In a thin layer of liquid crystal (a substance that flows like a liquid but has molecules arranged in order, as in a solid) vortices smaller than the thickness of a human hair are born. These vortices resemble tiny spinning tops: they can move without breaking apart and behave almost like real particles.

By applying an electric field to the layer, scientists made such a vortex travel along a pre-drawn line, like a tram on rails. The speed can be changed on the fly by simply adjusting the voltage. The secret is that the liquid crystal molecules bend slightly under the field, and this bending pushes the vortex forward.

This trick is a step toward creating microrobots that could swim inside living tissues, deliver drugs precisely to a specific cell, or assemble tiny components. Wireless, motorless motion control is an old dream of engineers, and now it's one step closer.