  Viscoelastic fluids impact the locomotion of swimming microorganisms and can
be harnessed to devise new types of self-propelling devices. Here we report on
experiments demonstrating the use of normal stress differences for propulsion.
Rigid dumbbells are rotated by an external magnetic field along their axis of
symmetry in a Boger fluid. When the dumbbell is asymmetric (snowman geometry),
non-Newtonian normal stress differences lead to net propulsion in the direction
of the smaller sphere. The use of a simple model allows to rationalise the
experimental results and to predict the dependence of the snowman swimming
speed on the size ratio between the two spheres.

Fluid Dynamics;Soft Condensed Matter