Speaker
Description
Active emulsions, droplets of liquid crystalline active matter encapsulating passive isotropic cores, represent a versatile and experimentally realisable class of topological active matter. Here, we present results from three-dimensional Lattice Boltzmann (LB) simulations of multiphase active nematic emulsions, developed and validated as part of the use case "Large Scale Simulations of Complex Systems". We developed an optimised MPI-parallelised LB solver enabling us to resolve the rich spatiotemporal dynamics of these confined active systems in 3D.
We demonstrate that the number of passive cores embedded in the outer active droplet controls the global topology of the director field, with profound consequences for the emergent dynamics. A topologically trivial single-core emulsion undergoes a sequence of activity-driven motility transitions — from quiescence to directed translation, periodic rotation, meandering, and finally chaotic motion — all while remaining defect-free. In contrast, a two-core emulsion is topologically non-trivial: the homeotropic anchoring at all interfaces forces the bulk liquid crystal to carry an odd hedgehog charge, nucleating a charged disclination loop. At low activity this loop acts as a self-assembled rotor, while at high activity, the loop stretches, writhes, and undergoes topological recombination, providing an example of an active living polymer. These results[1] establish active double emulsions as a platform for designing and selecting flow and topological patterns in active matter in a controlled way, with potential applications in drug delivery and self-propelled functional materials.
[1]Negro, G., Head, L.C., Carenza, L.N. et al. Topology controls flow patterns in active double emulsions. Nat Commun 16, 1412 (2025). https://doi.org/10.1038/s41467-025-56236-8