Anisotropic Stokes drag and dynamic lift on spheres sedimenting in a nematic liquid crystal

Langmuir. 2013 Feb 19;29(7):2104-7. doi: 10.1021/la3050412. Epub 2013 Feb 7.

Abstract

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 θ 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 θ quantitatively obey theoretically predicted forms.