Bulletin of the American Physical Society
APS March Meeting 2019
Volume 64, Number 2
Monday–Friday, March 4–8, 2019; Boston, Massachusetts
Session Y58: Soft materials in Disordered EnvironmentsFocus
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Sponsoring Units: GSOFT DPOLY DBIO GSNP Chair: H. Jeremy Cho Room: BCEC 257A |
Friday, March 8, 2019 11:15AM - 11:51AM |
Y58.00001: Imaging and Modeling Multiphase Flow and Reactive Transport in Disordered Porous Media: Spatio-Temporal Complexities Invited Speaker: Branko Bijeljic Understanding of multiphase flow, transport and reaction phenomena in disordered porous media has recently been transformed by the advances in X-ray and NMR imaging, which inspired new concepts in pore-scale modeling. More accurate static and dynamic experimental description of solid and fluid(s) distributions in the pore space enabled simplifications in descriptions of spatio-temporal complexities through introduction of the intrinsic functions characterizing flow, transport and reaction in the form of distributions, rather than average values. |
Friday, March 8, 2019 11:51AM - 12:03PM |
Y58.00002: Disorder-mediated wetting transitions in unstable imbibition Amir Pahlavan, Luis Cueto-Felgueroso, Gareth McKinley, Ruben Juanes An archetypical example of pattern formation is the front instability that emerges when a less viscous fluid displaces a more viscous fluid in a Hele-Shaw cell. This instability, however, has been studied only in drainage—when the invading fluid is nonwetting. Here we show that the interplay between wettability and disorder leads to novel instability regimes. We inject a more wetting liquid into a rough Hele-Shaw cell filled with a less wetting, more viscous liquid. At low injection rates, the displacement is full across the cell gap. Above a critical injection rate, however, a wetting transition occurs and thin films of the invading liquid become entrained on the rough surfaces. This wetting transition is accompanied by a drastic change of the front instability, leading to a dendritic pattern. Our observations point to the crucial role of disorder in pattern formation during fluid-fluid displacement, and its important implications for multiphase flows in porous media. |
Friday, March 8, 2019 12:03PM - 12:15PM |
Y58.00003: Suppressing fingering instabilities using gradients in porous media Nancy B Lu, Janine Nunes, Sujit Datta Drainage, the displacement of a wetting fluid from a porous medium by an immiscible non-wetting fluid, arises in key technological problems including oil recovery, groundwater contamination, and waste CO2 sequestration. When the displacing non-wetting fluid is less viscous than the displaced fluid, Viscous Fingering occurs. By contrast, when the displacing fluid is more viscous than the displaced fluid, Capillary Fingering occurs. These two processes lead to disordered finger-like displacement pathways. For both cases, we find that a pore size gradient stabilizes the flow--the fluid flows uniformly without fingering. For Viscous Fingering, this stabilization only occurs below a threshold flow rate [1], while for Capillary Fingering, it only occurs when the gradient exceeds a static geometric criterion. Knowing these two suppression criteria provides a new way to control fingering instabilities in porous media. |
Friday, March 8, 2019 12:15PM - 12:27PM |
Y58.00004: Cooperative mobilization of emulsion droplets in porous media Shima Parsa Moghaddam, Mohamad Ali Bijarchi, Maria Jimenez, David A Weitz We study the cooperatives dynamics of monodisperse droplets in 2D porous media using confocal microscopy and particle tracking. The size of the droplets are of the same order of the pore sizes of the medium and are generated on demand and injected into the porous media. |
Friday, March 8, 2019 12:27PM - 12:39PM |
Y58.00005: Transport of Microgels in a Microfluidic Constrictive Channel Shuaijun Li, Jing Fan The transport of soft bodies in narrow channels are remarkably common in biological systems and industrial processes. During the transport process, the soft body deforms and blocks the channel, and thus induces a pressure drop across the channel. In this work, we study the motion and deformation of microgels in a constrictive channel with a circular cross-section. Employing elasticity theory with small deformation assumption, we find the correlation among the built-up pressure, the mechanical properties of microgels, and the geometry of the channel. An approximate method is applied to estimate stress distribution at the contact surface between the deformable microgel and the channel. We then conduct experiments in constrictive micro-channels using microgels with well controlled sizes and mechanical properties to validate the effectiveness of our analysis. Compared to previous studies on microgel transport through constrictive channels, our result features an optimal balance between simplicity and accuracy. The methodology can be easily extended to various natural and engineered processes involving transport of soft bodies in narrow channels. |
