  We consider the translocation of a neutral (uncharged) nanoparticle through a
pore in a thin membrane with constant surface charge density. If the
concomitant Debye screening layer is sufficiently thin, the resulting forces
experienced by the particle on its way through the pore are negligible. But
when the Debye length becomes comparable to the pore diameter, the particle
encounters a quite significant potential barrier while approaching and entering
the pore, and symmetrically upon exiting the pore. The main reason is an
increasing pressure which acts on the particle when it intrudes into the
counter ion cloud of the Debye screening layer. In case the polarizability of
the particle is different (usually smaller) than that of the ambient fluid, a
second, much smaller contribution to the potential barrier is due to
self-energy effects. Our numerical treatment of the problem is complemented by
analytical approximations for sufficiently long cylindrical particles and
pores, which agree very well with the numerics.
