Viscoelastic Measurements Research Articles

Stomatitis Healing via Hydrogels Comprising Proline, Carboxyvinyl Polymer, and Water

Chemotherapy using anticancer agents and radiotherapy of cancers frequently induce the development of stomatitis as a side effect. In the present study, hydrogels for effective stomatitis healing under anticancer drug administration were developed using three components, namely proline, carboxyvinyl polymer, and water (denoted proline gels). Characterization including tilting, Fourier transform infrared spectra, and viscoelasticity measurements indicated that proline gels with proline concentrations over 300 μmol/g could retain water on the tongue of mice. The degradation and release behavior of proline gels in serological environments were evaluated, revealing that proline gels were degraded by serological salt concentrations, and the cumulative amount of proline released from proline gels depended on the concentration of proline in the gel. Proline gels were applied to the stomatitis area on the tongue of mice under anticancer drug administration, with subsequent reduction in the stomatitis area and regeneration of the mucosal epithelium layer, demonstrating effective stomatitis healing by proline gels with proline concentrations over 500 μmol/g. Other control samples including the carboxyvinyl polymer or proline alone did not reduce the stomatitis area in model mice. These results suggested that the proline gel is promising for the mucosa regeneration of anticancer drug-induced stomatitis.

Cold Pressed Oil from Japanese Quince Seeds (Chaenomeles japonica): Characterization Using DSC, Spectroscopic, and Monolayer Data

The cold-pressed oil from Japanese quince seeds (JQSO) is notable for its favorable fatty acid profile, low oxidation rate, and bioactive compounds like antioxidants, sterols, and carotenoids. This study offers a detailed molecular-level physical characterization of JQSO and its minor components using differential scanning calorimetry (DSC), Langmuir monolayer studies, and various spectroscopic methods, including UV–vis absorption, fluorescence, and FTIR. DSC analysis identified five peaks related to triglyceride (TG) fractions and provided insights into the melting and crystallization behavior of JQSO. The Langmuir monolayer studies revealed high compressibility, indicative of superior emulsification properties. Viscoelastic modulus measurements suggested strong intermolecular interactions, contributing to the oil’s resilience under stress—an attribute typical of oils high in saturated or monounsaturated fatty acids. Spectroscopic methods confirmed the presence of phenolic acids, tocopherols, carotenoids, and their derivatives. The total fluorescence spectra highlighted prominent peaks at 290 nm/330 nm and 360 nm/440 nm, while the total synchronous fluorescence spectra revealed key excitation–emission regions (10–50 nm/300 nm and 40–140 nm/360 nm), corroborating the presence of tocopherols, phenols, polyphenols, flavones, and carotenoids. No evidence of chlorophyll was detected. The ATR-FTIR spectra validated the presence of fatty acids and triacylglycerols, emphasizing a high degree of esterification and the dominance of unsaturated fatty acids in oil structures. The methods used provided the opportunity to perform a label-free, fast, and reliable determination of the properties of JQSO. The findings confirmed that crude, cold-pressed JQSO retains its valuable bioactive components, aligning with previous research on its chemical and physical properties.

A fundamental rheological approach to determine the optimum water absorption capacity of a model gluten-free dough system: soy flour dough.

Determining the optimum water absorption capacity of gluten-free flours for an improved breadmaking process has been a challenge because there is no standard method. In the present study, large amplitude oscillatory shear (LAOS) tests were performed to explore the impact of different levels of added water on non-linear viscoelastic response of soy flour dough in comparison to wheat flour dough at a consistency of 500 BU. Among the LAOS parameters, large strain modulus (G'L) and large strain rate viscosity (η'L) were found to better probe the impact of added water amount on non-linear viscoelastic properties of soy flour dough. Although soy flour dough with 160:100 (water: soy flour, v/w) and wheat flour dough had overlapping η*(ω) in the linear viscoelastic region, LAOS sweeps revealed similar tan δ, G'L and η'L values along with similar elastic and viscous Lissajous-Bowditch curves at γ0 = 200% for soy flour dough with 175:100 (water: soy flour, v/w) to those of wheat flour dough. Considering the large deformations involved in breadmaking process and the poor capability of the linear viscoelastic measures to predict loaf volume, the present study suggests using the LAOS parameters to determine the optimum water absorption capacity and to optimize the strain-stiffening and shear-thinning behaviors of gluten-free flours to improve end-product quality. © 2025 Society of Chemical Industry.

