardiovascular flow and to have available assays that can be used to study effects of turbulence. The objective of the current communication is to 1) provide clarity and guidance for how to clinically identify turbulence, 2) define standard measures of turbulence that can allow the recreation of flow conditions in a benchtop assay, and 3) review how cells and proteins in the blood can be impacted by turbulence based on current literature.

Shear rate induced viscosity change of human blood samples and blood mimicking fluids.

Purpose: The aim of this study was to measure blood and blood mimicking fluids viscosity at different shear rates (on the interval of 0.1-5000 1/s and 0.1-10000 1/s) while taking into consideration the measuring device's capability and blood's characteristics. We also provided the measurement results of the most accurate measuring program. Methods: We measured blood samples from five donors, and four different blood mimicking fluid compositions. The measurements were done on an Anton Paar Physica MCR301 rotational rheometer with two measuring programs varying in the shear rate intervals, the number of measuring points and the measuring point durations. Results: The results confirmed the significant shear thinning and thixotropic effects of blood. Blood mimicking fluids also had these characteristics. The measured blood viscosity values are in agreement with those of the literature. Conclusions: It can be concluded that the step test program was able to give more stable results as the measured torque was over the nominal limit of 0.05 ìNm over 0.1 1/s and over the selected torque limit of 0.5 ìNm over 31.6 1/s. Blood mimicking fluid measurement results were different from that of the literature due to different measuring conditions. The sample consisting of water, glycerol and starch mimicked well blood's behaviour and viscosity values at 37 degrees Celsius.

Microfluidic Shape Analysis of Non-spherical Graphite for Li-Ion Batteries via Viscoelastic Particle Focusing.

The size and shape of graphite, which is a popular active anode material for lithium-ion batteries (LIBs), significantly affect the electrochemical performance of LIBs and the rheological properties of the electrode slurries used in battery manufacturing. However, the accurate characterization of its size and shape remains challenging. In this study, the edge plane of graphite in a cross-slot microchannel via viscoelastic particle focusing is characterized. It is reported that the graphite particles are aligned in a direction that shows the edge plane by a planar extensional flow field at the stagnation point of the cross-slot region. Accurate quantification of the edge size and shape for both spheroidized natural and ball-milled graphite is achieved when aligned in this manner. Ball-milled graphite has a smaller circularity and higher aspect ratio than natural graphite, indicating a more plate-like shape. The effects of these differences in graphite shape and size on the rheological properties of the electrode slurry, the structure of the coated electrodes, and electrochemical performance are investigated. This method can contribute to the quality control of graphite for the mass production of LIBs and enhance the electrochemical performance of LIBs.

Dissolution of denim waste in N-methyl morpholine-N-oxide monohydrate for fabrication of regenerated cellulosic film: Experimental and simulation study.

Despite the significant amount of denim waste and its potential as a cellulose source, its use has been neglected. This study uses N-methyl morpholine-N-oxide, an eco-friendly solvent, to dissolve denim (including 100 % cotton) and create a denim film. Achieving a 10 % denim record solubility, a cellulosic film was also fabricated for comparison. Characterisation techniques were applied, and molecular dynamics simulations explored intramolecular interactions and the influence of indigo dye on dissolution process. FTIR spectra indicated no chemical reactions during dissolution and regeneration, though a shift in OH stretching suggested a change in crystallinity, confirmed by XRD results showing decreased crystallinity and a structural shift from cellulose I to cellulose II. 13C NMR analysis revealed disruptions in interchain hydrogen bonds after regeneration. TGA results showed lower decomposition temperatures for both films compared to the powders. Testing mechanical properties showed the denim film had higher elongation at break but lower tensile strength than the cellulose film. MD simulations indicated indigo dye did not significantly affect fundamental interactions but decreased denim solubility by reducing the diffusion coefficient. Rheological tests supported the simulation results, showing higher viscosity and molecular weight for the denim solution compared to cellulose.

Non-Newtonian behaviour of suspensions and emulsions: Review of different mechanisms.

