Bulletin of the American Physical Society
APS March Meeting 2019
Volume 64, Number 2
Monday–Friday, March 4–8, 2019; Boston, Massachusetts
Session Y61: Multiphase Physics: Soft Matter Research at the Interface of Industrial and Academic InterestsCareers Focus Industrial Undergraduate
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Sponsoring Units: GSOFT FIAP Chair: Joshua Dijksman, Wageningen University & Research Room: BCEC 258B |
Friday, March 8, 2019 11:15AM - 11:51AM |
Y61.00001: Moisture and density measurements in powders: from geophysics to pharmacy Invited Speaker: Michel Louge The quality of pharmaceutical powders depends on fine control of their density and moisture content. Meanwhile, their processing requires availability of non-invasive instrumentation. We exploit recent advances in quantitative measurements of complex dielectric permittivity in hyper-arid desert sands to design capacitance instruments that can detect subtle changes in density and moisture in pharmaceutical processes and storage. We illustrate the technique with measurements of non-linear moisture diffusion through an excipient powder. |
Friday, March 8, 2019 11:51AM - 12:03PM |
Y61.00002: Antigraivty static frictional force on the walls of confined granular columns Payman Jalali, Yuchen Zhao, Joshua Socolar, Robert P Behringer We measure the static frictional force exerted by a granular material on the side wall of a vertical tube as a function of the filling height. We consider a cylindrical tube of diameter D = 5.2 cm filled to heights up to 6D , which is smaller than the Janssen screening length. We use either glass beads (4 mm monodisperse spherical beads) or sand (0.5 mm polydisperse quasi-spherical particles). The grains are added in discrete steps in such a way that the top of the column remains flat, with a fixed mass per step and a fixed waiting time between steps. For sand, the vertical force on the tube remains zero up to a height of approximately 2D, then increases linearly in the downward direction. Surprisingly, for glass beads the force on the container rises in the upward direction up to a turning height h ~ 2D, above which it declines linearly. The variation in frictional force during a waiting period between steps becomes large for heights near h. Discrete element method simulations of frictional spheres show qualitative agreement with experiments. |
Friday, March 8, 2019 12:03PM - 12:15PM |
Y61.00003: Particle formation in spray drying of Amorphous Solid Dispersions: a challenge for soft matter physics Pedro Valente, Ricardo Sousa, Masahiro Nakai In this presentation we discuss the mathematical modeling of the various concurrent physical phenomena that a polymer solution with an Active Pharmaceutical Ingredient (API) undergo prior to forming an amorphous solid dispersion particle, such as atomization, co-solvent evaporative dynamics, propensity for phase separation and shell formation. We show a set of case studies comparing computational predictions against data from spray drying experiments. |
Friday, March 8, 2019 12:15PM - 12:27PM |
Y61.00004: Stratification of drying particle suspensions: Comparison of implicit and explicit solvent simulations Shengfeng Cheng, Yanfei Tang, Gary Grest Novel stratification phenomena have recently been discovered in drying suspensions of polydisperse mixtures of particles. In this process, molecular dynamics (MD) modeling has played an important role. One challenge faced by the MD approach is how to treat the solvent in a computational model. We use large scale MD simulations to study drying suspensions of a binary mixture of large and small particles. The solvent is first modeled explicitly and then mapped to a uniform viscous medium by matching the diffusion coefficients of the particles while keeping all the interactions unchanged. “Small-on-top'” stratification of the particles, with an enrichment of the smaller ones at the liquid/vapor interface during drying, is observed in both models under the same drying conditions. Using the implicit solvent model, we study the effect of the initial film thickness and show that the degree of stratification is controlled by the Péclet number defined with the initial film thickness as the characteristic length scale. When the Péclet numbers of large and small particles are much larger than 1, the degree of “small-on-top” stratification is first enhanced and then diminished as the Péclet numbers are increased. |
Friday, March 8, 2019 12:27PM - 12:39PM |
Y61.00005: Control Stratification in Drying Particle Suspensions via Temperature Gradients Yanfei Tang, Gary Grest, Shengfeng Cheng The drying of polydisperse particle suspensions has recently attracted great attention as the particles may stratify according to sizes after drying, which may lead to new fabrication methods of multilayered films. We use molecular dynamics simulations to study a drying suspension of bidisperse nanoparticles and demonstrate a strategy of controlling stratification. When the suspension is kept isothermal during fast drying, it can exhibit “small-on-top” stratification with the smaller particles accumulated in the top region of the drying film. However, when only the region near the substrate is thermalized, a negative thermal gradient develops in the suspension because of evaporative cooling. Since the associated thermophoresis is stronger for larger nanoparticles, relatively more larger nanoparticles migrate into the top region of the drying film. The net result is either diminished “small-on-top” or converted “large-on-top”. By imposing a positive thermal gradient in the drying suspension via thermalizing the vapor at a higher temperature than the solvent, we observe very strong “small-on-top” stratification. Possible experimental approaches to realize various thermal gradients are suggested. |
