Active Brownian Filamentous Polymers under Shear Flow

Abstract

The conformational and rheological properties of active filaments/polymers exposed to shear flow are studied analytically. Using the continuous Gaussian semiflexible polymer model extended by the activity, we derive analytical expressions for the dependence of the deformation, orientation, relaxation times, and viscosity on the persistence length, shear rate, and activity. The model yields a Weissenberg-number dependent shear-induced deformation, alignment, and shear thinning behavior, similarly to the passive counterpart. Thereby, the model shows an intimate coupling between activity and shear flow. As a consequence, activity enhances the shear-induced polymer deformation for flexible polymers. For semiflexible polymers/filaments, a nonmonotonic deformation is obtained because of the activity-induced shrinkage at moderate and swelling at large activities. Independent of stiffness, activity-induced swelling facilitates and enhances alignment and shear thinning compared to a passive polymer. In the asymptotic limit of large activities, a polymer length- and stiffness-independent behavior is obtained, with universal shear-rate dependencies for the conformations, dynamics, and rheology.

Active Brownian ring polymers

“…However, theoretical studies of active polymers exposed to shear flow predict an activity-depending shear thinning. 37,39 The latter could also play a role in swimming of bacteria. 87 Dedicated experiments to characterize the polymer properties are feasible and interesting and would yield direct evidence for activity-induced features.…”

“…Such fluctuations affect the structural, conformational, and dynamical properties of soft matter systems, e.g., comprised of filaments, polymers, or vesicles/cells, which render active soft matter a promising new class of materials. 6 The connectivity of active particles, as in linear chains 14,15,17,20,21,[26][27][28][29][30][31][32][33][34][35][36][37][38][39] or other arrangements, e.g., triangles or squares, 40 gives rise to particular interesting conformational and dynamical features due to the intimate coupling between conformation and activity.…”

“…[68][69][70] Activity is taking into account as colored noise, i.e., by a Gaussian but non-Markovian stochastic process. 18,20,[37][38][39]60,71 Studies of the properties of linear polymers by the same model 20,38,39 yield substantial conformational changes with varying activity. Flexible linear polymers exhibit a monotonic swelling with increasing activity, which saturates in the asymptotic limit of very large activity.…”

Active Brownian filaments with hydrodynamic interactions: conformations and dynamics

“…Valuable insight into the properties of self-propelled filaments and polymers, or their passive counterparts embedded in an active environment, is obtained by computer simulations and analytical theory. Thereby, typically active Brownian polymers (AB-POs), neglecting hydrodynamic interactions (HI) (in the following, we will denote such polymers as ABPOs-HI), have been considered [32][33][34][35][36][37][38][39][40][41][42][43][44][45] , but also particular aspects of fluid-mediate interactions have been studied 31,[46][47][48][49][50] . Filaments are modeled as semiflexible polymers, with an implementation of activity adapted to the particular propulsion mechanism.…”

Phase Separation by Entanglement of Active Polymerlike Worms

“…The T. tubifex worms that we investigate are active swimmers and approximately 300 μm thick and 10-40 mm long (see Supplemental Material [21]). The thermal random motion of the worms (estimated from the Stokes-Einstein equation) is negligible compared to their active motion, so they constitute a good model system for active polymers [25][26][27][28][29][30]. When randomly distributed over a volume of water, the worms aggregate spontaneously (Fig.…”