Study on the motion characteristics of chiral microswimmers near the wall with slip boundary conditions

Using a three-dimensional lattice Boltzmann method, this study investigates the swimming behavior of chiral spherical microswimmers near a wall with slip boundary conditions. The chirality is introduced via a rotational dipole, and the slip length along the wall decays exponentially in the streamwise direction. Through numerical simulations, we systematically analyze the influence of the propulsion type parameter β, chirality parameter χ, slip length scale L, and initial orientation angle on the dynamics of both pusher- and puller-type microswimmers. Results show that with a constant slip length, pushers consistently show stable Y+ deflection with a “nose-up” orientation, whereas pullers switch from Y+ to Y− deflection as β increases. The duration of wall-following behavior and the overall swimming mode are determined by the slip length L. As β or L increases, pullers shift from wall-escaping trajectories to compact circular orbits, while pushers only display wall-following motion at small L and tend to escape the wall at larger L. The curvature of the trajectory and the evolution of swimmer orientation are modulated by the chirality parameter χ. Notably, when χ ≈ 2.8, pullers develop helical trajectories, while pushers, though exhibiting stronger helicity, ultimately still escape the wall. The initial orientation angle significantly affects the swimming path and dynamic mode; large pitch angles induce new behaviors in pushers, such as Y− deflection, and enhance their alignment and lateral drift rates along the wall. These findings provide insight into the near-wall locomotion of microswimmers and offer potential strategies for manipulating their behavior in practical applications.