Catalytic nanomotors: Fabrication, mechanism, and applications

Catalytic nanomotors are nano-to-micrometer-sized actuators that carry an on-board catalyst and convert local chemical fuel in solution into mechanical work. The location of this catalyst as well as the geometry of the structure dictate the swimming behaviors exhibited. The nanomotors can occur naturally in organic molecules, combine natural and artificial parts to form hybrid nanomotors or be purely artificial. Fabrication techniques consist of template directed electroplating, lithography, physical vapor deposition, and other advanced growth methods. Various physical and chemical propulsion mechanisms have been proposed to explain the motion behaviors including diffusiophoresis, bubble propulsion, interfacial tension gradients, and self-electrophoresis. The control and manipulation based upon external fields, catalytic alloys, and motion control through thermal modulation are discussed as well. Catalytic nanomotors represent an exciting technological challenge with the end goal being practical functional nanomachines that can perform a variety of tasks at the nanoscale.