Confinement Controls the Active Assembly of Elastic Networks

Fascin crosslinks actin filaments into bundles and elastic networks. We study how chaotic active fluids influence the structure, mechanics, and dynamics of actin-fascin networks. Actin networks in quasi-2D confinements contract into sheets at the sample midplane whereas 3D confined networks undergo isotropic contraction. We quantify how the active fluid controls the structure of the emerging actin-fascin network, as well as how the active fluid responds to the evolving network structure. By varying the dimensions of the sample confinement, we tune the hydrodynamic screening effects which control the characteristic length scale of the active fluid. Modulating confinement geometry in this way enables us to characterize the role of active stresses in shaping both the coarse and fine structures of the elastic network. These experiments are a first step towards elucidating how active fluids can be used to assemble tunable viscoelastic materials beyond the limits of thermally-driven self-assembly.