Active fluids exhibit spontaneous flows with complex spatiotemporal structure, which have
been observed in bacterial suspensions, sperm cells, cytoskeletal suspensions, self …

When interacting motile units self-organize into flocks, they realize one of the most robust
ordered states found in nature. However, after 25 years of intense research, the very …

As the constituent particles of a flock are polar and in a driven state, their interactions must,
in general, be fore-aft asymmetric and nonreciprocal. Within a model that explicitly retains …

We propose a general formalism to characterize orientational frustration of smectic liquid
crystals in confinement by interpreting the emerging networks of grain boundaries as objects …

The coordination of cell proliferation and migration in growing tissues is crucial in
development and regeneration but remains poorly understood. Here, we find that, while …

We show that incompressible polar active fluids can exhibit an ordered, coherently moving
phase even in the presence of quenched disorder in two dimensions. Unlike such active …

We show from experiments and simulations on vibration-activated granular matter that self-
propelled polar rods in an elastic medium on a substrate turn and move towards each other …

Active materials, composed of internally driven particles, have properties that are
qualitatively distinct from matter at thermal equilibrium. However, the most spectacular …

How fast must an oriented collection of extensile swimmers swim to escape the instability of
viscous active suspensions? We show that the answer lies in the dimensionless …

Directed collective cell migration is central to morphogenesis, wound healing and cancer
progression. Although the molecular anisotropy of the microenvironment guides this …