Evaluation of a Point-of-Care-Viscoelastic Coagulation Device in Hispaniolan Amazon Parrots (Amazona ventralis).

Viscoelastic testing evaluates the formation and lysis of a clot over time, allowing more complete assessment of patient hemostasis in real time, whereas traditional tests, such as prothrombin time and partial thromboplastin time, only measure coagulation factor function. Patient-side viscoelastic coagulation monitors are easy to use, portable, and provide faster turnaround time than commercial laboratories. Viscoelastic testing requires only 0.2 mL of blood and is useful in diagnosing and treating hemostatic disorders. Currently, there is no standardized coagulation testing method across bird species. In this cross-sectional study, a viscoelastic coagulation device, the Entegrion Viscoelastic Coagulation Monitor-Vet (VCM-Vet), was evaluated. Blood samples were obtained from 26 Hispaniolan Amazon parrots (HAPs) (Amazona ventralis) under manual restraint. Results were recorded on the device as graphical output with quantitative viscoelastic measurements. Results were reported using standard rotational thromboelastometry terminology, including clotting time, clot formation time, alpha angle, maximum clot firmness, clot firmness amplitude at 10 and 20 minutes after clot formation, and clot lysis at 30 and 45 minutes. The median clotting time was 463 seconds (reference interval: 56-1635 seconds), the mean clot formation time was 704.7 seconds (reference interval: 172-1697 seconds), the mean alpha angle was 27.3 (reference interval: 7-60), and the mean maximum clot firmness was 15.4 (reference interval: 7-25). Statistical analysis found that all parameters were normally distributed aside from clotting time in seconds. There was no appreciable breakdown of the clot during the 60-minute device runtime, and there was no significant difference in any parameter based on sex. The VCM-Vet produced clotting times for this population of HAPs and enabled the creation of reference intervals. Based on our findings, the VCM-Vet can be used to assess clot potential in HAPs and possibly other avian species.

Identification of viscoelastic properties with fluid inertia in a parallel plate with effective mechanical system analyses

Measurement of viscoelastic properties in small amplitude oscillatory shear (SAOS) can be affected by fluid inertia, especially at high frequencies. In this study, we introduce an effective mechanical system approach to address the effects of fluid inertia on the viscoelastic measurement with a SAOS test, employing a parallel plate geometry. In the effective mechanical system approach, viscous, elastic, and inertial properties of a fluid system are modeled systematically by a rotational drag coefficient, a torsional spring constant, and a second moment of inertia, respectively. In this way, we established the analytic solution for the linear viscoelastic behavior of a fluid in the presence of fluid inertia. The shear modulus on the frequency, obtained by the effective mechanical system, reveals that fluid inertia only affects the storage modulus and not the loss modulus. We investigate the behavior of the storage modulus as a function of the gap size, the oscillation frequency, and the disk radius, demonstrating the dependence on the gap size and the frequency. Comparison was made for the shear modulus from the effective mechanical system with viscoelastic flow simulation, employing two viscoelastic (Oldroyd-B and Giesekus) fluid models to validate the accuracy of this approach. The maximum error was found less than 3.3% over the frequency range from 1 to 100 rad/s.

Chitin nanofiber-stabilized pickering emulsion interacting with egg white protein: Structural features, interfacial properties, and stability

The application of chitin has significantly expanded, particularly in the formulation of protein-based complexes stabilized by electrostatic interactions, which are crucial in the development of Pickering emulsions. This study systematically investigates how variations in pH affect the molecular structure, interfacial properties, and emulsifying performance of egg white protein (EWP) complexes with chitin nanofibers (ChNFs). The findings reveal that electrostatic interactions between ChNFs and EWP substantially influence the dispersion and morphology of the complexes across a pH range of 2.0–9.0. Spectral analysis indicates that the incorporation of ChNFs leads to a slight reduction in surface hydrophobicity and fluorescence intensity of EWP, enhancing the protein's structural flexibility. Additionally, adsorption kinetics and dilational viscoelasticity measurements demonstrate that ChNFs significantly increase EWP's equilibrium interfacial pressure (up to 25 mN/m) and viscoelastic modulus, indicating improved stability at the oil-water interface. Notably, emulsions stabilized by EWP/ChNF complexes at pH values between 5.0 and 7.0 exhibit a more uniform droplet size (approximately 200 nm) and enhanced stability, with turbidity measurements reaching maximum values of 0.85. These results underscore the potential of chitin nanofibers as sustainable emulsifiers in food applications, providing a viable alternative to synthetic emulsifiers.

