  Motivated by the recent theoretical study of (bright) soliton diode effects
in systems with multiple scatterers, as well as by experimental investigations
of soliton-impurity interactions, we consider some prototypical case examples
of interactions of dark solitons with a pair of scatterers. In a way
fundamentally opposite to the case of bright solitons (but consonant to their
"anti-particle character"), we find that dark solitons accelerate as they pass
the first barrier and hence cannot be trapped by a second equal-height barrier.
A pair of unequal barriers may lead to reflection from the second one, however
trapping in the inter-barrier region cannot occur. We also give some examples
of dynamical adjusting the barriers to trap the dark soliton in the
inter-barrier region, yet we show that this can only occur over finite time
horizons, with the dark soliton always escaping eventually, contrary again to
what is potentially the case with bright solitons.
