Controlling Flow Patterns and Topology in Active Emulsions

Active emulsions and liquid crystalline shells are intriguing andexperimentally realisable types of topological matter. Here we numericallystudy the morphology and spatiotemporal dynamics of a double emulsion, whereone or two passive small droplets are embedded in a larger active droplet. Wefind activity introduces a variety of rich and nontrivial nonequilibrium statesin the system. First, a double emulsion with a single active droplet becomesself-motile, and there is a transition between translational and rotationalmotion: both of these regimes remain defect-free, hence topologically trivial.Second, a pair of particles nucleate one or more disclination loops, withconformational dynamics resembling a rotor or chaotic oscillator, accessed bytuning activity. In the first state a single, topologically charged,disclination loop powers the rotation. In the latter state, this disclinationstretches and writhes in 3D, continuously undergoing recombination to yield anexample of an active living polymer. These emulsions can be self-assembled inthe lab, and provide a pathway to form flow and topology patterns in activematter in a controllable way, as opposed to bulk systems that typically yieldactive turbulence.