Passive particles driven by self-propelled particle: The wake effect

This work focuses on numerically studying hydrodynamic interaction between a passive particle and a self-propelled particle, termed a squirmer, by using a two-dimensional lattice Boltzmann method (LBM). It is found that the squirmer can capture a passive particle and propel it simultaneously, provided the passive particle is situated within the squirmer's wake. Our research shows that the critical capture distance, which determines whether the particle is captured, primarily depends on the intensity of the squirmer's dipolarity. The stronger dipolarity of squirmer results in an increased critical capture distance. Conversely, the Reynolds number is found to have minimal influence on this interaction. Interestingly, the passive particle, when driven by the squirmer's wake, contributes to a reduction in the squirmer's drag. This results in a mutual acceleration for both particles. Our findings can provide valuable perspectives for formulating the principles of reducing the drag of micro-swimmers and help to achieve the goal of using micro-swimmers to transport goods without physical tethers.