Korea-Australia Rheology Journal最新文献

A cylinder rotating in an off-center position across a microchannel is known to generate a net flow for highly viscous Newtonian fluids. The mechanism is also known to be a viable option for the transport of viscoelastic or viscoplastic fluids albeit with a slight drop in performance. In the present work, the applicability of this mechanism is numerically investigated for the transport of (inelastic) time-dependent fluids obeying the structural-based Quemada model. By numerically solving the equations of motion, it is predicted that viscous micropumps can be used for the transport of thixotropic fluids although the obtained numerical results suggest that there exists a critical thixotropy number (a dimensionless number related to the fluid’s natural time) at which the flow rate is at its lowest value. It is shown that the critical thixotropy number can be avoided from the response of the fluid by properly choosing the geometrical parameters of the device. The general conclusion is that viscous micropumps can be deemed as an efficient mechanism for the transport of thixotropic fluids in microfluidic systems provided that the thixotropy number is sufficiently small, i.e., the fluid is strongly thixotropic. The device is predicted to be more suitable for anti-thixotropic fluids.

Liposomes have emerged as pivotal entities in the field of therapeutics, particularly in the domain of protein and vaccine administration. Hence, the development of novel liposomal formulations has garnered considerable interest. Liposomal delivery systems are considered advantageous as medication carriers, especially in the field of dermatology, owing to their moisturizing and restorative characteristics. Nevertheless, a significant drawback in the utilization of liposomes in topical applications is the inherent fluidity of the formulation, which might result in leakage following delivery to the skin surface. The use of liposomes inside the gel matrix, while maintaining the integrity of the vesicles, presents a potentially appealing method for topical administration. The primary objective of this work is to develop a liposomal-loaded gel formulation and assess its in vitro release characteristics as well as its rheological profile, including viscoelastic properties and flow behaviour. This study incorporated two different types of drugs, namely hydrophilic (specifically diphenhydramine hydrochloride) and hydrophobic (namely curcumin), inside its formulations. A liposome, composed of a long alkyl chain lipid such as DPPC with a chain length of 16, was synthesized using the thin film hydration process and subsequently integrated into a carbopol gel. It is noteworthy that the introduction of diphenhydramine hydrochloride (DPH) resulted in a substantial decrease in the elastic modulus and cohesiveness of the liposomal gel. Conversely, the incorporation of curcumin-loaded liposomal gel led to an increase in critical strain and cohesiveness when compared to the plain liposomal gel. In contrast, the liposomal gel containing DPH and curcumin demonstrated a reduced release rate compared to the plain liposomal gel, spanning a duration of 48 h. The in vitro release studies offer the potential for the utilization of liposomal gels as a sustained delivery system.

The capability of a polymer to be molded by the injection molding process is referred to as its moldability. Injection molding technicians typically estimate moldability using a parameter known as the Melt Flow Index (MFI), but this metric can be misleading as it reflects the polymer’s ability to flow under specific conditions that may differ considerably from those encountered during injection molding. A more relevant parameter is the flow length, which represents the distance a polymer travels in a thin, cold mold cavity during the injection molding process. In this study, three types of commercial polypropylene were injection molded in cavity and the flow lengths were measured based on injection pressure and temperature. The outcomes were then compared to the polymer’s rheological properties. The findings indicate that the MFI is not a reliable indicator of polypropylene’s moldability. An empirical equation is suggested to predict polypropylene’s flow length as a function of injection pressure.

The rheological behavior of anode slurries for lithium-ion batteries, containing both natural and synthetic graphite as active material, was investigated with a focus on the different graphite morphologies. When the solid content is low, slurries containing synthetic graphite with a discotic shape display greater viscoelasticity than slurries containing natural graphite with a relatively more spherical shape. This result is attributed to the anisotropic geometry and interparticle force of the synthetic graphite. When the solid content is high, slurries comprising synthetic graphite exhibit lower viscoelasticity than slurries containing natural graphite. Tap density and sedimentation experiments reveal that, due to discotic shape and surface-to-surface attraction, synthetic graphite aggregates to a more densely packed aggregate than natural graphite. Consequently, in conditions of high solid contents where graphite has a greater chance of formation of densely packed aggregates, it is expected that synthetic graphite will have a more compact aggregate structure and a smaller effective volume. The smaller viscoelasticity of synthetic graphite slurries at more concentrated regions, where the effective volume of clusters plays more important role than in dilute regions, is attributed to the surface-to-surface aggregated structure of the synthetic graphite and the resulting small effective volume. Although the effective volume fraction of the graphite aggregates is reduced, slurries made of synthetic graphite demonstrate significant strain stiffening. Our findings suggest that the strain stiffening observed may originate from the anisotropic morphology, which possesses a significant surface area and is accompanied by jamming and high friction.