Harnessing Extreme Internal Damping in Polyrotaxane‐Incorporated Liquid Crystal Elastomers for Pressure‐Sensitive Adhesives

AbstractLiquid crystal elastomers (LCEs) exhibit extraordinary energy dissipation due to their unique viscoelastic response, resulting from the rotation of mesogens under mechanical stress. While recent studies demonstrate the LCE‐based pressure‐sensitive adhesives (PSAs) by exploiting the enhanced damping, all previous studies have focused on LCEs with covalent crosslinks. Here, a new class of PSAs is developed by integrating movable polyrotaxane crosslinkers into an LCE matrix (PRx‐LCEs). Dynamic viscoelastic measurements reveal that PRx‐LCE exhibits a remarkably high energy dissipation, as indicated by a large tan δ. Interestingly, the secondary tan δ peak associated with LCE damping is more pronounced than the primary peak of the glass transition. The exceptional energy dissipation in PRx‐LCE results in superior adhesion strength (≈1864 N m−1), which is 3.5 times higher than conventional LCEs and 13 times higher than commercial PSAs in the peel test. Additionally, PRx‐LCEs demonstrate thermally reversible adhesion, enabling clean removal at elevated temperatures. Furthermore, the sliding effect in PRx‐LCE enhances both deformability and stress relaxation under load, resulting in deeper indentation, and superior adhesion during the probe tack test. The combination of LCE and slidable crosslinks provides robust and switchable adhesion, making them promising for applications in biomedical engineering, display, and semiconductor industries.

Engineering water-shut-off operations: Application of rheological time-temperature superposition approach for organically-crosslinked polymer gel systems

Polymer-based gels have been extensively utilized in reservoirs to prevent excessive water production and improve oil recovery. In this study, a sulfonated-hydrolyzed polyacrylamide polymer (HPAM-S) and low-toxic organic crosslinkers (hydroquinone and hexamethylenetetramine) were mixed in brine at specified concentrations to formulate the polymer-crosslinker fluid system. The quantitative rheological analysis, along with the TTS (Time-Temperature Superposition) approach, was examined for the first time to achieve the water shut-off operations in high-temperature reservoirs (90 °C–150 °C). The TTS approach was defined as modelling of the viscosity vs. time data obtained at various temperatures using an appropriate empirical shift factor (at) such that a single master curve is established for the viscosity evolution of the given fluid system. This approach facilitates the prediction of the gelation behavior of polymer-crosslinker fluid systems as a function of time at varied reservoir temperatures especially over time scales that are not experimentally accessible. The time-dependent rheological evolution of the fluid system was experimentally investigated using batch-wise bottle testing methods as well as viscosity and viscoelastic measurements by employing an advanced rheometer. The TTS approach was applied to the obtained rheological data at varied temperatures. The model was validated for an unknown set of temperature vs. viscosity data. Based on the TTS approach, the term ‘gelation time’ was defined as the time required to reach a pre-specified viscosity to signify a transition from the liquid-like state to the solid-like state. The gelation time decreases with increasing temperatures. After the gelation time, at each temperature, a swift increase in the fluid viscosity was observed, indicating the initiation of the rapid crosslinking in the fluid systems. It was found that beyond the gelation time, the batch-wise bottle testing showed (G-I) gel strength (qualitative). Analogously, the visco-elasticity test demonstrated a rapid rise in elastic modulus (G′) beyond the gelation time. An underlying mechanism based on polymer hydrolysis was utilized to explain the evolution of distinct viscous and viscoelastic properties as a function of temperature. Moreover, the modeling predictions for the fluid systems were examined for in-situ rock plugging with the help of core-flood equipment. The core-flooding tests confirmed a 99% reduction in the rock permeability beyond the gelation time. The gelation time values obtained from both the batch-wise bottle testing method and rheological tests for the polymer-crosslinker fluid systems were found in agreement with each other, with a tolerance of (±5%).

