Autonomous walking dynamics of a nanorobot on a nanopore track driven by salt concentration gradients.

This article focuses on the autonomous walking dynamics of a DNA nanorobot with three single-stranded DNA (ssDNA) legs along a nanopore track powered by an ion concentration gradient. Using Langevin dynamics simulations combined with free energy analyses, the study reveals that variations in local ion concentrations modulate the electrostatic interactions between the nanorobot legs and nanopores, thereby influencing walking modes, velocity, and directionality. Three distinct walking modes are identified: a three-legged (3L) mode at low ion concentrations where all legs cooperate, a two-legged (2-2L) mode at high ion concentrations where the lagging leg can leave independently, and a transitional two-to-three-legged (2-3L) mode. These modes correspond to different free energy landscapes—ranging from potential wells to barriers and platforms—that govern the nanorobot's movement characteristics, including the probability of reverse walking and step duration. The findings provide insights into controlling DNA nanorobot locomotion via ion concentration gradients without the need for direct nanopore surface charge modification.