Friday, March 8, 2019 12:39PM - 12:51PM |
Y58.00006: Fluid-solute-colloid interactions in porous media and its implications for enhanced oil recovery Sangwoo Shin Flows of colloidal suspensions containing a variety of solutes in porous media are widely found in nature as well as artificial settings such as hydrocarbon recovery, blood flow, water purification, and coastal habitats. Such environments often exhibit spatiotemporal inhomogeneity in the solute and colloid distribution. While it is naively expected that the colloidal particles advect with the flow, non-equilibrium interactions between the fluid, solute, and the colloids may lead to unique colloidal dynamics. We present a number of scenarios in which the colloidal particles can be captured and accumulate continuously in localized regions in porous media despite the presence of strong pore flow due to the fluid-solute-colloid interactions. We link our findings to the chemical flooding process to provide useful insights into the enhanced oil recovery. |
Friday, March 8, 2019 12:51PM - 1:03PM |
Y58.00007: Phase change in disordered media: intermolecular forces control simultaneous evaporation and condensation Ke Xu, Amir Pahlavan, Ruben Juanes We investigate phase change and fluid-fluid redistribution in porous media using micromodel experiments, in which air is injected to displace water. At late times, long after injection stops, we expect the system to arrive at a steady-state equilibrium configuration. Instead, we observe the condensation and growth of liquid droplets at the expense of the evaporation of liquid bridges. This is surprising, given that the liquid bridges are at lower pressure than the liquid droplets. We show that this counterintuitive behavior emerges from the influence of intermolecular forces on the instability of condensing thin liquid films. Our observations therefore point to a new physical mechanism for phase change in disordered media, which drives fluid organization at the pore scale, and has important implications for multiphase-flow properties at the macroscale. |
Friday, March 8, 2019 1:03PM - 1:15PM |
Y58.00008: Effect of extreme nanoconfinement on the capillary rise of glassy polymers into densely packed nanoparticle packings R Bharath Venkatesh, Jyo Lyn Hor, Haonan Wang, Zahra Fakhraai, Daeyeon Lee Capillarity is a powerful driving force at the micro- and nanoscales. We show that polymers annealed above the glass transition temperature infiltrate into densely packed nanoparticle packings regardless of their degree of polymerization. Bilayers of glassy polymer film and nanoparticle packing are annealed at different temperatures and the rate of capillary rise is monitored using ellipsometry. By using the Lucas-Washburn model, we infer the effective viscosity of highly confined polymers undergoing capillary rise through nanoparticle packings. The extent of confinement is varied over a wide range by changing the size of nanoparticles and the molecular weight of the polymers. The physical confinement of the unentangled polystyrene in SiO2 nanoparticle packings results in a significant increase in the viscosity and glass transition of the polymer. The magnitude of increase is independent of the polymer-nanoparticle attraction as determined by the use of poly(2-vinyl pyridine) but varies strongly with the extent of confinement. Entangled polystyrene exhibits different trends than the unentangled counterparts under such extreme nanoconfinement. |
Friday, March 8, 2019 1:15PM - 1:27PM |
Y58.00009: Disorder Suppresses Chaotic Viscoelastic Flow Derek Walkama, Nicolas Waisbord, Jeffrey S. Guasto Viscoelastic fluids transition from a steady to a chaotic and time-dependent flow beyond critical flow conditions, but little is known about the implications of geometric order/disorder for this transition. Utilizing microfluidics, we flow a purely elastic fluid through a hexagonal array of cylindrical pillars at a range of flow speeds, where the transition to chaotic flow occurs at a critical ratio of the polymer relaxation time to flow time scale (Deborah number), De ~ 1/2. The introduction of finite disorder to the system – corresponding to a random perturbation of the pillars by 10% of the lattice spacing – delays the transition to Deborah number, De ~ 1, and reduces the magnitude of the chaotic velocity fluctuations. Larger disorders appear to completely suppress the transition within the tested flow range up to De ~ 5. Examination of the Lagrangian strain rate correlations reveal that disorder broadens the distribution of excitation frequencies in the system, suggesting a potential mechanism for stabilizing the elastic flow. |
