Three linked spheres micro-swimmers: a stokesian dynamics study

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

Hannover

Workshop; INTERNATIONAL WORKSHOP ON MICRO- AND NANOMACHINES; 2014

Self-propulsion of microorganisms and artificial micro and molecular swimmers is only possible through the generation of motility strategies that are able to overcome the absence of inertia. This condition enables the success of only those swimming strategies that are timeirreversible. One of the simplest swimmers fullfilling this requirement is the three-linked-spheres swimmer1, TLS, a toy-swimmer built upon three spheres linked by two arms that contracts asynchronously. This simple TLS has received significant attention because it can be studied both, analytically and numerically. Using stokesian dynamics simulations we investigate in detail the forces acting on each of the swimmer's components and the power consumption during its periodic motion. We have compared two swimming strategies within this model, corresponding to a square or circular phase-space cycle. If the efficiency is defined as the ratio between power dissipation and the work needed to produce the same motion by an external force, we show that the most effcient swimmer is the one with almost maximum (maximum) arms contraction for the square (circular) cycle. Interestingly, under these optimum conditions, the analytical predictions based on point force approximations of the hydrodynamic equations differ signi cantly from those found in our more accurate simulations. This fact highlights the importance of a more accurate treatement of hydrodynamic interactions. We believe that our results would be very useful when designing real artificial swimmers of this kind. Figure 1. (a) Three linked spheres swimmer parameters. (b) Square and circle cycle sketch. Acknowledgement. Funding from CONICET and Secyt -UNC, Argentina and FNRS(Belgium)- CONICET(Argentina) bilateral project. References. [1] A. Najafi and R. Golestanian, Phys. Rev. E 69, 062901