paper

Buckling instability causes inertial thrust for spherical swimmers at all scales

arXiv:1710.07033 · doi:10.1103/PhysRevLett.119.224501

Abstract

Microswimmers, and among them aspirant microrobots, generally have to cope with flows where viscous forces are dominant, characterized by a low Reynolds number (). This implies constraints on the possible sequences of body motion, which have to be nonreciprocal. Furthermore, the presence of a strong drag limits the range of resulting velocities. Here, we propose a swimming mechanism, which uses the buckling instability triggered by pressure waves to propel a spherical, hollow shell. With a macroscopic experimental model, we show that a net displacement is produced at all regimes. An optimal displacement caused by non-trivial history effects is reached at intermediate . We show that, due to the fast activation induced by the instability, this regime is reachable by microscopic shells. The rapid dynamics would also allow high frequency excitation with standard traveling ultrasonic waves. Scale considerations predict a swimming velocity of order 1 cm/s for a remote-controlled microrobot, a suitable value for biological applications such as drug delivery.

arXiv commentTo appear in Phys. Rev. Lett See demonstration movie on https://www.youtube.com/watch?v=cEXMsFwEqsQ

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