Abstract : Swimming in a fluid at microscopic scale is at the heart of many questions pertaining to biology, soft matter physics and micro-robotics.
It usually involves a complex balance of hydrodynamics, elasticity and internal activity, yielding a wide range of issues requiring various mathematical viewpoints, from modelling the fluid-structure interaction to optimal propulsion and efficient control of the swimmer's trajectory, with perspectives on future applications to biomedical micro-robots. This minisymposium brings together a group of young and experienced researchers to share their contributions to some of the latest developments in the theoretical and numerical analysis of micro-swimmers.
[03028] Results on Classical Elastohydrodynamics for a Swimming Filament
Format : Talk at Waseda University
Author(s) :
Laurel A Ohm (University of Wisconsin--Madison)
Abstract : We consider two models of an immersed inextensible filament undergoing planar motion: (1) the classical elastohydrodynamic model using resistive force theory and Euler-Bernoulli beam theory, and (2) a novel curve evolution incorporating effects of linear viscoelasticity. We mention our recent PDE results on these models and highlight how this analysis can help to understand undulatory swimming at low Reynolds number. This includes the development of a novel numerical method to simulate inextensible swimmers.
[04238] A limiting model for a low Reynolds number swimmer with N passive elastic arms
Format : Talk at Waseda University
Author(s) :
Jessie Levillain (CMAP, Ecole Polytechnique)
François Alouges (Centre Borelli, École Normale Supérieure Paris-Saclay)
Aline Lefebvre-Lepot (CMAP, École polytechnique)
Abstract : We study a simple model of artificial microswimmer, consisting of a rigid extensible arm followed by an $N$-mass-spring system.
We further study the limit as the number of springs tends to infinity and the parameters are scaled conveniently, and provide a rigorous proof of the convergence of the discrete model to the continuous one.
Numerical experiments show performances of the displacement in terms of frequency or amplitude of the oscillation of the active arm.
[05406] Activation processes of flagellated micro-swimmers
Format : Online Talk on Zoom
Author(s) :
Irene Anello (SISSA)
Jessie Levillain (CMAP, Ecole Polytechnique)
François Alouges (Centre Borelli, Ecole Normale Supérieure Paris-Saclay)
Aline Lefebvre-Lepot (CMAP, Ecole Polytechnique)
Antonio De Simone (SISSA)
Abstract : We study the activation processes of flagellated micro-swimmers investigating microscopic details inside the flagellum.
The flagellum is composed of a structure called axoneme, composed of nine filament pairs along which are disposed force-generating elements called molecular motors.
After describing the biology behind it, we first model these motors individually before introducing a mathematical representation of the whole system.
The aim is to couple this microscopic description with a macroscopic beam equation for flagellated swimmers.
[02171] Emergent rheotaxis of shape-changing swimmers in Poiseuille flow
Format : Talk at Waseda University
Author(s) :
Benjamin Benjamin Walker (University of Bath)
Kenta Ishimoto (Kyoto University)
Clement Moreau (RIMS, Kyoto University)
Eamonn Gaffney (University of Oxford)
Mohit Dalwadi (University College London)
Abstract : The complexity of microscale swimming has driven the development of simple, representative models. In this talk, we'll examine an apparently simple model of a swimming cell in a channel and reveal a surprisingly complex dynamics that evolves on three distinct timescales. Through an asymptotic analysis, we'll show how the long-time behaviours of this system can be reduced to the study of a single ordinary differential equation, whose evolution turns out to be remarkably simple.
[03303] Nonlinear dynamics, bifurcations and stability transitions in motion of periodically-actuated micro-swimmers
Format : Online Talk on Zoom
Author(s) :
Yizhar Or (Mechanical Engineering, Technion)
Abstract : We study simple models of robotic-like microswimmers with periodic actuation. We start from the well-known Purcell’s three-link swimmer model, and modify it in order to add realistic effects of passive elasticity and/or mechanical actuation, rather than kinematic control. We also focus on minimal models of magnetically-actuated microswimmers. We show that the nonlinear dynamics of such models include bifurcations and stability transitions of periodic solutions, which can be analyzed both numerically and analytically using asymptotic methods.
[05278] Low-Reynolds-number swimming via reinforcement learning
Format : Online Talk on Zoom
Author(s) :
Alan C. H. Tsang (University of Hong Kong)
Yangzhe Liu (University of Hong Kong)
Zonghao Zou (Cornell University)
Ali Gurbuz (Santa Clara University)
On Shun Pak (Santa Clara University)
Abstract : The application of machine learning methods in the development of microswimmers has garnered significant interest recently. In particular, reinforcement learning has proven to be valuable in empowering microswimmers to learn effective propulsion strategies through their interactions with the environment. In this talk, we will discuss our latest progress in integrating reinforcement learning techniques into the design of smart microswimmers capable of performing complex tasks relevant to their biomedical applications.
[03505] Controllability of microswimming systems with and without drift
Format : Talk at Waseda University
Author(s) :
Clement Moreau (RIMS, Kyoto University)
Abstract : In this talk, I will discuss the controllability properties of microswimmer models, i.e. their capacity to reach a given target, depending on important assumptions such as the way the swimmer's deformation is controlled and its environment. I will focus on the example of a magneto-elastic swimmer to present a result on the local controllability of control-affine systems with a drift.
[03844] Recent trends in micro-swimming
Format : Talk at Waseda University
Author(s) :
Marta Zoppello (Politecnico di Torino)
Marco Morandotti (Politecnico di Torino - P. IVA 00518460019)
Abstract : Inertialess hydrodynamics is notorious for its time-reversibility constraint, which leads to the well known "Scallop Theorem”. One way to overcome it is to couple two or more micro-swimmer units. In this talk we will show some recent results about the controllability of more than one micro-swimmer immersed in a viscous fluid, highlighting the crucial role of hydrodynamic interaction in achieving it.
