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Clogging is ubiquitous. It happens in a wide range of material processing and causes severe performance degradation or process breakdown. In this study, we investigate clogging dynamics in a single micropore by controlling the surface property of the particle and processing condition. Microfluidic observation is conducted to investigate particle deposition in a contraction microchannel where polystyrene suspension is injected as a feed solution. The particle deposition area is quantified using the images taken using a CCD camera in both upstream and downstream of the microchannel. Pressure drop across the microchannel is also measured. When the particle interaction is repulsive, the deposition occurs mostly in downstream, while an opposite tendency is identified when the particle interaction is attractive. More complex deposition characteristics are found as the flow rate is changed. Particle flux density and the ratio of lift force to colloidal force are introduced to explain the clogging dynamics. This study provides a useful insight to alleviate clogging issues by controlling the colloidal interaction and hydrodynamic stress.

The dynamics of model colloidal gels under a steady shear flow is studied by means of a Brownian dynamics (BD) simulation while applying orthogonal superposition rheometry, which superimposes a small amplitude oscillatory flow orthogonal to the main flow direction. Orthogonal dynamic frequency sweep (ODFS) curves are obtained at various magnitudes of the main flow, which shows shear thinning behavior of the colloidal gel. The viscoelastic spectra of the ODFS can be superimposed onto a master curve by the horizontal shift factor, which is equivalent to particle viscosity. That is, the shear rate controls a single master clock for all viscoelastic spectra of the ODFS in the form of a time–shear rate superposition, which bears an analogy with the time–temperature superposition of polymeric systems. In the low-frequency region of the master curve, both orthogonal moduli are well superimposed onto a single master curve, whereas the loss modulus deviates slightly from the master curve in the high-frequency region, which coincides with the experimental findings. We observe spatial and time-varying structural properties in both low- and high-frequency regions on the ODFS curves by decomposing the pair distribution function. It is verified that each flow condition shifted onto the same stress level on the master curve shows identical spatial orthogonal moduli at all radial distances despite the differences in the aggregate size and average particle connectivity.

Capillary suspension processing, which uses a ternary system consisting of solid/fluid/fluid, has recently been proposed as a method for manufacturing Li-ion battery electrodes to enhance the coati...

We propose a groove-embedded partitioned pipe mixer (GPPM) and conduct an in-depth numerical study on the flow and mixing characteristics of the GPPM in the creeping flow regime. The GPPM is a variant of a previously reported mixer, the barrier-embedded partitioned pipe mixer (BPPM), and is designed to achieve better energy-efficient mixing compared to the BPPM. In this paper, we first introduce the working principle of the GPPM and its mixing protocols. Then, the flow system affected by mixing protocols and geometrical parameters of the GPPM is investigated using Poincare sections. As for mixing characteristics, the flux-weighted intensity of segregation is employed for quantitative mixing analysis. It turns out that a GPPM with a proper set of design parameters can indeed lead to a globally chaotic mixing. More importantly, the best GPPM showed better mixing in terms of energy consumption compared to its counterpart, the best BPPM.

The mechanical properties of injectable and thermo-responsive ABC triblock copolymer hydrogels are enhanced by the electrostatic attraction between oppositely charged moieties introduced in the mid-blocks. The triblock copolymers are composed of biodegradable poly(e-caprolactone) (PCL), hydrophilic cationic or anionic mid-block, and temperature-responsive poly(N-isopropylacrylamide) (PNIPAM) with quadruple hydrogen bonding units. PCL blocks and PNIPAM blocks form separate micellar cores, and the mid-blocks make a bridge between the cores. The dynamic nature and thermo-responsiveness of the PNIPAM block primarily endow the temperature- and shear-responsiveness to the hydrogel, and therefore make the hydrogel injectable and self-healable. In particular, the electrostatic attraction introduced in the mid-blocks results in the enhanced mechanical properties of the hydrogels. The dual-responsive hydrogel with the improved moduli will aid in designing soft materials in the field of biological and biomedical applications.

