We present a lattice Boltzmann study of the hydrodynamics of a fully resolvedsquirmer, radius R, confined in a slab of fluid between two no-slip walls. Weshow that the coupling between hydrodynamics and short-range repulsiveinteractions between the swimmer and the surface can lead to hydrodynamictrapping of both pushers and pullers at the wall, and to hydrodynamicoscillations in the case of a pusher. We further show that a pusher movessignificantly faster when close to a surface than in the bulk, whereas a pullerundergoes a transition between fast motion and a dynamical standstill accordingto the range of the repulsive interaction. Our results critically requirenear-field hydrodynamics; they further suggest that it should be possible tocontrol density and speed of squirmers at a surface by tuning the range ofsteric and electrostatic swimmer-wall interactions.
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