Shear Storage Modulus Research Articles

Bulk and Interfacial Behavior of Potato Protein-Based Microgels.

This study aims to understand the bulk and interfacial performance of potato protein microgels. Potato protein (PoP) was used to produce microgels of submicrometer diameter via a top-down approach of thermal cross-linking followed by high-shear homogenization of the bulk gel. Bulk "parent" gels were formed at protein concentrations [PoP] = 5-18 wt %, which subsequently varied in their bulk shear elastic modulus (G') by several orders of magnitude (1-100 kPa), G' increasing with increasing [PoP]. The PoP microgels (PoPM) formed from these parent gels had diameters varying between 100 and 300 nm (size increasing with increasing G' and [PoP]), as observed via dynamic light scattering and atomic force microscopy (AFM) of PoPM adsorbed onto silicon. Interfacial rheology (interfacial shear storage and loss moduli, Gi' and Gi″) and interfacial tension (γ) of adsorbed films of PoP (i.e., nonheated PoP) and PoPM (both at tetradecane-water interfaces) were also studied, as well as the bulk rheology of the PoPM dispersions. The results showed that PoPM dispersions (at 50 vol %) had significantly higher bulk viscosity and shear thinning properties compared to the nonmicrogelled PoP at the same overall [PoP], but the bulk rheological behavior was in sharp contrast to the interfacial rheological performance, where Gi' and Gi″ of PoP were higher than for any of the PoPM. This suggests that the deformability and size of the microgels were key in determining the interfacial rheology of the PoPM. These findings may be attributed to the limited capacity for "unfolding" and lateral interactions of the larger PoPM at the interface, which are presumed to be stiffer due to their production from the strongest PoP gels. Our study further confirmed that heating and cooling the adsorbed films of PoPM after their adsorption showed little change, highlighting that hydrogen bonding was limited between the microgel particles.

Influence of Rheological Modifications on Primary Network Chemical and Structural Cure Kinetics for an Interpenetrating Polymer Network Resin.

The development of non-contact in situ techniques for monitoring cure kinetics has the potential to greatly improve both resin formulation and processing. We have recently shown that low-frequency Raman spectroscopy is a viable method for assessing resin structural cure kinetics and complements the traditional chemical conversion determined from the fingerprint region of the spectrum. In this work, we further evaluate the relationship between structural and chemical conversion by investigating two chemically identical yet rheologically different interpenetrating polymer network resin formulations. Rheological analysis demonstrates a relationship between structural conversion and storage modulus, which is not observed in the chemical conversion data. We show that one can produce master cure kinetics curves with comparable kinetic constants using both the chemical and structural conversion methodologies. Parametric analysis of the structural conversion, chemical conversion, and photorheological conversion was combined with a semi-empirical model for the storage shear modulus as a function of the extent of cure.

Characterizing dispersion in bovine liver using ARFI-based shear wave rheometry

Background: Dispersion presents both a challenge and a diagnostic opportunity in shear wave elastography (SWE). Shear Wave Rheometry (SWR) is an inversion technique for processing SWE data acquired using an acoustic radiation force impulse (ARFI) excitation. The main advantage of SWR is that it can characterize the shear properties of homogeneous soft media over a wide frequency range. Assumptions associated with SWR include tissue homogeneity, tissue isotropy, and axisymmetry of the ARFI excitation). Objective: Evaluate the validity of the SWR assumptions in ex vivo bovine liver. Approach: SWR was used to measure the shear properties of bovine liver tissue as function of frequency over a large frequency range. Assumptions associated with SWR (tissue homogeneity, tissue isotropy, and axisymmetry of the ARFI excitation) were evaluated through measurements performed at multiple locations and probe orientations. Measurements focused on quantities that would reveal violations of the assumptions. Main results: Measurements of shear properties were obtained over the 25–250 Hz range, and showed a 4-fold increase in shear storage modulus (from 1 to 4 kPa) and over a 10-fold increase in the loss modulus (from 0.2 to 3 kPa) over that decade-wide frequency range. Measurements under different conditions were highly repeatable, and model error was low in all cases. Significance and Conclusion: SWR depends on modeling the ARFI-induced shear wave as a full vector viscoelastic shear wave resulting from an axisymmetric source; it is agnostic to any specific rheological model. Despite this generality, the model makes three main simplifying assumptions. These results show that the modeling assumptions used in SWR are valid in bovine liver over a wide frequency band.

