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Capillary Interfacial Tension in Active Phase Separation

Fausti, G. and Tjhung, E. and Cates, M. E. and Nardini, C. (2021) 'Capillary Interfacial Tension in Active Phase Separation.', Physical review letters., 127 (6). 068001.


In passive fluid-fluid phase separation, a single interfacial tension sets both the capillary fluctuations of the interface and the rate of Ostwald ripening. We show that these phenomena are governed by two different tensions in active systems, and compute the capillary tension σ cw which sets the relaxation rate of interfacial fluctuations in accordance with capillary wave theory. We discover that strong enough activity can cause negative σ cw . In this regime, depending on the global composition, the system self-organizes, either into a microphase-separated state in which coalescence is highly inhibited, or into an “active foam” state. Our results are obtained for Active Model B + , a minimal continuum model which, although generic, admits significant analytical progress.

Item Type:Article
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Publisher statement:Reprinted with permission from the American Physical Society: Fausti, G., Tjhung, E., Cates, M. E. & Nardini, C. (2021). Capillary Interfacial Tension in Active Phase Separation. Physical Review Letters 127(6): 068001. © (2021) by the American Physical Society. Readers may view, browse, and/or download material for temporary copying purposes only, provided these uses are for noncommercial personal purposes. Except as provided by law, this material may not be further reproduced, distributed, transmitted, modified, adapted, performed, displayed, published, or sold in whole or part, without prior written permission from the American Physical Society.
Date accepted:02 July 2021
Date deposited:08 November 2021
Date of first online publication:03 August 2021
Date first made open access:08 November 2021

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