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Optimum inertial self-propulsion design for snowman-like nanorobot (Vol. 45 No.5-6)

A new study investigates the effects of small but finite inertia on the propulsion of micro and nano-scale swimming machines that could have implications for biomedical applications.

Scale plays a major role in locomotion. Swimming microorganisms, such as bacteria and spermatozoa, are subjected to relatively small inertial forces compared to the viscous forces exerted by the surrounding fluid. Such low-level inertia makes self-propulsion a major challenge. Now, the authors have found that the direction of propulsion made possible by such inertia is opposite to that induced by a viscoelastic fluid. This study could help optimise the design of self-propelled micro- and nanoscale artificial swimming machines to improve their mobility in medical applications. The study shows that a rotating dumbbell propels with the large sphere due to intertial forces in the fluid and the small sphere ahead in a pure viscoelastic fluid. The authors then derive the optimal dumbbell geometry for a self-propelling small-scale swimmer.

F. Nadal, O. S. Pak, L. Zhu, L. Brandt and E. Lauga, “Rotational propulsion enabled by inertia”, Eur. Phys. J. E 37, 60 (2014)
[Abstract]