(443b) Topography-Driven Control of Active Filaments

Curvatures on mammalian cell membranes are known to facilitate the collective motion and organization of the underlying cytoskeleton, allowing cells to regulate force generation at cell surfaces. However, we do not have a mechanistic understanding of the dynamic interplay between surface topography and the motion of self-propelled constituents along curved surfaces. In this work, we study how surface topography and active forces modulate the ordered dispersion of 2D active filaments. We study the dynamics of actin filaments that are propelled by molecular motors tethered to substrates with etched patterns, which provide a soft confinement potential due to filament bending penalties posed by the valley edges. We find that specific topographies facilitate the formation of swarming nematic bands of actin filaments along the etched substrates. Furthermore, the swarming nematic bands appear only at intermediate motor activity and topographical spacing length, leading to a “dynamic phase diagram” describing the collective behavior of actin filaments on etched surfaces. Our work advances the basic understanding of the coupling between surface topography and active forces at 2D interfaces, and provides new techniques to control the spatial and temporal onset of swarming transitions in active nonequilibrium systems.