Living Matter

Collective movement can be observed throughout the living world, from bacterial colonies and tissue cells to schools of fish and flocks of birds. Despite the significant biological differences among these systems, they exhibit similar patterns and dynamics, suggesting universal principles independent of microscopic details.

Updates

Living systems like bacterial swarms and tissue cells are full of tiny nematic defects — points where rod-like cell alignment breaks down, then heals. We found this process is irreversible and breaks mirror symmetry: it doesn't look the same in reverse or reflected. This irreversibility is a hallmark of life, and the symmetry breaking hints at hidden order that standard active nematics models miss.🔗🔗🔗

Join us for exciting opportunities:

We have funded positions for MSc, and PhD candidates to explore the physics of multicellular organization, develop advanced microscopy, and image analysis methods (more details).

Research

About the Lab

We investigate how tissues self-organize, focusing on the physical mechanisms underlying collective cell motion. By combining quantitative experiments with theoretical models, we seek the physical laws that govern self-organization in multicellular systems. We study a range of biological systems—from cell colonies to bacterial swarms—focusing on the emergence of order, symmetry breaking, and active flows at the mesoscale.

In parallel, we develop experimental tools to measure and control multicellular organization, including live-cell microscopy, microfabricated confinement environments, and custom image analysis algorithms for tracking cells, flows, and topological defects.

Research topics

Collective cell dynamics & Multicellular self-shaping
Structure - Dynamics - Function interplay in cellular tissues
Experimental methods for characterization of multicellular properties
Optical methods for live cell imaging
Microscopy & Image analysis automation for cell imaging

AIducation

AI-generated video offering an accessible explanation of "Irreversibility and symmetry breaking in the creation and annihilation of defects in active living matter" (🔗Nature Physics 2026), * though not with complete accuracy

Publications

Topological defects in multi-layered swarming bacteria

V. Yashunsky, D. J. G. Pearce, G Ariel, A. Be'er, Soft Matter, (2024), arXiv:2401.05560

Chiral edge current in nematic cell monolayers

V. Yashunsky, D. J. G. Pearce, C. Blanch-Mercader, F. Ascione, P. Silberzan and L. Giomi, Physical Review X, (2022) 12, 041017, arXiv: 2010.15555

☞ video1 ☞ video2

Crisscross multilayering of cell sheets

T. Sarkar, V. Yashunsky, L. Brézin, CM. Mercader, T. Aryaksama, M. Lacroix, T. Risler, JF. Joanny, P. Silberzan, PNAS Nexus, (2023), 2(3), 034, bioRxiv: 2021.06.22.449403

Turbulent Dynamics of Epithelial Cell Cultures

Blanch-Mercader C, Yashunsky V, Garcia S, Duclos G, Giomi L, and Silberzan P.

Physical Review Letters (2018), 120, arXiv:1711.01568

Spontaneous shear flow in confined cellular nematics

Duclos G, Blanch-Mercader C, Yashunsky V, Salbreux G, Joanny JF, Prost J and Silberzan P, Nature Physics, (2018) 14

☞ Live streaming, Francesc Sagués (News & Views)

Controlling Confinement and Topology to Study Collective Cell Behaviors

Duclos G, Deforet M, Yevick H, Cochet-Escartin O, Ascione F, Moitrier S, Sarkar S, Yashunsky V, Bonnet I, Buguin A, Silberzan P., Cell Migration. Methods in Molecular Biology, (2018), 1749: 387-399, Humana Press, New York, NY