Figure 6. Superimposed time-lapse images of selective actuation of an acoustic microswimmer from within a group.

Two swimmers with bubbles of different size were immersed in an acoustic field of variable frequency. (a), Swimmer A, with the larger bubble, begins acoustically-driven motion at 74 kHz, with little simultaneous motion of swimmer B. A video of this behaviour is available as Supplementary Video 6. (b), With further increase in frequency, swimmer A stops; swimmer B begins to move at 91 kHz, with swimmer A remaining essentially stationary. A video of this behaviour is available as Supplementary Video 7.