Bulletin of the American Physical Society
APS March Meeting 2019
Volume 64, Number 2
Monday–Friday, March 4–8, 2019; Boston, Massachusetts
Session E59: Rheology and Flow of Soft Matter IIFocus
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Sponsoring Units: GSOFT Chair: Scott Franklin, Rochester Institute of Technology Room: BCEC 257B |
Tuesday, March 5, 2019 8:00AM - 8:12AM |
E59.00001: Dynamical correlation lengths in shape-based models of confluent tissue Daniel Sussman, John Devany, Margaret Gardel, M. Lisa Manning It has become increasingly clear that the rheology of densely packed cells in confluent tissue helps control processes ranging from multicellular development to wound healing to cancer tumor development. However, the impact on tissue rheology of cell-autonomous active processes, such as active alignment of cell motility and cell proliferation, remains unclear. Moreover, our recent observations of cell monolayers that undergo extensive cell division indicate that tissue rheology changes dramatically as cells proliferate, with interesting dynamical correlation length scales that depend on the mechanical environment. To understand these observations, we extend shape-based models of confluent tissues to include both cell alignment and proliferation. We find that shape-based models quite naturally generate the time-varying trends in cell density, cell shape, and cell motility observed in our monolayers, and that a coupling mechanism like cell-cell alignment is necessary to generate the observed correlation length scales. In this context, we additionally investigate the effects of using metric vs topological alignment rules in active matter systems where the interaction potential is itself explicitly topological. |
Tuesday, March 5, 2019 8:12AM - 8:24AM |
E59.00002: Percolations induced by quasistatic shear in athermal systems with weak attraction Yuchuan Wang, Youjin Deng, Ning Xu When quasistatically shearing athermal particulate systems with weak attraction, we observe both connectivity percolation and solidlike transitions over a wide range of packing fractions below the jamming transition point. It is already known that without shear connectivity percolation for the same system occur at specific packing fraction, φcp. It is interesting that driven by shear the system undergoes percolation transition even far below φcp. We find that φcp and another specific packing fraction approximately separate the whole packing fraction regimes into three parts, in which the connectivity percolation exhibits apparent differences. Combining the static structure factor, we come up with a novel phase diagram with percolation transitions, and regimes of phase separation, gelation, shear jamming, and jamming. |
Tuesday, March 5, 2019 8:24AM - 8:36AM |
E59.00003: Pressure Decay in 2D Molecular Dynamics Simulation with Varied Filter Pore Width and Fluid Impurity Diameter Kevin VanSlyke, Surajit Sen Time dependent pressure in a 2D molecular dynamics model using Lennard-Jones Argon atoms is studied in a semi-periodic chamber containing a simple porous filter. In each case an initial velocity bias towards the filter leads to the buildup of pressure in a region adjacent to the filter. The pressure in this region is shown to exhibit damped oscillatory behavior as the pulse is reflected and travels across periodic boundary conditions. The effects of pore width and fluid impurity diameter on the exponential decay time constant are evaluated in detail. Our results demonstrate a negative linear relation between time constant and pore width for systems with a fixed impurity diameter, and a positive linear relation beetwen time constant and impurity diameter in systems with a fixed pore width. |
Tuesday, March 5, 2019 8:36AM - 8:48AM |
E59.00004: ABSTRACT WITHDRAWN
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Tuesday, March 5, 2019 8:48AM - 9:00AM |
E59.00005: 2d Shear of Granular Annular Sector Particles (ASPs) Scott Franklin, Elyse Rood, Theodore Anthony Brzinski, Sykes Cargile We study the shear of granular annular sector particles (ASPs), open semi-circular rings that have previously been studied at colloidal scales. ASPs can be characterized by two dimensionless numbers: the subtended opening angle and the ratio of inner and outer radii. We place granular ASPs in an annular-planar Couette shear cell and visualize the entire 360° with six cameras. Particle tracking software identifies the position and orientation of each ASP and enables measurement of large-scale motion and particle-particle interactions. ASPs can entangle to form dimers, trimers and other structures and we measure the distribution, creation and annihilation of these structures. Dimers can be characterized by the dot product of constituent ASP orientations. I will describe our initial experiments and compare with collaborative experiments in avalanching geometries. |
Tuesday, March 5, 2019 9:00AM - 9:12AM |
E59.00006: Effect of Acid Hydrolysis on the Rheology of Phytoglycogen Nanoparticles Hurmiz Shamana, Michael Grossutti, John Dutcher Phytoglycogen is a natural polysaccharide produced in the form of compact 35 nm diameter nanoparticles by some varieties of plants such as sweet corn. The highly-branched, dendrimeric structure of phytoglycogen leads to interesting and useful properties that make the particles ideal as unique additives in personal care, nutrition and biomedical formulations. One such property is the unusual polysaccharide rheology of aqueous dispersions of phytoglycogen nanoparticles [1]. When added to water, the zero-shear viscosity of the dispersions remains small up to large concentrations (~20% w/w). For higher concentrations, the zero-shear viscosity increases dramatically, reaching values that exceed that of water by more than a factor of 106 at the highest concentrations of 30% w/w. We have used acid hydrolysis to partially digest the phytoglycogen nanoparticles, which not only reduces their diameter, but also removes the hairy chains on the outer surface of the particles thereby altering the interaction between particles. We compare the concentration dependence of the zero-shear viscosity of the smaller, acid hydrolyzed particles to that of the native particles. These results suggest new applications for the acid hydrolyzed particles. |
