  Advancements in the fabrication of superconducting 3D nanostructures, along
with the creation of artificial pinning sites, pave the way to novel
applications and enhancement of nanosensors, bolometers, and quantum
interferometers. The dynamics of magnetic flux quanta (Abrikosov vortices) in
3D nanoarchitectures reveal a rich palette of phenomena unseen in planar
counterparts. Here, we consider two types of superconductor 3D nanostructures
-- open nanotubes and nanopetals -- carrying an azimuthal transport current in
a homogeneous external magnetic field. The complex 3D geometry of the
structures induces an inhomogeneity of the magnetic field and makes the
vortices to move along preferred paths. By introducing a lattice of asymmetric
pinning sites along these paths, we realize a non-reciprocal flux transport and
study a vortex ratchet effect, which is revealed to be stronger than in the
respective planar (unrolled) membranes. The enhancement of the vortex ratchet
effect becomes apparent via a factor-of-two difference in the depinning current
under the current reversal, and it is attributed to the
inhomogeneous-field-induced vortex channeling through the areas containing the
asymmetric pinning sites. Our results demonstrate that the ratchet efficiency
can be enhanced via extending a superconducting film into the third dimension,
without increase in the number of asymmetric pinning sites.
