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SUMMARY:Freezing of drops - Detlef Lohse\, University of Twente
DTSTART:20240301T160000Z
DTEND:20240301T170000Z
UID:TALK210424@talks.cam.ac.uk
CONTACT:Professor Grae Worster
DESCRIPTION:An immersed soft particle or oil droplet is severely deformed 
 when engulfed into an advancing ice front. This deformation strongly depen
 ds on the engulfment velocity\, even forming pointy-tip shapes for low vel
 ocities. We found that such singular deformations are mediated by interfac
 ial flows in nanometric thin liquid films separating the nonsolidifying di
 spersed soft particles or droplets and the solidifying bulk. The competing
  forces in the thin film originate from the disjoining pressure and the su
 rface tension gradient (Marangoni forces). We analytically modelled the fl
 uid flow in these intervening thin films\, using a lubrication approximati
 on in the boundary layers. In an exact analytical calculation and with a f
 ormal analogy to a nonlinear pendulum\, we then related the fluid flow to 
 the deformation sustained by the dispersed droplet. We find it astounding 
 that the nanoscopic interaction (van der Waals forces\, disjoining pressur
 e) determines the shape of the macroscopic immersed soft particle or dropl
 et. \n\nWe then extended this line of research to the interaction of sever
 al immersed soft particles or droplets over which a solidification front i
 s passing. This time it is the relative thermal conductivity of the soft p
 articles and the liquid which determines whether the two soft particles re
 pel or attract. We call the effect the frozen Cheerios effect. \n\nFinally
 \, we identified a freezing-induced topological transition of a double-emu
 lsion\, i.e.\, an oil droplet with an immersed water droplet inside\, and 
 as a whole immersed in water\, passing through a freezing front. Whether t
 he water droplet inside the oil droplet survives or whether it literally b
 ursts due to pressure forces emerging at solidification depends on the con
 trol parameters\, in particular the freezing front velocity. \n
LOCATION:MR2
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