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The collective dynamics of active swarms such as bird flocks and fish schools emerge from the complex, and often competing, interaction involving alignment, cohesion and collision avoidance. The authors propose a minimal flocking model with vison-based steering interactions, revealing a unique transition from order to disorder reminiscent of a Berezinskii-Kosterlitz-Thouless transition, which could enhance understanding of rapid flock responses in biological systems.

Swarmalators offer a framework to study how spatial organization and internal dynamics co-evolve in natural and engineered collectives. Here, the authors present an experimental colloidal swarmalator system with tunable synchronization-motion coupling, revealing emergent collective states and a novel synchronization-dependent interaction mechanism.

How cells actively change their shape is an open question. Now, a reconstituted minimal cytoskeleton composed of microtubules and molecular motors is shown to produce membrane fluctuations that drive active shape changes in synthetic cells.

Experiments and simulations show that local non-equilibrium forces exerted by self-propelled particles trapped inside a giant unilamellar lipid vesicle induce dramatic shape changes in the vesicle.

Directed, active transport of cargo is essential for life on all length scales. A new system of artificial microtubules — consisting of a fibre with an embedded periodic array of magnetic inclusions — provides controlled active transport of microcargo by a rotating magnetic field, even under adverse flow conditions.

Cellular adhesions have the remarkable property that they adapt their stability to the applied mechanical load. Here, authors describe a generic physical mechanism that explains self-stabilization of idealized adhesion systems under shear.

The mechanism allowing sperm to steer is not fully understood. The authors find that superposition of two harmonic waves breaks the flagellar beat symmetry temporally rather than spatially, and that this mechanism is enhanced by the sexual hormone progesterone, which changes the motility pattern.

The study of self-organisation of pedestrian movement at crossing is important for the design of strategies facilitating pedestrian flow in crowded areas and the mitigation of crowd-related accidents. The authors study the motion of pedestrians using a model inspired from active matter systems finding interesting phases of three interacting streams of agents, including jamming, and the emergence of a vortex state.

The properties of cognitive microswimmers in fluids are determined by their capability to sense a target, process information, and adapt the motion, and by hydrodynamic interactions. To gain insight on this process, the authors investigate pursuer-target pairs, for pursuers with implicitly sensing, and self-steering with limited maneuverability.

Active matter consists of energy-consuming units, which self-propel, exert forces on their neighbours and act collectively, resulting in emergent non-equilibrium behaviour. This Review surveys computational models that describe a wide range of active systems, from synthetic microswimmers to animal herds.

Microswimmers are ubiquitous in nature and present highly-dynamic collective motion. This study presents computational simulations of spheroidal model-microswimmers confined between two walls, revealing two collective dynamic states, giant motile clusters and active turbulence, depending on density and hydrodynamic interactions.

The dynamics of chiral active fluids is characterised by a multitude of interacting dynamic vortices whose maximum size varies for each system. Here we show how the friction induced by the substrate is related to a damping length which is ultimately responsible of limiting the maximum size of the vortices.

The investigation of a chiral active fluid composed of a carpet of standing and spinning colloidal rods, combined with simulations for synchronously rotating hard discs in a hydrodynamic explicit solvent reveals here the simultaneous occurrence and relation of two seemingly separate phenomena: active turbulence and odd viscosity.

Adhesion forces due to active pili govern the formation of biofilms by a wide range of bacteria. Using simulations, this work shows how such active adhesions determine the morphology of bacterial collectives, their non-equilibrium fluctuations, and the spreading dynamics in different geometries.

Cells are in constant movement inside tissues, but often remain cohesive nevertheless, i.e., single cells do not escape from the colony edges. Using an active Brownian-particle model with attraction, in this paper the authors develop an interaction potential that reproduces experimental observations describing the motion of epithelial sheets under different conditions.