Due to the rapid growth of the global electric vehicle and electronics markets, lithium has become an indispensable resource for our lifestyle, and numerous methods for securing lithium are being actively attempted. For fast and environment-friendly lithium extraction, the electrochemical lithium recovery (ELR) system was studied in recent years. However, there are a limited number of studies regarding the system behavior and most of them are focused on a batch operation, which is far from practical usage. In this study, a flow-type rocking-chair ELR system based on the λ-MnO2/LiMn2O4 electrode pair is proposed for efficient recovery of lithium ions from influents. A lab-scale electrochemical experiment and a two-dimensional numerical simulation are performed to comprehensively analyze the system behavior. It is confirmed that lithium can be simultaneously captured and released at each electrode without any extra electrode regeneration steps. Apart from identifying its behavior experimentally, the spatiotemporal concentration distribution of Li+ in the separator channel is analyzed through numerical simulation. In our system, Li+ is found to be successfully recovered from the source with an energy consumption of 0.56 Wh mol–1 at 6.25 × 10–2 mA cm–2.

There are many factors that affect the increase or decrease of viscosity of the whole blood. Because of this, measuring the viscosity of whole blood is difficult to correlate with specific etiologies, so it tends to disregard the information on blood viscosity. This study is to find out the characteristics of the method of measuring the viscosity of whole blood using the parallel plate method, which is officially registered as a medical device with the approval of the Korea Food and Drug Administration (KFDA), and to apply it to the measurement of whole blood viscosity. The accuracy of the parallel plate measurement is verified by comparing with the measurement results using the commercially available scanning capillary method. In addition, statistically meaningful results are obtained between the viscosity and some components of the whole blood. It is expected that the research will be carried out to understand the correlation between the viscosity of whole blood and specific components of blood and to identify the prognostic signs of etiology in certain diseases, especially in cardiovascular and cerebral vessels diseases.

In order to investigate how particle aggregation affects tensile mechanical performance of composite, a ductile biopolymer (poly(caprolactone)) was melt-compounded with CaCO3 particles over a wide concentration range from 10 to 60 wt.%. The aggregation of CaCO3 particles in poly(caprolactone) (PCL) is investigated depending on particle concentration and surface modification (with stearic acid (2.5 wt.%)) based on rheological assessment. If the composite is mixed with a high concentration of particles (> 30 wt.%), morphological observations and a thermal behavior analysis do not find a difference in the particle aggregation regardless of particle surface modification. However, the linear viscoelastic moduli of the composites distinguishes the difference in particle aggregation regarding to surface modification, indicating induced aggregation behavior with surface-modified CaCO3 (sCC). The composite with sCC starts to form network structure of particles at a lower concentration (30 wt.%) than that with unmodified particles (40 wt.%). When particles form the network structure above the particle percolation threshold, the yield strength of the composite begins to decrease even though Young’s modulus is still increasing. In contrast to the expectation of the better dispersion of particles by surface modification as well as improved tensile mechanical performance with better dispersion, sCC rather induced aggregation with a lower concentration of particle than unmodified particles which resulted in decrease in yielding performance. This study showed that rheological study, especially for the composite with high concentration of particles, is useful to figure out the particle dispersion against a limit at morphology observation.

The nonlinear rheology of a concentrated lithium-ion battery anode slurry was examined under large amplitude oscillatory shear and interpreted with a sequence of physical process (SPP) analysis. A complex interplay of three anode slurry components—graphite (Gr) as an active material, carbon black (CB) as a conductive additive, and carboxymethyl cellulose (CMC) as a binder—leads to a two-step yielding behavior, represented as the secondary plateau in dynamic strain and stress sweep tests. We demonstrate that a two-step yielding behavior is manifested as double deltoids in SPP analysis through the study of intra-cycle rheological transition under oscillatory shear flow. Slurries of Gr-CMC exhibit the two-step yielding behavior; slurries of CB-CMC do not, suggesting that Gr and CMC are the primary causes of two-step yielding in an anode slurry. A sedimentation test on a dilute Gr-CMC solution yielded phase separation between graphite particles, with CMC adsorbed on their surface and graphite particles aggregated via hydrophobic attraction. This indicates two possible types of interactions in a concentrated slurry: a hydrophobic interaction between graphite particles and a physicochemical interaction caused by CMC adsorbed on graphite particles. The first yielding step relates to the hydrophobic attraction between graphite particles, resulting in a network structure that is expected to be brittle and rupture at a small strain. The second yielding step is attributed to the interaction between concentrated CMC, which is corroborated by the overlap of the secondary deltoid of the anode slurry and the single deltoid of the concentrated CMC solution in SPP analysis.

