Two-sphere swimmers in viscoelastic fluids

We examine swimmers comprising of two rigid spheres which oscillate periodically along their axis of symmetry, considering when the spheres oscillate both in phase and in antiphase, and study the effects of fluid viscoelasticity on the swimmers' motion. These swimmers display reciprocal motion in Newtonian fluids and consequently, no net swimming is achieved over one cycle in such fluids. Conversely, in viscoelastic fluids, we find that the effect of viscoelasticity acts to propel the swimmers forward in the direction of the smaller sphere when the two spheres are of different sizes. Finally, we compare the motion of rigid spheres oscillating in viscoelastic fluids with elastic spheres in Newtonian fluids where we find similar results.