  We study the dynamics of neutral and charged rods embedded in varying-section
channels. By means of systematic approximations, we derive the dependence of
the local diffusion coefficient on both the geometry and charge of the rods.
This microscopic insight allows us to provide predictions for the permeability
of varying-section channels to rods with diverse lengths, aspect ratios and
charge. Our analysis shows that the dynamics of charged rods is sensitive to
the geometry of the channel and that their transport can be controlled by
tuning both the shape of the confining walls and the charge of the rod.
Interestingly, we find that the channel permeability does not depend
monotonically on the charge of the rod. This opens the possibility of a novel
mechanism to separate charged rods.
