Colloids in Cholesterics: Size-Dependent Defects and Non-Stokesian   Microrheology
  We simulate a colloidal particle (radius R) in a cholesteric liquid crystal (pitch p) with tangential order parameter alignment at the particle surface. The local defect structure evolves from a dipolar pair of surface defects (boojums) at small R/p to a pair of twisted disclination lines wrapping around the particle at larger values. On dragging the colloid with small velocity v through the medium along the cholesteric helix axis (an active microrheology measurement), we find a hydrodynamic drag force that scales linearly with v but superlinearly with R-in striking violation of Stokes' law, as generally used to interpret such measurements. 
J. S. Lintuvuori, K. Stratford, M. E. Cates, D. Marenduzzo
cond-mat.soft cond-mat.mtrl-sci physics.flu-dyn