Motion control at the nanoscale.

Synthetic nanoscale motors represent a major step in the development of practical nanomachines. This Review summarizes recent progress towards controlling the movement of fuel-driven nanomotors and discusses the challenges and opportunities associated with the achievement of such nanoscale motion control. Regulating the movement of artificial nanomotors often follows nature's elegant and remarkable approach for motion control. Such on-demand control of the movement of artificial nanomotors is essential for performing various tasks and diverse applications. These applications require precise control of the nanomotor direction as well as temporal and spatial regulation of the motor speed. Different approaches for controlling the motion of catalytic nanomotors have been developed recently, including magnetic guidance, thermally driven acceleration, an electrochemical switch, and chemical stimuli (including control of the fuel concentration). Such ability to control the directionality of artificial nanomotors and to regulate their speed offers considerable promise for designing powerful nanomachines capable of operating independently and meeting a wide variety of future technological needs.