Friday, March 8, 2019 12:39PM - 12:51PM |
Y61.00006: Cement cohesion from the structuring of ions and water Abhay Goyal, Katerina Ioannidou, Roland JM Pellenq, Emanuela Del Gado Reducing the environmental impact of cement production is central to reducing greenhouse gas emissions of the construction industry. However, any modification of cement is hindered by an incomplete understanding of the setting process due to its complexity at the nano- and meso-scales. During setting, the precipitation and non-equilibrium aggregation of charged particles into a percolating, porous network is responsible for the overall mechanical properties. But what is the origin of adhesion between these particles? Previous studies suggest that spatial organization of multivalent ions can lead to attraction between highly charged surfaces, but the role of the solvent is largely overlooked. The solvent itself can also exhibit a great deal of structure due to confinement and strong electrostatic forces. To investigate these effects, we combine a primitive model for ions and surfaces with an explicit representation of water. We find that the presence of water proves to have a strong impact on the ordering of ions and greatly enhances the strength of attraction between two surfaces. By identifying quantitatively the link between chemistry and cohesive forces in cement, these results may open new paths for designing stronger cements, more durable and more sustainable. |
Friday, March 8, 2019 12:51PM - 1:03PM |
Y61.00007: ABSTRACT WITHDRAWN
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Friday, March 8, 2019 1:03PM - 1:15PM |
Y61.00008: Lattice Boltzmann simulations of complex flows in fibrous porous media Fang Wang, Ulf Schiller Flow phenomena in porous media are relevant in many industrial applications including filters, membranes, and biomedical implants. For instance, nonwoven membranes can be used as filtration media with tailored permeability range and controllable pore size distribution. Predicting the structure-property relations that arise from specific porous microstructures remains a challenging task, and theoretical approaches have been limited to simple geometries. Computer simulations are a cost-effective way of validating semi-empirical relations and predicting the precise relations between macroscopic transport properties and microscopic pore structure. In this contribution, we discuss lattice-based modeling approaches for multiphase flow in porous media and demonstrate their application to nonwoven fibrous membranes and coalescence filtration. |
Friday, March 8, 2019 1:15PM - 1:27PM |
Y61.00009: New Class of Model Porous Materials Prepared by Colloidal Self-assembly Methods Hongyu Guo, Yun Liu Understanding the properties of complex fluids (both liquid and gas) in porous media is crucial for both fundamental science and application, especially for many industrial problems, such as water filtration, protein chromatography, reservoir capacity estimation and productivity of shale gas. Confinement, at the scale observed in many porous media, can lead to dramatic shifts in physical properties such as gas density, phase transitions, and diffusivity. With the development of many nanoscale processing techniques it has become increasingly urgent that detailed structural and phase behavior of materials be probed with the confinement length scales from 1 nm- 10 µm. For this purpose, a model porous material with well controlled pore properties (size, shape and surface chemistry) need be developed. We herein introduce a new class of model porous materials prepared by self-assembly of colloidal particles. |
Friday, March 8, 2019 1:27PM - 2:03PM |
Y61.00010: TBD Invited Speaker: Simeon Stoyanov expert in the field |
Friday, March 8, 2019 2:03PM - 2:15PM |
Y61.00011: Atmospheric Pressure Plasma - Soft Matter interactions for controlled Materials Synthesis Shomeek Mukhopadhyay, Zachary Fishman, Michael Loewenberg Atmospheric pressure plasmas are a unique system which has been recently harnessed by engineers in a large number of industrial applications like water treatment to medical applications. Obsidian Advanced Manufacturing (Yale university spinoff) has been pioneering an approach to directly print complex materials for applications like flexible electronics using the interaction of atmospheric pressure plasmas with liquid drops carrying suitable reactants. In this talk we will present some key results of the ongoing collaboration to understand and control the reaction diffusion dynamics in these complex non-equilibrium systems. The interactions of atmospheric pressure plasmas which are essentially non-equilibrium allows us to synthesize materials ( semiconductors and metals) with properties and shapes which are usually difficult using conventional techniques. |
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