Control of Microparticles Through Hydrodynamic Interactions

Henry Shum, Marta Zoppello, Michael Astwood, Marco Morandotti

Published 2024-06-07Version 1

The controllability of passive microparticles that are advected with the fluid flow generated by an actively controlled one is studied. The particles are assumed to be suspended in a viscous fluid and well separated so that the far-field Stokes flow solutions may be used to describe their interactions. Applying concepts from geometric control theory, explicit moves characterized by a small amplitude parameter $\varepsilon$ are devised to prove that the active particle can control one or two passive particles. The leading-order (in $\varepsilon$) theoretical predictions of the particle displacements are compared with those obtained numerically and it is found that the discrepancy is small even when $\varepsilon\approx 1$. These results demonstrate the potential for a single actuated particle to perform complex micromanipulations of passive particles in a suspension.