No abstract

Based on the general model of thermally-driven Brownian motors, an equivalent cycle system is established and the Onsager coefficients and efficiency at the maximum power output of the system are analytically calculated from non-equilibrium thermodynamics. It is found that the Onsager reciprocity relation holds and the Onsager coefficients are affected by the main irreversibilities existing in practical systems. Only when the heat leak and the kinetic energy change of the particle in the system are negligible, can the determinant of the Onsager matrix vanish. It is also found that in the frame of non-equilibrium thermodynamics, the power output and efficiency of an irreversible Brownian motor can be expressed to be the same form as those of an irreversible Carnot heat engine, so the results obtained here are of general significance. Moreover, these results are used to analyze the performance characteristics of a class of thermally-driven Brownian motors so that some important conclusions in literature may be directly derived from the present paper.

On the basis of the double-well potential which can be calculated theoretically and implemented experimentally, the influence of the time delay, number of particles and asymmetric parameter of the potential on the performance of a delayed feedback ratchet is investigated. The center-of-mass velocity of Brownian particles, average effective diffusion coefficient and Pe number are calculated. It is expounded that the parameters are affected by not only the time delay and number of particles but also by the asymmetric parameter of the double-well ratchet potential. It is very interesting to find that the current transport reversal may be obtained by varying the number of particles of the system. It is expected that the results obtained here may be observed in some physical and biological systems because the double-well ratchet potential is realizable experimentally.