Active nematic response to a deformable body or boundary: elastic deformations and anchoring-induced flow

Abstract

A body immersed in a nematic liquid crystal disturbs the fluid's preferred molecular configuration and increases its stored elastic energy. In an active nematic, the fluid components also generate a stress in the bulk fluid. By introducing either an immersed body or boundary, a large scale flow can be triggered due to anchoring boundary conditions alone -- a global pressure built by active stresses at equilibrium is instantly released everywhere. The fluid then imposes viscous, elastic, and active stresses on such surfaces which, if compliant, may result in a surface deformation. We study the deformations and stresses of a linearly elastic body placed in an active nematic in two dimensions. Using complex variables techniques, exact expressions for the fluid flow, director field, surface tractions, and body deformation are derived. Qualitative differences between elastic and active stress-driven deformations are identified, depending on an active Ericksen number, anchoring conditions, and body material properties, thereby suggesting a new method for measuring mechanical stresses in active anisotropic environments. Flow profiles, external confinement, and anchoring-induced stirring are also addressed.

Paper: 9 pages, 4 figures; Supplemental Material: 8 pages

References in corpus (25)

• The Mechanics and Statistics of Active Matter
• Spontaneous motion in hierarchically assembled active matter
• Hydrodynamic fluctuations and instabilities in ordered suspensions of self-propelled particles
• Topology and Dynamics of Active Nematic Vesicles
• Fluid dynamics of bacterial turbulence
• Spontaneous symmetry breaking in active droplets provides a generic route to motility
• Velocity Correlations in an Active Nematic
• Liquid Crystal Colloids
• Instabilities and Topological Defects in Active Nematics
• Spontaneous division and motility in active nematic droplets
• Excitable Patterns in Active Nematics
• Banding, Excitability and Chaos in Active Nematic Suspensions
• Walls Inhibit Chaotic Mixing
• Cortical microtubule nucleation can organise the cytoskeleton of $Drosophila$ oocytes to define the anteroposterior axis
• Swimming in Complex Fluids
• Rectified Rotational Dynamics of Mobile Inclusions in Two-Dimensional Active Nematics
• Fingering Instability of Active Nematic Droplets
• Defect driven shapes in nematic droplets: analogies with cell division
• A nematic liquid crystal with an immersed body: equilibrium, stress, and paradox
• Dynamics of a Passive Droplet in Active Turbulence
• Stability of the interface of an isotropic active fluid
• Equilibrium morphology of tactoids in elastically anisotropic nematics
• Exact and approximate solutions for elastic interactions in a nematic liquid crystal
• Object Transport by a Confined Active Suspension
• Variational bounds and nonlinear stability of an active nematic suspension