We carry out a numerical study to investigate the dynamics of non-Brownian hard-sphere suspensions near the liquid and crystal coexistence region in small to large amplitude oscillatory shear flow. The first normal stress difference (N1) and related rheological functions are carefully analyzed, focusing on the strain stiffening phenomenon, which occurs in the large strain amplitude region. Under oscillatory shear, we observe several unique behaviors of N1. A negative nonzero mean value of N1 (N1,0) is observed for the applied strain amplitudes. The change of the sign, from negative to positive, at the maximum value of N1 (N1,max) is observed at a specific point, which is not consistent with the critical strain amplitude (γ0,c) at which the modulus begins to deviate from linear viscoelasticity. The behavior of N1 in the oscillatory shear flow is different from that of N1 in steady shear flow, that is, the characteristics of N1 in strain stiffening and shear thickening are quite distinguished from each other. We also perform structural analysis to confirm the relationship between the rheological properties and microstructure of the suspension. A strong correlation is observed between the global bond order parameter (Ψ6) and the distortions in both nonlinear shear and normal stresses. The most noticeable characteristic is captured through the maximum of the global bond order parameter (Ψ6,max). The strain amplitude at the slope change of Ψ6,max corresponds to the point where a unique behavior of N1 is observed, i.e. the change of the sign in N1,max, but a strong correlation is not captured at γ0,c. This demonstrates that the normal stress responds to particle ordering more sensitively than other rheological functions based on shear stress like dynamic moduli. As far as we are concerned, the behavior of N1 has rarely been fully explored and related with the strain stiffening of non-Brownian suspensions so far. Therefore, this study has significance as the first report to strictly analyze strain stiffening along with the first normal stress difference N1.

A systematic study using a model negative electrode slurry with poly(acrylic acid) as a binder is conducted aiming at the control of both dispersion quality and rheology in the electrode manufacturing process. Rheological properties of the model slurries vary considerably with the neutralization degree α. Optical microscope and Turbiscan measurements show that the rheological change is accompanied by the change in particle aggregation tendency. Adsorption and zeta potential measurements reveal that α-dependent adsorption of poly(acrylic acid) is the key factor that controls the rheology of the slurries. The difference in α of the slurry results in a significant difference in the surface roughness and the carbon black particle distribution in the electrode. From this study, it is concluded that the adjustment of neutralization degree of poly(acrylic acid)-based binder critically affects the heterogeneity of the electrode, which can influence the performance as well as the rheological stability in the electrode manufacturing process.

In this study, the transport and deposition of colloidal particles onto a patterned membrane surface are analyzed by both numerical simulation and experiment. The channel Reynolds number (Re) and the size ratio of the particle to the pattern (a/h) are chosen as the major simulation parameters. With an increase in Re and a/h, the number of deposited particles decreases and the rate of permeate flux decline is reduced. Under certain specific combinations of the design parameters, the suspended particles are impeded to access the patterned membrane surface. Based on the particle trajectory analysis, it is claimed that “inaccessible zones”, where the suspended particles cannot be accessed by the flow, are formed near the patterned membrane surface, with the increase in Re and a/h. Cross-flow microfiltration experiments using a poly(methyl methacrylate) (PMMA) particle suspension are also conducted to verify the trend in particle deposition observed in simulation. As the radius of the PMMA particle increases, the number of deposited particles is reduced and the critical flux for the onset of the particle deposition is increased, which qualitatively matches well with simulation. It is found that a patterned membrane can reduce tremendous amounts of colloidal fouling by prohibiting the access of the suspended particles to the membrane surface with the appropriate choice of design parameters such as Re and a/h.

We investigate the drying process of monodisperse colloidal film over a wide range of Péclet number (Pe) by using the Brownian dynamics simulation. We analyze the detailed process in three aspects; accumulation front, normal stress, and microstructure. The evolution of particle distribution is quantified by tracking the accumulation front. The accumulated particles contribute to the continuous increase of the normal stress at the interface. At the substrate, the normal stress first stays constant and then increases as the accumulation front touches the substrate. We quantitatively analyze the stress development by a scaled normal stress difference between the two boundaries. At all tested Pe, the stress difference increases to the maximum, followed by a decrease during drying. Interestingly, a mismatch is observed between the stress difference maximum and the initial stress increase at the substrate. The microstructural analysis reveals that this mismatch is related to the microstructural development at the substrate.

