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SUMMARY:Droplet formation and control in microfluidics - Francois Gallaire
  (EPFL\, Lausanne)
DTSTART:20110218T160000Z
DTEND:20110218T170000Z
UID:TALK28853@talks.cam.ac.uk
CONTACT:Doris Allen
DESCRIPTION:In this talk\, I will highlight two aspects of droplet-based m
 icrofluidics. First\, I will discuss if droplet formation in co-axial inje
 ctors can be understood in terms of the spatio-temporal propagation of ins
 tabilities\, concepts rarely used in the context of creeping flows. I will
  present our recent experimental analysis of the dripping and jetting regi
 mes and compare them to the theoretical predictions issuing from the insta
 bility theory in terms of frequency and wavenumber selection. We also expl
 ore the behavior of the jetting regime as a noise amplifier by means of a 
 pulsating laser beam to locally force the flow. While no reaction is obser
 ved in the dripping regime\, a strong synchronization occurs in the jettin
 g regime.\n\nSecond\, I will discuss how droplets flowing in microchannels
  can be guided and trapped by creating external surface energy gradients\,
  either by using a focussed laser beam or by introducing depth variations.
  I will present counterintuitive experiments\, conducted in presence of su
 rfactants\, where thermocapillary and solutocapillary effects enter in com
 petition.\n\nThis work is done in collaboration with M.-L. Cordero\, R. Da
 ngla and C. Baroud.
LOCATION:MR2\, Centre for Mathematical Sciences\, Wilberforce Road\, Cambr
 idge
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