Langmuir, Vol.29, No.7, 2104-2107, 2013
Anisotropic Stokes Drag and Dynamic Lift on Spheres Sedimenting in a Nematic Liquid Crystal
The motion of silica spheres with homeotropic anchoring sedimenting within nematic liquid crystal 4-cyano-4'-pentylbiphenyl (5CB) has been studied at low Ericksen number. The magnitude of the spheres' velocity depends on the angle theta between the far-field nematic director and the gravitational force, indicating an anisotropic Stokes drag. When the director is oriented at an oblique angle to the gravitational force, the velocity also acquires a component normal to the force, demonstrating the existence of a lift force generated by the fluid. The magnitude and direction of the velocity as functions of theta quantitatively obey theoretically predicted forms.