The acoustofluidic method holds great promise for manipulating
microorganisms. When exposed to the steady vortex structures of acoustic
streaming flow, these microorganisms exhibit intriguing dynamic behaviors, such
as hydrodynamic trapping and aggregation. To uncover the mechanisms behind
these behaviors, we investigate the swimming dynamics of both passive and
active particles within a two-dimensional acoustic streaming flow. By employing
a theoretically calculated streaming flow field, we demonstrate the existence
of stable bounded orbits for particles. Additionally, we introduce rotational
diffusion and examine the distribution of particles under varying flow
strengths. Our findings reveal that active particles can laterally migrate
across streamlines and become trapped in stable bounded orbits closer to the
vortex center, whereas passive particles are confined to movement along the
streamlines. We emphasize the influence of the flow field on the distribution
and trapping of active particles, identifying a flow configuration that
maximizes their aggregation. These insights contribute to the manipulation of
microswimmers and the development of innovative biological microfluidic chips.

Cet article explore les excursions dans le temps et leurs implications.

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