Friday, March 8, 2019 1:27PM - 1:39PM |
Y58.00010: Mesoscale Structure of Elastic Turbulence in Porous Media Christopher Browne, Audrey Shih, Sujit Datta Polymer solutions are a promising tool for groundwater remediation and enhanced oil recovery (EOR); in some cases, the modified flow allows the flooding fluid to sweep a greater portion of the aquifer or reservoir. This enhanced sweep is believed to be linked to unstable flow observed above a threshold flowrate. However, field applications have been limited because the flow structure is not well understood in porous media. We directly observe the flow of polymer solutions in model porous media using confocal microscopy. However, we find that the flow is not purely chaotic, as is commonly assumed: it can adopt two distinct structures, which switch stochastically. We understand this switching as a dynamic coupling between single-polymer conformations and pore-scale flow. We develop dimensionless criteria to describe the spatial and temporal structure of the flow. Understanding and controlling this structure will be integral in robustly applying polymer solutions to groundwater remediation and EOR. |
Friday, March 8, 2019 1:39PM - 1:51PM |
Y58.00011: Diffusion-controlled drug delivery: Dealing with the Stochastic Dilemma in Lattice Monte Carlo (LMC) simulations Mehran Bagheri, Gary William Slater Lattice Monte Carlo (LMC) methods are commonly used to study bio/chemical processes involving diffusion phenomena, including drug delivery systems. In such systems, the drug is encapsulated in a porous material (e.g., a hydrogel) which releases it through two processes: (i) disintegration of the material and (ii) diffusive escape of the drug molecules. One way to control the release is to design layered materials with various diffusivity regions. Diffusion in such systems is often studied numerically using LMC methods. However, modelling inhomogeneous systems, boundary conditions and diffusion at interfaces is somewhat ambiguous in LMC simulations. In this talk, we present computational studies of 2D systems consisting in two different sets of immobile obstacles that create two media with different effective viscosities, as well as their equivalent obstacle-free 1D systems with corresponding effective diffusion coefficients. Using this toy model, we examine how interfacial diffusion is treated by the various flavours of stochastic calculi, and we demonstrate that Isothermal calculus is the correct choice as opposed to the generally employed Ito calculus. We then explore the corrections that must be considered to simplify such nonuniform systems. |
Friday, March 8, 2019 1:51PM - 2:03PM |
Y58.00012: Hydrogels dehydrate liposomes: the structural fate of lipid nanoparticles in the extracellular matrix Sarith Bandara, Thomas Molley, Hojun Kim, Priyalini Bharath, Kristopher Kilian, Cecilia Leal Drug-loaded liposomes are the most successful nanomedicine to date, with multiple FDA-approved systems for a myriad of diseases. While liposome circulation time in blood and retention in tissues have been studied in detail, the structural fate of liposomes—and nanoparticles in general—in the body has not been extensively investigated. This presentation explores the structural fate of liposomes in a synthetic hydrogel system with the aim of understanding the possible restructuring effects that liposomes experience in the natural extracellular matrix. Small angle X-ray scattering, confocal microscopy, and cryogenic transmission electron microscopy data demonstrate that poly(ethylene glycol) (PEG), gelatin, and alginate hydrogels cause 200-nm liposomes of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) to transform into micrometer-sized aggregates. These aggregates are composed of multilamellar vesicles around 100 nm in diameter with a mean interlamellar separation of 5.5 nm. Protecting the liposomes with a corona of PEG damps this restructuring effect, making the multilamellar vesicles formed less stable. We attribute this unilamellar to multilamellar transition to an osmotic driving force from the hydrogel environment. |
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