Tuesday, March 5, 2019 9:12AM - 9:24AM |
E59.00007: Biased Brownian motion in a channel with symmetry and anisotropy Ki Wing To, Wei-hsuan Tseng We study biased Brownian motion of a bead in a quasi-two-dimensional horizontal channel consists of identical cells with asymmetric walls and anisotropic base connected in a circular loop. When the channel is shaken vertically, energy is injected to the bead by collisions with the base and converted to kinetic energy in the horizontal direction. Asymmetry and anisotropy of channel induce a driving force on the bead so that the bead performs biased Brownian motion along the channel axis with the drift velocity being proportional to the diffusivity. Furthermore, the distribution function of the escape time from a cell is found to be an exponentially decay function. These experimental results can be explained by the continuous time random walk theory (CTRW). |
Tuesday, March 5, 2019 9:24AM - 9:36AM |
E59.00008: Tuning the Shear Thickening Response using Acoustic Perturbations Prateek Sehgal, Meera Ramaswamy, Itai Cohen, Brian J. Kirby Shear thickening behavior of dense particle suspensions is generally not considered an externally tunable response. In this work, we present a novel method to dynamically tune the rheological response of a non-Brownian shear thickening suspension using local acoustic perturbations. We apply resonant perturbations in two different directions orthogonal to the primary shear flow and show a tunable viscosity response of the suspension in the transitioning regime and the shear-thickened regime of the flow curve. We find that the acoustic perturbations increase the onset strain rate of shear thickening in addition to decreasing the viscosity (de-thickening) of the suspension. We attribute the mechanism of de-thickening to the breaking of shear-induced force chains and disruption of solid-solid frictional contact between the particles by local acoustic perturbations. With the temporal amplitude modulation of the perturbations, we further demonstrate a periodic thickening/de-thickening of the suspension and show that the response is dynamically tunable. |
Tuesday, March 5, 2019 9:36AM - 9:48AM |
E59.00009: Anomalous single-file transport in short pores Andrew Rutenberg, Spencer Farrell For particles undergoing single-file diffusion, we have previously shown that switching between mobile and immobile particle states drives anomalously-slow collective transport [Farrell and Rutenberg, Phys Rev E 98 022114 (2018)] — for instance when particles bind to lateral walls of channels. The slowing was controlled by a density-dependent length-scale determined by the transition rates. Here we consider the anomalous transport within a pore of finite length L . We recover our earlier hydrodynamic regime for large L, with Fickian transport. For smaller L, we identify and characterize a new non-Fickian regime of anomalous transport. We characterize flux and fluctuations in this regime. We discuss the applications of our results to experimental nanopore systems, and within cells. |
Tuesday, March 5, 2019 9:48AM - 10:00AM |
E59.00010: Depletion Layer and Viscosity of Microfluidic Flow with Aggregating Red Blood Cells Chih-Tang Liao, Yeng-Long Chen In blood flow, many different kind of large proteins in the blood plasma induce attraction between red blood cells (RBCs) that results in aggregates known as rouleaux. To understand how polymer additives affect the aggregate structure of RBCs and blood viscosity, several experiments have probed the effects of polymers such as dextran or polyethylene oxide on RBC microstructures. A few studies have shown that the RBC aggregation size increases with the increase of the polymer concentration and reaches a maximum at higher polymer concentration. |
Tuesday, March 5, 2019 10:00AM - 10:12AM |
E59.00011: Avalanches and dynamics of granular aggregates made of oil micro-droplets spreading on a surface Jean-Christophe Ono-dit-Biot, Kari Dalnoki-Veress Granular materials display unusual properties and structures compared to continuous materials. Common examples of such materials are sand piles with shapes and mechanical properties that are determined by a balance between gravity and inter-grain friction. In this study, monodisperse lightly attractive oil droplets (radius approximately 10 microns) are produced one-by-one in an aqueous solution. Droplets are buoyant and accumulate underneath a glass slide which acts as the top of a liquid cell, forming 3D aggregates. Droplets initially arrange to form crystals growing along the vertical direction. As a critical height is reached, the aggregate collapses and spreads on the glass slide, in an event analogous to avalanches in sand piles. This process repeats. We find that the geometry of such crystals is controlled by the balance between the adhesion strength and buoyancy which can be modified by changing the size of the droplets. Finally, crystallization can be prevented by using two different droplet sizes leading to glassy aggregates spreading more easily on the glass slide. This study has potential implications in the understanding of the spreading of cells on a surface, or the physics of avalanches in a novel system. |
