The University of Hawaii at Manoa has created non-mechanical microbots made out of bubbles and propelled by lasers.
According to the University’s lab, “this project involves the manipulation and the assembly of micro-objects using an optically controlled bubble microrobot. This allows light patterns to control the movement of the microrobot. Objectives include the micro-assembly of objects, including live cells, and the parallel, independent control of multiple microrobots in one system.”
Discovery News explains how the microbot works: a 400 mW 980nm (that’s infrared) laser is shone through the bubble onto the heat-absorbing surface of the working area, the fluid moves from the hot area where the laser is pointing towards the colder side of the bubble, and this fluid flow propels the bubble towards the hot area. Moving the laser to different sides of the bubble gives you complete 360 degree steering, and since the velocity of the bubble is proportional to the intensity of the laser, you can go as slow as you want or as fast as about 4 mm/s.