The invention provides exemplary devices, systems and methods for mixing of fluids, such as biological fluids. One exemplary device comprises is particularly adapted for holding at least one cartridge having a chamber containing a biological fluid, with the chamber having a generally planar face. The device comprises a rotatable body having a rotational axis. The rotatable body includes at least one mounting element which is adapted to mount the rotatable body such that the face of the chamber is generally perpendicular to the rotational axis.