Abstract
Microswimmers, and among them aspirant microrobots, generally have to cope with flows where viscous forces are dominant, characterized by a low Reynolds number (Re). 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 Re regimes. An optimal displacement caused by nontrivial history effects is reached at intermediate Re. 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 for a remote-controlled microrobot, a suitable value for biological applications such as drug delivery.
- Received 19 June 2017
DOI:https://doi.org/10.1103/PhysRevLett.119.224501
© 2017 American Physical Society
Physics Subject Headings (PhySH)
Focus
Elastic Spherical Shell Can Swim
Published 27 November 2017
A sphere that alternately collapses and re-inflates makes a simple device that can propel itself and could work on the microscale for medical purposes.
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