N-heterocyclic carbenes (NHCs) are small, reactive ring molecules that bond well with metallic surfaces, and which over the past few years have attracted a great deal of interest in the field of the stable chemical modification of metallic surfaces. One property—discovered at the University of Münster in Germany a few years ago—is the ability that certain NHC derivatives have, not only to anchor themselves to individual metal atoms, but also to completely extract an individual atom from the surface. Having bonded with these so-called adatoms, the NHCs glide freely over the surface—like a ballbot, i.e., a robot that moves on a sphere.