Continuous Viscoelasticity Measurement of Cell Spheroids via Microfluidic Electrical Aspiration.

Measurement of viscoelastic characteristics of cells cultured in three-dimensional (3D) is critical to study many biological processes including tissue and organ growth. In this article, we present a unique electrical aspiration method to measure the viscoelastic properties of cell spheroids. A microfluidic sensor was created to demonstrate this method. Unlike the traditional optical aspiration method, the aspiration of the cell spheroids is monitored via monitoring the dynamic electrical resistance change of a symmetrical microfluidic aspiration channel. We first used the microfluidic device to measure the viscoelastic properties of two types of biological tissues derived from calfskin and porcine left ventricular myocardium. The equilibrium elastic modulus and creep time constants were measured to be 148.1 ± 24.1 kPa and 76.7 ± 3.5 s and 64.5 ± 7.7 kPa and 31.4 ± 2.7 s respectively, which matched well with reported data. The test validated the principle of the electrical aspiration method. Next, we applied the method for measuring cell spheroids made of human mesenchymal stem cells at different culture stages. The equilibrium elastic modulus and apparent viscosity decreased with increasing culture time. Compared to optical aspiration methods, this microfluidic electrical aspiration method has no reliance on transparent materials and image processing, which thus allows simple setup, fast data acquisition and analysis. The use of a symmetric aspiration channel and the linear half-space model enable measurements of a large number of viscoelastic properties via a single measurement with higher accuracy. This method will enable high throughput, continuous viscoelastic measurement of cell spheroids as well as other 3D cell culture models in flow conditions without the need for any optical measurements.

Direct computations of viscoelastic moduli of biomolecular condensates.

Biomolecular condensates are viscoelastic materials defined by time-dependent, sequence-specific complex shear moduli. Here, we show that viscoelastic moduli can be computed directly using a generalization of the Rouse model that leverages information regarding intra- and inter-chain contacts, which we extract from equilibrium configurations of lattice-based Metropolis Monte Carlo (MMC) simulations of phase separation. The key ingredient of the generalized Rouse model is a graph Laplacian that we compute from equilibrium MMC simulations. We compute two flavors of graph Laplacians, one based on a single-chain graph that accounts only for intra-chain contacts, and the other referred to as a collective graph that accounts for inter-chain interactions. Calculations based on the single-chain graph systematically overestimate the storage and loss moduli, whereas calculations based on the collective graph reproduce the measured moduli with greater fidelity. However, in the long time, low-frequency domain, a mixture of the two graphs proves to be most accurate. In line with the theory of Rouse and contrary to recent assertions, we find that a continuous distribution of relaxation times exists in condensates. The single crossover frequency between dominantly elastic vs dominantly viscous behaviors does not imply a single relaxation time. Instead, it is influenced by the totality of the relaxation modes. Hence, our analysis affirms that viscoelastic fluid-like condensates are best described as generalized Maxwell fluids. Finally, we show that the complex shear moduli can be used to solve an inverse problem to obtain the relaxation time spectra that underlie the dynamics within condensates. This is of practical importance given advancements in passive and active microrheology measurements of condensate viscoelasticity.

Viscoelastic and Birefringence Relaxation of Individualized Cellulose Nanofibers in the Dilute and Semidilute Regions.

Viscoelastic relaxation mechanisms of individualized cellulose nanofibers (iCNFs) dispersed in glycerol in the dilute and semidilute regions were investigated by linear viscoelastic and dynamic birefringence measurements. The birefringence relaxation of the iCNFs was described by the orientational and curvature modes of an existing viscoelastic theory for ideal semiflexible polymers (Shankar-Pasquali-Morse theory). However, the Shankar-Pasquali-Morse theory could not fully describe the iCNF viscoelastic relaxation at high frequencies. Considering the results for birefringence relaxation, the experimental tension mode of the iCNFs was evaluated to be higher than the theoretical value. These results show that the viscoelastic relaxations of the iCNFs are different from those of ideal semiflexible polymers, in contrast to cellulose nanocrystals (CNCs). As the iCNF concentration increased, the orientational mode dramatically slowed, which was more drastic than other semiflexible polymers, including CNCs. This anomalous behavior is likely due to the nonideal nature of iCNFs.

