  Self-propulsion of cellular microswimmers generates flow signatures, commonly
classified as pusher- and puller-type, which characterize hydrodynamic
interactions with other cells or boundaries. Using experimentally measured beat
patterns, we compute that flagellated alga and sperm oscillate between pusher
and puller. Beyond a typical distance of 100 um from the swimmer, inertia
attenuates oscillatory micro-flows. We show that hydrodynamic interactions
between swimmers oscillate in time and are of similar magnitude as stochastic
swimming fluctuations.

Cell Behavior;Soft Condensed Matter;Biological Physics