Théorique, numérique
Microorganisms, such as bacteria or microalgae, are often found in complex environments: from maze-like structures in soils to serpentine channels in the intestine. Numerous works have characterized the motion of microorganisms in the bulk. However, studies in realistic environments remain scarce. Recently [1], it was found that bacteria in porous media (a microscale maze-like 3D structure) exhibit a peculiar behavior and get trapped in specific spots. This is due to the time to flip their swimming direction. In addition, in Nature, environments dramatically evolve in time, from rainfalls which induce flows to soil mazes that continuously reorganize due to the presence of other microorganisms which create jams or open up pathways. Toinvestigate the motion of microorganisms in such fluctuating environments, we will explore a minimal model of active particles moving through a wiggling channel (=swimming in a fluctuating lane). We will study the diffusion and the drift of the particles according to the speed of the fluctuations [2]. We expect to uncover interesting regimes where motion is increased by collisions with the channel walls. We also expect odd behaviors associated with the interplay between different time scales in the system. We will characterize these different regimes. This internship will be in collaboration with Ruben Zakine (Ecole Polytechnique).