Wed February 22nd 2017
16:30 – 17:00
ZH286
Seminar Universal Nanodroplet Branches from Confining the Ouzo Effect
Martin Klein Schaarsberg

Details:

When water is added to the ancient Greek alcoholic drink ouzo, anise oils dissolved in the drink spontaneously form many stable fine droplets. The droplet formation depends on the types of solvents and the dynamics of mixing them. However, it remains challenging to disentangle the effects from concentration gradients, turbulent advection, diffusion, and collective interactions with the mixing dynamics. In this work, we confine the ouzo effect to a quasi-2D geometry where the mixing of the two solutions is dominated by diffusion. We find that in this geometry, the nucleating oil nanodroplets spontaneously form branches. The angles between these branches exhibit remarkable universality with a value around 74° ± 2°, independent of the various control parameters of the process. We show that the process is analogous to the ramification of stream networks happening on a scale more than 10 orders of magnitude larger, concluding that the geometry of the droplet nucleation is governed by the external diffusive field. We also demonstrate that the formation of droplet branches from the confined ouzo effect drives rapid autonomous motion of colloidal particles by a local oil concentration gradient, providing new opportunities to dramatically enhance the local transport of colloids in highly confined 2D space. Finally, we employ the nucleated nanodroplets branches for nanoextraction of an hydrophobic solute in confined space.
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