Collective behavior

Length scale

Physics

Glass transition

Liquid crystal

Sociology

Demography

Exponential decay

Anthropology

Turbulence

Programming language

Condensed matter physics

Active matter

Constant (computer programming)

Dynamical heterogeneity

Population

Computer science

Nuclear magnetic resonance

Polymer

Mechanics

Nucleation

Quantum mechanics

Biology

Cell biology

Thermodynamics

Physical Review Letters

We investigate the large length and long time scales collective flows and structural rearrangements within in vitro human bronchial epithelial cell (HBEC) cultures. Activity-driven collective flows result in ensembles of vortices randomly positioned in space. By analyzing a large population of vortices, we show that their area follows an exponential law with a constant mean value and their rotational frequency is size independent, both being characteristic features of the chaotic dynamics of active nematic suspensions. Indeed, we find that HBECs self-organize in nematic domains of several cell lengths. Nematic defects are found at the interface between domains with a total number that remains constant due to the dynamical balance of nucleation and annihilation events. The mean velocity fields in the vicinity of defects are well described by a hydrodynamic theory of extensile active nematics.

Turbulent Dynamics of Epithelial Cell Cultures