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Séminaire de Stephan Herminghaus

Active emulsions : non-equilibrium dynamics and multi-scale self-assembly


Stephan Herminghaus

MPI Göttingen, Germany

We call an emulsions ’active’ if its droplets are prepared in a state sufficiently far from thermal equilibrium to exhibit autonomous dynamic behaviour. For droplets containing a chemical oscillator, it is shown that bilayer membranes can serve for subtle coupling of neighboring oscillators in self-assembled droplet arrangements. This leads to a plethora of collective behaviour, such as target and spiral waves, as well as quorum sensing. When the volume fraction of the emulsion is reduced, the droplets are free to move and exhibit self-sustained locomotion. Collective behaviour is now apparent as swarming, and we can try to apply concepts of phase transitions and critical phenomena to understand swarming morphologies on the basis of fundamental concepts. Liquid crystal droplets in aqueous solution, which exhibit particularly long durations of locomotion, recommend themselves as model systems to test such concepts. Finally, geometries beyond the simple droplet shape, like micron-scale ropes, pearl bracelets, and coils, can be shown to form spontaneously if the system is suitably prepared.