  We explore numerically the feasibility of using chemical patterning to
control the size and polydispersity of micron-scale drops. The simulations
suggest that it is possible to sort drops by size or wetting properties by
using an array of hydrophilic stripes of different widths. We also demonstrate
that monodisperse drops can be generated by exploiting the pinning of a drop on
a hydrophilic stripe. Our results follow from using a lattice Boltzmann
algorithm to solve the hydrodynamic equations of motion of the drops and
demonstrate the applicability of this approach as a design tool for micofluidic
devices with chemically patterned surfaces.
