Tiny objects can be propelled in a controlled fashion when placed in an electric field.

Gabriel Loget and Alexander Kuhn at the University of Bordeaux in France tested metallic, conducting beads — with diameters ranging from a few hundred micrometres to 1 millimetre — that become positively charged on one side and negatively charged on the other in an electric field. This drives oxidation and reduction reactions at opposite sides of the beads when they are in solution. The reactions produce different quantities of gas bubbles at the surface of each side, driving the beads in one direction.

The authors used their system to induce a cross-shaped object more than a centimetre wide to spin.

Nature Commun. 10.1038/ncomms1550 (2011)