Impact of Annealing Chemistry on the Properties and Performance of Microporous Annealed Particle Hydrogels.

Microporous annealed particle (MAP) hydrogels are a promising class of in situ-forming scaffolds for tissue repair and regeneration. While an expansive toolkit of annealing chemistries has been described, the effects of different annealing chemistries on MAP hydrogel properties and performance have not been studied. In this study, we address this gap through a controlled head-to-head comparison of poly(ethylene glycol) (PEG)-based MAP hydrogels that were annealed using tetrazine-norbornene and thiol-norbornene click chemistry. Characterization of material properties revealed that tetrazine click annealing significantly increases MAP hydrogel shear storage modulus and results in slower in vitro degradation kinetics when microgels with a higher cross-link density are used. However, these effects are muted when the MAP hydrogels are fabricated from microgels with a lower cross-link density. In contrast, in vivo testing in murine critical-sized calvarial defects revealed that these differences in physicochemical properties do not translate to differences in bone volume or calvarial defect healing when growth-factor-loaded MAP hydrogel scaffolds are implanted into mouse calvarial defects. Nonetheless, the impact of tetrazine click annealing could be important in other applications and should be investigated further.

Viscoelastic Reversibility of Carrageenan Hydrogels under Large Amplitude Oscillatory Shear: Hybrid Carrageenans versus Blends.

The viscoelastic response of carrageenan hydrogels to large amplitude oscillatory shear (LAOS) has not received much attention in the literature in spite of its relevance in industrial application. A set of hybrid carrageenans with differing chemical compositions are gelled in the presence of KCl or NaCl, and their nonlinear viscoelastic responses are systematically compared with mixtures of kappa- and iota-carrageenans of equivalent kappa-carrageenan contents. Two categories of LAOS response are identified: strain softening and strain hardening gels. Strain softening gels show LAOS non-reversibility: when entering the nonlinear viscoelastic regime, the shear storage modulus G' decreases with increasing strain, and never recovers its linear value G0 after successive LAOS sweeps. In contrast to this, strain hardening carrageenan gels show a certain amount of LAOS reversibility: when entering the nonlinear regime, G' increases with strain and shows a maximum at strain γH. For strains applied below γH, G0 shows good reversibility and the strain hardening behavior is maintained. For strains larger than γH, G0 decreases significantly indicating an irreversible structural change in the elastic network. Strain hardening and elastic recovery after LAOS prevail for hybrid carrageenan and iota-carrageenan gels, but are only achieved when blends are gelled in NaCl, suggesting a phase separated structure with a certain degree of co-aggregated interface for mixed gels.

The Importance of Adhesion in Solid-State Batteries

Solid-state batteries are one of the key technologies to expedite the electrification of the economy. Compared with traditional liquid electrolytes, solid-state electrolytes are intrinsically safer and can enable high-energy designs by pairing with high-capacity cathodes and lithium metal anodes. However, maintaining the solid/solid contact between electrode and electrolyte during electrochemical cycling is non-trivial and the main challenge for all-solid-state batteries. The common strategy for combatting the contact issue is applying stack pressure, which is a sort of scientific shortcut that masks the real challenges of maintaining good contact between the different electrodes and electrolytes. Improving the adhesion between different battery components is a more effective and commercially viable strategy. We hypothesized that increasing the adhesion between electrode and electrolyte will improve electrode integrity, mitigate contact loss, and increase Coulombic efficiency and cycle life.There are very few studies on the adhesion of battery materials. This is primarily due to limited techniques to measure adhesion at the nanometer and micrometer scales relevant to the battery operation. In this work, we proposed to use atomic force microscopy (AFM) with customized probes to investigate adhesion between a model solid polymer electrolyte (SPE) consisting of crosslinked poly(ethylene oxide) (xPEO) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), and a model cathode active material, LiNi0.6Mn0.2Co0.2O2 (NMC622). We showed that a two-fold increase in polymer stiffness (storage shear modulus, G’) from increasing the crosslinking density, leads to a 40% reduction in the bulk ionic conductivity in the SPE. However, we show evidence that this trade-off relationship between stiffness and ionic conductivity does not significantly impact the battery performance. In drastic contrast, it leads to a decrease in the work of adhesion at the electrolyte|cathode interface, which has a profound impact on the resulting discharge capacity of the battery. How the crosslinking density of the polymer affects the NMC-xPEO adhesion at the microscale and how this affects battery performance remain open questions, which the authors wish to gain insight into from the discussions.

