Colloids in cholesteric
- Event time: 1:00pm
- Event date: 6th December 2010
- Speaker: Juho Lintuvuori (Formerly School of Physics & Astronomy, University of Edinburgh)
- Location: Room 2511, James Clerk Maxwell Building (JCMB) James Clerk Maxwell Building Peter Guthrie Tait Road Edinburgh EH9 3FD GB
I'll present a serie of Lattice Boltzmann simulations studies of colloidal particles immersed into cholesteric liquid crystal. I show that the defect structure around the particle depends crucially on the ratio between particle size and cholesteric pitch i.e. the diameter to pitch ratio D/P . Both, tangential and homeotropic, surface anchoring conditions will be discussed. I then model an ideal active microrheology experiment, in which the colloid is pulled through the liquid crystal medium and its force-velocity relation is analyzed. This is done both perpendicular and along the helical axis. The main result is that, surprisingly, the effective viscosity along the helical axis, in the small (but not inﬁnitesimal) Ericksen number regime, depends on the size of the probe. This is tantamount to an effective drag which, along the cholesteric helix, is approximately proportional to the square of the particle size, thereby providing a striking example of giant violation of the Stokes formula.
This is a weekly series of informal talks given primarily by members of the soft condensed matter and statistical mechanics groups, but is also open to members of other groups and external visitors. The aim of the series is to promote discussion and learning of various topics at a level suitable to the broad background of the group. Everyone is welcome to attend..