The settling stability of magnetorheological fluid (MRF) is an important aspect of magnetorheological research and an important indicator of MRF quality. The discrete element method (DEM) was proposed to study the multi-particle settling process of particles dispersed in silicon oil with different iron powder content, particle size, base viscosity, and added magnetic field. Then by preparing MRF, the zero-field viscosity, dynamic magnetic field viscosity, and settling stability of various MRF were measured and analyzed. The results show that the average kinetic energy of MRF settling decreases as particle content, particle size, and base fluid viscosity increase. With 50% iron powder content, 300 nm particle size, and 5% bentonite additive, MRF has the highest viscosity under zero field; under a dynamic magnetic field, the larger the particle size, the larger the viscosity; the MRF settling rate decreases by 18% with a change in iron powder content, decreases by 22.5% with a change in particle size to 300 nm, and decreases by 22% with a change in bentonite content. Under the application of a magnetic field, MRF hardly settles. The final experimental and simulation results are comparable, indicating that the MRF settlement characteristics can be predicted to some extent with the help of DEM simulation.

The main objective of food rheology is to identify food structure and texture by rheological measurements, thereby reducing the requirement for sensory analysis in evaluating food products. However, determining food texture and structure exclusively from rheological measurements can be challenging because of the complicated composition and structure of food, as well as the complexities of factoring in the changes that occur during food mastication. This article provides a comprehensive review of the current experimental, computational and machine learning techniques used in food rheology to probe the structure and texture of food products. The textural attributes and structural information that can be inferred from each measurement technique is discussed and recent studies that carried out the measurements are highlighted. Also presented in this review are the recent progress in the experimental techniques and challenges.

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Bacterial biofilms, as viscoelastic materials, have significant implications in various fields of human life encompassing health, manufacturing, and wastewater treatment. The detailed rheological characterization of mechanical properties, viscoelastic characteristics, and shear behaviors of biofilms is crucial for both scientific insight and practical applications. This review provides an exhaustive examination of bacterial biofilm formation and growth through rheological techniques, representing a critical intersection between microbiology and materials science. It explores different rheological methods, geometries, and devices, offering a comprehensive understanding of how rheological measurements can be applied to study biofilms. The advantages, limitations, and challenges of rheological techniques are also analyzed, emphasizing the importance of choosing appropriate methods for specific applications.

Graphical abstract

Particulate flows occur in various natural and technological settings. Understanding what influences the flow characteristics and how they can be manipulated is significant from scientific and engineering perspectives. In this paper, we review the lattice Boltzmann method combined with the smoothed profile method (LBM–SPM), one of the promising simulation methods for studying particle-containing systems. We present the background theory and numerical schemes of the LBM–SPM, then review several applications of this method for particulate flows; suspension rheology, deposition and clogging of particles within the flow, and the dynamics of particles in non-Newtonian media and at the fluid interface. Finally, we confirmed the versatility and feasibility of LBM–SPM for investigating particulate flows.

Computer simulation and modeling have proven to be powerful tools in the fields of engineering and polymer science. These computational methods not only enable us to verify experimentally observed behaviors, but also provide answers to unsolved phenomena. This review addresses the current status and trends of computational and theoretical studies in polymer blends. We briefly discuss the fundamental aspects of polymer blends, including experimental observations, theories, and a variety of molecular simulations and models for mixtures of two or more polymeric materials. In particular, this study deals with the description of coarse-grained techniques that can offer perspectives into the collective behavior and properties of complicated systems. Additionally, a detailed analysis of their structural, rheological, and mechanical properties via computation is also examined. Lastly, we summarize important findings and highlight points to be carefully considered in modeling polymer blends system accompanied by an outlook on the extension of current studies to complicated systems of many blending types.