Preparation of an Antibacterial Branched Polyamide 6 via Hydrolytic Ring-Opening Co-Polymerization of ε-Caprolactam and Lysine Derivative.

In this study, we successfully realized the hydrolytic ring-opening co-polymerization of ε-caprolactam (CPL) and lysine derivative. A novel antibacterial modified polyamide 6 with a branched structure was obtained after the quaternization of the co-polymers. The co-polymers exhibited a significant increase in zero shear viscosity, melt index and storage modulus at the low frequency region. The quaternized co-polymers displayed thermal properties different from pure PA6 and good mechanical (tensile) properties. The antibacterial activity of the quaternized co-polymers depends on the quaternary ammonium groups' incorporated content. At 6.2 mol% incorporation of quaternary ammonium groups, the strong antibacterial activity has been introduced to the co-polymers. As the quaternary ammonium groups approached 10.1 mol%, the antibacterial polymers demonstrated nearly complete killing of Staphylococcus aureus (Gram positive) and Escherichia coli (Gram negative). The above research results provided a new approach for the study of high-performance nylon.

Ultrashort echo time magnetic resonance elastography for quantification of the mechanical properties of short T2 tissues via optimal control-based radiofrequency pulses.

The aim of the current study is to demonstrate the feasibility of radiofrequency (RF) pulses generated via an optimal control (OC) algorithm to perform magnetic resonance elastography (MRE) and quantify the mechanical properties of materials with very short transverse relaxation times (T2 < 5 ms) for the first time. OC theory applied to MRE provides RF pulses that bring isochromats from the equilibrium state to a fixed target state, which corresponds to the phase pattern of a conventional MRE acquisition. Such RF pulses applied with a constant gradient allow to simultaneously perform slice selection and motion encoding in the slice direction. Unlike conventional MRE, no additional motion-encoding gradients (MEGs) are needed, enabling shorter echo times. OC pulses were implemented both in turbo spin echo (OC rapid acquisition with refocused echoes [RARE]) and ultrashort echo time (OC UTE) sequences to compare their motion-encoding efficiency with the conventional MEG encoding (classical MEG MRE). MRE experiments were carried out on agar phantoms with very short T2 values and on an ex vivo bovine tendon. Magnitude images, wave field images, phase-to-noise ratio (PNR), and shear storage modulus maps were compared between OC RARE, OC UTE, and classical MEG MRE in samples with different T2 values. Shear storage modulus values of the agar phantoms were in agreement with values found in the literature, and that of the bovine tendon was corroborated with rheometry measurements. Only the OC sequences could encode motion in very short T2 samples, and only OC UTE sequences yielded magnitude images enabling proper visualization of short T2 samples and tissues. The OC UTE sequence produced the best PNRs, demonstrating its ability to perform anatomical and mechanical characterization. Its success warrants in vivo confirmation in further studies.

Nanofiller‐and basalt fiber‐reinforced recycled polyamide 6 hybrid composites

AbstractThe influence of nanofillers (cellulose nanofibers (CNF) and halloysite nanotubes (HNTs)), and basalt fibers (BF) on the morphology, mechanical and thermal of recycled polyamide 6 (PA6) composites were investigated through scanning electron microscopy (SEM), mechanical testing, rotational rheometry, dynamic mechanical analysis (DMA), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). CNF, HNTs and BF were relatively well‐dispersed in the PA6 matrix and the incorporation of these nanofillers and BF increased the strength of the matrix, which indicates a good dispersion of the nanofillers and BF. CNF and HNTs‐filled PA6 nanocomposites increased the tnsile strength by 14% and 6% compared to the neat PA6, respectively. The composites elongation at break decreased with nanofiller, BF and combined nanofillers and BF. The shear storage modulus values of PA6/20B5C, PA6/20B5H, and PA6/25B are significantly elevated compared to neat PA6, with increases of 3.7, 2.8, and 2.5 times, respectively, at an angular frequency of 100 rad/s. PA6/20B5H composites with 20 wt.% BF and 5 wt.% HNTs exhibited the highest storage modulus (9.5 GPa) from the DMA study. Thermal stability and ash content at 800°C increased with the incorporation of HNTs and BF. The DSC findings showed that the glass transition (Tg) and melting temperature (Tm) of the composites did not exhibit any notable changes when nanofillers and BF were added to the resin. The nucleation ability of PA6 was enhanced attributable to BF and hybridization of BF and nanofillers since the crystallization temperatures of PA6 in BF filled and hybrid composites were around 5°C greater than neat PA6. The results suggest hybrid composites with potential environmental characteristics and higher mechanical properties can be utilized in semi‐structural applications in automotive and construction as a sustainable and lightweight alternative to steel and other materials.Highlights The addition of HNTs, CNF, BF and hybridization of nanofillers with BF reduced the brittleness of PA6. Nanoreinforced and hybrid PA6 composites achieved higher storage modulus than neat PA6. Thermal stability and ash content increased with the incorporation of HNTs and BF. The hybrid composites have a higher complex viscosity compared to PA6. The sustainable hybrid composites can be utilized in automotive and construction industries.

