Locally tuned hydrodynamics of active polymer chains

Abstract: We employ mesoscopic simulations to study active polymers in a solvent via multi-particle collision dynamics. We investigate linear chains in which either the head or tail monomer exerts an active force, directed away from or towards its neighbor, respectively, while the remaining monomers are passive. We find that, in contrast to flexible chains, for stiff chains the position of the active monomer has minimal influence on both the structural and dynamic properties of the chain. An active head monomer pulls the chain behind it, straightening the backbone -- an effect that can be interpreted as activity-induced stiffening. In contrast, an active tail pushes into the chain, causing crumpling. This leads to faster decorrelation of the polymer backbone over time, rendering the active motion less persistent. These effects occur regardless of whether hydrodynamic interactions are included or not. Hydrodynamics is included by the imposition of a local counter-force in the surrounding fluid, as opposed to distributing the former equally to all fluid elements. By specifying the position of this counterforce onto the fluid, we can tune the hydrodynamic flow fields of the active polymers being both contractile and extensile. Interestingly, the emerging pusher- and puller flow fields are strongly influenced by the force propagation inside the polymer chain.