Nowadays, technologies such as 3D bioprinting boost the fabrication of various tissue and organ models. One of the challenging models is tubular structures preset in various body parts. Although there are different methods for fabrication of these hollow structures, lack of control on geometries of complex models is a drawback.

۳D bioprinting technology integrated with coaxial nozzles has recently shown great interest in the fabrication of core/shell or hollow structures. OmidAfarinan company now provides different coaxial nozzles compatible with its bioprinters. One of the advantages of this method is the manufacture of core/shell structures with different bio-inks impregnating different cell types.