The universality of self-organisation: a path to an atom printer?

Abstract: In 1989, Eigler and Schweizer spelt the letters IBM by positioning 35 individual Xenon atoms at 4 Kelvin temperature. The arrangement took approximately 22 hours. This was an outstanding demonstration of control over individual atoms. Since then, 3D printers developed into a near-ubiquitous technology. Nevertheless, with typical resolutions in the micrometres, they are far from the atomic scale of control that the IBM demonstration seemed to herald. Even the highest resolution achieved with ultrafast lasers driving two-photon polymerization barely reaches 100 nm, three orders of magnitude distant from the atomic scale. Here, we adopt a long-term view when we ask about the possibility of a 3D atom printer, which can build an arbitrarily shaped object of macroscopic dimensions with control over its atomic structure at room temperature. After discussing the state-of-the-art technology based on direct laser writing, we identify three fundamental challenges. The first is the fat fingers problem, i.e., laser wavelengths are much larger than the size of the atoms. The second one is complexity explosion; namely, the number of processing steps scales with the inverse cube of the resolution, leading to prohibitively long processing times. The third challenge is the increasing strength of random fluctuations as we approach the atomic scale. This requires control over the fluctuations, which we call mischief of fluctuations. Although direct-writing techniques offer sufficient resolution, speed, and excellent flexibility for the mesoscopic scale, each of the three fundamental problems appears enough to render the atomic scale unreachable. In contrast, these three challenges are not fundamental limitations to self-organisation. We propose a potential path to a 3D atom printer, where laser-driven self-organisation can complement direct-writing techniques by bridging the atomic and mesoscopic scales.