Fig. 2: Controlled movement of particle dimers.

a The sketch on the left shows two microrobots aligned with an AC electric field. The orientation of the AC electric field is indicated with a black double arrow. The movement direction is indicated with a blue pointer and is opposite for the two microrobots due to their opposite orientations. The image sequence on the right shows successive frames of a microscopy video demonstrating the resulting anti-synchronous movement in an electric field with slowly changing orientation. b By applying joystick-controlled AC voltages a microrobot is maneuvered through a slalom course around stationary monomer particles. The image shows an overlay of successive frames of a recorded microscopy video. Due to Brownian motion, the monomer particles appear as particle clouds, but they do not respond the applied AC electric field. c A microrobot is maneuvered along a race track adopted from a well-known video game. The image shows an overlay of successive frames of a recorded microscopy video and the racetrack.