Entropic rectification and current inversion in a pulsating channel

CARUSELA M.F.; J. MIGUEL RUBI

JOURNAL OF CHEMICAL PHYSICS

AMER INST PHYSICS

Lugar: New York; Año: 2017 vol. 146

0021-9606

We show the existence of a resonant behavior of the current of Brownian particlesconned in a pulsating channel. The interplay between the periodic oscillationsof the shape of the channel and a force applied along its axis leads to an increaseof the particle current as a function of the noise level. A regime of currentinversion is also observed for particular values of the oscillation frequency andthe applied force. The model proposed to obtain these new behaviors of thecurrent is based on the Fick-Jacobs equation in which the entropic barrier andthe eective diusion coecient depend on time. The phenomenon observedcould be used to optimize transport in microuidic devices or biological channels.I. INTRODUCTIONTransport of particles through corrugated narrow channels is frequently found in physicochemicaland biological systems in which particles move along a main transport direction1{4.Connement changes signicantly the transport properties of the particles and the energyconversion mechanisms5{7. The presence of boundaries yield a nontrivial contribution to thedynamics that manifests in the appearance of entropic forces in the Fick-Jacobs equation. Itprovides a very accurate description of entropic transport in 2D and 3D channels of varyingcross-section. This equation is equivalent to a Smoluchowski equation in 1D dimension8{13.In many of the studies carried out up to now, channels are considered as rigid structuresas for kinetics of molecular motors and diusion in zeolites14{17, cell membrane channels orion translocation through protein channel18{20 . However in some cases the exible natureof the channel plays a very important role in the transport properties, as in the case ofvascular21,22 or peristaltic channels23 and exible DNA nanochannels24.Our purpose in this article is to propose an entropic transport model to analyze the transportof particles under the inuence of a driving force, through a pulsating channel whosewalls undergo an oscillatory motion. The variation in time of the shape of the channel makesthat the entropic barrier depend on time. A resonant transport of particles in a channelwith periodically oscillating walls was found when the force is perpendicular to the directionof the ow but diusion is constant25{27. We propose to include the eect of the entropicbarrier on the diusion constant. Specically we consider an external constant force acting2