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SUMMARY:Towards an ideal synthetic system for active matter - Debasish Das
  (University of Cambridge)
DTSTART:20190502T154500Z
DTEND:20190502T160000Z
UID:TALK123916@talks.cam.ac.uk
CONTACT:Ferdia Sherry
DESCRIPTION:How are groups of living organisms such as flocks of birds\,\n
 sheep\, schools of fish and bacterial colonies able to self-organize\nand 
 display collective motion? This question has fascinated scientists\nfor de
 cades and has given rise to the new field of ‘active matter’.\nOne of 
 the key features of active matter is that it is composed of\nself-propelle
 d units that move by consuming energy from their\nsurrounding with a direc
 tion of self-propulsion typically set by their\nown anisotropy\, either in
  shape or functionalisation\, rather than by\nan external field. In this t
 alk\, I will use an electrohydrodynamic\ninstability called Quincke rotati
 on to develop an ideal self-propelled\nparticle. Dielectric particles susp
 ended in a weakly conducting fluid\nare known to spontaneously start rotat
 ing under the action of a\nsufficiently strong uniform DC electric field d
 ue to Quincke rotation.\nThis rotation can be converted into translation w
 hen the particles are\nplaced near a surface providing useful model system
 s for active\nmatter. Using a combination of numerical simulations and the
 oretical\nmodels\, we demonstrate that it is possible to convert the spont
 aneous\nQuincke rotation into spontaneous translation even in the absence 
 of\nsurfaces by relying on geometrical asymmetry instead. The resulting\nn
 ovel type of active particle (i) is capable of autonomous self\npropulsion
 \, i.e. the direction of propulsion is not set and controlled\nby an exter
 nal field\, (ii) does not require the presence of a surface\nand (iii) is 
 amenable to theoretical analysis from first principles.\nSuspensions of ra
 ndomly-shaped particles under Quincke rotation would\nthus be expected to 
 perform collective motion by exploring the full\nthree-dimensional space w
 ith unspecified swimming direction\, opening\nthereby the door to a potent
 ially new type of active matter.
LOCATION:Centre for Mathematical Sciences\, MR2
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