  A fiber withdrawn from a bath of a dilute particulate suspension exhibits
different coating regimes depending on the physical properties of the fluid,
the withdrawal speed, the particle sizes, and the radius of the fiber. Our
experiments indicate that only the liquid without particles is entrained for
thin coating films. Beyond a threshold capillary number, the fiber is coated by
a liquid film with entrained particles. We systematically characterize the role
of the capillary number, the particle size, and the fiber radius on the
threshold speed for particle entrainment. We discuss the boundary between these
two regimes and show that the thickness of the liquid film at the stagnation
point controls the entrainment process. The radius of the fiber provides a new
degree of control in capillary filtering, allowing greater control over the
size of the particles entrained in the film.

Fluid Dynamics