Fig. 2

Fluorescence and tomography analysis. a–d Images of fluorescent bacteria in the vicinity of a rotating particle. White color corresponds to higher concentration of bacteria. Images are made from the bottom. The frequency of rotation is 160 Hz. a The initial distribution of live bacteria near the bottom of the film before the onset of rotation. b Uniform distribution of bacteria immediately after the onset of rotation. c Stationary distribution of swimming bacteria around the rotating particle. Bacteria are concentrated in the close proximity of the particle. Red dashed circles illustrate the size of the particle. d Distribution of dead (non-motile) bacteria remains uniform. Scale bar is 50 μm. e The OCT images showing bacterial distribution around the particle in a vertical cross-section at different moments of time after cessation of rotation. The OCT probe is scanning from the bottom. Bright white color corresponds to higher bacterial concentration, n _m  = 10¹¹ cm⁻³. The bottom part of the spinning particle (dashed red circle) and concentrated bacteria are visible as a bright spot near the center of the first image. The droplet of concentrated bacteria is expanding along the bottom surface of the film in four consecutive images. Scale bar is 200 μm. f Averaged radial distributions of bacteria around the particle at different moments of time after cessation of rotation. n₀ is concentration of bacteria far from the particle