Emulsion patterns in the wake of a liquid–liquid phase separation front

Miscible liquids can phase separate in response to a composition change. In bulk fluids, the demixing begins on molecular-length scales, which coarsen into macroscopic phases. By contrast, confining a mixture in microfluidic droplets causes sequential phase separation bursts, which self-organize int...

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Bibliographic Details
Published in:Proceedings of the National Academy of Sciences - PNAS 2018-04, Vol.115 (14), p.3599-3604
Main Authors: Moerman, Pepijn G., Hohenberg, Pierre C., Vanden-Eijnden, Eric, Brujic, Jasna
Format: Article
Language:English
Subjects:
Capillaries
Computational fluid dynamics
Condensation
Confining
Decomposition
Demixing
Droplets
Emulsions
Immiscibility
Liquid phases
Liquids
Mass transport
Metabolism
Microfluidics
Miscibility
Numerical analysis
Phase separation
Physical Sciences
Scaling
Scaling laws
Self-similarity
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Summary:Miscible liquids can phase separate in response to a composition change. In bulk fluids, the demixing begins on molecular-length scales, which coarsen into macroscopic phases. By contrast, confining a mixture in microfluidic droplets causes sequential phase separation bursts, which self-organize into rings of oil and water to make multilayered emulsions. The spacing in these nonequilibrium patterns is self-similar and scale-free over a range of droplet sizes. We develop a modified Cahn–Hilliard model, in which an immiscibility front with stretched exponential dynamics quantitatively predicts the spacing of the layers. In addition, a scaling law predicts the lifetime of each layer, giving rise to a stepwise release of inner droplets. Analogously, in long rectangular capillaries, a diffusive front yields large-scale oil and water stripes on the time scale of hours. The same theory relates their characteristic length scale to the speed of the front and the rate of mass transport. Control over liquid–liquid phase separation into large-scale patterns finds potential material applications in living cells, encapsulation, particulate design, and surface patterning.
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.1716330115