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DTSTART;TZID=America/New_York:20251215T163000
DTEND;TZID=America/New_York:20251215T173000
DTSTAMP:20260410T174053
CREATED:20251124T150428Z
LAST-MODIFIED:20251211T145044Z
UID:10003836-1765816200-1765819800@cmsa.fas.harvard.edu
SUMMARY:The active Young-Dupré equation
DESCRIPTION:Colloquium \nSpeaker: Julien Tailleur\, MIT \nTitle: The active Young-Dupré equation \nAbstract: The Young-Dupré equation is a cornerstone of the equilibrium theory of capillary and wetting phenomena. In the biological world\, interfacial phenomena are ubiquitous\, from the spreading of bacterial colonies to tissue growth and flocking of birds\, but the description of such active systems escapes the realm of equilibrium physics. I will show how a microscopic\, mechanical definition of surface tension allows building an Active Young-Dupré equation able to account for the partial wetting observed in simulations of active particles interacting via pairwise forces. Remarkably\, the equation shows that the corresponding steady interfaces do not result from a simple balance between the surface tensions at play but instead emerge from a complex feedback mechanism. The interfaces are indeed stabilized by a drag force due to the emergence of steady currents\, which are themselves a by-product of the symmetry breaking induced by the interfaces. These currents also lead to new physics by selecting the sizes and shapes of adsorbed droplets\, breaking the equilibrium scale-free nature of the problem. Finally\, I will demonstrate a spectacular consequence of the negative value of the liquid-gas surface tensions in systems undergoing motility-induced phase separation: partially-immersed objects are expelled from the liquid phase\, in stark contrast with what is observed in passive systems. These results lay the foundations for a theory of wetting in active systems.
URL:https://cmsa.fas.harvard.edu/event/colloquium-121525/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Colloquium
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