  In recent literature there has been a lot of interest in the phenomena of
noise induced transport in the absence of an average bias occurring in
spatially periodic systems far from equilibrium. One of the main motivations in
this area is to understand the mechanism behind the operation of biological
motors at molecular scale. These molecular motors convert chemical energy
available during the hydrolysis of ATP into mechanical motion to transport
cargo and vesicles in living cells with very high reliability, adaptability and
efficiency in a very noisy environment. The basic principle behind such a
motion, namely the Brownian ratchet principle, has applications in
nanotechnology as novel nanoparticle separation devices. Also, the mechanism of
ratchet operation finds applications in game theory. Here, we briefly focus on
the physical concepts underlying the constructive role of noise in assisting
transport at a molecular level. The nature of particle currents, the energetic
efficiency of these motors, the entropy production in these systems and the
phenomenon of resonance/coherence are discussed.
