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CATEGORIES:DAMTP BioLunch
SUMMARY:Collective Microswimmer Motility in Complex Enviro
 nments - Fabian Schwarzendahl (Max-Planck-Institut
 e for Dynamics and Self-Organization)
DTSTART;TZID=Europe/London:20190528T140000
DTEND;TZID=Europe/London:20190528T150000
UID:TALK125398AThttp://talks.cam.ac.uk
URL:http://talks.cam.ac.uk/talk/index/125398
DESCRIPTION:The behavior of microswimmers is strongly influenc
 ed by the interaction with their environments whic
 h can be other microorganisms or confining walls.\
 nI will first report on the swimming behavior of t
 he green alga Chlamydomonas reinhardtii in confine
 ment where we find an increased probability of the
  cell swimming close to the confining wall. We dis
 covered that the near-wall swimming probability sc
 ales with the local wall curvature. The model that
  we propose\, consisting of an asymmetric dumbbell
 \, describes the near-wall swimming accurately and
  does not require any fitting parameter. In fact\,
  we found that the important ingredient to the cur
 vature guided navigation is the torque stemming fr
 om the asymmetry of the organism.\n\nSecondly\, I 
 will report on the influence of hydrodynamic inter
 actions between microswimmers. We introduce a nove
 l model for biological microswimmers that creates 
 the flow field of the corresponding microswimmers\
 , and takes into account the shape anisotropy of t
 he swimmer's body and stroke-averaged flagella. By
  employing multiparticle collision dynamics\, we d
 irectly couple the swimmer's dynamics to the fluid
 's. We characterize the nonequilibrium phase dia- 
 gram\, as the filling fraction and Péclet number 
 are varied\, and find density heterogeneities in t
 he distribution of both pullers and pushers\, due 
 to hydrodynamic instabilities. We find a maximum d
 egree of clustering at intermediate filling fracti
 ons and at large Péclet numbers resulting from a 
 competition of hydrodynamic and steric interaction
 s between the swimmers. We develop an analytical t
 heory that supports these results. This maximum mi
 ght represent an optimum for the microorganisms' c
 olonization of their environment.\n\n
LOCATION:MR11\, Centre for Mathematical Sciences\, Wilberfo
 rce Road\, Cambridge
CONTACT:Anne Herrmann
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