Fig. 3: Cargo pick-up, transport and release.

a A microrobot approaches a cargo particle. The direction of motion of the microrobot is indicated with a blue pointer and the cargo particle is labeled with a green dot. The orientation of the AC electric field is indicated with a black double arrow. The fluid flow arising around the microrobot and the cargo particle is illustrated with curved blue arrows in the sketch above and leads to an attraction. b A microrobot sticks to a cargo particle via induced dipole-dipole forces. Both are maneuvered around another monomeric particle. The instantaneous induced dipole moments are indicated with white arrows in the sketch above, the electric field is indicated with a black arrow. c A cargo particle is released from a microrobot by a quick change in direction of the external electric field. The fluid flow arising around the microrobot and the cargo particle now leads to repulsion.