An elastic two-sphere swimmer in Stokes flow
  Swimming at low Reynolds number in Newtonian fluids is only possible through non-reciprocal body deformations due to the kinematic reversibility of the Stokes equations. We consider here a model swimmer consisting of two linked spheres, wherein one sphere is rigid and the other an incompressible neo-Hookean solid. The two spheres are connected by a rod which changes its length periodically. We show that the deformations of the body are non-reciprocal despite the reversible actuation and hence, the elastic two-sphere swimmer propels forward. Our results indicate that even weak elastic deformations of a body can affect locomotion and may be exploited in designing artificial microswimmers. 
Babak Nasouri, Aditi Khot, Gwynn J. Elfring
physics.flu-dyn