“Catapulting” of topological defects through elasticity bands in active nematics

ORAL

Abstract

Local injection of energy in active liquid crystals (LC) results in spontaneous defect generation and emerging complex flows. Elucidating the role of competition between activity and nematic elasticity is crucial to understanding this phenomenon. Here, we present our experimental results on nematic LCs composed of short actin filaments, driven by myosin motors where the elasticity is tuned by varying the filament length, l. We find that for l = 2 µm where the elasticity is high compared to an LC with l = 1 µm, elongated regions of uniform bend distortions form, which we define as elasticity bands. The bands are evocative of domain walls observed in hydrodynamic simulations of active nematics. The emergence of a shoulder in the elastic energy distribution provides an explanation – a nematic LC with high elasticity tends to minimize the total elastic deformation by localizing it to narrow regions in space. Moreover, we find that as the activity decays, the LC dissipates excess elastic energy by eliminating these bands resulting in “catapulting” of +1/2 defects at a very high speed which scales inversely with the width of the band. Our results are fully supported by hydrodynamic simulations of active nematics and advance our understanding of complex flows in active liquid crystals.

–

Presenters

  • Rui Zhang

    University of Chicago, Institute for Molecular Engineering, University of Chicago

Authors

  • Nitin Kumar

    University of Chicago, James Franck Institute, University of Chicago

  • Rui Zhang

    University of Chicago, Institute for Molecular Engineering, University of Chicago

  • Steven Redford

    University of Chicago, James Franck Institute, University of Chicago

  • Juan De Pablo

    University of Chicago, Chemical Eng., University of Chicago, The Institute for Molecular Engineering, The University of Chicago, Institute for Molecular Engineering, University of Chicago, Institute for Molecular Engineering, The University of Chicago, Institute for Molecular Engineering, Argonne National Laboratory

  • Margaret Gardel

    University of Chicago, Department of Physics, University of Chicago, Physics, The University of Chicago, James Franck Institute, University of Chicago