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SUMMARY:Flow-induced phase separation of active colloids is controlled by 
 boundary conditions - Rajesh Singh (University of Cambridge)
DTSTART:20180607T120000Z
DTEND:20180607T130000Z
UID:TALK105313@talks.cam.ac.uk
CONTACT:Anne Herrmann
DESCRIPTION:Active colloids - autophoretic particles\, microorganisms\, an
 d self-propelling droplets - are known to self-organize into ordered struc
 tures at fluid-solid boundaries. Their mutual entrainment in the attractiv
 e component of the flow has been postulated as a possible mechanism underl
 ying this phenomenon. In this talk\, we describe this fluid-induced phase 
 separation by combining experiments\, theory\, and numerical simulations\,
  and demonstrate its control by changing the hydrodynamic boundary conditi
 ons. We show that\, for flow in Hele-Shaw cells\, metastable lines or stab
 le traveling bands of colloids can be obtained by varying the cell height\
 , while for flow bounded by a plane\, dynamic crystallites are formed. At 
 a plane no-slip wall\, these crystallites are characterized by a continuou
 s out-of-plane flux of particles that circulate and re-enter at the crysta
 llite edges\, thereby stabilizing them\, while the crystallites are strict
 ly two-dimensional at a plane where the tangential stress vanishes. These 
 results are elucidated by deriving\, using the boundary-domain integral fo
 rmulation of Stokes flow\, exact expressions for dissipative\, long-ranged
 \, many-body active forces and torques between them in respective boundary
  conditions.
LOCATION:MR11\, Centre for Mathematical Sciences\, Wilberforce Road\, Camb
 ridge
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