A ternary composite of poly(lactic acid) (PLA), poly(caprolactone) (PCL), and carbon black (CB) shows the PCL-induced CB self-aggregation and percolation formation when the amount of the PCL phase as the secondary phase is as small as the amount of CB. Furthermore, when the drop size of the PCL phase becomes smaller, the ternary composite forms a percolation of high order structure, resulting in a remarkable enhancement of the electrical conductivity (~4 &times, 10&minus, 2 S/m with 4 wt.% CB). To further control the percolation structure, the composite fabrication is controlled by splitting a typical single-step mixing process into two steps, focusing on the dispersion of the secondary PCL phase and the CB particles separately. Under the single-step mixing protocol, the ternary composite shows a structure with greater CB aggregation in the form of a high aspect ratio and large aggregates (aggregate perimeter~aggregate size 0.7). Meanwhile, the two-step mixing process causes the CB aggregates to expand and create a higher structure (aggregate perimeter~aggregate size 0.8). The reduced size of the secondary phase under a mixing condition with high shear force prior to the addition of CB provides a larger interfacial area for CB to diffuse into the PCL phase during the subsequent mixing step, resulting in a further expansion of CB aggregation throughout the composite. The particle percolation of such a high order structure is attributed to high storage modulus (G&prime, ), high Young&rsquo, s modulus, high dielectric loss (&epsilon, &Prime, ), and negative&ndash, positive switching of dielectric constant at high frequency (of 103 Hz) of composite.

A binder plays a critical role in dispersion of coating liquids and the quality of coating. Poly(vinylidene fluoride) (PVDF) is widely used as a binder in cathode slurries, however, its role as a binder is still under debate. In this paper, we study the role of PVDF on the rheology of cathode battery slurries consisting of Li(Ni1/3Mn1/3Co1/3)O2 (NCM), carbon black (CB) and N-methyl-2-pyrrolidone (NMP). Rheology and microstructure of cathode slurries are systemically investigated with three model suspensions: CB/PVDF/NMP, NCM/PVDF/NMP and NCM/CB/PVDF/NMP. To highlight the role of PVDF in cathode slurries, we prepare the same model suspensions by replacing PVDF with PVP, and we compare the role of PVDF to PVP in the suspension rheology. We find that PVDF adsorbs neither onto NCM nor CB surface, which can be attributed to its poor affinity to NCM and CB. Rheological measurements suggest that PVDF mainly increases matrix viscosity in the suspension without affecting the microstructure formed by CB and NCM particles. In contrast to PVDF, PVP stabilizes the structure of CB and NCM in the model suspensions, as it is adsorbed on the CB surface. This study will provide a useful insight to fundamentally understand the rheology of cathode slurries.

We suggest a numerical method to describe particle dynamics at the fluid interface. We adopt a coupling strategy by combining the color gradient lattice Boltzmann method (CGLBM) and smoothed profile method (SPM). The proposed scheme correctly resolves the momentum transfer among the solid particles and fluid phases while effectively controlling the wetting condition. To validate the present algorithm (CGLBM-SPM), we perform several simulation tests like wetting a single solid particle and capillary interactions in two solid particles floating at the fluid interface. Simulation results show a good agreement with the analytical solutions available and look qualitatively reasonable. From these analyses, we conclude that the key features of the particle dynamics at the fluid interface are correctly resolved in our simulation method. In addition, we apply the present method for spinodal decomposition of a ternary mixture, which contains two-immiscible fluids with solid particles. By adding solid particles, fluid segregation is much suppressed than in the binary liquid mixture case. Furthermore, it has different morphology, such as with the jamming structure of the particles at the fluid interface, and captured images are similar to bicontinuous interfacially jammed emulsion gels in literature. From these results, we confirm the feasibility of the present method to describe soft matters; in particular, emulsion systems that contain solid particles at the interface.

Two-dimensional steady thermocapillary flows in a liquid layer over a substrate, which has a uniform temperature and sinusoidal topography, are investigated by asymptotic theory. Here, the buoyancy effect is negligible and the interface is not significantly disturbed under low Marangoni number and low capillary number. A temperature gradient along the gas/liquid interface causes recirculating flows. For a small aspect ratio, which yields a sinusoidal topography with a long wavelength relative to the mean depth of the liquid layer, the second-order solutions are obtained analytically. The basic solutions show vertical diffusion of heat and vorticity from the substrate and interface, respectively. In the second corrections, the horizontal diffusion of heat weakens the overall flow and the convection of heat intensifies it.

