Themed collection Active Matter

Moumita Das, Michael Murrell and Christoph Schmidt introduce the Soft Matter collection on active matter.

The cytoskeleton of a cell controls all the aspects of cell shape changes. Such conserved and effective control over the mechanics of the cell makes the cytoskeletal components great candidates for bottom-up synthetic biology studies.

Transient supramolecular self-assembly with tunable lifetime is achieved by coupling an alkali-generating clock reaction to a slow acid generator.

Topology-based machine learning classifies complex spatial patterns of epithelial cells into distinct phases. The presence and stability of spatially-connected loops is an effective measure of topological similarity, even when population size varies significantly due to proliferation.

Unusual phase separation dynamics with distinct morphologies of compact and dispersed clusters in a binary mixture of mechanically soft, less adhesive cells (red) and mechanically stiff, more adhesive cells (green).

Active stiffening and weakening both occur in active gels, which causes local compression that rapidly transmits in large distances.

ATP-assisted actin network self assembly in vitro is acompanied by an overshoot of the viscoelastic moduli followed by a relaxation to steady-state values.

The pure effect of actin polymerization through branching, triggered at the membrane surface, generates both dendritic (conical) and conventional filopodia-like (cylindrical) membrane deformations depending on the initial heterogeneity in the actin network.

Active matter systems exhibit rich emergent behavior due to constant injection and dissipation of energy at the level of individual agents. We characterize the dissipation of single active colloids.

We present large-scale simulations, supplemented by experiments, on flocking, banding and broken-symmetry excitations in a monolayer of polar rods and spherical beads, confined between horizontal plates and rendered active by vertical vibration.

Microtubules (left) and actin filaments (right) show low mobility when in bundles because actin is swept up into static microtubule bundles.

We use continuum simulations to study the impact of anisotropic hydrodynamic friction on the emergent flows of active nematics.

The physical cues from the extracellular environment mediates cell signaling spatially and temporally.

In this computational study of the myosin motility assay, we demonstrated that volume-exclusion effects lead to distinct collective behaviors of actin filaments, whereas actin cross-linking proteins induce contractile behaviors of actin filaments.

We quantify neuronal growth on substrates with controlled geometries and present a theoretical approach that describes the motion of axons.

Direct visualization reveals how bacterial motility in a porous medium is regulated by pore-scale confinement and cellular activity, yielding fundamental insights into the behavior of active matter under confinement.

We carry out numerical studies of both amorphous and ordered packings of frictionless superellipsoidal particles in three spatial dimensions to understand their structural and mechanical properties.

Actin–myosin networks exhibit macroscopic contraction due to the activity of myosin motors. Contraction is preceded by thousands of seconds by changes of the microscopic dynamics, in analogy to dynamic precursors in passive gels under external loads.

We show that 2-point non-equilibrium measures of fluctuating probe particles in an active system reveal features of the internal driving.

Receptor–receptor competition for uptake reduces the probability of receptor partitioning into endocytic structures as described by an equilibrium thermodynamics model.

We study the linear stability of an isotropic active fluid in three different geometries: a film of active fluid on a rigid substrate, a cylindrical thread of fluid, and a spherical fluid droplet.