This work introduces the reader to the topic of active matter physics and focuses on self-propulsion phenomena at the nanoscale. Active matter physics is an emerging research area that studies particles that convert chemical energy into motion. Progress in nanoscience has enabled the creation of many synthetic active systems, from Janus micromotors to “living” crystals. Catalytic self-propelled nanomotors constitute an important class of active materials, and their synthesis and propulsion mechanisms are at the forefront of nanotechnology. Nanomotors are of fundamental interest in nonequilibrium physics and also have potential applications in nanomedicine as effective drug delivery carriers.
This chapter reviews phoretic propulsion mechanisms, including self-electrophoresis and self-diffusiophoresis. Theories that model the enhancement in diffusivity observed in some enzymes are critically compared. The synthesis of sub-100 nm nanomotors becomes a challenge at the nanoscale, and traditional lithographic methods can be complemented by bottom-up approaches, such as wet-chemical synthesis of asymmetric nanoparticles. Finally, the main measurement tools for characterizing the motion of self-propelled nanomotors are presented. These include microscopy tracking methods, Dynamic Light Scattering, Fluorescence Correlation Spectroscopy, and Nanoimpact Voltammetry.