Directed Mechanical Motion in Nonequilibrium Nanosystems: Occurrence Conditions and Kinematic Controllability

摘要

The directed mechanical motion of nanoscale objects along a phase boundary can result from strongly nonequilibrium processes, which transfer the energy of various external sources to the system. This effect is particularly relevant in Brownian (molecular or biological) motors known for their high efficiency of chemical-to-kinetic energy conversion. Here, we formulate the necessary conditions for nanoparticle surface-parallel motion to occur under the action of external nonequilibrium fluctuations of various nature; the ways to provide such conditions are also considered. As shown, the magnitude and sign of the average directed velocity are dictated by the competition between the spatial and temporal asymmetry of the potential energy. The theoretical models are exemplified by high-efficiency Brownian nanoengines, molecular pumps, dipole rotators, and photo-induced molecular motors. The latter serve to illustrate the kinematic controllability of motors by varying their molecular structure and photoexcitation parameters.