Extensile to contractile transition in active microtubule-actin composites generates layered asters with programmable lifetimes

Abstract

We study a reconstituted composite system consisting of an active microtubule network interdigitated with a passive network of entangled F-actin filaments. Increasing viscoelasticity of the F-actin network controls the emergent dynamics, inducing a transition from turbulent-like flows to bulk contractions. At intermediate F-actin concentrations, where the active stresses change their symmetry from anisotropic extensile to isotropic contracting, the composite separates into layered asters that coexist with the background turbulent fluid. Contracted onion-like asters have a radially extending microtubule-rich cortex that envelops alternating layers of microtubules and F-actin. The self-regulating layered organization survives aster merging events, which are reminiscent of droplet coalescence, and suggest the presence of effective surface tension. Finally, the layered asters are metastable structures. Their lifetime, which ranges from minutes to hours, is encoded in the material properties of the composite. Taken together, these results challenge the current models of active matter. They demonstrate that the self-organized dynamical states and patterns, which are evocative of those observed in the cytoskeleton, do not require precise biochemical regulation but can arise due to purely mechanical interactions of actively driven filamentous materials.

23 pages, 11 figure

References in corpus (6)

• Spontaneous motion in hierarchically assembled active matter
• Tunable dynamics of microtubule based active isotropic gels
• Interplay of Structure, Elasticity and Dynamics in Actin-Based Nematic Materials
• Measuring cohesion between macromolecular filaments, one pair at a time: Depletion-induced microtubule bundling
• Uncovering the dynamic precursors to motor-driven contraction of active gels
• How crosslink numbers shape the large-scale physics of cytoskeletal materials

Cited by in corpus (9)

• Metastability of Constant-Density Flocks
• Self-mixing in microtubule-kinesin active fluid from nonuniform to uniform distribution of activity
• Spontaneous rotation of active droplets in two and three dimensions
• Reconfiguration, Interrupted Aging and Enhanced Dynamics of a Colloidal Gel using Photo-Switchable Active Doping
• Mechanochemical Topological Defects in an Active Nematic
• Closed-loop control of active nematic flows
• Acoustic signaling enables collective perception and control in active matter systems
• Active assembly and non-reciprocal dynamics of elastic membranes
• Interfacial instability of confined 3D active droplets