Deformation and breakup of a single agglomerate exposed to pure planar extensional flow in a cross-channel were experimentally investigated. Aggregation was generated by applying shear with destabilized polystyrene particles, and the fractal dimension, df, of the agglomerate was 2.25. The aggregation focused on the center of the channel by sheath flow was rotated while approaching stagnant point. Then, the aspect ratio increased as it deformed close to the stagnant point. The probability of the breakup and the fragment distribution were dependent upon the viscosity and flow rate and were superimposed on a master curve as a function of applied stress. With the increase in stress, the projected area of the fragment that was split by the flow decreased with a power-law relationship, and the exponent was in agreement with the model prediction.

The effect of particles on the development of instability patterns during the capillary thinning process of a poly(ethylene oxide) solution has been experimentally studied in an effort to clarify the filament breakup behavior of particulate systems. We focus on breathing and formation of the first bead in particular, which as this bead initiate blistering. Changes in instability patterns due to an addition of PMMA particles are investigated by observing the evolution of a filament undergoing capillary thinning. The addition of particles accelerates breathing and the formation of the first bead. By comparing the extensional properties of a PMMA/PEO suspension to those of glycerin/PEO solutions which has the same shear viscosity, surface tension and polymer concentration, it was found that the addition of particles has little effect on the behavior of polymer chains under an extensional flow. Meanwhile, the flow becomes heterogeneous with the fluctuation of the local particle concentration, inducing rapid thinning at the neck region, which propagates throughout the filament as capillary thinning proceeds. The addition of particles also influences the position of the first bead. For a pure polymer solution and a polymer solution with a small amount of particles (∼2 wt.%), the first bead mostly appears near the upper neck. However, as the particle concentration increases to 10 wt.%, the first bead appears at random locations along the filament, with similar probabilities. The randomization of the position of the first bead is attributed to the non-uniform distribution of particles inside a thinning filament due to the fluctuation of the local particle concentration.

In this paper we investigated numerically the flow and mixing characteristics of the barrier-embedded partitioned pipe mixer (BPPM) in non-creeping flow conditions. Numerical simulations are conducted for three mixing protocols of the BPPM, co-rotational, mirrored co-rotational, and counter-rotational protocols in the range of the Reynolds number (Re), 0.1≤Re≤300, focusing on the effect of the Reynolds number, the barrier height, and the mixing protocols on the mixing in the BPPM. Each mixing protocol creates two crosssectional flow portraits with crossing streamlines. Poincare sections were plotted to investigate the flow system affected by the Reynolds number and the barrier height. Mixing in a specific BPPM is characterized using the intensity of segregation in terms of the compactness and the energy consumption. The dependency of the barrier height and the Reynolds number on the final mixing state of the BPPMs was identified by mixing analyses. The co-rotational protocol results in an efficient mixing in the creeping flow regime. Meanwhile, mirrored co-rotational and counter-rotational protocols, which lead to poor mixing in the creeping flow regime, turned out to be efficient protocols in the higher Reynolds number regime.

We investigate the influence of inter-particle affinity on the microstructure and rheological behavior in the bimodal suspension systems. For this purpose, we design the suspensions using two kinds of polystyrene beads (PS, size ∼530 nm) as a large particle which are electrostatically stabilized and are different in surface properties only, while keeping unstable alumina coated silica (Al-silica, size ∼12 nm) as a small particle. To change the affinity, hydrogen bonding is induced by modifying surface of PS as poly (vinyl pyrrolidone) (PVP). The influence of affinity between large and small particles is investigated by observing the changes in rheological properties and microstructure. Even with the same, the formation of Al-silica cluster which connects large particles is dominant when sulfate modified PS is used and the affinity between the particles is not strong. On the contrary, the Al-silica particles cover the surface of large particles rather than making bridges when PVP modified PS is used and the affinity is strong. The phase map which shows fluid-gel transition according to the composition of the suspension is also obtained. The affinity is found to affect the shape of the phase map too. This research explains how the differences in affinity between large and small particles affect the bimodal suspensions according to the surface properties of the particles, and provides an insight on the complex behavior of particulate fluids.