The value of viscoelastic platelet function measurements with Sonoclot in patients with acute coronary syndrome undergoing percutaneous coronary intervention

PurposePlatelets play an important role in the pathogenesis of acute coronary syndrome (ACS), and adequate platelet inhibition is a cornerstone during invasive management with percutaneous coronary intervention (PCI). Despite this, pivotal role routine measurement of platelet function is not done. We aimed at using the using the Sonoclot device for measuring platelet activity and predicting outcome in patients with ACS undergoing PCI.MethodsThis was a cohort longitudinal study involving 50 patients who were admitted with ACS and undergoing emergent PCI in the critical care department at Cairo University from November 2020 to July 2021. Three parameters will be obtained: platelet function, ACT, and coagulation rate.ResultsAccording to the 1st parameter (platelet function), adequate platelet inhibition was achieved in 54% of our cases. To study the impact of this analysis, our population was classified into 2 groups (well-inhibited platelets vs. poorly inhibited platelets). The 2nd and 3rd parameters (ACT, CR) could separate our patients into 2 groups according to whether patients were well anticoagulated or not. Classification 1, well vs. poorly inhibited platelets, both groups were comparable. However, epicardial coronary flow (TIMI flow) and myocardial blush grade post-stenting were better in the well-inhibited platelets group. Classification 2, well vs. poor anticoagulation, there were no significant differences between the 2 groups.ConclusionAdequate platelet inhibition as measured by Sonoclot device can predict better outcomes in patients with ACS undergoing PCI.

Chemiluminescent Reaction Induced by Mixing of Fluorescent-Dye-Containing Molecular Organogels with Aqueous Oxidant Solutions.

Chemiluminescence in solution-based systems has been extensively studied for the chemical analysis of biomolecules. However, investigations into the control of chemiluminescence reactions in gel-based systems, which offer flexibility in reaction conditions (such as the softness of the reaction environment), have only recently begun in polymer materials, with limited exploration in low-molecular-weight gelator (LMWG) systems. In this study, we investigated the chemiluminescence behaviors in the gel states using LMWG systems and evaluated their applicability to fluorescent-dye-containing molecular organogel systems/oxidant-containing aqueous systems. Using diethyl succinate organogels composed of 12-hydroxystearic acid as a molecular organogelator, we examined the fluorescent properties of various fluorescent dyes mixed with oxidant aqueous solutions. As the reaction medium transitioned from the solution to the gel state, the emission color and chemiluminescence duration changed significantly, and distinct characteristics were observed, for each dye. This result indicates that the chemiluminescence behavior differs significantly between the solution and gel states. Additionally, visual inspection and dynamic viscoelastic measurements of the mixed fluorescent dye-containing molecular gels and oxidant-containing aqueous solutions confirmed that the chemiluminescence induced by the mixing occurred within the gel phase. Furthermore, the transition from the solution to the gel state may allow for the modulation of the mixing degree, thereby enabling control over the progression of the chemiluminescence reaction.

Potential application of novel Janus amphiphilic nanoparticles to improve the viscoelasticity of polymer solution for enhanced oil recovery

Nanomaterials were widely employed to improve the physicochemical properties of various chemicals in enhanced oil recovery (EOR). In the present study, the novel Janus amphiphilic silica nanoparticle (JNS) was successfully prepared, whose structure and property were confirmed via Fourier transform infrared spectroscopy, Zeta potential measurement, transmission electron microscopy, interfacial tension and contact angle measurements. Then the effects of JNS, hydrophilic silica nanoparticles (HLS) and hydrophobic silica nanoparticles (HBS) on the viscosity of the hydrophobic modified HPAM (HOA101) solution were studied. It was found that JNS exhibited a greater ability to enhance the viscosity, temperature resistance and salt resistance of HOA101 solution in comparison to the other two polymer nanofluids. The interaction mechanisms between nanoparticles and HOA101 were proposed, which were verified by the viscoelasticity measurements and control experiments. Core flooding experiments and micromodel flooding tests demonstrated that the JNS/HOA101 dispersion could effectively expand the sweep efficiency to highly increase the oil recovery from 8.4% to 14.3%.

