Catalytic Motors-Quo Vadimus?

Self-propelled, active colloidal systems are of great current interest from both fundamental as well as practical standpoints, with potential applications in nanomachinery, nanoscale assembly, robotics, fluidics, and chemical/biochemical sensing. This perspective focuses on chemically powered catalytic nano- and micromotors. We review the major advances to date in motor design, propulsion mechanisms and directional control, and inter-motor communication leading to collective behavior. We conclude by discussing the next steps in going forward: the fundamental questions that remain to be addressed and new design principles required for useful applications.