The mechanisms of non-Newtonian behaviour of suspensions and emulsions in steady shear flow are reviewed. The review is divided into two parts. In the first part, the mechanisms of non-Newtonian behaviour in suspensions and emulsions composed of Newtonian matrix are reviewed. Both dilute and concentrated systems are discussed. In the second part, the mechanisms of non-Newtonian behaviour in suspensions and emulsions composed of non-Newtonian matrix are reviewed. Where appropriate, mathematical models describing the rheology are included.

The Hofmeister series: Anion effect on microbial transglutaminase cross-linked soybean protein isolate hydrogels.

In this paper, the possibility of the kosmotropic anion (CO32-, Citrate3-, SO42-, H2PO4-, CH3COO- and Cl-) to improve the gel properties of microbial transglutaminase (MTG)-crosslinked soybean isolate protein (SPI)-based hydrogels was explored using a soaking strategy. The results of this experiment demonstrated that the hardness of the hydrogel undergoes different degrees of enhancement after different salt treatments in the following order: H2PO4- > CH3COO- > SO42- > Citrate3- > Cl- > CO32-. Rheological results showed that salt treatment led to enhancement of the energy storage modulus of the hydrogels. Further experiments indicated that the water-binding capacity of different salts depended on the salting out effect. Based on the Hofmeister effect, hardness-enhanced SPI-based hydrogels were successfully prepared. The Hofmeister effect offers a simple, an effective and a novel method for the preparation of functional SPI hydrogels.

Flow structure of okra mucilage in rotating wall vessel system.

The rotating-wall vessel (RWV) bioreactor, a 3D suspension culture system, faces challenges related to non-uniform tissue growth during the incubation of bone and heart tissues. Okra mucilage, an extract from okra pods with non-Newtonian rheological properties, has shown potential as a plasma replacement agent and has no induced cytotoxic effects. In this study, we investigated the flow structure of okra mucilage in rotating wall vessel system. By modifying the RWV and adding okra mucilage, we analyzed the flow structure using a high-speed camera and particle image velocimetry (PIV). Our results showed that okra mucilage creates a concentric circle-shaped rigid-like rotation at all rotation speeds (1-50 rpm). The high viscosity of okra mucilage resulted in a low terminal velocity for microparticles and quick response to rotational movements. These findings suggest that okra mucilage has the potential to enhance the uniformity of tissue growth in RWV systems by stabilizing the flow structure and reducing microparticle sedimentation.

Modulation of acid-induced pea protein gels by gellan gum and glucono-δ-lactone: Rheological and microstructural insights.

This study investigated the effect of gellan gum (GG) and glucono-δ-lactone (GDL) on the acid-induced gel properties of pea protein isolate (PPI) pretreated with media milling. The inclusion of GG substantially enhanced the gel hardness of PPI gel from 18.69 g to 792.47 g though slightly reduced its water holding capacity (WHC). Rheological analysis showed that GG increased storage modulus (G') and decreased damping factor of gels in the small amplitude oscillatory shear region and transformed its strain thinning behavior into weak strain overshoot behavior in the large amplitude oscillatory shear region. SEM revealed that GG transformed the microstructure of gel from a uniform particle aggregate structure to a chain-like architecture composed of filaments with small protein particles attached. Turbidity and zeta potential analysis showed that GG promoted the transformation of PPI from a soluble polymer system to an insoluble coagulant during acidification. When GG content was relatively high (0.2 %-0.3 %), high GDL content increased the electrostatic interaction between PPI and GG molecules, causing their rapid aggregation into a dense irregular aggregate structure, further enhancing gel strength and WHC. Overall, GG and GDL can offer the opportunity to modulate the microstructure and gel properties of acid-induced PPI gels, presenting potential for diversifying food gel design strategies through PPI-GG hybrid systems.

Dosage by design - 3D printing individualized cabozantinib tablets with immediate release.