Mechanochromic Polymer Film with High Sensitivity toward Tensile Strain by the Post-Curing Ring-Closure Induced Pre-Stretching.

Mechanochromic materials have received broad research interests recently, owing to its ability to monitor the in situ stress/strain in polymer materials in a straightforward way. However, one major setback that hinders the practical application of these materials is their low sensitivity toward tensile strain. Here a new strategy for pre-stretching of the mechanochromic agent in a polymer film on the molecular scale, which can effectively enhance the mechanochromic sensitivity of a polymer film toward tensile strain, is shown. In situ fluorescent measurement during tensile test shows an early activation of the mechanochromic agent at tensile strain as low as 50%. The pre-stretching effect is realized by first inducing ring-opening of the mechanochromic agent by molecular functionalization, and then compelling the ring-closure process in the cured film by elevated temperature. This post-curing ring-closure process will result in pre-stretched mechanochromic agent in a crosslinked network. The mechanism for mechanochromic activation of polymer films with different composition is elaborated by visco-elastic measurements, and the effect of pre-stretching is further confirmed by films with other compositions. Combined with the simplicity of the method developed, this work could offer an alternative strategy to enhance the sensitivity of different mechanochromic agents toward tensile strain.

Evaluation of optical and self-healing properties of Titania/ionic liquid/poly(butyl methacrylate) hybrid material based on thermally reversible Diels–Alder chemistry

ABSTRACT In this study, we report the development of a hybrid polymer material comprising poly(butyl methacrylate) and titania, which exhibits the three key elements of visible-light transparency, UV shielding, and self-healing. Nanodispersion of titania in the polymers was achieved using the sol – gel method using titanium propoxide as the raw material. Furthermore, by adding tetrabutylphosphonium chloride, an ionic liquid, we suppressed visible light absorption due to charge transfer between poly(butyl methacrylate) and titania, resulting in enhanced visible light transmittance. An approach involving crosslinking points comprising Diels – Alder functional groups was used to heal scratches in the hybrid material at 75°C for 30 min. Dynamic viscoelastic measurements and microscopic observations were conducted to investigate the self-healing mechanism. These findings suggested that this phenomenon occurred through the fluidization of the polymer matrix and the recombination reaction of the crosslinking points, which comprise Diels – Alder and titania. The development of intelligent materials with combined transparency, UV protection, and self-healing capabilities provides potential avenues for future research to enhance and broaden their versatile characteristics for widespread applications.

Asphalt binder characterization using waveform-based viscoelastic measures and time-temperature superposition principle under large strains

In the United States, currently peak-to-peak oscillatory shear stress-strain data is used in the asphalt binder characterization protocols. This practice necessitates the measurement, usage, and reporting of only peak responses for material characterization and specification even though a sinusoidal waveform is applied. However, in this paper it is argued that with the proliferation of modified binding systems, it is critical to capture and examine the complete waveform data when subjected to both small and large strains. This approach will help properly differentiating between materials. In this study, four modified binders were tested at small and large strain levels while recording the complete response waveform. The recorded waveform data was then used to examine the linear and nonlinear viscoelastic characteristics of these binders. The orthogonal stress decomposition technique was used to delineate elastic and viscous contributions in the nonlinear regime. This study examined the time-temperature dependency under both linear and nonlinear regimes. The time-temperature shift factors obtained from linear regime were effectively applied in the nonlinear regime. Further, all the tested binders showed strain stiffening and shear thinning behavior under most of the testing conditions. This study provides useful insights about the material behavior under nonlinear regime and can serve as a benchmark for further investigation of nonlinear viscoelastic behavior of asphalt binders.

