  The physics of diffusion phenomena in nano and micro channels has attracted a
lot of attention in recent years, due to its close connection with many
technological, medical and industrial applications. In the present paper we
employ a kinetic approach to investigate how the confinement in nanostructured
geometries affects the diffusive properties of fluid mixtures and leads to the
appearance of properties different from those of bulk systems. In particular,
we derive an expression for the friction tensor in the case of a bulk fluid
mixture confined to a narrow slit having undulated walls. The boundary
roughness leads to a new mechanism for transverse diffusion, and can even lead
to an effective diffusion along the channel larger than the one corresponding
to a planar channel of equivalent section. Finally we discuss a reduction of
the previous equation to a one dimensional effective diffusion equation in
which an entropic term encapsulates the geometrical information on the channel
shape.
