20 June: Giuseppe Gonnella for the IAComplexFluids seminar series


Speaker: Giuseppe Gonnella

Controlling flow patterns and topology in active emulsions

We first review the  general description of fluid mixtures dynamics also considering  the presence of active liquid crystals. We then apply a Lattice Boltzmann approach to study active emulsions, where one or two passive small droplets are embedded in a larger active droplet. We find that activity introduces a variety of rich and nontrivial nonequilibrium states in the system. First, a double emulsion with a single active droplet becomes self-motile, and there is a transition between translational and rotational motion: both of these regimes remain defect-free, hence topologically trivial. Second, a pair of particles nucleate one or more disclination loops, with conformational dynamics resembling a rotor or chaotic oscillator, accessed by tuning activity. In the first state, a single, topologically charged disclination loop powers the rotation. In the latter state, this disclination stretches and writhes in 3D, continuously undergoing recombination to yield an example of an active living polymer. These emulsions can be self-assembled in the lab and provide a pathway to form flow and topology patterns in active matter in a controllable way, as opposed to bulk systems that typically yield active turbulence.

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