Negative stiffness and modulated states in active nematics

Pragya Srivastava, Prashant Mishra, M Cristina Marchetti

Research output: Contribution to journalArticle

12 Citations (Scopus)

Abstract

We examine the dynamics of an active nematic liquid crystal on a frictional substrate. When frictional damping dominates over viscous dissipation, we eliminate flow in favor of active stresses to obtain a minimal dynamical model for the nematic order parameter, with elastic constants renormalized by activity. The renormalized elastic constants can become negative at large activity, leading to the selection of spatially inhomogeneous patterns via a mechanism analogous to that responsible for modulated phases arising at an equilibrium Lifshitz point. Tuning activity and the degree of nematic order in the passive system, we obtain a linear stability phase diagram that exhibits a nonequilibrium tricritical point where ordered, modulated and disordered phases meet. Numerical solution of the nonlinear equations yields a succession of spatial structures of increasing complexity with increasing activity, including kink walls and active turbulence, as observed in experiments on microtubule bundles confined at an oil-water interface. Our work provides a minimal model for an overdamped active nematic that reproduces all the nonequilibrium structures seen in simulations of the full active nematic hydrodynamics and provides a framework for understanding some of the mechanisms for selection of the nonequilibrium patterns in the language of equilibrium critical phenomena.

Original languageEnglish (US)
Pages (from-to)8214-8225
Number of pages12
JournalSoft Matter
Volume12
Issue number39
DOIs
StatePublished - 2016

Fingerprint

Elastic constants
stiffness
Stiffness
Nematic liquid crystals
Nonlinear equations
Phase diagrams
Oils
Turbulence
Hydrodynamics
elastic properties
Tuning
Damping
Water
Substrates
nonlinear equations
bundles
dissipation
oils
damping
Experiments

ASJC Scopus subject areas

  • Chemistry(all)
  • Condensed Matter Physics

Cite this

Srivastava, P., Mishra, P., & Marchetti, M. C. (2016). Negative stiffness and modulated states in active nematics. Soft Matter, 12(39), 8214-8225. https://doi.org/10.1039/c6sm01493c

Negative stiffness and modulated states in active nematics. / Srivastava, Pragya; Mishra, Prashant; Marchetti, M Cristina.

In: Soft Matter, Vol. 12, No. 39, 2016, p. 8214-8225.

Research output: Contribution to journalArticle

Srivastava, P, Mishra, P & Marchetti, MC 2016, 'Negative stiffness and modulated states in active nematics', Soft Matter, vol. 12, no. 39, pp. 8214-8225. https://doi.org/10.1039/c6sm01493c
Srivastava, Pragya ; Mishra, Prashant ; Marchetti, M Cristina. / Negative stiffness and modulated states in active nematics. In: Soft Matter. 2016 ; Vol. 12, No. 39. pp. 8214-8225.
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