Entropically-induced asymmetric passage times of charged tracers across corrugated channels

We analyze the di usion of charged and neutral tracers suspended in an electrolyte embedded in a channel of varying cross section. Making use of systematic approximations, the di usion equation governing the motion of tracers is mapped into an e ective 1D equation describing the dynamics along the longitudinal axis of the channel where its varying-section is encoded as an e ective entropic potential. This simpli ed approach allows us to characterize tracer di usion under generic con nement by measuring their mean rst passage time (MFPT). In particular, we show that the interplay between geometrical con nement and electrostatic interactions strongly a ect the MFTP of tracers across corrugated channels hence leading to alternative means to control tracers translocation across charged pores. Finally, our results show that the MFPTs of a charged tracer in opposite directions along an asymmetric channel may di er We expect our results to be relevant for biological as well synthetic devices whose dynamics is controlled by the detection of diluted tracers.