Two methods are widely used to quantitatively analyze the nonlinear stress in large amplitude oscillatory shear (LAOS) flow; one is to analyze the stress in time domain and the other in strain or strain rate domain. Distinguished from these two methods, this paper exploits the concept of work and energy to analyze the oscillatory shear stress. The inner area in the strain-stress Lissajous curve after one cycle is known to be related with work, and that of the strain rate-stress Lissajous with energy. To precisely analyze the nonlinear stress, it helps to consider work and energy not only after a complete cycle but also during the cycle. In this paper, we trace the work and energy during the oscillation, together with their derivatives. We apply this concept to perfectly elastic solid, purely viscous liquid, and viscoelastic fluid. By this approach, it is shown that a rheological behavior such as strain thinning can be originated by various origin in the perspective of work and energy, which means that the rheological behavior can be subclassified in terms of work and energy. This approach is useful because it can analyze nonlinear stress without mathematically intriguing higher harmonics and it can be easily applied to any type of material with different stress shape.

In this study, we examine the complex interplay between particulate fouling and flow disturbance via particle simulation and microfluidic experiments. From the experiment, it is found that a particle is transported and deposited following the streamline, which is affected by the existing particle deposit. Inspired by this microfluidic observation, we develop a novel coarse-grained particle simulation, which continuously updates the flow field by considering the particle deposits, to investigate particulate fouling more intensively. Four physical factors are proposed to describe quantitatively the particulate fouling: effective collision, hydrodynamic boundary layer, inaccessible zone, and high shear stress region. In the initial stage of fouling, a number of particles are deposited within the growing hydrodynamic boundary layer, where effective collisions are readily achieved. In the latter stage of fouling, the inaccessible zone and high shear stress region are expanded, which causes the particle deposition rate to decrease. This result provides a comprehensive understanding of the particulate fouling through the combination of the four physical factors.

Brownian dynamics simulations under large amplitude oscillatory shear flow at an intermediate volume fraction in both hard and soft sphere systems have been carried out. Elastic and viscous stresses for the two systems are calculated by using the stress decomposition method. Careful investigation of “double peaks,” which are experimentally observed only in the elastic stress of hard sphere systems, has been conducted. When comparing hard and soft sphere systems in simulation, double peaks are observed only in hard sphere systems, within a specific strain amplitude range. The structures of hard sphere systems at different strain amplitudes, where double peaks appear and not, are compared. Excess entropy concept is adopted to evaluate the extent of particle alignment during the cycle. According to the structural analyses, double peaks are created when the structural difference between maximum-ordered and minimum-ordered states is large during 1 cycle.

For a composite of poly(lactic acid) containing graphene nanoplatelets (GNPs) at a low concentration (0.34 vol%), this study examined growths of mechanical and electrical properties under an alternating current (AC) electric field, focusing on field-induced GNP structures governing those properties. The composite was subjected to the AC field (60 Hz) of various intensities E for various times t E at 190 °C. A fraction of randomly oriented GNPs was aligned by the field and then connected into columns, as suggested from optical microscopy. This structural evolution led to qualitatively similar growths of low-frequency storage modulus and static electrical conductivity. The key quantity for understanding this growth was a time t E* for occurrence of short circuit that detected formation of GNP columns conductively bridging the electrodes. The growths of both modulus and conductivity for various E were summarized as functions of a reduced variable, t E/t E*, confirming the growths commonly reflected the evolution of the GNP columns. However, the modulus grew fast and leveled off by t E/t E* ~ 1, whereas the conductivity kept growing gradually even at t E/t E* > 1. This difference was discussed in relation to the matrix chains and leftover GNPs out the column.

