  We show that molecular dynamics simulations can furnish useful boundary
conditions at a solid surface bounding a two-component fluid. In contrast to
some previous reports, convective-diffusive flow is consistent with continuum
equations down to atomic scales. However, concentration gradients can produce
flow without viscous dissipation that is inconsistent with the commonly used
Navier slip condition. Also, differential wetting of the two components coupled
to a concentration gradient can drive convective flows that could be used to
make nano-pumps or motors.
