Mathematics of Microswimming

Thursday, June 17 at 04:15am (PDT)
Thursday, June 17 at 12:15pm (BST)
Thursday, June 17 08:15pm (KST)

SMB2021 SMB2021 Follow Wednesday (Thursday) during the "MS18" time block.
Note: this minisymposia has multiple sessions. The second session is MS19-MMPB (click here).

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Qixuan Wang (UC Riverside, United States), Bhargav Rallabandi (UC Riverside, United States), Mykhailo Potomkin (UC Riverside, United States)


Microorganisms are the most abundant in nature. Their ability to move autonomously and develop diverse strategies to survive in various environments is at the core of understanding life. Motility of numerous types of microorganisms, relevant for biological and medical applications, occurs in fluids. Such microorganisms, called microswimmers and exemplified by bacteria or spermatozoa, are relevant for many biological and medical applications. Recent advances in studies of biological microswimmers have inspired development of synthetic microrobots with potential medical applications such as drug delivery, decrease of biofluid viscosity or tissue repair. In this special session, we bring together experts in this area to discuss how the state-of-the-art techniques in modeling, theory and experiments can elucidate microwimming phenomena, develop new directions in this interdisciplinary research and provide new applications of microswimmers.

Chaouqi Misbah

(CNRS and Univ. Grenoble, France)
"Swimming of Cells and Artificial Particles Driven by Shape Changes and Chemical Activity"
Locomotion is essential for living cells. It enables bacteria and algae to explore space for food, cancer to spread, and immune system to fight infections. Amoeboid swimming will be first discussed exhibiting variety of behaviors (like navigation, asymmetric motion in a channel, etc.). Then we discuss generic trajectories obtained for active particles driven by a chemical activity. These types of particles display trajectories of intriguing complexity, from regular (e.g. circular, helical, and so on) to irregular motions (run-tumble), the origin of which has remained elusive for over a century. This dynamics versatility is conventionally attributed to the shape asymmetry of the motile entity, to the suspending media, and/or to stochastic regulation. A universal approach highlighting that these movements are generic, occurring for a large class of cells and artificial microswimmers, without the need of invoking shape asymmetry nor stochasticity, but are encoded in their inherent nonlinear evolution. We show, in particular, that for a circular and spherical particle moving in a simple fluid, circular, helical and chaotic motions (akin to a persistent random walk) emerge naturally in different regions of parameter space. This establishes the operating principles for complex trajectories manifestation of motile systems, and offers a new vision with minimal ingredients.

Kirsty Wan

(University of Exeter, United Kingdom)
"Locomotor patterning in quadriflagellate microswimmers: lessons from quadrupeds and robots"
When animals first evolved from underwater to terrestrial living, they first had to overcome the formidable challenge of coordinating and controlling their limbs to generate effective legged locomotion involving gaits such as crawling, walking galloping. Surprisingly, it was recently discovered that many species of single-celled algae exhibit similar gaits for swimming, despite being only tens of micrometers across and lacking in a nervous system. Among these, species that have four flagella (whip-like appendages that can bend and deform actively in a fluid) are particularly abundant in nature. Species that appear morphologically similar may nonetheless be associated with distinct gaits and swimming speeds. In this talk i will discuss our recent efforts to integrate fluid dynamical modelling, live-cell experiments, and robophysical models to understand the swimming gaits of quadriflagellate algae. Continuing research into these microscopic swimmers may provide key insights into the evolutionary origins of decentralized locomotor control in living systems.

Hermes Gadêlha

(Department of Engineering Mathematics and Bristol Robotics Laboratory, University of Bristol, United Kingdom)
"Coarse-graining formulations for sperm swimming and other flagellates"
The inertialess fluid-structure interactions of active and passive inextensible filaments and slender-rods are ubiquitous in nature. The coupling between the geometry of deformation and the physical interaction governing the fluid dynamics is complex. Governing equations negotiate multi-scale interactions with non-holonomic constraints. Such systems are structurally convoluted, prone to numerical errors, often requiring penalization methods and high-order spatio-temporal propagators. In this talk we will discuss how the coarse-graining formulation greatly simplifies the several biophysical interactions and overcomes numerical instability. The dynamical system is straightforward and intuitive to implement, and allows for a fast and efficient computation. Only basic knowledge of systems of linear equations is required, and implementation achieved with any solver of choice. Generalizations for complex interaction of multiple rods, Brownian polymer dynamics, active filaments and non local hydrodynamics are also straightforward.

Ye Chen

(New Jersey Institute of Technology, United States)
"Helical locomotion in a porous medium"
Microorganisms and artificial microswimmers often need to swim through environments that are more complex than purely viscous liquids in their natural habitats or operational environments, such as gel-like mucus, wet soil and aquifer. The question of how properties of these complex environments affect locomotion has attracted considerable recent attention. In this work, we focus on helical locomotion for its ubiquity as a propulsion mechanism adopted by many swimming bacteria. We present a theoretical model to examine how the additional resistance due to the network of stationary obstacles in a porous medium affects helical locomotion. Compared with previous theoretical and experimental results, we will elucidate the effects of the resistance on various types of helical locomotion. We also remark on the limitations as well as potential connections of our results with experimental measurements of bacterial swimming speeds in polymeric solutions.

Hosted by SMB2021 Follow
Virtual conference of the Society for Mathematical Biology, 2021.