Séminaire Programme Gradué Chimie PSL

Ranabir Dey from IIT Hyderabad, Université de Bordeaux. The title of Ranabir’s talk is:

** How self-propelling microswimmers adapt to complex confined environments **

Outline: Biological microswimmers have developed various locomotion strategies and responses to adapt to changes in their local environments. For example, bacteria, algae, and sperm cells alter their locomotion in confined environments, like near walls, interfaces, pores and corners, resulting in circular trajectories, geometry-guided motion, trapping, and accumulation.  In this seminar, we show that self-propelling artificial microswimmers also exhibit autonomous changes in their motility to adapt to local complex environments, by considering self-propelling active droplets as a model system.

First, we demonstrate the fascinating emergence of run-and-tumble-like motility in active droplets with increasing softness of the walls in strong confinements. We connect such emergent swimming dynamics in a soft microchannel to the underlying alterations in chemo-hydrodynamics using fluorescence microscopy techniques and boundary integral method-based numerical simulations. Next, we demonstrate how self-propelling microswimmers adapt to confined liquid-air and liquid-liquid meniscus corners- ubiquitous elements of natural and engineered environments. Combining experiments, theory and simulations, we show that pusher-type microswimmers are attracted towards a meniscus corner, followed by transient trapping and eventual escape. We further map the dependence of swimming trajectories on the microswimmer type, the corner geometry, and the viscosity ratio across the liquid interface.

Understanding these alterations in swimming strategy for artificial microswimmers (model systems) serves two main purposes- one, it provides insights into the fluid dynamical aspects of the underlying adaptation mechanisms for biological microswimmers by circumventing the biological complexity; two, it helps in planning a roadmap for using artificial microswimmers like active droplets as state-of-the-art autonomous, microrobots in many biotechnology/biomedical applications.

References:

[1] Sontakke, S. S., Kajampady, A., Rizvi, M. S., & Dey, R. (2025). Emergence of run-and-tumble-like swimming in self-propelling artificial swimmers in soft microchannels. arXiv preprint arXiv:2508.04443.
[2] Guchhait, S., Tiwari, H., Thampi, S. P., & Dey, R. (2026). Hydrodynamic capture and release of a microswimmer by a meniscus corner. arXiv preprint arXiv:2604.19552.