Conversion of heat to work: An efficient inchworm

Abstract

The paper discusses natural emergence of directed motion in a dimer system due to a structural symmetry breaking. A generalised solution is obtained for the transport of such a system which is driven entirely by bath fluctuations. The result shows existence of ratcheting driven solely by bath fluctuations. If this component of energy conversion driven by bath is taken into account the high efficiency of molecular motors as opposed to paradigmatic ratcheting models can probably be explained.

Thermal equilibrium of a Brownian particle with coordinate dependent diffusion: comparison of Boltzmann and modified Boltzmann distributions with experimental results

“…Diffusion is a major source of transport in numerous biological systems and the space remains quite crowded in such cases where the coordinate dependence of the diffusion could be the rule and not an exception. Moreover, coordinate dependence of diffusion could have other counter-intuitive effects of producing directed motions in structured objects as is shown in [30,31]. These two effects of coordinate dependence of diffusion i.e.…”

Spontaneous collective transport in a heat--bath

“…is the symmetry breaking term in the presence of coordinate dependence of damping, in general, and otherwise not when Γ i 's are even different constants. [13][14][15].…”

“…It is important to note that even when dx dt = 0, the other average velocity dz dt has to be identically zero under equilibrium conditions [13][14][15]. Equilibrium fluctuations of the system are function of the internal coordinate z and there cannot be any average current existing on the centre of the dimer frame (z-coordinates) although the centre of dimer itself can maintain a constant average velocity.…”

“…The collection of dimers interact by dipole-interactions where similar poles repel and opposite poles attract keeping intact the excluded volume. We have already shown that, in a one-dimensional space, a symmetry broken dimer will show directed motion caused by coordinate dependence of diffusion [13][14][15]. However, in a two (or higher) dimensional space, this directed motion of such an individual dimer will be lost due to the presence of rotational degrees of freedom.…”

“…In the present paper we show that thermal fluctuations alone can drive collective motion in the presence of coordinate or state dependent diffusion where no activation of the system is necessary. It has been shown by Bhattacharyay and coauthors [13][14][15] that a symmetrybroken dimer in the presence of coordinate dependent damping/diffusion, in general, can filter Brownian motion to produce directed transport. It has also been shown by Bhattacharyay and coworkers [16,17] that in the presence of coordinate-dependent damping it is possible to keep Stokes-Einstein relation locally intact everywhere in a heat bath which ensures thermal equilibrium of the system.…”