Preparation and performance evaluation of intelligent plugging agent for thermo‐sensitive water‐based drilling fluid

AbstractIn the process of unconventional oil and gas exploitation, the invasion of a large amount of drilling fluid into the formation is one of the most critical reasons leading to wellbore instability. A temperature‐sensitive polymer (AOS) was synthesized from acrylamide, oligo (ethylene glycol) methyl ether methacrylate (OEGMA), and sodium p‐styrene sulfonate by emulsion polymerization. The material is a solid‐free fluid with good fluidity at room temperature, after injection into the formation, the fluid is gradually transformed into hard gel above the lower critical solution temperature (LCST) (90°C), thus blocking micro‐fractures and improving wellbore stability. Infrared and NMR characterization confirmed the successful preparation of the target product. The transmittance of AOS with ambient temperature was measured by UV–vis spectrophotometer, and the LCST behavior of AOS was verified by rheological and viscoelastic measurements. The interaction mechanism between AOS and sodium bentonite was evaluated according to the American Petroleum Institute standard. The results show that after aging at 180°C, the filtration loss is reduced by 93%, and the medium permeability (100, 200 mD) formation is effectively plugged, with a plugging efficiency is as high as 74.7%.

On the relationship between viscoelasticity and water diffusion in soft biological tissues

Magnetic resonance elastography (MRE) and diffusion-weighted imaging (DWI) are complementary imaging techniques that detect disease based on viscoelasticity and water mobility, respectively. However, the relationship between viscoelasticity and water diffusion is still poorly understood, hindering the clinical translation of combined DWI-MRE markers.We used DWI-MRE to study 129 biomaterial samples including native and cross-linked collagen, glycosaminoglycans (GAGs) with different sulfation levels, and decellularized specimens of pancreas and liver, all with different proportions of solid tissue, or solid fractions. We developed a theoretical framework of the relationship between mechanical loss and tissue-water mobility based on two parameters, solid and fluid viscosity. These parameters revealed distinct DWI-MRE property clusters characterizing weak, moderate, and strong water-network interactions. Sparse networks interacting weakly with water, such as collagen or diluted decellularized tissue, resulted in marginal changes in water diffusion over increasing solid viscosity. In contrast, dense networks with larger solid fractions exhibited both free and hindered water diffusion depending on the polarity of the solid components. For example, polar and highly sulfated GAGs as well as native soft tissues hindered water diffusion despite relatively low solid viscosity.Our results suggest that two fundamental properties of tissue networks, solid fraction and network polarity, critically influence solid and fluid viscosity in biological tissues. Since clinical DWI and MRE are sensitive to these viscosity parameters, the framework we present here can be used to detect tissue remodeling and architectural changes in the setting of diagnostic imaging. Statement of significanceThe viscoelastic properties of biological tissues provide a wealth of information on the vital state of cells and host matrix. Combined measurement of viscoelasticity and water diffusion by medical imaging is sensitive to tissue microarchitecture. However, the relationship between viscoelasticity and water diffusion is still poorly understood, hindering full exploitation of these properties as a combined clinical biomarker. Therefore, we analyzed the parameter space accessible by diffusion-weighted imaging (DWI) and magnetic resonance elastography (MRE) and developed a theoretical framework for the relationship between water mobility and mechanical parameters in biomaterials. Our theory of solid material properties related to particle motion can be translated to clinical radiology using clinically established MRE and DWI.

Effect of hydrothermal treatment on the rheological properties of xanthan gum

In this study, the effect of hydrothermal treatment with different temperatures (120–180 °C) on the rheological properties of xanthan gum was evaluated. When the temperature of hydrothermal treatment was relatively low (120 °C), the rheological properties of the hydrothermally treated xanthan gum was similar to the untreated xanthan gum (pseudoplastic and solid-like/gel-like behavior). However, as the temperature of hydrothermal treatment was higher, the rheological properties of the hydrothermally treated xanthan gum changed greatly (e.g., a wider range of Newtonian plateaus in flow curves, existence of a critical frequency between the storage modulus (G') and the loss modulus (G") in the dynamic viscoelasticity measurement, variation of complex viscosity). Although the hydrothermal treatment showed little influence on the functional groups of xanthan gum, it altered the micromorphology of xanthan gum from uneven and rough lump-like to thinner and smoother flake-like. In addition, higher concentration (2 %) of hydrothermally treated xanthan gum made its viscosity close to that of the untreated xanthan gum (1 %). Besides, hydrothermal treatment also affected the effect of temperature and salt (CaCl2) adding on the rheological properties of xanthan gum. Overall, this study can provide some useful information on the rheological properties of xanthan gum after hydrothermal treatment.