Bulletin of the American Physical Society
77th Annual Meeting of the Division of Fluid Dynamics
Sunday–Tuesday, November 24–26, 2024; Salt Lake City, Utah
Session A03: Low Reynolds Swimming I: Bioinspired |
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Chair: Bruce Rodenborn, Centre College Room: Ballroom C |
Sunday, November 24, 2024 8:00AM - 8:13AM |
A03.00001: Mobility dynamics of rotationally driven particles in a structured environment Pamud Akalanka Bethmage, Andrey Sokolov, Brennan Sprinkle, Michelle M Driscoll Understanding how active particles migrate in a complex landscape is vital when designing micron-scale devices, targeted medicine, and controlled self-assembly. Recent work reveals that interactions with structure lead to rich and complex behavior such as fluctuation-induced particle trapping near cylindrical obstacles and geometry induced changes in mobility. Here, using both simulations and experiments, we study the mobility dynamics of rotationally driven micro-spheres and how these dynamics are altered due to hydrodynamic interactions with confined structures. Multi-photon lithography is used to create structures on the order of the particle size to experimentally investigate how mobility dynamics are altered under strong confinement. Here we explore single-particle dynamics, and how they are altered by flow-structure interactions, as well as how collective interactions in dense suspensions alter them. Lubrication corrected Brownian dynamics simulations are used in tandem with experiments to fully understand the mechanism behind geometry-induced mobility changes. We find that individual particle velocity is strongly controlled by spatial confinement and moreover in dense suspensions, emergent structures tend to compete with mobility and can completely arrest suspension flows.
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Sunday, November 24, 2024 8:13AM - 8:26AM |
A03.00002: Stability of the Co-Swimming Condition in Non-Spherical Active Droplet Systems Amin Balazadeh Koucheh, Herve Nganguia, Ebru Demir Micro-swimmers are playing an increasingly critical role in biomedical applications such as drug delivery. Our previous work in this realm considered a model micro-swimmer encapsulated in a viscous droplet. We identified conditions necessary for the micro-swimmer and the droplet to move at the same speed, namely, co-swimming. Building on our previous work, we will present a time-dependent, numerical analysis of the stability of the co-swimming state for a range of swimmer and droplet's geometries, as well as biologically relevant fluid environments. |
Sunday, November 24, 2024 8:26AM - 8:39AM |
A03.00003: Biomimetic locomotion study of floating microswimmers with light-driven particle hinges on water/air interface Jesus Becerra, Kuan-Lun Ho, Nathan Snowden, Joey Hale, Jing Ding, Mingjun Wei, Shih-Kang Fan Microswimmers with individually light-driven hinges are studied experimentally in the form of two-hinge and four-hinge “Purcell” swimmers for their capability to reproduce biomimetic locomotion on a water/air interface through lateral propulsion. Floating microswimmers hold great potential in applications of active environmental monitoring and miniaturized cargo transportation but are currently hindered by the availability of locomotion and maneuverability on a millimeter/micrometer scale. Light and magnetic fields have been used in driving previous microswimmers, but unless the application of external stimuli has a fine spatial and temporal resolution, individually driven hinges of similar characteristics are impossible. In this study, an electromicrofluidic (EMF) printing platform, that independently drives and assembles hydrogel droplets and suspended particles, is adapted to fabricate hydrogel Purcell swimmers with color-varied particle-embedded hinges driven by light. The responsiveness of the differently colored hinges to the exposure of light and the two-dimensional movement of the microswimmers will be characterized and compared to similar biomimetic movement. |
Sunday, November 24, 2024 8:39AM - 8:52AM |
A03.00004: Abstract Withdrawn
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Sunday, November 24, 2024 8:52AM - 9:05AM |
A03.00005: Calibrating the method of regularized Stokeslets using macroscopic experimental measurements Kathleen Margaret Brown, Jonathan McCoy, Ricardo Cortez, Amelia Gibbs, Frank Healy, Hoa Nguyen, Orrin Shindell, Bruce E Rodenborn The swimming of microorganisms is typically studied using biological experiments and/or numerical simulations. However, numerical simulations of microorganisms are not often compared to precise measurements because it is difficult to make microscopic measurements of forces and torques in biological experiments. The Trinity Centre Collaboration, instead, uses macroscopic dynamically similar table-top experiments in highly viscous silicone oil to test theories and create a library of forces and torques on simple geometric shapes such as helices, cylinders, and spheres (see Shindell et al. 2021). These geometries can be used to model bacilli and cocci bacteria such as Escherichia coli, Pseudomonas aeruginosa, and Rhodobacter sphaeroides. The forces and torques on the macroscopic models can be measured directly, and the results scaled to biologically relevant sizes. Our recent sphere measurements experimentally verified the theory of Lee and Leal (1980) for the force and torque on a sphere moving near a wall with much greater precision than previously reported. The force and torque data from our experiments and the Lee and Leal theory were used to calibrate the Method of Images for Regularized Stokeslets and the Generalized System of Images for Regularized Stokeslets for use as a noninvasive probe of bacterial swimming dynamics by modeling bacterial motion from microscopic image data. Our optimized computational parameters and a numerical implementation of theory are available via ArXiv (arXiv:2401.16214). |
Sunday, November 24, 2024 9:05AM - 9:18AM |
A03.00006: Rigid microspheres in a Stokes fluid: motion due to random forces. Irene Erazo, Lisa J Fauci, Scott Mckinley This study investigates the dynamic behavior of small spherical particles subjected to externally applied random forces while immersed in a viscous fluid. Our computational approach uses a regularized Stokeslet formulation. In contrast to the stochastic immersed boundary method, which averages fluctuating random forces within the particle location, here, these forces are in the surrounding fluid, external to the particle surfaces. We assume the particles are spheres with rigid rotations and translations due to the applied transient forces. |
Sunday, November 24, 2024 9:18AM - 9:31AM |
A03.00007: Abstract Withdrawn
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Sunday, November 24, 2024 9:31AM - 9:44AM |
A03.00008: Run and tumble dynamics as Levy flights in orientation: Theory and Experiment Taylor Joshsua Whitney, Thomas H Solomon, Kevin A Mitchell Many microorganisms exhibit run and tumble dynamics. This behavior is usually modeled as smooth runs followed by discrete random tumble events. However, in the lab, we see a wide spectrum of tumbling behavior. We offer a new model that may explain this wide variety of tumbling behavior, not as discrete tumbling events, but as a continuum of random reorientations that follow a Lorentzian (or Cauchy) distribution. This means microbes undergo Levy flights in their angular dynamics. The corresponding Fokker Planck equation for a stochastic differential equation with Lorentzian noise is exactly solvable. We construct the time evolution of a probability distribution from experimental data and show it closely matches the modified Fokker Planck equation for Lorentzian noise. We also extract the noise strength of the Lorentzian distribution for several populations of microbes (all with different behaviors), and run Monte Carlo simulations that closely reproduce the statistics. This is strong evidence that run and tumble dynamics can be modeled as Levy flights in orientation. |
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