The influence of cooling on biomechanical time since death estimations using ovine brain tissue

The significance of biomechanical analyses for forensic time since death estimations has recently been demonstrated. Previous biomechanical analyses successfully discriminated post-mortem brain tissue from tissue with a post-mortem interval of at least one day when held at 20 °C. However, the practical utility of such analyses beyond day one at 20 °C was limited. This study investigates the storage, loss, and complex shear modulus of various brain regions in sheep stored at 4 °C in 24-hour intervals over four days post-mortem using rheometry tests. The aim is to identify the critical biomechanical tissue property values to predict post-mortem time and assess the temperature sensitivity of the rheometry method by comparing results to recent findings at 20 °C. Thirty sheep brains were examined, including the frontal lobe, parietal lobe, anterior and posterior deep brain, superior colliculi, pons, medulla, and cerebellum. Rheometry tests were conducted, and receiver operator characteristic analyses were employed to establish cut-off values. At 4 °C storage, all investigated biomechanical properties of the examined brain regions remained stable for at least one day post-mortem. Using cerebellar samples stored at 4 °C, a post-mortem interval of at least two days could be determined with excellent diagnostic ability. Complex shear modulus values below 1435 Pa or storage modulus values below 1313 Pa allowed prediction of two or more days post-mortem. Comparisons between 4 °C and 20 °C revealed brain region-specific results. For instance, the complex shear moduli of the anterior deep brain at 4 °C were significantly higher on all individual testing days when compared to 20 °C. In contrast, the combined medulla and pons samples were similar on each day. Rheometry testing of brain tissue consistently stored at 4 °C since death proved valuable for forensic time since death estimations starting from two days after death.

Interfacial mechanics of β-casein and albumin mixed protein assemblies at liquid-liquid interfaces

Protein emulsifiers play an important role in formulation science, from food product development to emerging applications in biotechnologies. The impact of mixed protein assemblies on surface composition and interfacial shear mechanics remains broadly unexplored, in comparison to the impact that formulation has on dilatational mechanics and surface tension or pressure. In this report, we use interfacial shear rheology to quantify the evolution of interfacial shear moduli as a function of composition in bovine serum albumin (BSA)/β-casein mixed assemblies. We present the pronounced difference in mechanics of these two protein, at oil interfaces, and observe the dominance of β-casein in regulating interfacial shear mechanics. This observation correlates well with the strong asymmetry of adsorption of these two proteins, characterised by fluorescence microscopy. Using neutron reflectometry and fluorescence recovery after photobleaching, we examine the architecture of corresponding protein assemblies and their surface diffusion, providing evidence for distinct morphologies, but surprisingly comparable diffusion profiles. Finally, we explore the impact of crosslinking and sequential protein adsorption on the interfacial shear mechanics of corresponding assemblies. Overall, this work indicates that, despite comparable surface densities, BSA and β-casein assemblies at liquid–liquid interfaces display almost 2 orders of magnitude difference in interfacial shear storage modulus and markedly different viscoelastic profiles. In addition, co-adsorption and sequential adsorption processes are found to further modulate interfacial shear mechanics. Beyond formulation science, the understanding of complex mixed protein assemblies and mechanics may have implications for the stability of emulsions and may underpin changes in the mechanical strength of corresponding interfaces, for example in tissue culture or in physiological conditions.

Enhancement of Magnetorheological Fluids with Size and Morphology-Optimized Fe3O4 Nanoparticles: Impacts on Rheological Properties and Stability.

