Speaker
Description
Topological active soft matter includes fluids characterized by orientational ordering of constituting entities, ranging from anisotropic particles that extract energy from their surroundings to biological and living systems that convert chemical energy. Due to its softness, topological soft matter rarely exhibits homogeneous orientational order. Most of the frustration arising from the competing effects of chirality, anisotropic elasticity, confining geometries, surface anchoring, and external fields leads to stable and metastable point defects, disclination lines, and solitons in the orientational order-parameter field. The dynamics of ordering and defects are accompanied by flows that strongly depend on activity. The low-activity dynamics of defect structures, with increasing activity, evolve from stationary to chaotic 3D motion — active nematic turbulence [1-4]. Here we focus on thin active nematic shells in a passive nematic with free boundaries that exhibit spontaneous activity-driven swimming. The synchronization of the dynamics of two such active nematic shells entangled by a disclination in a surrounding unconfined passive nematic is demonstrated [5].
Studies were done in collaboration with groups from Ljubljana (Miha Ravnik, Simon Čopar, Žiga Kos, Nika Kralj, and Andraž Gnidovec) and ESPCI Paris (Teresa Lopez Leon with students).
[1] A. Doostmohammadi, J. Ignés-Mullol, J. M. Yeomans & F. Sagués, Active nematics, Nature Comm. 9, 3246 (2018)
[2] S. Čopar, J. Aplinc, Ž. Kos, S. Žumer, and M. Ravnik, Topology of three-dimensional active nematic turbulence confined to droplets, Physical Review X 9, 031051 (2019).
[3] N. Kralj, M. Ravnik, and Ž. Kos, Defect Line Coarsening and Refinement in Active Nematics, Phys. Rev. Lett. 130, 128101 (2023).
[4] N. Kralj, M. Ravnik, and Ž. Kos, Chirality, anisotropic viscosity and elastic anisotropy in three-dimensional active nematic turbulence, Comm. Phys. 7, 222 (2024).
[5] N. Kralj, et al., in preparation.