Bulletin of the American Physical Society
APS March Meeting 2022
Volume 67, Number 3
Monday–Friday, March 14–18, 2022; Chicago
Session K14: Soft Matter in Low GravityInvited Live Streamed
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Sponsoring Units: DSOFT Chair: Jacinta Conrad, University of Houston Room: McCormick Place W-183B |
Tuesday, March 15, 2022 3:00PM - 3:36PM |
K14.00001: NASA's Complex Fluids/Soft Matter Program Overview Invited Speaker: Fran Chiaramonte The presentation will provide an overview of the current and future microgravity Complex Fluids/Soft Matter Program including solicitation plans. The presentation will also include future solicitations for the NASA Physical Sciences Informatics Program. |
Tuesday, March 15, 2022 3:36PM - 4:12PM |
K14.00002: Phase-field modeling of colloid-polymer mixtures in microgravity Invited Speaker: Anand U Oza We present a theoretical model for colloid-polymer mixtures in a microgravity environment. The addition of polymer to a colloidal suspension induces weakly attractive forces between the colloids and leads to a three-phase coexistence region, wherein a "liquid" phase coexists with a low-density gas phase and a high-density crystal phase. Colloid-polymer mixtures are thus an archetype for modeling phase transition processes, but the details of the observed colloidal structures remain poorly understood. We construct, analyze and numerically simulate a phase-field model for structure evolution in colloid-polymer mixtures. The model consists of the Cahn-Hilliard equation, which describes phase separation processes in multicomponent mixtures, coupled with the Stokes equation for viscous fluid flow. The results of the model will be compared against experiments performed on the International Space Station, using data available on the NASA Physical Sciences Informatics system. |
Tuesday, March 15, 2022 4:12PM - 4:48PM |
K14.00003: Phase separation and emergent dynamics of paramagnetic suspensions in toggled magnetic fields Invited Speaker: Eric M Furst Colloids and nanoparticles self-assemble in external fields, a property which enables functional and smart materials like magnetorheological fluids and potentially new ones in which structure controls the transport of heat, light, or chemical species. A model to study these phenomena are suspensions of paramagnetic colloids. In a strong, steady magnetic field, paramagnetic colloids form system-spanning, kinetically arrested networks similar to a gel. From this state, it is possible to phase separate and condense the suspension by toggling the external field. During its evolution towards the equilibrium state, the suspension undergoes a Rayleigh-Plateau instability for a range of field strengths and toggle frequencies. The particles initially chain together to form a percolated network that coarsens diffusively. With time, the surface of the growing domains in the network become unstable. The amplitude of the waves eventually reaches a critical value and the columns pinch off and condense into ellipsoidal-like structures. |
Tuesday, March 15, 2022 4:48PM - 5:24PM |
K14.00004: granular/particle simulation Invited Speaker: Addie Dove
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Tuesday, March 15, 2022 5:24PM - 6:00PM |
K14.00005: Acoustically Levitated Granular Matter Invited Speaker: Melody X Lim From protoplanetary disks to the rings of Saturn, many astrophysical systems are composed of granular matter. Forces that are negligible in earthbound experiments --- such as electrostatic attraction and self-gravity --- play an important role in driving the assembly and dynamics of such matter. These dynamics often take place over millions of years, and while numerical models can be constructed to probe their underlying physics, there remains a need for tabletop experiments that controllably test models of granular materials in low gravity environments. In this talk, I will outline a new direction for tabletop experiments that aims to probe and model these interaction forces in astrophysical granular matter. We levitate particles in an ultrasonic standing wave to compensate forces due to gravity, and enable substrate-free assembly and manipulation. We mimic the effects of gravitational attraction via secondary scattering, which generates controllable attractive forces between particles. In addition, the small viscosity of air allows for the exploration of underdamped dynamics, where inertial effects are crucially important. I will discuss two areas in which it provides new insights into astrophysical phenomena: granular contact charging, and the rotational disruption of rubble-pile asteroids. Our results suggest a path toward the study of “tabletop asteroids", where astrophysical processes that take millions of years, on the scale of kilometers, can be observed and controlled in minutes. |
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