In this study, we synthesized Fe3O4 nanoparticles (Fe3O4 NPs) of varying sizes and morphologies using the solvothermal method and incorporated them as additives into carbonyl iron magnetorheological fluids (CI-MRFs). We tested the shear stress, yield stress, viscosity and storage modulus of the MRFs using a magnetorheometer to investigate how the size and morphology of Fe3O4 NPs influence the performance of MRFs. Our results indicate that the size of the additive nanoparticles significantly enhances the MR properties of MRFs more than their morphological attributes. This enhancement results from optimizing and stabilizing the CI magnetic chain structure of the nanoparticles in the presence of a magnetic field. Specifically, MRFs with Fe3O4 NPs averaging 250 nm in size exhibit higher yield stress and storage modulus and show increased resistance to shear strains. Although the nanoparticle morphology has a modest effect on the rheological properties of MRFs, hexahedral and octahedral particles can enhance rheological properties through increased internal friction compared to spherical particles. Additionally, Fe3O4 NPs of different sizes and morphologies improve the sedimentation stability of MRFs, with those around 250 nm being particularly effective at slowing down sedimentation. Both hexahedral and octahedral Fe3O4 NPs slow down sedimentation more effectively than spherical Fe3O4 NPs. This paper investigates the rheological properties of CI-MRFs by controlling the additive particle size and morphological features, providing a research foundation for the design and optimization of MRFs.

Agarose as a Tissue Mimic for the Porcine Heart, Kidney, and Liver: Measurements and a Springpot Model.

Agarose gels are often used as a tissue mimic. The goal of this work was to determine the appropriate agarose concentrations that result in mechanical properties that match three different porcine organs. Strain tests were carried out with an amplitude varying from 0.01% to 10% at a frequency of 1 Hz on a range of agarose concentrations and porcine organs. Frequency sweep tests were performed from 0.1 Hz to a maximum of 9.5 Hz at a shear strain amplitude of 0.1% for agarose and porcine organs. In agarose samples, the effect of pre-compression of the samples up to 10% axial strain was considered during frequency sweep tests. The experimental measurements from agarose samples were fit to a fractional order viscoelastic (springpot) model. The model was then used to predict stress relaxation in response to a step strain of 0.1%. The prediction was compared to experimental relaxation data, and the results agreed within 12%. The agarose concentrations (by mass) that gave the best fit were 0.25% for the liver, 0.3% for the kidney, and 0.4% for the heart. At a frequency of 0.1 Hz and a shear strain of 0.1%, the agarose concentrations that best matched the shear storage modulus of the porcine organs were 0.4% agarose for the heart, 0.3% agarose for the kidney, and 0.25% agarose for the liver.

Mechanistic study of the stabilization of dentin-bonded restorative interfaces via collagen reinforcement by multi-acrylamides

Hydrolytically and enzymatically-stable multi-acrylamides have been proposed to increase the long-term durability of dental adhesive interfaces as alternatives to methacrylates. The aim of this study was to investigate the mechanical and biochemical properties of experimental adhesives containing multi-functional acrylamides concerning collagen reinforcement and metalloproteinases (MMP) activity. Multi-functional acrylamides, TMAAEA (Tris[(2-methylaminoacryl) ethylamine) and DEBAAP (N,N-Diethyl-1,3-bis(acrylamido) propane), along with the commercially available DMAM (N,N-dimethylacrylamide) (monofunctional acrylamide) and HEMA (2-Hydroxyethyl methacrylate) (monofunctional methacrylate - control) were tested for stability against enzymatic hydrolysis by cholesterol esterase/pseudocholinesterase (PC/PCE) solutions for up to 30 days. Collagen-derived substrate and gelatin zymography were performed to examine the effect of the compounds on the biological activity of human recombinant and dentin-extracted gelatinases MMP-2 and MMP-9. In situ zymography was carried out by fluorescent collagen degradation combined with confocal microscopy analysis. Hydroxyproline content was measured in collagen derived from dentin extracts though reaction with Ehrlich's reagent p-dimethylaminobenzaldehyde (DMAB), generating a stable chromophore measured at 550 nm. Storage shear modulus of demineralized dentin discs treated with the tested compounds was measured by oscillatory rheometry, in order to investigate potential collagen reinforcement. FT-IR was performed to determine qualitative differences in collagen based on observed changes in amide bands. The results were analyzed by ANOVA/Tukey's test (α = 0.05). Multi-acrylamides survived 30 days of incubation in cholinesterase/pseudo-cholinesterase (PC/PCE) solutions, while HEMA showed approximately 70 % overall degradation. Incubation with multi-acrylamides reduced collagen degradation as evidenced by the reduced hydroxyproline levels and by the 30 % increase inshear storage modulus. Biochemical and zymography assays showed no noticeable inhibition of recombinant and extracted MMPs enzymatic activity. The infra-red spectroscopy results for multi-functional acrylamides treated samples demonstrated shifts of the amide II bonds and marked increase in intensity of the bands 1200 cm-1, which may indicate partial collagen denaturation and some degree of cross-linking of the compounds with collagen, respectively. The multi-acrylamides exhibited not only comparable mechanical properties but also demonstrated significantly enhanced biochemical stability when compared to the widely used methacrylate control.Clinical relevance: These findings highlight the potential of multi-acrylamides to increase the bonding stability to tissues and, ultimately, contribute to the longevity of dental restorations.