Tuesday, March 5, 2019 10:12AM - 10:24AM |
E59.00012: Angular dynamics of cellulose nanofibrils in channel flow Tomas Rosen, Chengbo Zhan, Ruifu Wang, Shirish Chodankar, Benjamin S Hsiao New materials from nanocellulose have the potential to replace many high performance materials today. The mechanical properties of nanocellulose are highly dependent on the internal structure of nanofibril network, which in turn can be controlled through hydrodynamic alignment of cellulose nanofibers (CNFs). This process is typically followed by a transition from the dispersion to the arrested (gel) state with the structure locked in a non-isotropic configuration and the subsequent drying of the aligned gel. The orientation distribution of the fiber depends on many parameters, including concentration, flow geometry and flow rates. The present study takes the particular focus on the orientation of CNF in the shear layers of a channel flow. The orientation of CNF is studied using small-angle X-ray scattering, where the results are compared with simulations of dilute anisotropic Brownian particles. Furthermore, we demonstrate how polarized microscopy can be used to both characterize the rotary diffusion of the birefringent CNF dispersion as well as study the average orientation direction in the channel. The results from this study provide an insight into the dynamics of dispersed CNF and lead to new strategies for controlling the assembly of nanofibrous materials. |
Tuesday, March 5, 2019 10:24AM - 10:36AM |
E59.00013: Geometric frustration induces the transition between rotation and counterrotation in swirled granular media Lisa Lee, John Paul Ryan, Miranda Holmes-Cerfon, Shmuel Rubinstein Marbles in a swirled teacup exhibit a curious dynamical transition: at small densities, the marbles circulate in the same direction as the container, but at larger densities, they transition to circulating in the opposite direction. This phenomenon occurs in a range of swirled and vibrated granular systems, from industrial vibration mills to baby rattles, each observation challenging our intuitive understanding of angular momentum conservation. Using an accelerating coordinate system, we use experiments and simulations to identify the cause for the transition to counterrotation. At low densities, the grains roll freely in the container, but as density increases, antiferromagnetic-like frictional interactions between beads lead to geometrical frustration, resolved only via global circulation. I will furthermore show that in the new frame of reference this system resembles a rotating drum. |
Tuesday, March 5, 2019 10:36AM - 10:48AM |
E59.00014: Predicting and measuring shear rheology of soft interfaces Aditya Raghunandan, Nicholas Debono, Nicholas Pearson, Patrick Underhill, Juan Manuel Lopez, A Hirsa Measuring the non-Newtonian shear responses of monomolecular films or macromolecules like proteins at fluid-fluid interfaces has been limited by using linear (Newtonian) constitutive equations to determine rheological properties. Predicting this nonlinear behavior is integral to comprehending many biophysical processes such as breathing and in the pathology of diseases such as Alzheimer’s, which are marked by protein denaturation in vivo. We present a generalized 2-D constitutive equation for interfaces under steady shear with the interfacial shear viscosity generalized to be a function the imposed shear-rate. We introduce non-Newtonian material properties that control nonlinear and linear shear responses of an interfacial system. Combining flow field predictions from the new equation and experiments in a knife-edge flow geometry, we demonstrate that monomolecular films of DPPC – the primary constituent of mammalian cell walls and pulmonary surfactant – are shear-thinning at near-physiological surface packing over six decades of shear-rate. Also, the role of interfacial rheology of an adsorbed protein film of insulin in the process of denaturation and subsequent amyloid fibril formation at the air/water interface is delineated. |
Tuesday, March 5, 2019 10:48AM - 11:00AM |
E59.00015: Slip-link Simulations under Fast Flows: Effect of the Stretch/Orientation-Induced Reduction of Friction Takeshi Sato, Takashi Taniguchi Macroscopic flows of entangled polymer melts are tightly connected with the microscopic polymer chain dynamics. One possible solution to this problem could be obtained with a multiscale simulation (MSS) approach, where a microscopic model is combined with a macroscopic model. To develop the MSS technique that can address polymer processing conditions, we need to develop a microscopic model that can correctly predict rheological behaviors under fast flows. However, the molecular mechanisms of entangled polymer chains under fast flows have not been fully understood. Yaoita et al. have introduced the concept of the stretch/orientation-induced reduction of molecular friction (SORF) to their slip-link (SL) model and found that SORF can improve the predictions of rheological behaviors under fast uniaxial elongational flows [Yaoita et al., 2012]. In this study, we have investigated the effect of SORF on the more coarse-grained SL model [Doi et al., 2003]. As a result, we have found that SORF can improve the rheological properties obtained from our SL model especially under uniaxial elongational flows. This result will help us to develop the MSS technique for fast entangled polymer melt flows. |
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