  The breakup dynamics of a capillary bridge on a hydrophobic stripe between
two hydrophilic stripes is studied experimentally and numerically using direct
numerical simulations. The capillary bridge is formed from an evaporating water
droplet wetting three neighboring stripes of a chemically patterned surface. By
considering the breakup process in a phase space representation, the breakup
dynamics can be evaluated without the uncertainty in determining the precise
breakup time. The simulations are based on the Volume-of-Fluid (VOF) method
implemented in Free Surface 3D (FS3D). In order to construct physically
realistic initial data for the VOF simulation, Surface Evolver is employed to
calculate an initial configuration consistent with experiments. Numerical
instabilities at the contact line are reduced by a novel discretization of the
Navier-slip boundary condition on staggered grids. The breakup of the capillary
bridge cannot be characterized by a unique scaling relationship. Instead, at
different stages of the breakup process different scaling exponents apply, and
the structure of the bridge undergoes a qualitative change. In the final stage
of breakup, the capillary bridge forms a liquid thread that breaks up
consistently with the Rayleigh-Plateau instability.
