A mechanism for generating an orbital motion for mixing a fluidic sample. The mechanism may comprise a first and second cogwheel each having a through hole and a plurality of cogs. A drive shaft having a concentric first section and an eccentric second section is guided through a respective through hole of the first and second cogwheel. A coupling body engages part of the cogs to thereby generate the orbital motion of the second cogwheel and a sample holder to be mounted so as to follow a motion of the second cogwheel upon rotating the first section of the drive shaft.