Viscoelastic and elastomeric active matter: Linear instability and nonlinear dynamics

Abstract

We consider a continuum model of active viscoelastic matter, whereby an active nematic liquid-crystal is coupled to a minimal model of polymer dynamics with a viscoelastic relaxation time ${\tau }_C$. To explore the resulting interplay between active and polymeric dynamics, we first generalise a linear stability analysis (from earlier studies without polymer) to derive criteria for the onset of spontaneous heterogeneous flows (strain rate) and/or deformations (strain). We find two modes of instability. The first is a viscous mode, associated with strain rate perturbations. It dominates for relatively small values of ${\tau }_C$ and is a simple generalisation of the instability known previously without polymer. The second is an elastomeric mode, associated with strain perturbations, which dominates at large ${\tau }_C$ and persists even as ${\tau }_C\to \infty$. We explore the novel dynamical states to which these instabilities lead by means of direct numerical simulations. These reveal oscillatory shear-banded states in 1D, and activity-driven turbulence in 2D even in the elastomeric limit ${\tau }_C\to \infty$. Adding polymer can also have calming effects, increasing the net throughput of spontaneous flow along a channel in a new type of "drag-reduction". Finally the effect of including strong, antagonistic coupling between nematic and polymer is examined numerically, revealing a rich array of spontaneously flowing states.

25 pages, 21 figures; v2 fixed rendering issue with fig 4, updated to published version

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Cited by in corpus (15)

• Active Turbulence
• Viscoelastic control of spatiotemporal order in bacterial active matter
• Active matter in a viscoelastic environment
• Scaling regimes of active turbulence with external dissipation
• Permeation Instabilities in Active, Polar Gels
• Activity pulses induce spontaneous flow reversals in viscoelastic environments
• Active nematic gels as active relaxing solids
• Active-gel Theory for Multicellular Migration of Polar Cells in the Extra-cellular Matrix
• Self-sustained patchy turbulence in shear-thinning active fluids
• Vortex pattern stabilization in thin films resulting from shear thickening of active suspensions
• Rheologically tuned modes of collective transport in active viscoelastic films
• Self-sustained oscillations of active viscoelastic matter
• Unified description of viscous, viscoelastic, or elastic thin active films on substrates
• Active viscoelastic nematics with partial degree of order
• Microswimming in viscoelastic fluids