Bulletin of the American Physical Society
APS March Meeting 2022
Volume 67, Number 3
Monday–Friday, March 14–18, 2022; Chicago
Session K12: Transport Phenomena in Heterogeneous and Dynamic Environments: From Colloids to Active MatterFocus Recordings Available
|
Hide Abstracts |
Sponsoring Units: DFD Chair: Amir Pahlavan, Yale University Christina Kurzthaler, Princeton University Room: McCormick Place W-181C |
Tuesday, March 15, 2022 3:00PM - 3:36PM |
K12.00001: Autochemotactic droplet swimmers shape their environment Invited Speaker: Corinna C Maass Self-propelled agents require fuel to move, which they commonly take up from their surroundings, for example swimmers in a solution of fuel or nutrient. If the fuel depletion equilibrates slower than the timescale on which the swimmers move, this can cause measurable chemorepulsive effects: swimmers avoid areas of depleted fuel, leading to interparticle signaling and the emergence of complex collective phenomena. |
Tuesday, March 15, 2022 3:36PM - 3:48PM |
K12.00002: Modelling bacteria in porous media: density dependent reorientation Ehsan Irani, Zahra Mokhtari, Annette Zippelius It has recently been reported that bacteria, such as E.coli and P. putida, perform distinct |
Tuesday, March 15, 2022 3:48PM - 4:00PM |
K12.00003: Visualization and modeling of soil bacteria under confinement Moniellen P Monteiro, Sofía Montagna, Juan Pablo Carrillo, Aníbal Lodeiro, María Luisa Cordero, Verónica I Marconi Bradyrhizobium diazoefficiens is a soil bacterium that fixes atmospheric N2 in symbiosis with soybean, used as biofertilizer in sustainable agronomy. It has two different flagellar systems, a thick subpolar flagellum, and several thin lateral flagella. The motility parameters (average speed, characteristic reorientation time and angle) were measured for two B. diazoefficiens strains, the wild type with both flagellar systems, and a mutant with only the subpolar flagellum. Confinement effects on their swimming behavior were studied using microfluidics devices designed to imitate the soil intricated structure. Realistic models were proposed for each strain and simulated, using the same experimental geometries and measured swimming parameters, with Langevin equations of motion. The diffusion properties of B. diazoefficiens populations were investigated, for each strain motility parameters as well as for multiple soil porosities. Our contributions and methods from physics hope to bring light to long searched improvements of bioproducts used for soybean crops for more than 20 years, which are yet far from being efficient. |
Tuesday, March 15, 2022 4:00PM - 4:12PM |
K12.00004: Solute-mediated transport of colloids in disordered media Amir A Pahlavan, Suin Shim, Niki Abbasi, Janine Nunes, Howard A Stone Solutal gradients due to mixing and reactions in disordered media are ubiquitous. At the scale of a single pore (tens of microns), these gradients generate osmotic flows that can significantly enhance the rate of transport of colloids. Yet, it is not known how solutal gradients can influence the transport on macroscopic length scales. Here, using microfluidic experiments and numerical simulations, we show that solutal gradients can considerably hinder or enhance the transport of colloids through disordered media, and we develop a theoretical model that explains this coupling. |
Tuesday, March 15, 2022 4:12PM - 4:24PM |
K12.00005: Capture dynamics of colloidal particles in microfluidic model membrane channels Alice L Thorneywork, Stuart F Knowles Studies of transport across membranes often focus on particle dynamics in confining channels. Yet flux can be critically limited by the rate of entry to the pore. This process is governed by a complex interplay of factors including the entropic barrier to pore entry, particle-particle/particle-pore interactions, and the external driving force. Here, we use video microscopy to study the capture dynamics of colloidal particles driven through microfluidic devices. By obtaining full trajectories for particles as they move from the bulk into confining channels, we map the spatial velocity and concentration fields for the system in detail. We consider behaviour in conservative and non-conservative flow fields, for different flow velocities, and at different packing fractions. Furthermore, by comparing to COMSOL models of fluid flow we assess the effect of many-body interactions on the capture process and how these modify stochastic fluctuations in the capture rate. Our results provide new insights into the concept of a 'capture radius' – the distance at which a particle is irrevocably drawn into the pore – which plays a key role in transport models for biological channels and nanopore sensors. |
Tuesday, March 15, 2022 4:24PM - 4:36PM |
K12.00006: Manipulating transport properties of passive tracers in channels via cross section Manuchehr Aminian Traditionally, theory developed for dispersion of passive tracers has focused on predicting the effect of anomalous diffusion which occurs as the result of laminar flow. This theory has had success matching with both experiment and numerical simulation. However, precise control of tracer distribution is more challenging. Our prior work has established similar agreements between theory, simulation, and experiment in predicting a tracer distribution's skewness. In particular, we developed asymptotic theory which predicts the sign differences seen in skewness depending on cross section -- and this showed agreement with experiment. However, these studies relied mainly on idealized cross-sectional shapes, and left an open question about questions of optimality and channel design for specific purposes. Here, I will present a computational framework to extend this work past idealized cross sections and explore questions in shape optimization towards precise control of the tracer distribution. |
Tuesday, March 15, 2022 4:36PM - 4:48PM |
