Nanorobots: Machines Squeezed between Molecular Motors and Micromotors

The development of a new set of tools is often a culminating point in humanity's understanding and harnessing of nature. So-called “micro/nanomotors” are artificial machines that convert chemical energy to propulsion and have already served as building blocks for many futuristic applications. With the never-ending push toward miniaturization in every aspect, the combined recent efforts of multiple disciplines will create genuinely nanosized artificial machines, with all dimensions below 1,000 nm. However, there is a strong fundamental and methodological barrier in the creation and utilization of nanomachines that sets them apart from their microscale counterparts: the strong dominance of Brownian forces and the difficulty of analyzing their motion. In this review, we critically assess the new fully nanosized robots and compare them with current microrobot technology and applications.