Production of patient-specific dosage forms is important to improve patient adherence and effectiveness while reducing the prevalence and severity of adverse effects. Due to its possibility of rapid prototyping 3D printing can be used to produce individual dosages while utilizing techniques such as hot melt extrusion to increase the bioavailability of poorly soluble drugs. In this work, Parteck MXP and Kollicoat IR were used as water-soluble polymer bases for formulation development for 3D printing of various dosages incorporating cabozantinib while enabling immediate release. The effect of tablet design and the excipients sorbitol, croscarmellose sodium, and sodium starch glycolate was investigated for this goal. A way to calculate the size of tablets for predetermined dosages is proposed to enable the printing of individual strengths from one formulation. Rheological data were collected to deepen the understanding of the role of melt viscosity in 3D printing and hot melt extrusion processes. The production of immediate-release cabozantinib tablets containing every therapeutically relevant dosage in a single unit produced by two-step 3D printing was realized.

Mechanical and Thermal Properties of Epoxy Resin upon Addition of Low-Viscosity Modifier.

Thermoset-based polymer composites containing functional fillers are promising materials for a variety of applications, such as in the aerospace and medical fields. However, the resin viscosity is often unsuitably high and thus impedes a successful filler dispersion in the matrix. This challenge can be overcome by incorporating suitable low-viscosity modifiers into the prepolymer. While modifiers can aptly influence the prepolymer rheology, they can also affect the prepolymer curing behavior and the mechanical and thermal properties of the resulting matrix material. Therefore, this study investigates the effects that a commercial-grade low-viscosity additive (butyl glycidyl ether) has on a common epoxy polymer system (diglycidyl ether of bisphenol-A epoxy with a methylene dianiline curative). The weight percentage of the modifier inside the epoxy was varied from 0 to 20%. The rheological properties and cure kinetics of the resulting materials were investigated. The prepolymer viscosity decreased by 97% with 20 wt% modifier content at room temperature. Upon curing, 20 wt% modifier addition reduced the exothermic peak temperature by 12% and prolonged the time to reach the peak by 60%. For cured material samples, physical and thermo-mechanical properties were characterized. A moderate reduction in glass transition temperature and an increase in elastic modulus was observed with 20 wt% modifier content (in the order of 10%). Based on these findings, the selected material system is seen as an expedient base for material design due to the ease of processing and material availability. The present study thus provides guidance to researchers developing polymer composites requiring reduced prepolymer viscosity for successful functional filler addition.

Structural Rheology in the Development and Study of Complex Polymer Materials.

The progress in polymer science and nanotechnology yields new colloidal and macromolecular objects and their combinations, which can be defined as complex polymer materials. The complexity may include a complicated composition and architecture of macromolecular chains, specific intermolecular interactions, an unusual phase behavior, and a structure of a multi-component polymer-containing material. Determination of a relation between the structure of a complex material, the structure and properties of its constituent elements, and the rheological properties of the material as a whole is the subject of structural rheology-a valuable tool for the development and study of novel materials. This work summarizes the author's structural-rheological studies of complex polymer materials for determining the conditions and rheo-manifestations of their micro- and nanostructuring. The complicated chemical composition of macromolecular chains and its role in polymer structuring via block segregation and cooperative hydrogen bonds in melt and solutions is considered using tri- and multiblock styrene/isoprene and vinyl acetate/vinyl alcohol copolymers. Specific molecular interactions are analyzed in solutions of cellulose; its acetate butyrate; a gelatin/carrageenan combination; and different acrylonitrile, oxadiazole, and benzimidazole copolymers. A homogeneous structuring may result from a conformational transition, a mesophase formation, or a macromolecular association caused by a complex chain composition or specific inter- and supramolecular interactions, which, however, may be masked by macromolecular entanglements when determining a rheological behavior. A heterogeneous structure formation implies a microscopic phase separation upon non-solvent addition, temperature change, or intense shear up to a macroscopic decomposition. Specific polymer/particle interactions have been examined using polyethylene oxide solutions, polyisobutylene melts, and cellulose gels containing solid particles of different nature, demonstrating the competition of macromolecular entanglements, interparticle interactions, and adsorption polymer/particle bonds in governing the rheological properties. Complex chain architecture has been considered using long-chain branched polybutylene-adipate-terephthalate and polyethylene melts, cross-linked sodium hyaluronate hydrogels, asphaltene solutions, and linear/highly-branched polydimethylsiloxane blends, showing that branching raises the viscosity and elasticity and can result in limited miscibility with linear isomonomer chains. Finally, some examples of composite adhesives, membranes, and greases as structured polymeric functional materials have been presented with the demonstration of the relation between their rheological and performance properties.

