Stokesian dynamics optimization of a three linked spheres micro-swimmer

I. BERDAKIN; V. I. MARCONI; A. J. BANCHIO

Córdoba

Workshop; Latin American Workshop on Nonlinear Phenomena; 2013

FaMAf, UNC.

Self-propulsion of microorganisms and artificial swimmers is only possible through the generation of motility strategies that are able to overcome the absence of inertia. This condition, implied in every low Reynolds number regime, enables the success of only those strategies that are irreversible in phase space. One of the simplest swimmers meeting this requirement is the three-linked-spheres, a swimmer built upon three spheres linked by two arms that contracts asynchronously. This simple swimmer has received a lot of attention because it can be studied both, analytically and numerically. In this work we use stokesian dynamics simulations to study in detail the forces acting on each of the swimmer´s components and the power consumption during its motion. We define efficiency as the ratio between power dissipation and the work needed to produce the same motion by an external force. We find that the most efficient swimmer is that in which its arms contracts almost absolutely. Interestingly, under these optimum conditions, the analytical predictions based on first order approximations of the hydrodynamic equations divert significantly from those found in our simulations, in which near field interactions are taken into account. This highlights the importance of considering the finite size of the spheres, as it is done by the method implemented here. We believe that the results shown in this work would be very useful when designing an artificial swimmer of this kind with the intention to test it experimentally.