Unidirectional rotation driven by random fluctuations

Ratchet effect might be responsible for the unidirectional movement of a couple of systems. The theoretical study of ratchet mechanism usually focuses on the particle or state properties on a prescribed ratchet potential. In contrast, this work starts with a real system and shows how one can manipulate the system setup to have a ratchet potential for the system state. The model consists of a rotor surrounded by several drivers on a 2D plane. Both the rotor and drivers are furnished with electric dipoles, through which they can interact with each other. During the rotational fluctuations of the driver dipoles between two states, the rotor may rotate unidirectionally, independent of whether the driver fluctuations are periodic or completely random. If the driver fluctuations come from the conformational change of certain protein subunits consuming ATP, the rotor behavior would be similar to the rotation of the central γ subunit of F
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F
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-ATPase in mitochondria. We compare the rotational properties of our model with that of the flashing ratchet and F
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F
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-ATPase. This model provides a feasible way for harvesting non-equilibrium energy from ambient noise, which could be used to design microscopic artificial machines.