Can man-made nanomachines compete with nature biomotors?

Biological nanomotors have evolved over million years to perform specific tasks with high efficiency. The remarkable performance of biomotors is inspiring scientists to create synthetic nanomachines that mimic the function of these amazing natural systems. This review discusses the challenges and opportunities facing artificial nanomotors and summarizes recent progress toward the development of such man-made nanomachines. Particular attention is given to catalytic nanowire motors propelled by the electrocatalytic decomposition of a chemical fuel. While artificial nanomotors pale compared to nature biomotors, recent advances indicate their great potential to perform diverse applications and demanding tasks. Such advances include significant improvements in the velocity, motion control, cargo-towing force, and lifetime of such catalytic nanomotors. As a result, artificial nanomotors can have velocities as large as 100 body lengths per second and relatively high powers to transport a "heavy" cargo within complex microchannel networks. Despite this impressive progress, man-made nanomachines still lack the efficiency, functionality, and force of their biological counterparts and are limited to a very narrow range of environments and fuels. Improved understanding of the behavior of catalytic nanomotors will facilitate the design of highly efficient and powerful artificial nanomachines for complex operations in diverse realistic environments, leading to practical nanoscale applications in the not-so-distant future.