Actin-microtubule networks as time-varying rigidly percolating double networks

The cytoskeleton is a dynamic composite scaffold made of networks of different types of biopolymers, primarily actin filaments and microtubules, and motor proteins. Here we present results from Langevin Dynamics simulations of a model that combines two structure-function frameworks: a double network (DN) made of a network of stiff filaments (microtubules) interacting with a network of flexible filaments (actin), and rigidity percolation theory. We present results for the collective time-evolving mechanical response of these composites with and without active elements (myosin and kinesin motors), and obtain a phase diagram in the space of concentrations of actin, microtubules, and motors. Our results can provide mechanistic insights into the contractility and restructuring of active cytoskeletal composites and the rational design of materials inspired by them.