  The leaves of many plants are superhydrophobic, a property that may have
evolved to clean the leaves by encouraging water droplets to bead up and roll
off. Superhydrophobic surfaces can also exhibit reduced friction and liquids
flowing over such surfaces have been found to slip in apparent violations of
the classical no-slip boundary condition. Here we introduce slip into a model
for rolling droplets on superhydrophobic surfaces and investigate under what
conditions slip might be important for the steady state motion. In particular,
we examine three limiting cases where dissipation in the rolling droplet is
dominated by viscous dissipation, surface friction, or contact line friction.
We find that in molecular dynamics simulations of droplets on ideal
superhydrophobic surfaces with large effective slip lengths, contact line
dissipation dominates droplet motion. However, on real leaves, droplet motion
is likely to be dominated by viscous shear, and slip, for the most part, can be
neglected.