Structure-Elasticity Relationships in Hybrid-Carrageenan Hydrogels Studied by Image Dynamic Light Scattering, Ultra-Small-Angle Light Scattering and Dynamic Rheometry.

Hybrid-carrageenan hydrogels are characterized using novel techniques based on high-resolution speckle imaging, namely image dynamic light scattering (IDLS) and ultra-small-angle light scattering (USALS). These techniques, used to probe the microscopic structure of the system in sol-gel phase separation and at different concentrations in the gel phase, give access to a better understanding of the network's topology on the basis of fractals in the dense phase. Observations of the architecture and the spatial and the size distributions of gel phase and fractal dimension were performed by USALS. The pair-distance distribution function, P(r), extracted from USALS patterns, is a new methodology of calculus for determining the network's internal size with precision. All structural features are systematically compared with a linear and non-linear rheological characterization of the gels and structure-elasticity relationships are identified in the framework of fractal colloid gels in the diffusion limit.

Impact of Sprouted Chickpea Grits and Flour on Dough Rheology and Bread Features.

This study investigated the effects of incorporating sprouted chickpeas, at a 25% enrichment level, into bread production as either grits (90% of particles ≥500 µm) or flour (90% of particles ≤250 µm). The focus was to investigate the role of particle size on dough and bread. In addition to the functional, mixing and pasting properties of ingredients, gluten aggregation, mixing, extensional, leavening, and pasting properties of the blends were assessed during bread-making, as well as bread volume and texture. Chickpea particle size influenced water absorption capacity (1.8 for grits vs. 0.75 g/g for flour) and viscosity (245 for grits vs. 88 BU for flour), with flour showing a greater decrease in both properties. With regard to dough properties, dough development time (16.6 vs. 5.3 min), stability (14.6 vs. 4.6 min), and resistance to extension (319 vs. 235 BU) was higher, whereas extensibility was lower (105 vs. 152 mm) with grits, compared to flour. During bread-making, grits resulted in a higher specific volume (2.5 vs. 2.1 mL/g) and softer crumb (6.2 vs. 17.4 N) at all the considered storage times. In conclusion, sprouted chickpea grits can be effectively used as a new ingredient in bread-making favouring the consumption of chickpea, without compromising product quality.

Effect of Flammulina velutipes Soluble Dietary Fiber on Dough Processing Characteristics and Micro-Fermented Dried Noodles Quality Properties.

Our research focused on the integration of Flammulina velutipes soluble dietary fiber (Fv-SDF) into wheat flour during the production of dried noodles, delving into the impact of different addition ratios of Fv-SDF on both dough processing characteristics and the quality of the micro-fermented dried noodles. The viscometric and thermodynamic analyses revealed that Fv-SDF notably improved the thermal stability of the mix powder, reduced viscosity, and delayed starch aging. Additionally, Fv-SDF elevated the gelatinization temperature and enthalpy value of the blend. Farinograph Properties and dynamic rheology properties further indicated that Fv-SDF improved dough formation time, stability time, powder quality index, and viscoelasticity. Notably, at a 10% Fv-SDF addition, the noodles achieved the highest sensory score (92) and water absorption rate (148%), while maintaining a lower dry matter loss rate (5.2%) and optimal cooking time (142 s). Gas chromatography-ion mobility spectrometry (GC-IMS) analysis showed that 67 volatile substances were detected, and the contents of furfural, 1-hydroxy-2-acetone, propionic acid, and 3-methylbutyraldehyde were higher in the Fv-SDF 10% group. These 10% Fv-SDF micro-fermented noodles were not only nutritionally enhanced, but also had a unique flavor. This study provides a valuable theoretical basis for the industrial application of F. velutipes and the development of high-quality dried noodles rich in Fv-SDF.