Inspired by the partitioned pipe mixer (PPM), a barrier-embedded partitioned pipe mixer (BPPM) is designed and analyzed using a numerical simulation scheme. The BPPM is a static mixer, composed of orthogonally connected rectangular plates with a pair of barriers, which divide, stretch, and fold fluid elements, leading to chaotic mixing via the baker's transformation. The aspect ratio of the plate (α) and the dimensionless height of the barrier (β) are chosen as design parameters to conduct a parameter study on the mixing performance. The flow characteristics and mixing performance are analyzed using the cross-sectional velocity vectors, Poincare section, interface tracking, and the intensity of segregation. The results indicate that several designs of the BPPM significantly enhance the PPM's mixing performance. The best BPPMs are identified with regard to compactness and energy consumption. © 2017 American Institute of Chemical Engineers AIChE J, 64: 717–729, 2018

In this study, the clogging mechanism of poly(styrene) particles in the flow through a single micro-pore was investigated. Together with the microscopic observation, the pressure drop was also measured. The pressure drop fluctuated according to the amount of particles deposited inside the channel. When the particles deposited and blocked the channel, the channel was clogged and the pressure drop increased sharply. During the clogging process, the particles were often detached by the flow, and interesting behaviors, such as “rolling” and “stick and detach”, were found to be the key factors that determine whether the clogging completely occurs or not. Above a certain flow rate, the channel was not clogged and the pressure drop did not increase further. The particles deposited in the upstream had an influence on the flow path. When the particles were deposited in the upstream, the flow detoured and the vortex was formed. The effect of viscosity was examined by controlling the concentration of glycerol solution. As the viscosity and the flow rate increased, the shear stress applied to the particles became larger and it was more difficult for the particles to get accumulated. The normalized clogging pressure drop decreased exponentially with shear stress. It was unity above a certain shear stress, in which the particles did not clog the channel completely.

Current heterogeneous cell assembly techniques in coculture systems rely on irreversible cell layering or a cell separation membrane. However, the techniques possess major drawbacks of inefficiency in direct interactions of the assembled cell layers and cell separation following coculture, which hamper characterization and therapeutic applications of the cells following coculture. Here, we develop a reversible cell layering platform for assembly of heterogeneous cells that allows both active direct cell–cell interactions and facile cell separation. Anionic maleimide-chondroitin-sulfate is grafted onto the surface membrane of myogenic C2C12 cells and human mesenchymal stem cells (hMSCs) to modify the surface charge of the cells without cytotoxicity. A highly porous chitosan thin film is formed in situ interspacing between the heterogeneous cell layers via ionic cross-linking of cationic chitosan and anionic functionalized cells, forming compactly assembled double-layered cell constructs. The chitosan film ...

We suggest a novel numerical algorithm based on the lattice Boltzmann method (LBM) to investigate particulate systems in which solid particles are suspended in a viscoelastic medium. In this model, polymer solution is described by the viscoelastic fluid based on the advection-diffusion LBM model, and it is coupled with the smoothed profile method (SPM) which describes the motion of rigid particles. To validate the present algorithm, we test three benchmark problems (two-dimensional simulation); viscoelastic flow past a cylinder, a single particle migration in a viscoelastic Couette flow, and dynamics of two particles in a viscoelastic Couette flow. Simulation results are carefully analyzed, and they are compared with previous simulation results implemented by finite element method (FEM) and finite volume method (FVM). In all test results, hydrodynamic properties and the motion of the particles induced by viscoelasticity are correctly captured, and they qualitatively as well as quantitatively correspond to previous reports. We conclude that both viscoelasticity and multi-body hydrodynamic interactions can be well incorporated in this new LBM algorithm. The present study has its significance as a first report, which strictly solves the flow behavior of solid particles immersed in a viscoelastic medium on the LBM framework.

Time-dependent viscoelastic properties of Oldroyd-B fluid were investigated by lattice Boltzmann method (LBM) coupled with advection-diffusion model. To investigate the viscoelastic properties of Oldroyd-B fluid, realistic rheometries including step shear and oscillatory shear tests were implemented in wide ranges of Weissenberg number (Wi) and Deborah number (De). First, transient behavior of Oldroyd-B fluid was studied in both start up shear and cessation of shear. Stress relaxation was correctly captured, and calculated shear and normal stresses agreed well with analytical solutions. Second, the oscillatory shear test was implemented. Dynamic moduli were obtained for various De regime, and they showed a good agreement with analytical solutions. Complex viscosity derived from dynamic moduli showed two plateau regions at both low and high De limits, and it was confirmed that the polymer contribution becomes weakened as De increases. Finally, the viscoelastic properties related to the first normal stress difference were carefully investigated, and their validity was confirmed by comparison with the analytical solutions. From this study, we conclude that the LBM with advection-diffusion model can accurately predict time-dependent viscoelastic properties of Oldroyd-B fluid.