Toward steering the motion of surface rolling molecular machines by straining graphene substrate.

The surface rolling molecular machines are proposed to perform tasks and carrying molecular payloads on the substrates. As a result, controlling the surface motion of these molecular machines is of interest for the design of nano-transportation systems. In this study, we evaluate the motion of the nanocar on the graphene nanoribbons with strain gradient, through the molecular dynamics (MD) simulations, and theoretical relations. The nanocar indicates directed motion from the maximum strained part of the graphene to the unstrained end of the substrate. The strain gradient induced driving force and diffusion coefficients of nanocars are analyzed from the simulation and theoretical points of view. To obtain the optimum directed motion of nanocar, we consider the effects of temperature, strain average, and magnitude of strain gradient on the directionality of the motion. Moreover, the mechanism of the motion of nanocar is studied by evaluating the direction of the nanocar's chassis and the rotation of wheels around the axles. Ultimately, the programmable motion of nanocar is shown by adjusting the strain gradient of graphene substrate.