Experimental and theoretical investigation on magnetorheological elastomers containing carbonyl iron particles coated with silane coupling agent

Magnetorheological (MR) elastomer composites, comprising soft silicone rubber, various additives, and different weight fractions of carbonyl iron particles (CIPs) coated with silane coupling agent, are produced via a novel manufacturing process in an anisotropic state. This study encompasses both experimental and modeling investigations into the dynamic viscoelastic properties of magnetorheological elastomer (MREs) in shear mode under varying magnetic fields, displacement amplitudes, and frequencies. Two MRE vibration mitigation devices are fabricated to experimentally assess the shear storage modulus and the loss factor of MREs. The experimental findings reveal a pronounced MR effect in the MRE devices, where both the shear storage modulus and the loss factor increase with rising magnetic fields, frequencies, and particle weight fractions, yet decrease with higher displacement amplitudes. A modified fractional-derivative equivalent parametric model, grounded in a magnetic field- and frequency-dependent shear modulus model along with internal variable theory, is proposed to describe the effects of these key influencing factors on the MREs’ dynamic viscoelastic properties. Comparative analysis of experimental and numerical data demonstrates that this refined mathematical model can accurately represent the dynamic viscoelastic properties of MREs.

A chemical interpretation for the post-reversion upturn in the natural rubber/accelerated sulfur system based on the viscoelastic properties and cross-link density measurements

The curing cycle of natural rubber (NR) with a conventional accelerated sulfur system (CV) generally exhibits three phases. The induction phase, the crosslinking phase, and the reversion phase. Prolonged curing of NR/CV system even at a temperature of 150 °C can show reversion. Many research reports are available in the literature with reference to the reversion behavior and the subsequent network modifications of natural rubber with accelerated sulfur. However, the literature regarding post-reversion curing behavior is scanty. This article describes the post-reversion upturn of natural rubber with a conventional accelerator sulfur system at a higher curing temperature. A network rebuilding after collapsing the initially formed network due to reversion was identified as the primary reason for the post-reversion upturn. The dynamic rheological testing capability of the Rubber Process Analyzer (RPA) was employed to characterize the network formed during curing, reversion and post-reversion phases. The cure-strain sweep data from the RPA indicated that the shear storage modulus (G′) of the broken network increased due to the post-reversion upturn. The chemical crosslink densities of the samples were also found to increase due to the upturn curing behavior. From these experimental results and the information conceived from the previous literature, two plausible mechanisms have been proposed to interpret the post-reversion upturn cure behavior.

A physics-guided deep learning model for predicting the magneto-induced mechanical properties of magnetorheological elastomer: Small experimental data-driven

Magnetorheological elastomer (MRE) is a novel intelligent material, which shows excellent potential in vibration control applications. Previous researches have fully demonstrated that the magneto-induced shear storage modulus of MRE largely determines the vibration control effect. However, both existing theoretical and experimental ways to measure the magneto-induced shear storage modulus of MRE face their own shortage. Therefore, a novel physics-guided deep learning model is proposed to efficient predict the magneto-induced mechanical properties of MRE based on Magnetic Dipole theory and data-driven methods. A small database is built by collecting the magneto-induced shear storage modulus of MRE with different material ratios tested on a special shear rheometer. The proposed model trained with small training samples and its prediction results fit well with experimental values (average R2 of 0.99) which is superior to existing constitutive models. The training only takes 25 s, which significantly shortens the time compared to the experiment. Furthermore, the proposed model effectively predicts the magneto-induced storage modulus of MRE and has good generalization and superior transfer performance.

