Active foams in mixtures of microtubules and tip-accumulating molecular motors

Extensive efforts have focused on understanding the non-equilibrium  behaviors of filamentous biopolymers driven by  molecular motors. Previously studied systems exhibited either robust contractions or extensile stresses that power turbulent flows. Despite these efforts, our understanding of how various microscopic parameters determine the symmetries of the emergent active stresses remains incomplete. To connect microscopic dynamics to macroscale behaviors, we measured the phase diagram of microtubule filaments and end-accumulating kinesin molecular motors. We describe a range of spatially heterogeneous non-equilibrium phases, including finite-sized radial asters, 1D wormlike chains, extended 2D bilayers, and system-spanning 3D active foams. We study the pulsatile dynamics of highly dynamical active foams that is driven by topological rearrangements. Finally, we also describe intricate kinetic pathways that yield the above-described microphase separated structures and arise from the inherent frustration between the orientational order of filamentous microtubules and the positional order of tip-accumulating molecular motors.

Part of the NSCS webinar series https://softmatterisrael.wixsite.com/nscs