K12.00007: Structure and Dynamics of Bulk and Confined Active Matter via Excess Entropy Scaling S.Arman Ghaffarizadeh, Gerald J Wang Active matter is composed of self-driven units that can convert stored or ambient free energy into motion. Systems containing active particles exhibit a fascinating array of transport phenomena, which are altogether distinct from their inactive counterparts. In this talk, building upon our recent work in this area, we present evidence that there exist robust excess entropy scaling relations that directly connect activity-modified transport coefficients with the static structure of an active system. These relations are in nearly direct analogy with excess entropy scaling results for binary fluid mixtures at equilibrium. Motivated by recent experimental developments in confined active matter, we also present results that highlight the interplay between activity and confinement in terms of structure, transport, phase segregation, and the applicability of excess entropy scaling relations. Throughout, we validate our results against extensive molecular-dynamics simulations, in which we vary the total fraction of active particles, the degree of activity for active particles, and various geometric factors. |
Tuesday, March 15, 2022 4:48PM - 5:00PM |
K12.00008: Spatial control of heat transport using Janus nanoparticles Fernando Bresme, Juan D Olarte-Plata, Jordan Gabriel, Pablo Albella, Mingxuan Jiang Janus Nanoparticles (JNP) are heterogeneous materials that bring unique opportunities to technological and medical applications. Here we present a non-equilibrium molecular dynamics simulations and theoretical investigation of the temperature field generated around heated Janus Nanoparticles to assess the performance of the particles in the generation of anisotropic heating. The contrasting thermal conductances of the fluid-material interfaces arising from the heterogeneous composition of the JNP provide a route to control the heat transport and thermal fields around the nanoparticle, leading to temperature differences between both sides of the nanoparticle that is significant for particles comprising regions with disparate hydrophilicity. We investigate the thermal transport in these heteregeneous materials using computational models of gold nanoparticles passivated with hydrophobic and hydrophilic theoretical continuum models that predict the temperature field as a function of the interfacial thermal conductance and nanoparticle size. |
Tuesday, March 15, 2022 5:00PM - 5:12PM |
K12.00009: Aerotactic response of bacteria: experimental characterization at the bacteria scale and population scale Julien Bouvard, Harold Auradou, Frederic Moisy, Carine Douarche, Peter Mergaert, Nicolas Busset Many environmental bacteria use their flagellar motility to find optimal regions for their development, they bias their swimming in response to chemical signals. The drift velocity associated to this response is proportional to the local concentration gradient of the signals and the chemotactic sensitivity coefficient. Although studied for many years, the dependence of this sensitivity coefficient with concentration is still debated. In our study, suspensions of Burkholderia contaminans are placed in a capillary sealed at one end and permeable to oxygen at the other end. The oxygen consumption of the bacteria in the capillary produces a gradient in which the bacteria move. By monitoring the concentration and velocity of bacteria, as well as the oxygen concentration along the capillary using encapsulated Ruthenium dye, we uncover the aerotactic sensitivity dependence on the oxygen concentration. In addition to this macroscopic approach, we also determine this cell sensitivity from modulation of the run-time distribution with swimming direction. Our multiscale approach sheds new light on the different theoretical models that have emerged from the Keller-Segel equations over the past fifty years. |
Tuesday, March 15, 2022 5:12PM - 5:24PM |
K12.00010: Spontaneous trail formation in populations of auto-chemotactic walkers Zahra Mokhtari, Robert Patterson, Felix Höfling Trail formation is known in animal populations. It originates in the traces (pheromones, footsteps, etc.) that individuals leave behind as they move and their response to those left by the others. Such a dynamic landscape, mediated by the traces, results in a delayed and long-range communication between the individuals, and trails may emerge spontaneously from a homogeneous state. We have studied a minimal model consisting of persistent walkers and their chemical secretions. The walkers are modelled as self-propelled particles that deposit and sense the chemicals and act according to an alignment rule: Changing their direction of motion. Based on extensive computer simulations, we identify a number of emerging stationary patterns and obtain qualitatively the non-equilibrium phase diagram of the model. In particular, we show that the model supports the spontaneous formation of persistent macroscopic trails, and we analyse the order parameter of this putative dynamic phase transition. Employing a dynamic model for few macroscopic observables, including the sub-population size of trail-following agents, we gain insight into the early phase of trail formation. |
Tuesday, March 15, 2022 5:24PM - 5:36PM |
K12.00011: Percolation Phase Transitions Involving Impermeable Torus Shaped Grains Donald J Priour Porous materials, often made up of impenetrable granular inclusions, admit the flow of fluid or charge through irregularly shaped voids among the grains. With large scale dynamical infiltration simulations, we calculate critical grain densities for randomly placed inter-penetrating torus-shaped barrier particles. A salient feature of the latter is their concave geometry. Moreover, we consider a range of torus shapes from barrier particles resembling spheres with small antipodal dimples to thin ring shaped toruses. This set of geometries straddles a topological transition as the dimples expand toward each other and join to form a central hole. We find a peak in the critical grain density coinciding with the increase in topological genus from zero to one, which we ascribe to the torus central holes serving as channels to increase the void network connectivity. We find that the percolation thresholds (in terms of percentage of void volume) for assemblies of randomly oriented very thin ring shapes with square and circular cross sections tend to the counterparts for square prisms and cyinders respectively in the high aspect ratio limit. The consistently lower critical concentrations for aligned grains may be due to a walling off of central holes from void volume networks. |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700