Design and Synthesis of P(AAm-co-NaAMPS)-Alginate-Xanthan Hydrogels and the Study of Their Mechanical and Rheological Properties in Artificial Vascular Graft Applications.

Cardiovascular diseases (CVDs) are the number one cause of mortality among non-communicable diseases worldwide. Expanded polytetrafluoroethylene (ePTFE) is a widely used material for making artificial vascular grafts to treat CVDs; however, its application in small-diameter vascular grafts is limited by the issues of thrombosis formation and intimal hyperplasia. This paper presents a novel approach that integrates a hydrogel layer on the lumen of ePTFE vascular grafts through mechanical interlocking to efficiently facilitate endothelialization and alleviate thrombosis and restenosis problems. This study investigated how various gel synthesis variables, including N,N'-Methylenebisacrylamide (MBAA), sodium alginate, and calcium sulfate (CaSO4), influence the mechanical and rheological properties of P(AAm-co-NaAMPS)-alginate-xanthan hydrogels intended for vascular graft applications. The findings obtained can provide valuable guidance for crafting hydrogels suitable for artificial vascular graft fabrication. The increased sodium alginate content leads to increased equilibrium swelling ratios, greater viscosity in hydrogel precursor solutions, and reduced transparency. Adding more CaSO4 decreases the swelling ratio of a hydrogel system, which offsets the increased swelling ratio caused by alginate. Increased MBAA in the hydrogel system enhances both the shear modulus and Young's modulus while reducing the transparency of the hydrogel system and the pore size of freeze-dried samples. Overall, Hydrogel (6A12M) with 2.58 mg/mL CaSO4 was the optimal candidate for ePTFE-hydrogel vascular graft applications due to its smallest pore size, highest shear storage modulus and Young's modulus, smallest swelling ratio, and a desirable precursor solution viscosity that facilitates fabrication.

Effect of two different Flammulina velutipes polysaccharides on the physicochemical and digestive properties of rice starch and their interaction mechanisms

This study investigated the interaction mechanisms between rice starch (RS) and two different Flammulina velutipes polysaccharides (FPs) obtained through water-extracted (WEFP) and alkali-extracted (AEFP) methods regarding the pasting, gelatinization, retrogradation, and in vitro digestive properties. The WEFP, with a majority of α-glucan and lower MW, and the AEFP, a high MW trihelix β-glucan, distinctly affected the physicochemical and digestive properties of RS in a dose-dependent manner. Both FPs reduced the leached amylose content, retrogradation, and digestibility of RS, and increased the shear stress, storage modulus, and loss modulus of RS. The swelling power and pasting viscosities of RS were inhibited by WEFP and enhanced with AEFP. Compared with the control RS gel, WEFP increased the gelatinization temperatures while AEFP accelerated the gelatinization of RS. Fourier-transform infrared analysis revealed WEFP enhanced the hydrogen bonding with starch and water molecules which increased the short-range ordered structures, and a more compact, wrinkle, and ordered network structures could be visualized in RS-WEFP gel, which attributed to the decreased glycemic responses of RS-WEFP gels. However, reduced hydrogen bonds were observed in RS-AEFP systems, and entanglement effect of viscous AEFP on starch granules resulted a thicker and more disordered RS-AEFP gel structure, which was the main factor restricted the digestion rates of RS. This study provides a theoretical insight about the application of FPs on RS-based hypoglycemic foods.

Rheological properties of starch isolated from longan kernels with protease-assisted alkali method

AbstractAs a byproduct from the deep processing of longan fruit, longan kernel is rich in starch and is a good source for starch production. In this study, the rheological properties of longan kernel starch (LS) extracted by protease-assisted alkali method were investigated. When the shear rate was from 1 to 100 s−1, the pastes containing 4%–7% (w/v) of LS showed a non-Newtonian fluid with a pseudoplastic fluid characteristic. Their shear stress, apparent viscosity, complex viscosity, storage modulus (G′), and loss modulus (G″) positively correlated with starch concentration. The loss factor (tan δ) of all LS pastes was less than 1. At same concentration, LS paste showed a stronger pseudoplastic fluid characteristic and higher elasticity than corn starch and pea starch pastes. Based on this, LS has potential in processing of jelly, soft sweets, ham sausage, and some other sauces.